EP3145642B1 - Novel process for obtaining superhydrophobic or superhydrophilic surfaces - Google Patents

Description

Summary of the invention

The present invention relates to a process for texturing surfaces giving them a superhydrophobic, superoleophobic, superhydrophilic or even superoleophilic character.

This process comprises i) a step of texturing the surface (via the deposition of nanoparticles of different sizes), ii) a step of crosslinking the surface thus textured (by a crosslinking agent), and optionally iii) a step of modifying the surface properties by perfluorinated (and therefore hydrophobic) molecules.

This process is suitable, among other things, for the treatment of surfaces and heat-sensitive and / or transparent materials. Indeed, none of the process steps uses a temperature above 100 ° C. Thus, the process of the invention is particularly suitable for treating transparent surfaces composed of non-mineral materials such as, for example, polycarbonate, of which it will not affect the transparency or the optical properties.

Description of the Prior Art

A surface is said to be superhydrophobic when its surface is very difficult to wet. This is the case with the lotus leaf, nasturtium or cabbage. It is the same for the duck feathers which remain dry at the exit of the water. Although the phenomenon of self-cleaning associated with lotus leaves has been known in Asia for at least 2000 years, its study is fairly recent.

The lotus effect is a phenomenon of superhydrophobia caused by a hierarchical roughness of the surface, both microscopic and nanoscopic. In the case of the lotus leaf, the double structure is formed by an epidermis. The outer layer (or cuticle) contains a layer of wax. The epidermis of the leaf is formed by papillae of a few microns on which the wax rests. This wax layer is hydrophobic and forms the second component of the double structure. The latter confers on the surface of the lotus leaf self-cleaning capacities: by flowing, the drops of water take with them dust and particles.

We can guess the practical interest that there can be in developing such superhydrophobic surfaces: the drops flee from them, and the surfaces remain dry after exposure to water. Stimulated by potential applications (self-cleaning glasses, rain shields, anti-icing coating, intolerable clothing, anti-humidity paints) chemists and physicists have multiplied since the 1990s the processes for manufacturing such surfaces. With the emergence of nanotechnologies and the development of manufacturing tools, new processes have emerged. It is now well established that two properties are required to obtain superhydrophobic surfaces: low surface tension (chemical property), and hierarchical roughness (physical property).

Similarly, a textured surface that does not have a hydrophobic character will tend to be highly hydrophilic or even superhydrophilic (the contact angle with water will then be close to 0 °). The surface is then completely wettable by water. The film of water created by condensation is continuous and therefore does not generate visual disturbance. This opens perspectives for application in the fight against condensation and fogging on transparent or mirror surfaces.

1. i) Une surface très rugueuse, qui peut piéger de l'air sous les gouttes d'eau, et
2. ii) Une couche de passivation de faible énergie de surface appliquée sur la texture rugueuse et très fine pour ne pas altérer la surface des aspérités.

More specifically, to create a superhydrophobic surface with high water mobility (Cassie-Baxter non-wetting state), it is advisable to use:

1. i) A very rough surface, which can trap air under the drops of water, and
2. ii) A passivation layer of low surface energy applied to the rough and very fine texture so as not to alter the surface of the roughness.

To obtain a superhydrophilic surface, only step i) is necessary.

These two successive treatments make it possible to obtain self-cleaning and anti-fouling surfaces, which is very important when they are used in particular outside and therefore exposed to climatic conditions.

The first commercial product that mimics the lotus effect was born in 1999 and consists of a self-cleaning paint for facades (Lotusan®). Other industry sectors have adopted this technology. Another area of use is self-cleaning glasses from Ferro GmbH: they have been installed in optical sensors located at toll booths on German motorways. EVONIK AG has developed prototypes of lacquers and plastics.

Other applications require, in addition to superhydrophobia or superhydrophilia, transparency. This is the case, for example, with optical equipment (windows, lenses, glasses) or solar cells.

However, transparency and roughness are generally contradictory properties. In fact, when the roughness increases, the transparency decreases due to the scattering of light due to the surface roughness. Light scattering can be described by Rayleigh scattering or Mie scattering depending on the size of the surface roughness (assuming the roughness behaves like spherical particles). According to these well-established principles, light scattering is a function of the roughness and the refractive index of the medium. Only a judicious compromise between the roughness and the refractive index of a material therefore makes it possible to make it both transparent and superhydrophobic / superhydrophilic.

Several techniques have been described for preparing surfaces which are both transparent and superhydrophobic by nano-texturing. Nanoparticles have in particular been proposed for controlling the roughness of surfaces with a view to increasing their hydrophobicity [ Deng X. et al, Advanced Materials. 23 (26): p.2962 ].

Different types of nanoparticles have been used to make porous hydrophobic films (TiO ₂ , ZnO, etc ...). Among these nanoparticles, those based on Silica (SiO ₂ ) have a modular size and excellent scratch resistance. They are now on the market, and their surface can be modified by silanization. Easy to use, they are currently used to cover surfaces using flat surfaces or microstructured substrates using several methods ("spin coating", "dip coating" and "spray coating").

More specifically, superhydrophobic and transparent surfaces were obtained by the “dip coating” of silica nanoparticles 60 nm in diameter on glass substrates treated with 3-aminopropyl triethoxysilane (APTES), followed by evaporation under vacuum of the perfluorodecyltriethoxysilane (PFTS) then thermal annealing (between 900 ° C and 1100 ° C for 30 to 120 min under O ₂ atmosphere) [ Ling XY et al., Langmuir, 2009.25 (5). p.3260-3263 ]. This high temperature annealing ensures adhesion and good mechanical stability of the coating. It is important to note that, without this high temperature annealing, the coating can be easily removed with an adhesive tape.

Another technique was developed by the team of Karunakaran et al (Langmuir. 27 (8). P.4594-4602 ). By the dip-coating process, silica nanoparticles of several sizes (100 nm, 50 nm and 20 nm) functionalized with APTES were deposited on different substrates (glass, silica, epoxy and fabrics), then annealed at 200 ° C or 400 ° C for 2 hours, in order to increase adhesion and ensure good mechanical stability. They were then covered with PFTS by vapor deposition. In this process, heat treatment is essential because it improves the stability of the coating of nanoparticles against PDMS molding while maintaining superhydrophobicity after exposure to UV light (200 mW. Cm ^-2 for 1 week) under the conditions ambient. In this case, the use of APTES allows a transient affinity of the different populations of particles, created by electrostatic bonds between the amine group of APTES (positively charged) and the hydroxyl groups of silica (negatively charged). The cohesion of the assembly is then ensured by a high temperature annealing phase.

Other techniques exist. For example, WO 2012/138992 proposes to texturize surfaces using nanoparticles of two different sizes, covered with a layer of polymer which was crosslinked by heating the surface. US 2013/0064990 proposes to dehydrate the surface and then treat it with SiCl4 in an anhydrous medium. Finally, US 2013/0115381 suggests texturing surfaces using mixtures complexes containing micro-powder and polymers which crosslink at high temperature.

These techniques are not, however, suitable for transparent and heat-sensitive materials, since they contain a step of heating at high temperature (above called “annealing”). Indeed, heating transparent thermosensitive materials generally results in an alteration of their transparency (they may crack and / or become opalescent). It is therefore essential not to heat these materials when their transparency must be preserved.

Other examples use a covalent grafting of the particles together to form so-called “raspberry” particles (ie, made up of an agglomerate of particles). We can cite Ming W. et al (Nano Letters. 5 (11). P.2298-2301 ) which reacts particles carrying epoxy functions (diameter 700nm) and particles carrying amine functions (diameter 70nm). The amine-epoxide interaction leads to the formation of a covalent bond between these particles. These particles are then included in an epoxy resin which must be partially or completely degraded to reveal a roughness but without ensuring mechanical strength. Furthermore, the particles are all functionalized before deposition, which does not leave a silica zone available for simple grafting of a hydrophobic molecule by a covalent bond, for example a perfluorinated silane. This method therefore does not meet the requirements for a transparent and robust surface.

On a similar principle, Zhao et al (Colloids and Surface A. 339. p.26-34 ) propose to produce from silica particles coated with APTES particles carrying isocyanate functions. These particles then have a high reactivity which allows them to react with another population of particles and thus form aggregates (or "raspberries"). Zhao et al obtain large aggregates (> 5 µm) from complex mixtures of organic molecules. These particles require at least two treatments to be reactive with each other. The addition of polymer makes the reactivity and cohesion of the aggregates difficult to control.

These different techniques, which are difficult to control given their complexity, are therefore not compatible with the constraints inherent in industrial applications.

In particular, they are not suitable for treating transparent and heat-sensitive surfaces in order to make them superhydrophilic or superhydrophobic.

The present inventors have sought to develop a process allowing an easy and lasting application of a superhydrophilic or superhydrophobic coating, in particular on a transparent and heat-sensitive material, without risking its transparency. This process should be simple and inexpensive, and contain only low temperature steps (<180 ° C, preferably <100 ° C). The superhydrophobic surfaces obtained by this process must nevertheless have good chemical resistance to detergents and solvents, as well as good physical resistance to abrasion and UV waves.

Description of the invention

The present inventors have been able to demonstrate that a recovery process comprising i) the successive or concomitant deposition of several populations of nanoparticles of different sizes, and ii) a phase of crosslinking of this layer at low temperature (<180 ° C., preferably <100 ° C) gives superhydrophilic properties to a large number of materials (transparent or not). In addition, the addition of a treatment with perfluorinated molecules makes it possible to transform these same surfaces into superhydrophobic and superoleophobic surfaces. Steps i) and ii) also make it possible, alone, to impart superhydrophobic and superoleophobic properties if the particles used are themselves hydrophobic. This process is suitable, among other things, for the treatment of heat-sensitive surfaces since none of these steps involves heating the material or its surface to a temperature above 180 ° C. It can even, in certain cases, be completely carried out at room temperature. This characteristic is important in that it makes it possible to treat transparent surfaces composed of non-mineral materials (such as polycarbonate for example) without affecting the transparency of said materials or its optical properties.

By “ superhydrophobic ” is meant, within the meaning of the present invention, a material which gives contact angles with water greater than 130 °, preferably greater than 140 °, even more preferably greater than 150 °. The contact angle is measured by depositing a drop of water on a flat surface of the material and measuring the angle made by the tangent of the drop with the material.

By “ superoleophobic ” is meant, within the meaning of the present invention, a material which gives contact angles with oils greater than 130 °, preferably greater than 140 °, even more preferably greater than 150 °. The contact angle is measured by depositing a drop of oil on a flat surface of the material and measuring the angle made by the tangent of the drop with the material.

By “ superhydrophilic ” is meant, within the meaning of the present invention, a material which gives contact angles with water of less than 10 °, preferably less than 5 °. The contact angle is measured by depositing a drop of water on a flat surface of the material and measuring the angle made by the tangent of the drop with the material.

By “ superoleophilic ” is meant, within the meaning of the present invention, a material which gives contact angles with oils less than 10 °, preferably less than 5 °. The contact angle is measured by depositing a drop of oil on a flat surface of the material and measuring the angle made by the tangent of the drop with the material.

In general, the method therefore comprises at least i) a step of texturing the surface (via the deposition of nanoparticles of different sizes) and ii) a step of crosslinking at low temperature (preferably at room temperature) of the surface thus textured (by a crosslinking agent). When the crosslinking agent is not sufficiently hydrophobic or is hydrophilic, it is possible to add, after this crosslinking step, a step of modifying the surface properties using hydrophobic molecules (for example perfluorinated molecules ).

1. a) Dépôt d'au moins deux populations de nanoparticules de tailles différentes sur le matériau à traiter, et
2. b) Réticulation de la surface recouverte de nanoparticules à l'aide d'un agent réticulant, à basse température.

In other words, the present application describes a method of covering surfaces comprising at least the steps:

1. a) depositing at least two populations of nanoparticles of different sizes on the material to be treated, and
2. b) Crosslinking of the surface covered with nanoparticles using a crosslinking agent, at low temperature.

In a preferred embodiment, the crosslinking agent is hydrophilic (for example if it is TEOS), this process therefore makes it possible to obtain superhydrophilic surfaces.

In a preferred embodiment, this method contains a third step (c) consisting in covering the surfaces obtained after steps a) and b) with perfluorinated molecules, which makes them superhydrophobic.

Advantageously, none of the steps a), b) and c) of this process involves heating the surface to be treated to a temperature above 180 ° C.

Surfaces to be treated

The method of the invention can be applied to the surface of a very wide variety of materials.

This surface can in particular consist of a composite containing carbon (graphene, carbon nanotubes, SiC, SiN, SiP, graphite), a polymeric material, a metal, an alloy, or an oxide metallic. In addition, it can be a composite of polymeric organic materials and inorganic materials. It can also be applied to organic materials such as wood or cotton.

More particularly, this surface can be made of steel, stainless steel, indium tin oxide (ITO), zinc, zinc sulfide, aluminum, titanium, gold, chromium or nickel. Alternatively, this surface may consist of silicon, aluminum, germanium or oxides thereof or their alloys such as for example quartz, borosilicate glasses such as BK7, or soda-lime. It can also be made of polycarbonate (PC), poly ethylene terephthalate (PET), poly methyl methacrylate (PMMA), polystyrene, polyethylene (PE), polypropylene (PP), poly (lactic acid), poly glycolic acid, polyester, poly (acrylic acid) (PAA), polyacrylate, polyacrylamide (PAM), alkyl polyacrylate (methyl polyacrylate (PMA), polyethylacrylate (PEA), polybutylacrylate (PBA)), poly (acid methacrylic) (PMA), polymethacrylate, polytetrafluoro ethylene (PTFE), or polyvinylidene fluoride (PVDF). These different polymeric materials can be present in a mixture or in the form of copolymers.

In a preferred embodiment, the method of the invention is applied to a surface consisting of at least 50%, preferably at least 75%, of silica, aluminum, germanium, oxides of those or alloys thereof. Ideally, it is a surface made up of 100% of these compounds. In a preferred embodiment, the surface is transparent, glass or silica or polycarbonate.

In a more preferred embodiment, the method of the invention is applied to a surface made of a heat-sensitive material.

By “ heat-sensitive material ” is meant in the present invention, a material whose structure, appearance, mechanical, optical, physical or chemical properties are altered when it is heated to a temperature above 180 ° C.

As an example of a heat-sensitive material, there may be mentioned certain polymeric materials containing compounds such as polycarbonates, poly methylmethacrylate (PMMA), polypropylene, polyvinyl acetate (PVA), polyamides (PA), Poly (terephthalate d (ethylene) (PET), polyvinyl alcohols (PVAI), polystyrenes (PS), polyvinyl chlorides (PVC) and polyacrylonitriles (PAN), whose properties (solidity, transparency, mechanical resistance ...) are altered when heated to temperatures above 180 ° C.

In an even more preferred embodiment, the method of the invention is applied to a material containing more than 50% of polycarbonate or of polycarbonate composites covered with an SiO _x group.

Activation / pre-treatment of the surface to be treated (optional)

The activation of a surface consists in rendering a material wettable and reactive while it is initially inert with respect to the superhydrophilic or superhydrophobic layer which it is desired to graft.

On polymeric surfaces such as for example polyethylenes, polypropylenes, polyurethanes, PMMA, or polycarbonates, the activation can be obtained by an ionizing treatment such as a UV-ozone, plasma, or corona treatment which will create free radicals on the surface and insert high energy groups like hydroxyl groups. These groups are then suitable for interaction with the superhydrophilic or superhydrophobic coatings described elsewhere in this document.

In a preferred embodiment, the material to be covered (or the surface to be treated) is activated by a physical treatment such as for example a UV-ozone treatment or a plasma treatment. The conditions of these treatments are well known to those skilled in the art (cf. example 14). This activation step is especially important when the surface consists of polymers, such as those described above.

This physical activation step is not essential when the surface to be covered consists of inorganic materials or metals such as those described above.

In addition, certain surfaces to be covered can advantageously be pretreated with an adhesion agent before steps a) and b).

1. 1) des fonctions d'accroche sur la surface (suivant le type de surface à traiter, ce groupement peut être par exemple un silane, un phosphonate ou un thiol), et
2. 2) des fonctions permettant d'assurer une affinité de la surface pour les nanoparticules, comme par exemple un groupement chimique réactif permettant la formation de liaisons covalentes.

In the context of the present invention, an " adhesion agent " is an organic chemical compound which makes it possible to create a strong interaction, such as for example a covalent bond, between the surface and the various nanoparticles which will be deposited thereon. Such adhesion agents are, for example, asymmetric organic molecules carrying two functions making it possible to react sequentially with particles. Said adhesion agents are preferably compounds of organic monomers comprising:

1. 1) attachment functions on the surface (depending on the type of surface to be treated, this group may for example be a silane, a phosphonate or a thiol), and
2. 2) functions making it possible to ensure an affinity of the surface for the nanoparticles, such as for example a reactive chemical group allowing the formation of covalent bonds.

Preferably, the adhesion agents which can be used for pretreating the surfaces in the process of the invention are the isocyanate silane compounds, among which mention may be made 3- (Trimethoxysilyl) propyl isocyanate (NCO-TMS) and 3- (Triethoxysilyl) propyl isocyanate. Mention may also be made of epoxy silane compounds such as for example 3-Glycidoxypropyltrimethoxysilane (GPTMS) or 3-Glycidoxypropyltriethoxysilane.

Such adhesion agents can be used when the surfaces to be treated are for example made of silicon, silica, glass, germanium, organic polymers, metal, alloy or metal oxide.

Contrary to what various teams propose, it is preferable not to cover the surface of interest with amino compounds such as the aminoalkyl silane compounds (among which 3-aminopropyl triethoxysilane (APTES), 3-aminopropyl trimethoxysilane (APTMS) , 4-aminobutyl triethoxysilane (ABTES), 3-aminopropyl tri-isopropoxysilane (APTiPrS), or even 3-aminopropyl trichlorosilane (APTCS)). It is also preferable not to cover the surface of interest with cationic polymers (such as poly-lysine, polyalkylamine hydrochloride, or even poly-N-vinylimidazole). Indeed, all of these compounds create weak bonds with the nanoparticles which will then be added, these weak bonds being detrimental to the stability and the resistance of the layer (cf. Example 12).

It should be noted that, in the case of a silica surface, it is possible not to use an adhesion agent. If an adhesion agent is however used, it will preferably be an agent making it possible to form covalent bonds, so as to increase the interaction between the particles and a surface.

To increase the interactions of the superhydrophobic or superhydrophilic coating with the material, a primary bonding layer can also be used. This primary layer may or may not be deposited in addition to activation by physical treatment. By “ primary bonding layer ” is meant the deposition of a uniform layer of a transition metal alkoxide such as for example tetra ethoxy silicate (TEOS). To facilitate this deposition, a surface can be activated beforehand by an ionizing treatment such as, for example, plasma or UV-Ozone treatments (cf. example 20).

This primary bonding layer is especially important when the surface to be covered is polymeric.

More precisely, it is advantageous, when the surface of interest consists of polymeric materials, to combine the two types of pre-treatments, that is to say to apply a physical pre-treatment (UV, ozone or plasma ) and a primary bonding layer (with TEOS for example). Preferably, the deposition of the primary bonding layer takes place after the physical pretreatment.

When the surface of interest consists of an inorganic or metallic material, it is not necessary to activate it, neither by a physical treatment, nor by a primary bonding layer. Furthermore, it is not necessary to treat this type of surface with an adhesion agent as defined above. These different treatments are therefore optional (on this type of surface).

In all cases, make sure that the surface is clean. If necessary, a cleaning / washing step can be added to the process of the invention.

In a preferred embodiment, physical activation of the surface is performed. It is followed by the deposition of a primary bonding layer. This primer is preferably an acid solution of TEOS. In this preferred embodiment, the TEOS solution is produced in water, alcohol or a mixture of these liquids, at a concentration between 1 mM and 1000 mM, more preferably between 10 mM and 500 mM, and , even more preferably, between 50 mM and 250 mM. The deposition of this primary layer can be done by dip-coating or by spray.

Nanoparticle populations

The first step of the process of the invention consists in depositing at least two populations of nanoparticles of different sizes on the surface to be treated.

By “ nanoparticle ” (or NP) is meant within the meaning of the invention very spherical solid particles of very small size, typically of nanometric to micrometric size. More specifically, the “nanoparticles” which can be used in the process of the invention have an average diameter of between 1 nm and 10 μm.

By “ population of nanoparticles ” is meant, within the meaning of the present invention, a set of nanoparticles of the same size or of similar size, ie, having the same shape and a homogeneous size. In practice, the diameter of nanoparticles within the same population follows a Gaussian distribution which can vary by a maximum of 30%.

The two populations of nanoparticles can be deposited successively (or sequentially) on the surface to be treated, or concomitantly. In this second case, they may have been agglomerated beforehand, generating larger nanoparticles called “raspberries” which will then be deposited on the surface. Raspberries can also form directly on the surface to be treated, when the two populations are added successively or concomitantly.

These “raspberry” nanoparticles are made up of large nanoparticles on the surface of which smaller nanoparticles are grafted (preferably in a single layer). They therefore consist of two populations of nanoparticles within the meaning of the present application. These assemblies of nanoparticles are at the origin of the roughness on the nanometric scale created on the surface. This roughness makes it possible to provide the superhydrophilic properties or even the superhydrophobic properties (if the rough surface is then treated with a hydrophobic compound).

These “raspberry” nanoparticles are obtained by using at least two different sizes of nanoparticles. It is therefore essential, in the context of the present invention, to use two categories of nanoparticles having distinct sizes (some substantially larger than the others).

In a preferred embodiment, the nanoparticles used in the process of the invention have diameters between 1 nm and 10 μm, more preferably between 5 nm and 1 μm, and, even more preferably, between 10 nm and 500nm. Ideally, the diameters of the populations of particles have a ratio of between 2 and 30, and preferably a ratio of between 3 and 10. This ratio corresponds to the ratio of the diameter of large particles to the diameter of small particles.

For applications on transparent surfaces using wavelengths in the visible and / or in the infrared, the nanoparticles used in step a) will have a preferred diameter of between 10 and 200 nm. Ideally, the diameters of the populations of nanoparticles have a ratio of between 2 and 30, and preferably have a ratio of between 3 and 10. This ratio corresponds to the ratio of the diameter of large nanoparticles to the diameter of small nanoparticles.

In a most preferred embodiment, the two populations of nanoparticles used in the process of the invention have a diameter of between 50 and 200 nm for some, and between 5 and 50 nm for others.

If the populations of monodisperse nanoparticles are preferred, polydisperse nanoparticles can also be used.

By " monodisperse " is meant particles having a diameter the variation of which does not exceed 10%. For example, a population of particles with a diameter of 50 nm will be considered to be monodisperse if the diameters of the particles within this population are between 50 nm ± 10%, ie between 45 and 55 nm.

By " polydisperse " is meant all other cases. Namely, populations of particles whose diameter varies by more than 10%, or else a mixture of two monodisperse populations.

By way of example, the inventors present below the results obtained by using two populations of polydisperse nanoparticles having a diameter of between 70 and 100 nm for some and between 10 and 15 nm for others.

• Les matériaux inorganiques (comme par exemple le silicium, l'aluminium, le titane, le zinc, le germanium et/ou leurs oxydes),
• les métaux, les alliages, les oxydes et les céramiques ou encore les composites contenant du carbone, et
• les polymères, parmi lesquels : le polycarbonate, le poly éthylène téréphtalate (PET), le poly methacrylate de méthyle (PMMA), le polystyrène, le polyéthylène, le polyester, le poly(acide acrylique) (PAA), le polyacrylate, le polyacrylamide (PAM), le polyacrylate d'alkyle (polyacrylate de méthyle (PMA), le polyacrylate d'éthyle (PEA), le polyacrylate de butyle (PBA)), le poly(acide méthacrylique) (PMA), le latex et le polyméthacrylate.

The nanoparticles used in the process of the invention can be made of different materials. Among them, we can cite:

• Inorganic materials (such as, for example, silicon, aluminum, titanium, zinc, germanium and / or their oxides),
• metals, alloys, oxides and ceramics or composites containing carbon, and
• polymers, among which: polycarbonate, polyethylene terephthalate (PET), poly methyl methacrylate (PMMA), polystyrene, polyethylene, polyester, poly (acrylic acid) (PAA), polyacrylate, polyacrylamide (PAM), poly (alkyl polyacrylate) (poly methyl acrylate (PMA), poly (ethyl acrylate) (PEA), polybutylacrylate (PBA)), poly (methacrylic acid) (PMA), latex and polymethacrylate.

Nanoparticles can also consist of a single compound or an alloy of several compounds of different natures.

The two populations of nanoparticles of different sizes can be made of different materials (for example silica and polycarbonate). However, in a preferred embodiment, the two populations of nanoparticles of different sizes are made of the same material (for example silica, or polycarbonate).

For applications in which the transparent properties must be maintained after treatment, preference will be given to nanoparticles whose refractive index is close to that of the material to be covered.

In a preferred embodiment, said nanoparticles are of the same material as the surface to be covered. Thus, they are preferably made of silica, aluminum, titanium, germanium, oxides thereof or alloys thereof, or polycarbonate.

Successive deposition of nanoparticles

In a preferred embodiment, the first layer of nanoparticles deposited on the surface has not been covered or will not be covered with any adhesion agent.

In another embodiment, the first layer of nanoparticles deposited has been covered or will be covered by an adhesion agent making it possible to increase the affinity of the particles with the surface and / or of the nanoparticles with each other. Said adhesion agent is an organic chemical compound which makes it possible to create a strong interaction, such as for example a covalent bond, between the various nanoparticles which will be deposited on the surface of said material. This agent must, itself, have a strong interaction with nanoparticles.

Such adhesion agents are, for example, asymmetric organic molecules carrying two functions making it possible to react sequentially with particles.

Such adhesion agents are, for example, the isocyanate silane compounds among which mention may be made of 3- (Trimethoxysilyl) propyl isocyanate. (NCO-TMS) or 3- (Triethoxysilyl) propyl isocyanate. Mention may also be made of epoxy silane compounds such as for example 3-Glycidoxypropyltrimethoxysilane (GPTMS) or 3-Glycidoxypropyltriethoxysilane.

In a preferred embodiment, the nanoparticles are made of silica and the adhesion agent deposited on their surface is GPTMS or NCO-TMS (cf. examples 12 and 18).

Contrary to what various teams propose, it is preferable not to cover the nanoparticles used in the process of the invention with amino compounds such as aminoalkyl silane compounds (among which 3-aminopropyl triethoxysilane (APTES), 3- aminopropyl trimethoxysilane (APTMS), 4-aminobutyl triethoxysilane (ABTES), 3-aminopropyl tri-isopropoxysilane (APTiPrS), or 3-aminopropyl trichlorosilane (APTCS)). It is also preferable not to cover the nanoparticles used in the process of the invention with cationic polymers (such as poly-lysine, polyalkylamine hydrochloride, or even poly-N-vinylimidazole). Indeed, all of these compounds create weak bonds which will be detrimental to the stability of the layer (cf. Examples 12 and 18).

• a0) Eventuellement, activation de la surface par un traitement physique (comme par exemple un traitement UV-Ozone ou un traitement plasma) suivi ou non du dépôt d'une couche primaire d'accrochage (comme par exemple le TEOS),
• a1) Eventuellement, traitement de la surface par un agent d'adhésion choisi par exemple parmi le NCO-TMS, le 3-(Triethoxysilyl)propyl isocyanate, le GPTMS ou le 3-Glycidoxypropyltriethoxysilane,
• a2) Dépôt d'une première population de nanoparticules sur la surface à traiter,
• a3) Eventuellement, traitement de la surface recouverte de la première population de nanoparticules par un agent d'adhésion par exemple choisi parmi le NCO-TMS, le 3-(Triethoxysilyl)propyl isocyanate, le GPTMS ou le 3-Glycidoxypropyltriethoxysilane),
• a4) Dépôt d'une deuxième population de nanoparticules de taille différente de celles utilisées à l'étape a2).

In a preferred embodiment, step a) of the method of the invention therefore comprises at least the sub-steps:

• a0) Optionally, activation of the surface by a physical treatment (such as a UV-Ozone treatment or a plasma treatment) followed or not by the deposition of a primary bonding layer (such as for example TEOS),
• a1) Optionally, treatment of the surface with an adhesion agent chosen, for example, from NCO-TMS, 3- (Triethoxysilyl) propyl isocyanate, GPTMS or 3-Glycidoxypropyltriethoxysilane,
• a2) Deposit of a first population of nanoparticles on the surface to be treated,
• a3) Optionally, treatment of the surface covered with the first population of nanoparticles with an adhesion agent, for example chosen from NCO-TMS, 3- (Triethoxysilyl) propyl isocyanate, GPTMS or 3-Glycidoxypropyltriethoxysilane),
• a4) Deposit of a second population of nanoparticles of size different from those used in step a2).

Step a2) is preferably carried out several times, i.e., between 2 and 10 times, even more preferably between 2 and 6 times.

The nanoparticles used in steps a2) and / or a4) may alternatively have been covered with said adhesion agent before they have been brought into contact with the surface. In this case, steps a1) and a3) are unnecessary.

In a preferred embodiment, the treatment of the surfaces with an adhesion agent during steps a1) and / or a3) is done either by evaporation or by sol-gel deposition.

In the case of " evaporation ", the surfaces (covered or not with nanoparticles depending on whether it is step a1 or a3) can be placed in an enclosure under reduced pressure in the presence of an agent membership. In this case, the reaction time is advantageously between 1 min and 24 hours, preferably between 5 min and 10 hours, even more preferably between 10 minutes and 2 hours. The pressure in the enclosure is for example between 1 and 100 mBar, preferably between 5 and 30 mBar.

In the case of a "sol-gel deposition", adhesion agents can be dissolved in a suitable solvent such as an alcohol, at a concentration of 10- ⁵ mol / L and 1 mol / L, preferably between 10 ^-3 and 10 ^-1 mol / L. This solvent is then preferably methanol, ethanol or isopropanol. In all cases, it is preferable that it be anhydrous. Preferably, said adhesion agent is GPTMS or NCO-TMS. The surface can be immersed in the solution for 1 to 60 minutes, then be rinsed with the solvent and optionally heated for 15 min at 60 ° C or at least one hour at room temperature.

It should be noted that these operations do not in any way require heating the surfaces to more than 100 ° C.

In another preferred embodiment, the particles are deposited on surfaces of the same type by carrying out several soaking of the surface in the same solution (or suspension) containing the nanoparticles.

In a preferred embodiment, the nanoparticles deposited in the first place (step a2) have a diameter between 70 and 200 nm, and the nanoparticles deposited in the second place (step a4) have a diameter between 5 and 50 nm. In a preferred embodiment, the nanoparticles deposited in the first place (step a2) have a diameter between 70 and 100 nm, and the nanoparticles deposited in the second place (step a4) have a diameter of 10 and 15 nm (cf. examples below).

In a preferred embodiment of the method of the invention, it is possible to deposit at least three populations of nanoparticles of different sizes, or even more (four or five). In this case, the surface preparation protocol and its covering (steps a0) to a4) above indicated) will be repeated as many times as necessary, i.e. by repeating, as many times as necessary, the deposition steps of an adhesion agent followed by deposition of a new population of particles.

In an even more preferred embodiment, the surface to be treated is made of silica, the nanoparticles deposited in steps a1) and a3) are made of silica and the adhesion agent deposited between the two layers of nanoparticles (step a2) is the NCO-TMS.

In a preferred embodiment, it is possible to add the deposition of a crosslinking agent during or after steps a2) and a4) (Examples 4 and 6).

Preparation and deposit of "raspberry " particles

• a'1) Recouvrement d'une première population de nanoparticules par un agent d'adhésion,
• a'2) Mise en contact de cette première population avec une ou plusieurs autre(s) population(s) de nanoparticules de manière à former des particules framboises,
• a'3) Eventuellement, purification des particules framboises ainsi formées,
• a'4) Dépôt des nanoparticules « framboises » sur la surface à traiter, ladite surface ayant éventuellement été activée et/ou pré-traitée comme décrit plus haut.

In another particular embodiment of the invention, nanoparticles of the “raspberry” type can be prepared before being brought into contact with the surface to be treated. In this case, the protocol is as follows:

• a'1) Covering of a first population of nanoparticles with an adhesion agent,
• a'2) Contacting this first population with one or more other population (s) of nanoparticles so as to form raspberry particles,
• a'3) Optionally, purification of the raspberry particles thus formed,
• a'4) Deposition of “raspberry” nanoparticles on the surface to be treated, said surface having possibly been activated and / or pre-treated as described above.

Optionally, the nanoparticles obtained after step a'3) can be treated again with an adhesion agent as in step a'1), then brought into contact with one or more other population of nanoparticles as in step a'2) and possibly re-purified, as in step a'3). These operations can be repeated as much as necessary to obtain raspberry nanoparticles of the desired size and roughness.

The populations of nanoparticles and the adhesion agent used to form these raspberry nanoparticles can be as described above.

In particular, said adhesion agent is preferably a silane isocyanate compound (NCO-TMS or 3- (Triethoxysilyl) propyl isocyanate) or an epoxy silane compound (GPTMS or 3-Glycidoxypropyltriethoxysilane). Preferably, said adhesion agent is not amino (in particular, it is not APTES), because the amination of the nanoparticles makes the covering fragile.

Note that it is also possible to obtain raspberry nanoparticles by the method of Stober et al. (J. Colloids and Interface Sciences. 26. p.62 ) by inducing the synthesis of small particles on the surface of large ones by growth of a layer of SiOx (based on TEOS.)

In a preferred embodiment, the treatment of the nanoparticles with an adhesion agent during step a'1) is done either by evaporation, or by spraying with a solution, or by soaking in a solution.

The evaporation protocol is the same as for the surfaces, described above. Briefly, the nanoparticles can be placed in an enclosure under reduced pressure in the presence of an adhesion agent, for 1 min to 24 hours, preferably 5 min to 10 hours, even more preferably 10 minutes to 2 hours, the pressure in the 'enclosure can for example be between 1 and 100 mBar, preferably between 5 and 30 mBar.

In the case of a reaction in solution, the adhesion agent can be dissolved in an appropriate solvent, such as for example toluene, at a concentration of 10 ^-5 mol / L and 1 mol / L, preferably between 10 ^-3 and 10 ^-1 mol / L. In all cases, it is preferable that said solvent is anhydrous. Preferably, the adhesion agent is NCO-TMS. The large nanoparticles can then be immersed in the solution containing the adhesion agent for 1 to 24 hours, then rinsed with the solvent and heated under vacuum for 4 hours at 50 ° C.

These nanoparticles can then be resuspended in an appropriate solvent, such as, for example, toluene. To this suspension is added the second population of nanoparticles, the amount of which preferably respects the ratio N described below. This mixture can be dispersed by ultrasound and brought to reflux overnight.

The N ratio allowing small nanoparticles to completely cover the largest nanoparticles (in a single layer) preferentially corresponds to the following formula: $$\mathrm{NOT}=\frac{\pi {\left(\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0006.png,imgf0014.png"\; state="\{\{state\}\}">R</figure-callout>}2+\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">R</figure-callout>}1\right)}^2}{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0006.png,imgf0014.png"\; state="\{\{state\}\}">R</figure-callout>}{2}^2}$$

Where R1 corresponds to the radius of large nanoparticles and R2 to the radius of small nanoparticles.

In a preferred embodiment, at least a ratio of N small nanoparticles per large nanoparticle is added to prepare the raspberry nanoparticles. In other words, in this embodiment, N times more small nanoparticles are added than large nanoparticles.

Optionally, a purification step may be required when the small nanoparticles have been added in excess compared to the nanoparticles of larger diameter. In this case, the purification makes it possible to eliminate the small nanoparticles which are not fixed, so that they do not interfere with the deposition of raspberry nanoparticles on the surfaces.

It may also be useful to purify the raspberry nanoparticles when they have been formed in a solvent which is not that used to deposit on the surface.

In this case, it is possible to dry the raspberry nanoparticles to re-disperse them in another solvent.

The purification step a'3) can, for example, be carried out by filtering or centrifuging the raspberry nanoparticles formed. A change of solvent between the preparation of the raspberry nanoparticles and their deposition can also be envisaged. The nanoparticles are then dried by evaporation of the solvent before being dispersed in a solvent suitable for deposition (see below).

The raspberry nanoparticles previously formed can then be deposited on the surface to be treated (possibly previously treated by a physical treatment and / or with an adhesion agent or TEOS, as described above).

• a"0) Eventuellement, activation et pré-traitement de la surface à traiter tels que décrit ci-dessus,
• a"1) Préparation des nanoparticules «framboises» selon le procédé décrit ci-dessus,
• a"2) Dépôt des nanoparticules « framboises » sur la surface à traiter,
• b) Réticulation de la surface recouverte des nanoparticules framboises à l'aide d'un agent réticulant, à basse température.

In a particular embodiment, the method of the invention then contains at least the steps:

• a "0) Optionally, activation and pre-treatment of the surface to be treated as described above,
• a "1) Preparation of the" raspberry "nanoparticles according to the process described above,
• a "2) Deposit of" raspberry "nanoparticles on the surface to be treated,
• b) Crosslinking of the surface covered with raspberry nanoparticles using a crosslinking agent, at low temperature.

In a particular embodiment, the method of the invention may contain an additional step, after step b), consisting in covering the crosslinked surface with unassembled nanoparticles. These additional nanoparticles are then preferably crosslinked in their turn, step b) is then reproduced (cf. examples 12, 16 and 18).

These unassembled nanoparticles can be of any size (small or large). Preferably, they have an average diameter between 1 and 150 nm, more preferably between 5 and 80 nm. Note that, if the surface to be treated must remain transparent, NPs larger than 150nm should not be used.

The raspberry nanoparticles and the unassembled nanoparticles can be deposited sequentially or simultaneously on the surfaces, to improve the performance of the coating (cf. example 12, protocol 2).

Steps a "1) and a" 2) described above can be carried out concomitantly (the raspberry particles then form directly on the surface) and / or repeatedly.

Deposition of isolated nanoparticles or raspberry nanoparticles on the surface

The nanoparticles can be deposited on the surface to be treated (in the form of distinct populations or raspberry particles) can be carried out by “dip-coating”, “spin coating”, “spray”, “flow coating”, or even by wiping.

By “ dip coating ” is meant a means of deposition where the surface to be treated is immersed and then removed from a solution / suspension at a defined speed ( LD Landau, VG Levich, Acta physicochimica, USSR, 17, (1942), 42 ).

By " spin coating " means a deposition means where a solution / suspension is deposited on the surface to be covered. This same surface is fixed on a spinner which makes it rotate at a controlled speed which allows the suspension solution to spread there and to wet all of it ( D. Meyerhofer, J. Appl. Phys., 49, (1978), 3993 ).

By " spray " is meant a means of deposition where the solution / suspension is sprayed into fine droplets on the surface using a means of propulsion such as for example a gas. The vaporized mixture is sprayed onto the surface so as to wet all of it.

By “ flow coating ” is meant a means of deposition where the solution / suspension is poured onto the surface to be covered so as to wet all of it.

By " wiping " means a deposition means by which a fabric, paper or brush, impregnated with the solution / suspension to be deposited, is applied to the surface to be treated. The fabric or paper is then rubbed so as to wet the entire surface.

In a particular embodiment, the particles (isolated or raspberries) are deposited on the surfaces by dip-coating at a speed between 1 and 500 mm / min, preferably between 5 and 150 mm / min with a soaking time stationary between 0 and 300 minutes. Preferably, the deposition is carried out at ambient temperature and makes it possible to obtain layer thicknesses between 50 and 1000 nm, and preferably between 100 and 500 nm. Preferably, the dip-coating operations are repeated at least twice, up to ideally 5 times, in order to reinforce the resistance of the coating (without affecting the transparency of the material).

In another particular embodiment, the particles (isolated or raspberries) are deposited by spray on the surfaces to be covered. Advantageously, it is sufficient to carry out this operation only once to obtain a resistant superhydrophilic or superhydrophobic coating (cf. examples 15 and 19).

It should be noted that these operations do not in any way require heating the surfaces to more than 100 ° C.

To carry out these recovery operations, the nanoparticles are preferably dispersed in a solvent, constituting a "suspension". Any type of solvent can be used to implement these different protocols. It is important to note that no solubilization is required, because the nanoparticles are in suspension in the solvent in question. The solvent must nevertheless allow the material to be covered to be properly wetted, which is the case with most liquids conventionally used for coating surfaces.

However, the inventors have found that, in certain cases, the choice of solvent influences the efficiency of the covering and the roughness obtained (cf. example 4). Thus, in a preferred embodiment, the solution containing the nanoparticles is an aqueous solution or an alcoholic solution. In an even more preferred embodiment, the nanoparticles are suspended in a solvent chosen from: water, methanol, ethanol, isopropanol, propan-1-ol, butan-1-ol, butan -2-ol, tert-butanol and their mixtures.

In a most preferred embodiment, the nanoparticles are suspended in ethanol, isopropanol, methanol, propan-1-ol, butan-1-ol, butan-2-ol, or tert-butanol.

Furthermore, it appears from the experiments carried out by the inventors that a better surface roughness is obtained by dip-coating when the mass concentration of the nanoparticles is between approximately 10 ¹⁵ and 10 ¹⁹ particles per liter, preferably between approximately 2.10 ¹⁵ and 7.10 ¹⁸ particles per liter, for one or other of the populations of nanoparticles.

In a particular embodiment, the concentration of the nanoparticles is 0.5% (m / v) for particles of 100 nm, and 0.25% (m / v) for particles of 15 nm (cf. example 3 ).

In a particular embodiment, the deposition is carried out by spray or by electrospray. In this embodiment, the nanoparticles are suspended in a polar solvent (preferably an alcohol), at a concentration of nanoparticles of for example between 10 ¹⁵ and 10 ¹⁹ nanoparticles per liter, whether the nanoparticles are deposited sequentially or simultaneously on the surface .

Step b): Crosslinking of the surface covered with nanoparticles

The second step of the process of the invention consists in allowing the crosslinking of the surface covered with nanoparticles using a crosslinking agent, at low temperature. By " low temperature " is meant here a temperature which does not exceed 180 ° C. Preferably, this temperature is between 10 ° C and 180 ° C, or even between 10 ° C and 100 ° C.

In the context of the invention, the crosslinking step is preferably carried out at a temperature below 180 ° C, and preferably below 100 ° C. This allows the method of the invention to be applied to the heat-sensitive surfaces described above.

In an even more preferred embodiment, the crosslinking takes place without having to heat the treated surface. In this case, it is therefore carried out at room temperature (between 15 ° C and 30 ° C). This crosslinking can be initiated by thermodynamic or radical means.

As demonstrated in the examples below, it is possible, thanks to the process of the invention, to obtain very resistant superhydrophilic or superhydrophobic layers without the need to heat the surfaces to be treated. This very important characteristic distinguishes the process of the invention from the processes described in the prior art.

This crosslinking step makes it possible to bond the particles to the surface, as well as the different particles between them. This makes it possible to make the superhydrophilic or superhydrophobic treatment of the invention durable and resistant to mechanical and chemical stresses (cf. examples 4, 6 and 7).

More precisely, this step consists in bringing the surface covered with nanoparticles or raspberry nanoparticles into contact with a crosslinking agent. This contacting can be sequential (first the nanoparticles, then the crosslinking agent, cf. examples 10 and 15) or concomitant. In this second case, it is advisable to prepare a mixture containing the raspberry nanoparticles or nanoparticles and the crosslinking agent (cf. examples 16 to 19).

Note, it is possible to add the crosslinking agent after each deposition of nanoparticles, alternately (cf. example 10), or then only at the end of the process, after all the nanoparticles have been deposited (cf. example 4 ).

By dip-coating, the thickness of the crosslinking agent layer is linked to the duration of this contacting. Care must therefore be taken to ensure that this contact does not promote the smoothing of the surface (which must remain rough).

The crosslinking agents which can be used in the context of the invention may consist of the same element as the nanoparticles such as the alkoxides of Ti (for example tetra-n-butyl titanate), or the alkoxides of Si (for example tetra ethyl ortho- silicate - or "TEOS"). Mention may also be made of zirconium alkoxides, aluminum alkoxides and, more generally, alkoxides of transition metals. In a preferred embodiment, the crosslinking agent is TEOS.

The deposition of said crosslinking agent is carried out for example by dip-coating at a speed of between 5 and 100 mm / min, with a stationary soaking time of between 0 and 300 minutes.

The crosslinking agent (for example TEOS) used in the invention is contained in a water / alcohol (preferably water / ethanol) acid mixture.

In a preferred embodiment, the crosslinking agent (for example TEOS) is deposited by spray in said water / alcohol mixture (preferably water / ethanol or water / tert-butanol).

When TEOS is deposited in an acid medium (7>pH> 0), the hydrolysis is faster than the condensation (cf. Brinker CJ et al, Thin Solid Films, Elsevier, 201 (1991) 97-108 ), which frees all of the monomers for the rapid formation of small nanoparticles (polyhedral units of a few tens of atoms) whose size does not exceed one nanometer. These nanoparticles then aggregate to form low density branched polymeric clusters, which in turn aggregate. These clusters remain in suspension without precipitating, this is the "soil". The clusters gradually occupy an increasingly large volume fraction up to a value close to unity. The viscosity of the medium then becomes significant and the liquid ends up freezing: it is gelation. Macroscopically, this assembly ends with the appearance of rigidity and elasticity of the solid type, coming from the "gel". Solid, transparent, the gel obtained therefore consists of a polymeric network of silica trapping the solvent and possibly clumps still in solution. This network has a porosity whose distribution ranges from the size of the nanoparticles to that of the clusters. Beyond the gelation, the chemical reactions continue and modify the size distribution of the pores of the gel.

When the medium containing TEOS is neutral or moderately basic, the condensation of the silicon species is faster than the hydrolysis, the polymer is then gradually supplied with monomers. The stage of formation of the elementary units is a monomer - cluster aggregation whose kinetics is limited. This mechanism leads to the formation of dense nanoparticles of silica. These, up to several hundred nanometers in size, are negatively charged. The resulting electrostatic repulsions prevent further aggregation between nanoparticles which remain in suspension in the solvent. The whole nanoparticles - solvent constitutes the "soil". Aggregation between nanoparticles leads to gelation as for the acid system. Finally, in a very basic medium (pH> 11), depolymerization (breaking of the siloxane bridges) prevails and the silica is transformed into soluble silicate.

The present inventors have observed that this assembly of nanoparticles produced in a neutral or basic medium is surprisingly less stable than when the crosslinking is carried out in an acid medium (cf. example 6).

In a preferred embodiment, the TEOS is therefore deposited at an acidic pH (i.e., at pH <7, preferably at pH <6) to promote the stability and the resistance of the layer thus formed.

In an even more preferred embodiment, the TEOS is contained in a hydroalcoholic solution (for example a water / ethanol mixture) having a pH of between 1 and 5, preferably between 1 and 3, preferably equal to 2.

In another even more preferred embodiment, the TEOS used to crosslink the nanoparticles is at a concentration between 1 and 30 mM, preferably between 5 and 24 mM, most preferably, is 10mM.

In a preferred embodiment, the steps of depositing the nanoparticles (raspberry or not) and depositing the crosslinking agent are concomitant, since the surface is brought into contact with a mixture containing the particles and the crosslinking agent.

• x sera compris entre 0.1 et 10, préférentiellement entre 1 et 5,
• y sera compris entre 0 et 5000, préférentiellement entre 1 et 1500,
• z sera compris entre 0 et 5000, préférentiellement entre 1 et 1500.

In a particular case, the nanoparticles within this mixture are raspberry nanoparticles preferably having a concentration of between 10 ¹⁵ and 10 ¹⁸ NP per liter of a TEOS / HCl / EtOH / H ₂ O solution in a ratio of 1 / X Y Z. In that case :

• x will be between 0.1 and 10, preferably between 1 and 5,
• will be between 0 and 5000, preferably between 1 and 1500,
• z will be between 0 and 5000, preferably between 1 and 1500.

• x sera compris entre 0.1 et 10, préférentiellement entre 1 et 5,
• y sera compris entre 0 et 5000, préférentiellement entre 1 et 1500,
• z sera compris entre 0 et 5000, préférentiellement entre 1 et 1500.

In another particular case, said mixture contains nanoparticles NP100 and NP15 which are suspended at concentrations between 10 ¹⁵ and 10 ¹⁸ (NP100) and between 10 ¹⁸ and 10 ²¹ (NP15) per liter of a TEOS / HCl / EtOH / H ₂ O solution in a ratio of 1 / x / y / z. In that case :

• x will be between 0.1 and 10, preferably between 1 and 5,
• will be between 0 and 5000, preferably between 1 and 1500,
• z will be between 0 and 5000, preferably between 1 and 1500.

Step c) (optional): cover the textured surfaces with a hydrophobic agent

In a particular embodiment, the method of the invention contains a final step consisting in covering the textured surface with a layer of hydrophobic organic molecules which will make the surface superhydrophobic.

This step is required when it is desired to obtain a superhydrophobic surface and the nanoparticles used are made of silica and the crosslinking agent is a Ti / Si alkoxide.

The deposition of these hydrophobic organic molecules can be done by dip-coating, spin-coating, by evaporation techniques well known to those skilled in the art (PVD, CVD), by spray, or by wiping.

In a preferred embodiment of the invention, these hydrophobic organic molecules can be hydrogenated polymers, for example polyethylenes (PE) or polystyrenes (PS). These molecules can also be totally or partially fluorinated polymers such as, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or even perfluoropolyethers (PFPE).

In another embodiment, it is also possible to use, as hydrophobic agent, a molecule fixed by a radical reaction on the surface to be treated. This molecule can for example be a diazonium aryl carrying a hydrophobic chain. The aryl group reacts with the surface via free radicals. This molecule then leaves its perfluorinated, fluorinated or alkyl chain available to make the surface hydrophobic.

• A est un groupement favorisant l'adhésion de la couche sur la surface,
• B est un linker, et
• C est un groupement fonctionnel apportant un caractère hydrophobe et ou oléophobe à la couche formée.

In another preferred embodiment of the invention, these molecules can be of monomeric nature in order to allow their arrangement in self-assembled monolayer. In this case, their general formula will be ABC, in which :

• A is a group promoting the adhesion of the layer to the surface,
• B is a linker, and
• It is a functional group providing a hydrophobic and or oleophobic character to the layer formed.

1. a) un groupement silane de formule :
   
   • dans laquelle R1, R2, et R3, représentent indépendamment l'un de l'autre un atome de chlore, de brome ou d'iode, un groupement hydroxyle OH, un groupement alkoxy (O-Alk) en C₁-C₁₀, tel que méthoxy (-O-CH₃), éthoxy (O-C₂H₅), ou isopropoxy (-O-C₃H₇) ;
   • dans laquelle, de préférence, R1, R2, et R3 sont identiques et représentent un groupement alkoxy,
2. b) un groupement thiol de formule -SH, ou
3. c) un groupement phosphonate de formule :
   
   dans laquelle :
   • R4 est un atome d'hydrogène H, de fluor F ou un groupement OH, et
   • R5 est un atome d'hydrogène H, de fluor F ou un groupement PO₃H₂,

In a preferred embodiment, the group A is chosen from:

1. a) a silane group of formula:
   
   • in which R1, R2 and R3 independently of one another represent a chlorine, bromine or iodine atom, a hydroxyl group OH, a C ₁ -C ₁₀ alkoxy group (O-Alk), such as methoxy (-O-CH ₃ ), ethoxy (OC ₂ H ₅ ), or isopropoxy (-OC ₃ H ₇ );
   • in which, preferably, R1, R2, and R3 are identical and represent an alkoxy group,
2. b) a thiol group of formula -SH, or
3. c) a phosphonate group of formula:
   
   in which :
   • R4 is a hydrogen atom H, fluorine F or an OH group, and
   • R5 is a hydrogen atom H, fluorine F or a PO ₃ H _{2 group} ,

• L est un groupement (CH₂)_m-X-, m étant un entier compris entre 0 à 100, de préférence compris entre 0 et 30, et X étant un groupement alkyle en C₀-C₁₀₀ saturé ou non, perfluoré ou partiellement fluoré, la chaîne alkyle pouvant être substituée ou interrompue par 0 à 10 groupements cycloalkyles ou aryles pouvant être perfluorés ou non ; X peut également être une simple liaison covalente, un groupement -(O-CH₂-CH₂)_m', -(O-CH₂-CH₂-CH₂)_m', -(O-CH₂-CH(CH₃))_m', -(O- CH(CH₃)-CH₂)_m', m' étant un entier compris entre 0 et 100, de préférence compris entre 0 et 50, et
• M est choisi parmi :
  1. a) une liaison chimique simple, un atome d'oxygène O, un atome de soufre S, ou un groupement S(CO), (CO)S, ou NR, (CO)NR, NR(CO), R étant un atome d'hydrogène ou un alkyle en C₁-C₁₀, ou
  2. b) les groupements suivants :
     

In a preferred embodiment, group B is an LM group where:

• L is a group (CH ₂ ) _m -X-, m being an integer between 0 to 100, preferably between 0 and 30, and X being a C ₀ -C ₁₀₀ alkyl group, saturated or unsaturated, perfluorinated or partially fluorinated, the alkyl chain possibly being substituted or interrupted by 0 to 10 cycloalkyl or aryl groups being able to be perfluorinated or not; X can also be a single covalent bond, a group - (O-CH ₂ -CH ₂ ) _{m '} , - (O-CH ₂ -CH ₂ -CH ₂ ) _m' , - (O-CH ₂ -CH (CH ₃ )) _{m '} , - (O- CH (CH ₃ ) -CH ₂ ) _m' , m 'being an integer between 0 and 100, preferably between 0 and 50, and
• M is chosen from:
  1. a) a single chemical bond, an oxygen atom O, a sulfur atom S, or a group S (CO), (CO) S, or NR, (CO) NR, NR (CO), R being an atom hydrogen or C ₁ -C ₁₀ alkyl, or
  2. b) the following groups:
     

In a preferred embodiment, the group C is chosen from a hydrogen atom, - (CF (CF ₃ ) CF ₂ O) _n -CF ₂ -CF ₂ -CF ₃ , - (CF ₂ CF (CF ₃ ) O) _n -CF ₂ -CF ₂ -CF ₃ , - (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ -CF ₂ -CF ₃ , - (CF ₂ CF ₂ O) _n CF ₂ -CF ₃ , - CF (CF ₃ ) -O- (CF (CF ₃ ) CF ₂ O) _n -CF ₂ -CF ₂ -CF ₃ , -CF (CF ₃ ) -O- (CF ₂ CF (CF ₃ ) O) _n - CF ₂ -CF ₂ -CF ₃ , -CF (CF ₃ ) -O- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ -CF ₂ -CF ₃ )) - CF ₂ -O- (CF ₂ CF ₂ O) _n -CF ₂ -CF ₃ or C _p F _{2p + 1} , in which n and p are integers between 1 and 100, preferably between 1 and 50.

1. a) A est un groupement silane de formule :
   
   dans laquelle R1, R2, et R3, représentent indépendamment l'un de l'autre un atome de chlore, de brome ou d'iode, un groupement hydroxyle OH, un groupement alkoxy (O-Alk) en C₁-C₁₀, tel que méthoxy (-O-CH₃), éthoxy (O-C₂H₅), ou isopropoxy (-O-C₃H₇) ;
2. b) B est un groupement L-M où :
   • L est un groupement (CH₂)_m-X-, m étant un entier compris entre 0 à 100, de préférence compris entre 1 et 30, de manière encore plus préférée entre 1 et 10, et
   • M est un groupement NR, (CO)NR, NR(CO), R étant un atome d'hydrogène ou un alkyle en C₁-C₁₀,
   et
3. c) C est un groupement -(CF(CF₃)CF₂O)_n-CF₂-CF₂-CF₃, -(CF₂CF(CF₃)O)_n-CF₂-CF₂-CF₃, -(CF₂CF₂CF₂O)_n-CF₂-CF₂-CF₃, -(CF₂CF₂O)_nCF₂-CF₃, -CF(CF₃)-O-(CF(CF₃)CF₂O)_n-CF₂-CF₂-CF₃, -CF(CF₃)-O-(CF₂CF(CF₃)O)_n-CF₂-CF₂-CF₃, -CF(CF₃)-O-(CF₂CF₂CF₂O)_n-CF₂-CF₂-CF₃, ,-CF₂-O-(CF₂CF₂O)_n-CF₂-CF₃ ou C_pF_2p+1-dans lesquels n et p sont des entiers compris entre 1 et 50, de préférence entre 1 et 30.

In an even more preferred embodiment, these hydrophobic molecules have a formula ABC in which:

1. a) A is a silane group of formula:
   
   in which R1, R2 and R3 independently of one another represent a chlorine, bromine or iodine atom, a hydroxyl group OH, a C ₁ -C ₁₀ alkoxy group (O-Alk), such as methoxy (-O-CH ₃ ), ethoxy (OC ₂ H ₅ ), or isopropoxy (-OC ₃ H ₇ );
2. b) B is an LM group where:
   • L is a group (CH ₂ ) _m -X-, m being an integer between 0 to 100, preferably between 1 and 30, even more preferably between 1 and 10, and
   • M is a group NR, (CO) NR, NR (CO), R being a hydrogen atom or a C ₁ -C ₁₀ alkyl,
   and
3. c) C is a group - (CF (CF ₃ ) CF ₂ O) _n -CF ₂ -CF ₂ -CF ₃ , - (CF ₂ CF (CF ₃ ) O) _n -CF ₂ -CF ₂ -CF ₃ , - (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ -CF ₂ -CF ₃ , - (CF ₂ CF ₂ O) _n CF ₂ -CF ₃ , -CF (CF ₃ ) -O- (CF (CF ₃ ) CF ₂ O) _n -CF ₂ -CF ₂ -CF ₃ , -CF (CF ₃ ) -O- (CF ₂ CF (CF ₃ ) O) _n -CF ₂ -CF ₂ -CF ₃ , -CF (CF ₃ ) -O- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ -CF ₂ -CF ₃ ,, -CF ₂ -O- (CF ₂ CF ₂ O) _n -CF ₂ -CF ₃ or C _p F _{2p + 1} -in which n and p are integers between 1 and 50, preferably between 1 and 30.

pour laquelle R représente un groupement alkyl en C₁-C₄, linéaire ou ramifié.In an even more preferred embodiment, these hydrophobic molecules have the structural formula:

for which R represents a linear or branched C ₁ -C ₄ alkyl group.

This molecule, once deposited on surfaces which have undergone the protocol of the invention, increases their hydrophobicity in a very advantageous manner (cf. measurements of contact angles in Example 4).

It is preferable to deposit these molecules in a thin layer (ie, in a layer whose thickness is less than 20 nm, preferably less than 10 nm) so as not to alter the roughness of the surface which has been textured by the previous process steps.

The choice of the hydrophobic organic molecules of step c) and of the chemical group which allows their bonding with the material can be a means of ensuring the durability of the effect. The nature of the chemical group in connection with the surface makes it possible to respond in a targeted manner to the application for which the surface is made. Thus, it is known that a silane exhibits a durable covalent bond on glass surfaces and that a bisphosphonate is permanently fixed on TiO ₂ surfaces. Conversely, a fatty acid such as oleic acid will only have weak bonds with these same surfaces which will be deteriorated by a simple rubbing or by a detergent washing, deteriorating by the same the hydrophobic effect without altering the texturing of the material.

In a preferred embodiment, if the crosslinking agent is a silicon alkoxide, then silane-based hydrophobic molecules will be preferred.

In another preferred embodiment, if the crosslinking agent is based on titanium, then hydrophobic molecules based on bisphosphonate will be preferred.

In all cases, a radical agent carrying a hydrophobic function can be used.

Uses of the inventive method

The process of the invention is advantageously used to texturize surfaces to make them superhydrophilic and / or superoleophilic or to make them superhydrophobic and / or superoleophobic. More generally, it can be used to increase the adhesion of liquid (superliquidophile) to improve visibility in the event of condensation or on the contrary reduce the adhesion of liquids, solids or any other contaminant on these surfaces, this in a sustainable way .

The method of the invention can be applied to all or part of the surface to be treated. In the case where only a part of the surface is to be made superhydrophobic / phile or superoleophobic / phile, it is possible to use masks, in order to avoid the covering of certain parts of the surface by the nanoparticles and thus ensure zones not functionalized by the superhydrophobic coating, at the end of the process. The mask can be removed or degraded at the end of the process by techniques known to those skilled in the art. Another possibility for sparing areas of the surface is to produce a localized projection of either nanoparticles or of the hydrophobic coating. In an application industrial, this has the advantage of making the surface grippable after deposition of the superhydrophobic treatment.

The present application also describes any superhydrophobic / phile and / or superoleophobic / phile surface obtained by the process of the invention. These surfaces are distinguished from those described in the prior art in that they are covered with at least two populations of nanoparticles of different sizes, and in that they have not been heated beyond 80 ° C. to obtain a durable and resistant coating. Such surfaces are preferably made up of more than 50%, preferably more than 75%, of a heat-sensitive material, such as polycarbonate (PC), poly methylmethacrylate (PMMA), polypropylene, polyvinyl acetate (PVA) ), polyamide (PA), Poly (ethylene terephthalate) (PET), polyvinyl alcohols (PVAI), polystyrene (PS), polyvinyl chloride (PVC) and polyacrylonitriles (PAN) whose temperatures glass transition temperatures are significantly lower than 200 ° C.

The surfaces thus treated can be used in different applications, for example in optical or optronic equipment (display systems, lenses, portholes, glasses, protective visor, helmet visor), renewable energies (solar panels), constructions (windows and doors), the automotive or aerospace industry, windshields, mirrors or telecommunications (for radars for example).

The surfaces thus treated can be used in particular in liquidophobic applications, anticorrosion, anti-icing or anti-fouling in industrial fields such as cryogenics, aeronautics, wind power, or even cycling.

The surfaces thus treated can alternatively be used in particular in liquidophilic, anti-condensation, anti-fogging, wetting applications.

Legends of figures

• The figure 1 offers images obtained by a scanning electron microscope (FEGSEM) of deposits made using the protocol of Example 1 (dip-coating of the slide glass in an aqueous solution of silica nanoparticles 60nm in diameter then grafting of fluorinated silane molecules).
• The figure 2 offers FEGSEM images of deposits prepared with ethanol as solvent in the bath used for deposition by the dip-coating technique (dip-coating of the glass slide in a solution of silica nanoparticles 60nm in diameter then grafting of fluorinated silane molecules).
• The figure 3 offers FEGSEM images of deposits prepared by the dip-coating technique from a mixture at 50% by volume of Silica nanoparticles of 0̸ = 100 nm (0.5% by mass in water) and 50% by volume of 0ice Silica nanoparticles = 15 nm (0.5% by mass in water).
• The figure 4 offers FEGSEM images of deposits prepared by the sequential dip-coating technique of 100 nm Silica nanoparticles and 15 nm nanoparticles.
• The figure 5 offers FEGSEM images of deposits prepared by the sequential dip-coating technique of 100 nm Silica nanoparticles and 15 nm nanoparticles with an intermediate stage of functionalization by APTES.
• The figure 6 offers FEGSEM images of deposits prepared by the sequential dip-coating technique from solutions of 100 nm Silica nanoparticles and 15 nm nanoparticles with an intermediate stage of functionalization with APTES, for different concentrations of nanoparticles: (A) 100 nm: 0.5% by mass in water; 15 nm: 0.5% by mass in water, (B) 100 nm: 0.5% by mass in water; 15 nm: 0.25% by mass in water, (C) 100 nm: 1% by mass in water; 15 nm: 0.25% by mass in water and (D) 100 nm: 1% by mass in water; 15 nm: 0.5% by mass in water.
• The figure 7 offers FEGSEM images of deposits prepared by the sequential dip-coating technique from suspensions of Silica nanoparticles of 100 nm and 15 nm in ethanol. An intermediate stage of functionalization by APTES was carried out.
• The figure 8 describes the transmittance of glass substrates and superhydrophobic coatings produced as a function of the wavelength.
• The figure 9 provides images obtained by a CCD camera, showing (A) on a superhydrophobic and transparent coating without TEOS treatment: scratch with the tip, (B) on a coating after TEOS treatment: absence of scratch by the tip
• The Figure 10 describes the characterization by FEGSEM of a coating of nanoparticles not consolidated by the crosslinking agent (TEOS) having undergone an adhesive tape test: the area delimited by a frame indicates the area where the adhesive tape has been torn off.
• The figure 11 describes the characterization by FEGSEM of a coating of nanoparticles after the TEOS consolidation step after the adhesive tape test: the area delimited by a frame indicates the area where the adhesive tape was torn off.
• The figure 12 describes the characterization by FEGSEM of a coating of nanoparticles after the steps of consolidation by TEOS and thermal annealing, after the test of the adhesive tape: the area delimited by a frame indicates the area where the adhesive tape was torn off.
• The figure 13 describes the characterization by FEGSEM of the friction test with a cotton swab carried out on a coating of nanoparticles, which has not undergone the TEOS consolidation step: the zone delimited by a frame indicates the zone evaluated.
• The figure 14 describes the characterization by FEGSEM of the friction test with a cotton swab carried out on a coating of nanoparticles, having undergone a consolidation step by TEOS: the zone delimited by a frame indicates the zone evaluated.
• The figure 15 describes the characterization by FEGSEM of the friction test with a cotton swab produced on a coating of nanoparticles, having undergone the steps of consolidation by TEOS and thermal annealing: the zone delimited by a frame indicates the zone evaluated.
• The figure 16 provides the image of a glass sample having received a superhydrophilic treatment on the left and no treatment on the right. This glass was cooled to -20 ° C and then returned to the atmosphere to assess the effects of condensation on transparency.

Examples 1. Protocol for depositing particles of a size

After cleaning with a detergent of a glass surface, molecules of 3-aminopropyl triethoxysilane (APTES) were adsorbed by evaporation for 10 minutes in a desiccator under vacuum (pressure = 8 mBar). The contact angle observed for these surfaces at equilibrium after functionalization and deposition of particles is of the order of 40 °.

• Préparation d'une suspension de particules (diamètre de 60 nm, 6 mg/mL) dans de l'eau,
• Dip coating (DC) de la lame de verre dans la suspension de nanoparticules de silice (Vitesse de retrait : 10 mm/min à 100 mm/min),
• Greffage de molécules de silanes fluorés (schéma 1) pendant 18 heures dans un dessiccateur sous vide à une pression de 8 mbar,
• Recuit pendant 1 heure à 90°C.
  

The particles are then deposited on the surface by the dip-coating technique in the following order of steps:

• Preparation of a suspension of particles (diameter of 60 nm, 6 mg / mL) in water,
• Dip coating (DC) of the glass slide in the suspension of silica nanoparticles (Withdrawal speed: 10 mm / min to 100 mm / min),
• Grafting of fluorinated silane molecules (diagram 1) for 18 hours in a vacuum desiccator at a pressure of 8 mbar,
• Annealed for 1 hour at 90 ° C.
  

The characterization by FEGSEM of the deposits obtained when the silica nanoparticles are suspended in water is reported on the figure 1 .

The results of this characterization show that the Silica nanoparticles are distributed randomly over the surface of the glass with the formation of particle islands in places in no apparent order. It can also be noted that the density of the particles on the surface of the glass varies very little with the speed of removal.

In order to remedy the agglomeration problem of nanoparticles, the particle-solvent interaction was modulated by replacing water with ethanol in the bath used for deposition by the dip-coating technique.

The results of the FEGSEM characterization of these deposits are presented on the figure 2 .

Analysis of the results shows that the use of ethanol as a solvent for nanoparticles makes it possible to obtain particles distributed randomly on the surface of the glass but better dispersed, and with very few aggregates.

After functionalization of these substrates with the fluorinated silane molecules for 18 hours, the equilibrium contact angles observed after one hour of annealing at 90 ° C. are 140 °.

This shows that by adopting a single size of nanoparticles, it is not possible to obtain surfaces whose angle is greater than 150 ° under the conditions of the test.

In this case, no mechanical resistance was obtained (deterioration of the coating on first friction due to the absence of crosslinking agent because the nanoparticles deposited were treated directly after deposition by the hydrophobic agent).

In addition, an identical experiment was carried out with 100nm particles and the addition of TEOS before the evaporation of the silane -PFPE. The results obtained for this surface are presented in the table below. Material AC (°) Test 9-1 (loss of contact angle in °) * glass 137 40 * see experimental conditions of example 9

The result of this example shows the poor resistance of the coating with a formulation containing only one particle population.

2. Protocol for depositing nanoparticles of two different sizes

In this example, the surfaces were washed and treated with APTES according to the protocol reported for the preparation of the substrate in the case of the deposition of a single size of nanoparticles (cf. example 1).

The deposition by the dip-coating technique was carried out with populations of silica nanoparticles of two different average diameters: Nanoparticles of 100 nm (NP100) having a size distribution between 70 and 100 nm in diameter and nanoparticles of 15 nm (NP15) with a size distribution between 10 and 15 nm in diameter. The withdrawal speed is 40 mm / min. The grafting of the surfaces with the superhydrophobic molecules was carried out for 18 hours in a vacuum desiccator. Annealing was carried out for 1 hour at 90 ° C.

2.1. Simultaneous deposition, at equal volume of Silica nanoparticles with a diameter of 100 nm and 15 nm

After the deposition of a layer of APTES (see example 1), the glass substrates were immersed in a solution of silica nanoparticles containing a mixture with equal volume of nanoparticles of 100 nm (0.5% by mass concentration) and 15 nm nanoparticles (0.5% mass concentration) in water. The characterization by FEGSEM of the deposits obtained is presented on the figure 3 .

The figure 3 shows the presence of the two sizes of Silica nanoparticles on the glass surface, those of 15 nm are much more numerous than those of 100 nm. These images also show a low coverage rate of the surface. We note that the realization of a coating of nanoparticles in a single step by dip-coating by mixing the two sizes of nanoparticles at equal volume and mass concentration does not lead to superhydrophobic surfaces. The contact angle observed at equilibrium after 18 h of exposure to the fluorinated silane molecule is 128 ° and the transmittance is 100% relative to the glass reference.

2.2. Sequential deposition of Silica nanoparticles with a diameter of 100 nm and 15 nm

After the deposition of a layer of APTES (see example 1), a first deposition by the dip-coating technique (withdrawal speed = 40 mm / min) in a solution containing 100 nm nanoparticles (0.5% of mass concentration) in water was performed. After drying of the substrates, a second deposition by the dip-coating technique (withdrawal speed = 40 mm / min) was carried out with 15 nm silica nanoparticles (0.5% by mass concentration) in water . The characterization by FEGSEM of the prepared deposits is presented on the figure 4 .

Following the sequential deposition, one can notice the coexistence of the two sizes of silica nanoparticles on the surface of the glass substrate with more large nanoparticles which cover the surface. At the same time, we can note the absence of small particles on the surface of the large ones. In addition, the figure 4 shows the existence of a double roughness scale. For these structures, the contact angle at equilibrium observed after 18 h of exposure to the fluorinated silane molecule is of the order of 150 ° and the transmittance is 100%.

2.3. Sequential deposition of Silica nanoparticles with a diameter of 100 nm and 15 nm with an intermediate stage of functionalization of the surface with APTES molecules.

In the same way as in the protocol used for the two previous deposits, the glass substrates were first washed and then functionalized with the APTES molecules. A first deposition by the dip-coating technique (withdrawal speed = 40 mm / min) was carried out using a solution containing 100 nm nanoparticles (0.5% mass concentration) in water.

After drying of the substrate, an additional stage of functionalization of the substrates was carried out with the molecules of APTES under vacuum in a desiccator for 10 minutes.

After this step, a second deposition cycle was carried out by the dip-coating technique (removal speed = 40 mm / min) using an aqueous solution of 15 nm Silica nanoparticles (0.5% mass concentration) .

The characterization by FEGSEM of the deposits obtained is presented on the figure 5 .

FEGSEM images from the figure 5 show that better roughness is obtained for this third process. Indeed, by introducing an intermediate stage of functionalization by APTES, the adhesion between large and small particles has been increased. This made it possible to obtain raspberry-shaped particles with the small particles which cover the surface of the large particles. The contact angle observed at equilibrium for these deposits after 18 h of exposure to the fluorinated silane molecule is greater than 150 ° and the transmittance is 100% (in the visible wavelengths).

3. Protocol for depositing nanoparticles of two different sizes - effect of particle concentration

Keeping the experimental protocol of Example 2.3, we varied the concentration of the silica nanoparticles by 15 nm, while keeping the mass concentration of the nanoparticles of 100 nm equal to 0.5% mass concentration.

To ensure better adhesion between the nanoparticles and between the nanoparticles and the substrate, and thus improve the mechanical properties of the deposits, a sol-silica gel deposition was carried out before the deposition of the hydrophobic layer. This deposition was also carried out by the dip-coating technique (removal speed = 40 mm / min, soaking = 2 hours).

The FEGSEM images of the prepared deposits are presented on the figure 6 .

1. a) quand la concentration des nanoparticules de 100 nm augmente, le recouvrement du substrat augmente.
2. b) quand la concentration des nanoparticules de 15 nm augmente, le recouvrement des plus grosses nanoparticules augmente.

The figure 6 shows that when the concentration of a nanoparticle size increases, the surface coverage increases. We can distinguish two situations:

1. a) when the concentration of nanoparticles of 100 nm increases, the covering of the substrate increases.
2. b) when the concentration of the nanoparticles of 15 nm increases, the overlap of the larger nanoparticles increases.

From these experiments, it appears that the best surface roughness is obtained with a mass concentration of 0.5% and 0.25% for, respectively, nanoparticle suspensions of 100 nm and 15 nm.

4. Protocol for depositing nanoparticles of two different sizes - effect of the solvent and the crosslinking agent

Nanoparticles agglomerate when water is used as a solvent. Keeping the experimental protocol of Example 2.3, we varied the nature of the solvent (water and ethanol). We have also added (or not) a crosslinking phase with TEOS before the deposition of the hydrophobic final layer.

TEOS is deposited by dip-coating (speed = 20 mm / min), with a soaking time of 2 hours. The solution used is a mixture of TEOS (1 volume) and ammonia (8 volumes) in ethanol.

The figure 7 shows the FEGSEM images of the developed repositories.

These results compared to those of Example 2.3. show that the particles have a less aggregated appearance, once deposited on the surface, when the deposit is carried out in ethanol as solvent.

The measurement of the contact angle was carried out at each of the process steps mentioned in this example. An untreated glass surface gives contact angles with water of the order of 20 °. The maximum contact angle that can be reached by functionalizing flat glass surfaces with the fluorinated silane molecule in diagram 1 is of the order of 110 °. After the step of texturing the glass surface by the different nanoparticle deposits, without TEOS deposit, and after depositing the same fluorinated molecules this angle is of the order of 150 °. After the deposition of TEOS and fluorinated molecules, the contact angle at equilibrium reaches 155 ° and the coating is superhydrophobic.

It appears from the results obtained in this example that the surface roughness is better when the deposition is carried out with a mass concentration of 0.5% in nanoparticles of 100 nm and 0.25% in nanoparticles of 15 nm in ethanol as solvent. Furthermore, the contact angles are slightly higher when the deposition of the crosslinking agent (TEOS) is carried out.

5. Transparency

The transparency is translated by a high transmittance close to 100%. For the coating of Example 2.3, a transmission spectrum in the visible wavelengths was produced. A transmittance of 100% was measured relative to the glass reference ( figure 8 ). This result is expected, since the roughness of the coatings is less than 100 nm.

6. TEOS crosslinking methods : 6.1 Comparison between surfaces crosslinked by TEOS in an acid medium and in a basic medium - adhesive tape test.

• un dépôt de TEOS en solution basique par dip-coating (vitesse = 40 mm/min), avec une durée de trempage de 2 heures. La solution utilisée est alors un mélange de TEOS et d'ammoniaque dans l'eau,
• un dépôt de TEOS en solution acide par dip-coating (vitesse = 20 mm/min), avec une durée de trempage de 2 heures. La solution utilisée est alors un mélange de TEOS et d'HCl dans un mélange eau/éthanol à pH 2.

The coating tested is similar to that described in Example 2.3. It is consolidated with either:

• deposition of TEOS in basic solution by dip-coating (speed = 40 mm / min), with a soaking time of 2 hours. The solution used is then a mixture of TEOS and ammonia in water,
• deposition of TEOS in acid solution by dip-coating (speed = 20 mm / min), with a soaking time of 2 hours. The solution used is then a mixture of TEOS and HCl in a water / ethanol mixture at pH 2.

Under basic conditions, the results show that, with or without thermal annealing, the superhydrophobic coating obtained does not withstand the test of the adhesive tape. At the end of the test, no particles are visible on the surface.

Conversely, after treatment in an acid medium, the surface shows no degradation linked to the adhesive strength of the tape and, after the test, the film of nanoparticles remains fully applied to the surface.

6.2 Optimization of the TEOS concentration used in an acid medium

1. 1) Prélavage
2. 2) 5 DC de NP100
3. 3) 3 DC de TEOS
4. 4) 1 DC de NP15
5. 5) 1 DC de TEOS
6. 6) Silane

Concentration en TEOS (mM) AC (°) Test 9-3 (perte d'angle de contact en °)* 8 149 -28 10 145 -10 12 147 -13 24 146 -10 80 128 -9 * voir conditions expérimentales de l'exemple 9 Brief protocol:

1. 1) Prewash
2. 2) 5 DC of NP100
3. 3) 3 DC of TEOS
4. 4) 1 DC of NP15
5. 5) 1 CD of TEOS
6. 6) Silane

TEOS concentration (mM) AC (°) Test 9-3 (loss of contact angle in °) * 8 149 -28 10 145 -10 12 147 -13 24 146 -10 80 128 -9 * see experimental conditions of example 9

Conclusion: Under these given experimental conditions, the optimal TEOS concentration value is between 10 and 24 mM.

7. Scratch resistance

In order to characterize the mechanical properties of the coatings produced and more precisely their scratch resistance, we used an optical profilometer fitted with a diamond tip with a radius of 12.5 µm. With this tip, we applied a maximum load of 15 mg to the substrate. This charge corresponds to a force of 147.1 µN, i.e. a pressure of 3061 g / cm ² .

In this case, the samples were prepared according to the protocol of Example 6. The TEOS was deposited under acidic conditions.

Without the TEOS deposit, the coatings produced can be easily scratched. But with this deposit, and thanks to the Si-O-Si bonds, these coatings remain intact after applying maximum pressure with the diamond tip ( figure 9 ).

8. Resistance of the coating to the adhesive tape test

In this test, double-sided adhesive tape was stuck on the coating and was removed with a sharp blow. This "tape" test is used to test the adhesion of nanoparticle films to the surface of the glass. In this example, none of the surfaces were treated with a hydrophobic compound to minimize the non-stick effect of the superhydrophobic coating and to model the adhesion of the particles to the material.

1. a) Dépôt selon l'exemple 2.3. sans ajout d'un agent réticulant
2. b) Dépôt selon l'exemple 2.3. avec ajout d'un agent réticulant (TEOS en milieu acide)
3. c) Dépôt selon l'exemple 2.3. avec ajout d'un agent réticulant (TEOS en milieu acide) et recuit à 80°C pendant 6 heures.

Once the “adhesive tape” test has been carried out, the surfaces are observed in FEGSEM and a comparison is made between the zones having undergone the tearing and the zones not tested. The areas evaluated are as follows:

1. a) Deposit according to example 2.3. without adding a crosslinking agent
2. b) Deposit according to example 2.3. with addition of a crosslinking agent (TEOS in acid medium)
3. c) Deposit according to example 2.3. with the addition of a crosslinking agent (TEOS in an acid medium) and annealing at 80 ° C for 6 hours.

a) Deposit according to example 2.3. without adding a crosslinking agent

In the case of a coating prepared according to the protocol of Example 2.3. and not having undergone the TEOS consolidation step, the nanoparticle film easily sticks to the adhesive tape ( figure 10 ). The zoom made on the figure 10B , shows an area devoid of particles (in the frame), while the non-evaluated area presents an arrangement of particles identical to the previous examples.

b) Deposit according to example 2.3. with addition of a crosslinking agent (TEOS in acid medium)

In another test, the protocol of example 2.3. was implemented and the surfaces were then crosslinked by adding TEOS. The results of the tape test on this sample ( Figures 11A and 11B ) show a very good resistance of the nanoparticle film to the adhesive force of the tape because the nanoparticle film always remains applied to the surface after the test.

c) Deposit according to example 2.3. with the addition of a crosslinking agent (TEOS in an acid medium) and annealing at 80 ° C for 6 hours.

In a third test, an additional annealing of 6 h at 80 ° C was applied to a surface having undergone the same covering as on the figure 11 . The results reported on the figure 12 show that the annealing step does not bring any major improvement in the resistance of the films of nanoparticles with respect to the figure 11 .

9. Resistance of the coating to the friction test by a cotton swab soaked in isopropanol

• Test 9-1 : Application de 100 frottements à sec avec un chiffon doux fixé sur une masse de 500g répartie sur 1cm²
• Test 9-2 : Application de 100 frottements à sec avec un chiffon doux fixé sur une masse de 1000g répartie sur 1cm²
• Test 9-3 : Application de 100 frottements avec un coton imbibé d'isopropanol fixé sur une masse de 100g répartie sur 1cm²
• Test 9-4 : Application de 100 frottements avec un coton imbibé d'isopropanol fixé sur une masse de 500g répartie sur 1cm²

This friction test makes it possible to evaluate the mechanical resistance of the surfaces having received a superhydrophobic coating. It consists in applying several types of friction to the surface and evaluating the evolution of the contact angle on these surfaces after the friction phase. The tests carried out are:

• Test 9-1: Application of 100 dry rubs with a soft cloth fixed on a mass of 500g distributed over 1cm ²
• Test 9-2: Application of 100 dry rubs with a soft cloth fixed on a mass of 1000g distributed over 1cm ²
• Test 9-3: Application of 100 rubs with a cotton soaked in isopropanol fixed on a mass of 100g distributed over 1cm ²
• Test 9-4: Application of 100 rubs with a cotton pad soaked in isopropanol fixed on a mass of 500g distributed over 1cm ²

1. a) Dépôt selon l'exemple 2.3. sans ajout d'un agent réticulant,
2. b) Dépôt selon l'exemple 2.3. avec ajout d'un agent réticulant (TEOS en milieu acide),
3. c) Dépôt selon l'exemple 2.3. avec ajout d'un agent réticulant (TEOS en milieu acide) et recuit à 80°C pendant 6 heures.

Test 9-3 was applied to the surfaces of Example 8, namely:

1. a) Deposit according to example 2.3. without adding a crosslinking agent,
2. b) Deposit according to example 2.3. with the addition of a crosslinking agent (TEOS in an acid medium),
3. c) Deposit according to example 2.3. with the addition of a crosslinking agent (TEOS in an acid medium) and annealing at 80 ° C for 6 hours.

Once the friction has been carried out, the surfaces are observed in FEGSEM and a comparison is made between the zones having undergone the friction and the zones not rubbed.

a) Deposit according to example 2.3. without adding a crosslinking agent

When a coating is formed only of silica nanoparticles without consolidation by TEOS, the nanoparticles easily leave with friction with the cotton swab ( figure 13 ).

b) Deposit according to example 2.3. with addition of a crosslinking agent (TEOS in acid medium)

In another test, the protocol of example 2.3. was implemented and the surfaces were then crosslinked by adding TEOS. The characterization by FEGSEM of the prepared coatings is presented on the figure 14 . It can be seen that the step of consolidation by TEOS brings a marked improvement in the films of nanoparticles to the resistance to the friction test by the cotton swab soaked in isopropanol.

c) Deposit according to example 2.3. with the addition of a crosslinking agent (TEOS in an acid medium) and annealing at 80 ° C for 6 hours.

In a third test, an additional annealing of 6 h at 80 ° C was applied to a surface having undergone the same covering as on the figure 14 . The results reported on the figure 15 show that the annealing step does not bring any major improvement in the resistance of the films of nanoparticles with respect to the figure 14 .

Consequently, this annealing step can be eliminated from our process for preparing nanoparticle films.

10. Protocol for depositing nanoparticles of two different sizes without an Amino silane bonding primer

1. at. After cleaning with a detergent of a glass surface, a first deposition by the dip-coating technique (removal speed = 100 mm / min) is carried out using a solution containing nanoparticles of 100 nm (0.5% of mass concentration) in alcohol. This step is repeated 5 times. The parts are dried at 80 ° C for one hour.
2. b. Deposition of TEOS in acid solution by dip-coating (speed = 100 mm / min), with a soaking time of 2 hours is carried out. The solution used is a mixture of TEOS and HCl (1 equivalent / 5 equivalents) in a water / alcohol mixture at pH 2. The concentration of TEOS in this bath is 10 mM. The parts are dried at 80 ° C for one hour.
3. vs. A second deposition cycle is carried out by the dip-coating technique (withdrawal speed = 100 mm / min) using a solution in alcohol of 15 nm silica nanoparticles (0.5% by mass concentration). The parts are dried at 80 ° C for one hour.
4. d. Deposition of TEOS in acid solution by dip-coating (speed = 100 mm / min), with a soaking time of 2 hours is carried out. The solution used is a mixture of TEOS and HCl (1 equivalent / 5 equivalents) in a water / alcohol mixture at pH 2. The concentration of TEOS in this bath is 10 mM. The parts are dried at 80 ° C for one hour.
5. e. Grafting of fluorinated silane molecules for 18 hours in a vacuum desiccator, annealing for 1 hour at 80 ° C.

Material AC (°) Sliding angle (°) Test 9-1 (loss in °) Test 9-2 (loss in °) Test 9-3 (loss in °) Test 9-4 (loss in °) Glass 1 147 - 8 9 12 11 Glass 2 150 7 - - 14 -

These results show that the superhydrophobic effect is achieved by this protocol and that the mechanical and chemical resistance is high.

11. Preparation of raspberry particles

For the purposes of our tests, several families of "raspberry" particles were synthesized on the basis of large silica particles on which a chemical group was grafted. These particles are then brought into contact with smaller particles of silica. The reactive groups presented are the amines ( Langmuir 2011, 27, 4594 ), epoxides ( Nano Lett. 2005, 5, 2298 ) and isocyanates.

1) MFN (amine)

NP100 (1g) and 50 ml of Ethanol (EtOH) are introduced into an anhydrous 100 ml flask equipped with a condenser. The mixture is immersed in a bath in the US for 30 min. The APTMS (450 μL) is then introduced into the syringe and the reaction medium is heated at reflux overnight. The reaction medium is cooled to room temperature (t.a.). After concentration under vacuum, the particles are suspended in 50 ml of toluene. The mixture is centrifuged at 3000 rpm for 10 min. The supernatant is discarded. This operation is repeated three times. The particles are then dried under vacuum at 50 ° C for several hours. These particles are then called NP100-NH2 particles.

NP100-NH2 (500 mg), NP15 (315 mg) and 40 ml of EtOH are introduced into an anhydrous 100 ml flask equipped with a condenser. The mixture is immersed in a bath in the US for 30 min, then the reaction medium is stirred overnight at 50 ° C. The mixture is cooled to r.t. Ethanol is introduced in order to prepare a solution at 0.5% by mass.

2) NPF (epoxy)

NP100 (1 g) and 50 ml of toluene are introduced into an anhydrous 100 ml flask equipped with a condenser. The mixture is immersed in a bath in the US for 30 min. The epoxy silane (530 μL) is then introduced into the syringe and the reaction medium is heated to 50 ° C. overnight. The reaction medium is cooled to r.t. The mixture is centrifuged at 3000 rpm for 10 min. The supernatant is discarded. This operation is repeated three times. The particles are then dried under vacuum at 50 ° C for several hours. These particles are then called NP100-epoxide particles.

NP100-epoxide (970 mg), NP15 (620 mg) and 20 ml of DMF (dimethylformamide) are introduced into an anhydrous 100 ml flask equipped with a condenser. The mixture is immersed in a bath in the US for 30 min, then the reaction medium is heated at reflux overnight. The mixture is cooled to r.t. The mixture is centrifuged at 3000 rpm for 10 min. The supernatant is discarded. The particles are then dried under vacuum at 50 ° C for several hours.

3) NPF (isocyanate)

NP100 (1g) and 30 ml of toluene are introduced into an anhydrous 100 ml flask equipped with a condenser. The mixture is immersed in a bath in the US for 30 min. The silane isocyanate (490 mg) is then introduced into the syringe and the reaction medium is stirred overnight at r.t. The mixture is centrifuged at 3000 rpm for 10 min. The supernatant is discarded. This operation is repeated three times. The particles are then dried under vacuum at 50 ° C for several hours. These particles are then called NP100-NCO particles.

NP100-NCO (760 mg), NP15 (480 mg) and 15 ml of toluene are introduced into an anhydrous 100 ml flask equipped with a condenser. The mixture is immersed in a bath in the US for 30 min, then the reaction medium is stirred overnight at reflux. The mixture is cooled to r.t. The solvent is evaporated and the particles are then dried under vacuum at 50 ° C for several hours.

12: Deposit of raspberry particles on glass slides

Several different protocols have been used to deposit particles on glass surfaces. Several variations were introduced to the protocol of Example 9 to achieve these surfaces. These include the number of dips in TEOS (3 dips) and the deposition of 15 nm nanoparticles followed by a deposition of TEOS (not performed in protocol 1, performed in protocol 2) performed after the deposition of MFN.

The MFNs used in this example are those prepared in Example 11.

Briefly the experimental conditions are summarized below: Protocol 1: Protocol 2: Prewash Prewash 5 NPF DC 5 NPF DC 3 DC of TEOS (10 mM) 3 DC of TEOS (10 mM) Silane 1 NP15 DC 1 CD of TEOS Silane

The parts are dried at 80 ° C. for one hour after each dip coating step and two hours after depositing the silane. NPF Protocol AC (°) Test 9-3 (loss in °) Amino 1 145 Not stable 2 143 Not stable Epoxy 1 143 26 2 143 23 Isocyanate 1 134 16 2 134 17

The surfaces covered with raspberry particles all have contact angles of the order of 134 ° to 145 °. After abrasion only the "Amino" particles are not stable. They degrade from the first abrasion cycle. All the other particles have intermediate holdings. This shows that the electrostatic bonds created between the different populations of particles by the amine groups are not sufficient to ensure resistance of the material formed.

13: Activation of polymeric materials by UV-ozone

Polymeric parts such as PMMA have little wetting when they do not undergo an activation treatment. This does not allow good spreading of the nanoparticle or TEOS solutions and then having a uniform covering of the surfaces. Certain surfaces have therefore been made wetting by activation under UV-ozone. The device used for UV / ozone activation is the Procleaner ™ Plus from Bioforce Nanosciences. The nominal power is 14.76 mW / cm ² to 1 cm from the source. The light intensity is distributed at 2% at 185 nm and at 45% at 254 nm. Before use, the device is preheated for 10 minutes. The PMMA sample, previously washed with an aqueous detergent and dried, is exposed to 2.5 cm from the UV source for 10 minutes.

The contact angle of a drop of water of 1 µL on the PMMA goes from approximately 80 ° before activation to 20 ° after activation.

14: Activation of polymeric materials by atmospheric plasma

Polymeric parts such as PMMA have little wetting when they do not undergo an activation treatment. This does not allow good spreading of the nanoparticle or TEOS solutions and then having a uniform covering of the surfaces. Certain surfaces have therefore been made wetting by activation by atmospheric plasma. The device used for plasma activation is the ULS spot (Acxys Technologies). The plasma is supplied by compressed air at 4 bars. The plasma is activated at a power of 800 W. The substrates (PMMA or PC) to be treated are scanned at a speed of 200 mm / s with a step of 4 mm. Two applications were provided. The contact angle of a 1 µL drop of water changes from approximately 80 ° to 20 °.

15: Deposit of particles by spray 15-1 On glass

The conditions for surface preparation are similar to Example 10. The same solutions were prepared and used. The nanoparticle solutions (NP100 and NP15) were then sprayed using a 50mL atomizer placed 15cm from the surface in an upright position.

• Prélavage
• 5 sprays de NP100
• 1 spray de TEOS (10 mM)
• 1 spray de NP15
• 1 spray de TEOS
• Silane

The protocol used is as follows:

• Prewash
• 5 NP100 sprays
• 1 TEOS spray (10 mM)
• 1 spray of NP15
• 1 TEOS spray
• Silane

Annealing at 80 ° C. is carried out for 1 hour after each spray step and 2 hours after deposition of the hydrophobic agent.

The results obtained are presented in the table below: Material AC (°) Sliding angle (°) Test 9-3 (loss in °) Glass 151 16 16

This result shows that it is possible to obtain a textured surface on glass using this method by carrying out the successive deposition of different populations of particles. This result also shows that this superhydrophobic treatment has good mechanical strength characteristics.

The conditions for surface preparation are similar to Example 10. The same solutions were prepared and used.

PMMA is previously activated by UV-Ozone and covered with a primary layer of TEOS as defined in Example 20.

The nanoparticle solutions (NP100 and NP15) were then sprayed using a 50mL atomizer placed 15cm from the surface in an upright position.

• Prélavage
• Activation UV-ozone
• 1 DC de TEOS
• 5 sprays de NP100
• 1 spray de TEOS
• 1 spray de NP15
• 1 spray de TEOS
• Silane

The protocol used is as follows:

• Prewash
• UV-ozone activation
• 1 CD of TEOS
• 5 NP100 sprays
• 1 TEOS spray
• 1 spray of NP15
• 1 TEOS spray
• Silane

The parts are dried at 80 ° C for two hours after the TEOS dip coating, one hour after each spray step and two hours after depositing the silane. Material AC (°) Test 9-3 (loss in °) PMMA 146 ° 20 °

16: Simultaneous deposition of a mixture of different particle sizes and TEOS by dip coating

Example 10 describes a sequential deposition of NP100, TEOS then NP15 and TEOS. In the present example, the process has been shortened by mixing the particles with the TEOS solution.

Several variations have been made. These include the number of dips in TEOS (samples A: 3 dips; samples B: 5 dips) and the deposit of 15nm nanoparticles followed by a deposition of TEOS (not carried out in protocol 1, carried out in protocol 2) carried out after the deposition of the nanoparticles in solution in TEOS.

Briefly the experimental conditions are summarized below:

Protocol 1

1. 1) Prewash
2. 2) Mixing of {NP100 + NP15 + TEOS solution (at 10 mM)} = Solution 1
3. 3) Dip Coating in Solution 1: 3 DC (A) and 5 DC (B)
4. 4) Silane

Protocol 2 :

1. 1) Prewash
2. 2) Mixing of {NP100 + NP15 + TEOS solution (at 10 mM)} = Solution 1
3. 3) Dip Coating in Solution 1: 3 DC (A) and 5 DC (B)
4. 4) 1 DC NP15
5. 5) 1 DC TEOS
6. 6) Silane

The parts are dried at 80 ° C. for one hour after each dip coating step and two hours after depositing the silane. Experimental conditions AC (°) Test 9-3 (loss in °) A1 154 20 A2 154 14 B1 157 16 B2 157 13

These results show a superhydrophobic effect and good mechanical and chemical resistance of the surfaces obtained by this process.

17: Simultaneous deposition of a mixture of different particle sizes and TEOS by spray

The surface preparation conditions is similar to Example 16. The same solutions were prepared and used.

PMMA is previously activated by UV-Ozone and covered with a primary layer of TEOS as defined in Example 20.

Briefly the experimental conditions are summarized below:

Protocol

1. 1) Prewash / Activation and deposition of the preliminary layer of TEOS
2. 2) Mixing of {NP100 + NP15 + TEOS solution (at 10 mM)} = Solution 1
3. 3) Spray Coating of Solution 1: 3 sprays (A) and 5 sprays (B)
4. 4) Silane

Solution 1 was sprayed using a 50mL atomizer placed 15cm from the surface in an upright position.

The parts are dried at 80 ° C for one hour after each spray step and two hours after depositing the silane Material protocol AC (°) Test 9-3 (loss in °) Glass AT 139 7 Glass B 146 13 PMMA AT 152 25 PMMA B 148 20

These results show the feasibility of spray deposition of different populations of nanoparticles on different supports. The coating obtained has the same resistance characteristics, regardless of the number of sprays used.

18: Simultaneous deposition of a mixture of raspberry particles and TEOS by dip-coating

For this example, the “NPF isocyanate” particles and the “NPF Amino” particles prepared in Example 11 were used. These were mixed with a TEOS solution and then they were deposited on glass surfaces by the protocol described below.

Protocol 1 :

1. 1) Prewash
2. 2) Mixing of {NPF (at 0.5% by mass) in the TEOS solution (at 10 mM)} = Solution 1
3. 3) 5 Dip-Coating Solution 1
4. 4) Silanization

Protocol 2 :

1. 1) Prewash
2. 2) Mixing of {NPF (at 0.5% by mass) in the TEOS solution (at 10 mM)} = Solution 1
3. 3) 5 DipCoating Solution 1
4. 4) 1 DipCoating NP15
5. 5) 1 DipCoating TEOS
6. 6) Silanization

The parts are dried at 80 ° C. for one hour after each dip coating step and two hours after depositing the silane. NPF Experimental conditions AC (°) Test 9-3 (loss in °) Amino 1 143 36 2 143 18 Isocyanate 1 151 10 2 153 12

These results show that the process using isocyanate NPFs is clearly more efficient than that using amino NPFs because the contact angles are greater by 8 to 10 ° and that their resistance to friction is greater. In the case of isocyanate NPFs, the addition of an additional NP15 population does not significantly improve the stability of the coating whereas it is necessary for Amino NPFs.

In the latter case, the stability is due to the accumulation of particle layers and not to the stability of the Amino NPFs themselves.

19: Simultaneous deposition of a mixture of raspberry particles and TEOS by spray

The surface preparation conditions are similar to those of Example 16. The same solutions were prepared and used. PMMA is previously activated by UV-Ozone and covered with a primary layer of TEOS as defined in Example 20. The raspberry nanoparticles used are isocyanate nanoparticles as prepared in Example 11.

Briefly the experimental conditions are summarized below:

Protocol:

1. 1) Prewash / Activation and deposition of the preliminary layer of TEOS
2. 2) Mixing of {NPF (at 0.5% by mass) in the TEOS solution (at 10 mM)} = Solution 1
3. 3) Spray Coating of Solution 1: 3 sprays (A) and 5 sprays (B)
4. 4) Silane

Solution 1 was sprayed using a 50mL atomizer placed 15cm from the surface in an upright position.

The parts are dried at 80 ° C. for one hour after each spray step and two hours after depositing the silane. Material protocol AC (°) Test 9-3 (loss in °) Glass AT 154 24 Glass B 153 25 PMMA AT 154 31 PMMA B 153 24

These results show the feasibility of spray deposition of raspberry nanoparticles on different supports. The coating obtained has the same resistance characteristics, whatever the number of sprays used and whatever the material.

20: Deposit of a TEOS bonding primer on polymers

After UV-ozone activation as described in Example 13, PMMA plates (5 ^∗ 5 cm ² ) are immersed in TEOS solutions at concentrations of (A) 10mM, (B) 80mM, (C) 250mM in a water-alcohol mixture.

Secondly, the plates are used to deposit a hydrophobic (protocol 1 ) or superhydrophobic (protocol 2 ) coating thereon according to the following procedures:

Protocol 1 :

1. 1) Pre-wash and UV-ozone activation
2. 2) deposition of TEOS primer by dip coating at concentrations of (A) 10mM, (B) 80mM, (C) 250mM
3. 3) Silane

Protocol 2:

1. 1) Pre-wash and UV-ozone activation
2. 2) deposition of the TEOS primer by dip coating at a concentration of (B) 80mM
3. 3) deposition of particles by dip coating according to the procedure of Example 10
4. 4) Silane

The parts are dried at 80 ° C for one hour after each dip coating step and two hours after depositing the silane. Protocol AC (°) Test 9-3 (loss in °) A1 117 31 B1 116 5 C1 117 5 B2 144 13

These results show that, without particles on the surface (protocol 1), it is possible to deposit a hydrophobic layer on PMMA previously treated with a primary layer of TEOS. This TEOS must have a sufficient concentration to allow a good resistance of the coating on the surface. In this example, the resistance for a TEOS concentration of 10 mM is lower than at higher concentrations. However, the mere deposition of a primary bonding layer followed by functionalization by a hydrophobic layer is not sufficient to obtain the superhydrophobic property (contact angle less than 130 °).

The results of protocol 2 show that it is possible to obtain superhydrophobic surfaces on PMMA previously treated with a primary layer of TEOS. In this example, protocol 2 gives results similar to those obtained for glass (cf. example 10).

21: Depositing a superhydrophilic coating on glass

In this example, the “NPF isocyanate” particles prepared in Example 11 were used according to a process similar to that of Example 18 with the exception of the deposition of the final hydrophobic layer which was not carried out.

These were mixed with a TEOS solution and then they were deposited on glass surfaces by the protocol described below.

Protocol:

1. 1) Prewash
2. 2) Mixture of {NPF (0.5% by mass) in the 10 mM TEOS solution} = Solution 1
3. 3) 5 Dip-Coatings Solution 1
4. 4) 1 hour drying at room temperature (condition A ) or at 80 ° C (condition B )

Material Experimental conditions AC (°) Glass AT <5 ° B <5 °

The superhydrophilic and anti-fog effect is illustrated in the figure 16 , where the image shows a glass cooled to -20 ° C which remains transparent on the treated part while it is disturbed by condensation on the untreated part.

The superhydrophilic characteristic is also clearly shown by the contact angles close to 0 °.

Claims (15)

1. A process for coating surfaces comprising at least the steps:

   a) Depositing at least two nanoparticle populations, of different sizes, on a surface to be treated, and

   b) Crosslinking the nanoparticle-coated surface using an acidic hydroalcoholic solution containing a transition metal alkoxide, preferably tetraethyl orthosilicate (TEOS), as crosslinking agent,

   said process not involving heating said surface above 180°C.
2. The process according to claim 1, characterized in that said nanoparticle populations are mixed with the solution containing said crosslinking agent before being deposited on said surface.
3. The process according to any one of claims 1 and 2, characterized in that step a) contains the following substeps:

   a1) Treating a first nanoparticle population with an adhesion agent,

   a2) Contacting this first nanoparticle population with one or more other nanoparticle populations,

   a3) Optionally, purifying the particles thus formed,

   a4) Depositing the particles formed in steps a2) or a3) on said surface.
4. The process according to claim 3, characterized in that said adhesion agent is an isocyanate or epoxy compound, preferably an isocyanate silane compound or an epoxy silane compound.
5. The process according to any one of claims 1 to 4, characterized in that said surface consists of a transparent material, preferably glass, silica or polycarbonate.
6. The process according to any one of claims 1 to 5, characterized in that said surface consists of a heat-sensitive material, preferably chosen from polycarbonate, polyurethane, poly-methacrylate (PMMA), polypropylene, polyvinyl acetate (PVA), polyamides (PA), polyethylene terephthalate (PET), polyvinyl alcohols (PVAI), polystyrenes (PS), polyvinyl chlorides (PVC) or polyacrylonitriles (PAN).
7. The process according to any one of claims 1 to 6, characterized in that one of the two nanoparticle populations has a diameter of between 50 and 200 nm, and the other a diameter of between 5 and 50 nm, and preferably consist of silicon, germanium, alumina, titanium, oxides or alloys thereof, or of polycarbonate.
8. The process according to any one of claims 1 to 7, characterized in that said surface is activated by an ozone, UV or plasma treatment prior to the deposition of said nanoparticles.
9. The process according to any one of claims 1 to 8, characterized in that the deposition of said nanoparticles and/or the deposition of the solution containing the crosslinking agent is carried out by dip-coating, spin-coating, spraying, flow-coating or wiping, preferably by spraying.
10. The process according to any one of claims 1 to 9, characterized in that said surface is covered with a layer of hydrophobic organic molecules, preferably perfluorinated organic molecules, for example the organic molecules of formula:

    

    where R represents a linear or branched C₁-C₄ alkyl group.
11. The process according to any one of claims 1 to 10, characterized in that the crosslinking step b) is carried out at room temperature.
12. Use of the process as described in any one of claims 1 to 11, for texturing surfaces to render them superhydrophobic.
13. Use of the process as described in one of claims 1 to 11, for coating surfaces of spectacle glasses, portholes, windows, visors, lenses, glass panes, solar panels, windshields, rear-view mirrors or radars.
14. Use of an acidic hydroalcoholic solution containing at least two nanoparticle populations of different sizes and a transition metal alkoxide, for texturing surfaces to make them superhydrophilic or superhydrophobic.
15. Use according to claim 14, characterized in that said hydroalcoholic solution is applied to said surfaces by spraying.

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