EP4076339A1

EP4076339A1 - Medical composition or device comprising oligo(ethylene glycol) polymers

Info

Publication number: EP4076339A1
Application number: EP20824611.6A
Authority: EP
Inventors: Eva DIEUZY; Laurent Billon; Christophe Derail; Valérie Alard; Kamel CHOUGRANI
Original assignee: Centre National de la Recherche Scientifique CNRS; LVMH Recherche GIE; Universite de Pau et des Pays de lAdour; Urgo Recherche Innovation et Developpement
Current assignee: Centre National de la Recherche Scientifique CNRS; LVMH Recherche GIE; Universite de Pau et des Pays de lAdour; Urgo Recherche Innovation et Developpement
Priority date: 2019-12-16
Filing date: 2020-11-27
Publication date: 2022-10-26
Also published as: FR3104419A1; US20230069954A1; WO2021123532A1

Abstract

The invention relates to a cosmetic or pharmaceutical composition for topical application, said composition comprising the combination of a crosslinked oligo(ethylene glycol) polymer in the form of an aqueous dispersion of microgels particles and a non-crosslinked water-soluble oligo(ethylene glycol) polymer. The invention also relates to a process for preparing said composition.

Description

Composition or medical device comprising polymers based on oligo (ethylene glycol)

Technical area

The present invention relates to a cosmetic, a pharmaceutical composition or a medical device for topical application or on mucous membranes, said composition comprising the combination of a polymer based on oligo (ethylene glycol) crosslinked in the form of an aqueous dispersion of colloidal particles of microgels and of a polymer based on oligo (ethylene glycol) soluble in water. The invention also relates to a process for the preparation of this composition.

Prior art

In the field of adhesive polymers, the modification of the viscoelastic modulus is mainly carried out by adding resins or sticky oils, which require complete miscibility with the polymer (Tse MF, Jacob L. Pressure Sensitive Adhesives Based on VectorR SIS Poiymers I. Rheoiogicai Mode! And Adhesive Design Pathways. The Journal of Adhesion. 1996 Apr 1; 56 (l-4): 79-95, and C. Derail, A. Allai, G. Marin, Ph. Tordjeman, Reiationship between viscoeiastic and peeling properties of mode! Adhesives. Part 1: Cohesive fracture, J. of Adhesion, 61, 123-157, 1997).

There remains a need to provide a new way of modulating the mechanical properties of films of cosmetic and pharmaceutical products which are intended to be applied to mucous membranes or to the skin.

It has been found in the context of the present invention that compositions based on poly (oligo- (ethylene glycol) methacrylate) microgels make it possible to achieve this object. The synthesis of aqueous dispersions of such microgels has been described in the literature, in particular in patent applications WO 2016/110615 and WO 2019/077404, and the publications Boularas et al., Polymer Chem., 2016, 7 , 350-363; and Aguirre et al., Polymer Chem., 9, 1155-1159. During the synthesis of these microgels, a side product is formed which consists of a water soluble polymer (WSP), cited as a free polymer. By evaporation of the aqueous solvent, the self-assembly of the purified microgels forms cohesive and elastic films.

[0006] There remains a need to provide cosmetic products, pharmaceutical products and medical devices which are intended to be applied to the skin or to the mucous membranes, said films being sufficiently flexible, cohesive and adhesive, in order to hold in place a times applied without breaking, crumbling or tearing. It is also desirable that these products can be removed by hand without tearing and without leaving residue on the skin.

[0007] However, it has been discovered by the inventors that the mixing of the purified microgels with the free polymer makes it possible to control and control the value of the viscoelastic modulus of the films without reducing the elongation at break. In particular, the free polymer makes it possible to increase the adhesion of a film of microgels without modifying its mechanical properties.

The addition of the free polymer at different concentrations makes it possible to control the rheological and mechanical properties of the films and consequently the tack, or in other words the tackiness.

In the present invention, the films obtained by drying the combination of the microgels and the free polymer exhibit particular mechanical properties of elasticity and tack. The inventors have surprisingly found that these properties can be modulated as a function of the microgel-polymer mass ratio. The inventors have discovered that the chemical composition of the free polymer is very comparable to that of microgels and allows good compatibility between the two components. In addition, the branched and crosslinked structure allows the preservation of the resistance to stretching of films obtained from their mixtures.

By evaporation of the aqueous solvent, the self-assembly of the microgel / polymer mixture forms a film with promising mechanical properties for skin applications: the elastic modulus is low, the deformability capacity is high and the elongation at break high. Reformulation with the free polymer potentially makes it possible to control and control the value of the viscoelastic modulus of the films without reducing the elongation at break.

The formation of microgel films with adjustable mechanical properties has never been reported in the literature. In this invention, the variation in the rheological properties of the films is directly obtained by virtue of a secondary synthesis product, the free polymer. This has the same chemical composition as the microgels and therefore has excellent compatibility with the latter. This has the advantage of not weakening the self-assembled network of the microgels, which results in the retention of resistance to stretching.

The addition of the free polymer can induce a variation of the real part of the complex shear modulus (G) between lxlO ³ and lxlO ⁵ Pa. This makes it possible to obtain films having a very pronounced tack up to films not showing any tackiness at all. However, the elongation at break, which reflects the cohesion of the microgel network at very large deformations, does not decrease with the addition of free polymer. The structural characterization of the free polymer by aqueous chromatography reveals a very branched polymer resembling nano-gels, whose structure explains the conservation of the resistance of the network which can thus follow the deformations of the skin or the mucous membranes without peeling off or breaking. .

General description of the invention

A first object of the invention is a composition, in particular a cosmetic composition, a pharmaceutical composition or a medical device, comprising a water-soluble polymer (WSP) and particles of microgels, in which the particles of microgels and the water-soluble polymer can be independently obtained, or are independently obtained, by aqueous phase precipitation polymerization of di (ethylene glycol) methyl ether methacrylate, an oligo (ethylene glycol) methyl ether methacrylate, and a vinyl monomer bearing a carboxyl group, in the presence of N, N'-methylenebisacrylamide as a crosslinking agent, in which the ratio between the mass of the water-soluble polymer and the mass of the microgel particles in the dry state is between 0% and 100%.

According to one embodiment, the ratio between the mass of the water-soluble polymer and the mass of the microgel particles is between 0% and 35%, or between 35% and 100%.

[0015] A second object of the invention is a method for the cosmetic treatment or the topical pharmaceutical treatment of the skin, nails, lips, mucous membranes or hair of a person, said method comprising a first step application of the cosmetic composition, of the pharmaceutical composition or of the medical device as defined above.

A third object of the invention is a process for the preparation of the cosmetic composition, the pharmaceutical composition or the medical device, said process comprising a step of preparing a mixture of microgel particles and a soluble polymer. in water, said step comprising:

- a first step of preparing microgel particles,

- a second step of preparing the water-soluble polymer, and

- a third step of mixing microgel particles and the water-soluble polymer, the ratio between the mass of the water-soluble polymer and the dry mass of the microgel particles being between 0% and 100%.

Description of figures

[0017] [fig. 1] Figure 1 is a graph of conformation of radius of gyration as a function of molar mass for MBA-WSP (red), OEGDA-WSP (blue), PEG35K (black). WSP comes from a synthesis with 2 mol% crosslinker. The dotted line is representative of a power law with an exponent of 0.6. The solid black line fits the MBA-WSP curve according to a power law of exponent 0.27.

[0018] [fig. 2] In Figure 2, the number and mass molecular weights, and the polydispersity index for different WSPs are shown. [0019] [fig. 3] FIG. 3 represents the curve of the storage modulus G ′ and of the loss modulus G ″ as a function of the frequency of an unpurified MBA film and an unpurified OEGDA film with different levels of crosslinking agent: 2 mole% and 8 mole%.

[0020] [fig. 4] Figure 4 is a table providing the mass composition of unpurified films, after synthesis.

[0021] [fig. 5A] FIG. 5A represents the expansion viscosity as a function of time of unpurified MBA films and OEGDA films with different levels of crosslinking agent: 2% by mole and 8% by mole.

[0022] [fig. 5B] Figure 5B is the elongation at break for MBA film and OEGDA film for different crosslink densities at 2 mole% and 8 mole%.

[0023] [fig. 6A] Figure 6A shows the modulus of conservation G ′ and the modulus of loss G ″ as a function of the frequency of a 2.0 mole% OEGDA-MG film with different levels of MG.

[0024] [fig. 6B] Figure 6B is the modulus of conservation G "and the modulus of loss G" as a function of the frequency of a 2.0 mole% MBA-MG film with different levels of MG.

[0025] [fig. 7] Are shown in Figure 7, G '(square symbol), G "(triangular symbol) and tan d (round symbol) as a function of the microgel content at w = 0.01 rad.s ^1. The full symbols correspond to OEGDA, the hollowed out symbols correspond to MBA.

[0026] [fig. 8A] Figure 8A is the expansion viscosity versus time curve for OEGDA-MG films at different MG contents.

[0027] [fig. 8B] Figure 8B is the extensional viscosity versus time curve of OEGDA-MG films for different MG contents.

[0028] [fig. 9] Fig. 9 is a bar graph showing the elongation at break for MBA film and OEGDA film for different MG contents. [0029] [fig. 10A] Figure 10A shows the extension viscosity versus time curve for pure OEGDA-MG films at different film forming temperatures.

[0030] [fig. 10B] Figure 10B is a bar graph showing the elongation at break values for pure OEGDA-MG films at different film forming temperatures.

[0031] [fig. 11] FIG. 11 shows two images obtained by AFM atomic force microscopy of the upper surface of films of OEGDA-MG (left image) and of MBA-MG (right image).

[0032] [fig. 12] Figure 12 shows two AFM images of a cross section of films of OEGDA-MG (left image) and MBA-MG (right image).

[0033] [fig. 13] FIG. 13 shows two images obtained by AFM atomic force microscopy of the upper surface of films of OEGDA-MG (left image) and of MBA-MG (right image) subjected to an elongation of 30%.

[0034] [fig. 14] Figure 14 shows AFMs in topographic contrast and images of the LogDMT module: (a) AFM in topographic contrast and (b) LogDMT module for 2 mol% MBA-MG films containing 25% MG, (c) AFM in topographic contrast and (d) LogDMT modulus for 2 mol% MBA-MG films containing 50% MG; (e) AFM in topographic contrast and (f) LogDMT modulus for 2 mol% MBA-MG films containing 75% MG.

Definitions

It is understood in the meaning of the invention that "microgel particles" are a crosslinked polymer in the form of spherical particles having an average size which can vary from 100 nm to 1000 nm in the dry state (c ' that is to say containing less than 2% by mass of water), preferably between 100 nm and 500 nm, from 350 to 450 nm, even better still 400 nm. The hydrodynamic radial distribution function of the microgels measured at an angle of 60 ° and at a temperature of 20 ° C may be less than 1.1. The microgel of the invention can be obtained by copolymerization in aqueous phase of several monomers. The average size of the microgel particles can vary depending on whether they contain water or not.

[0037] "Microgels", in the sense of the present description, can be in the form of an aqueous dispersion of "particles of microgels" or in the form of a film comprising particles of microgels as defined above. Microgels can trap cosmetic or pharmaceutical active organic molecules. A film comprising microgel particles can have a thickness of 1 micron to 10 millimeters, for example 10 microns to 500 microns, 100 microns to 400 microns or 500 microns to 1000 microns. In a particular embodiment, the microgel particles preferably do not include any inorganic material.

It is preferred that the microgel particles consist of organic compounds. The microgel particles do not contain, for example, silica, in particular silica as a support for the crosslinked polymer.

A "crosslink" is a group (part of a molecule) which links the chains of copolymers together. This crosslink originates from a "crosslinker" molecule which is mixed with the monomers during the polymerization process of the crosslinked polymer.

It is understood within the meaning of the invention that a "water-soluble polymer" is a polymer having a radius of gyration at 20 ° C which is from 5 nm to 80 nm, for example from 10 nm to 30 nm. The water soluble polymer may have an average molecular weight of 1 x 10 ⁵ g. mol ¹ to 1 x 10 ⁶ g. mol ¹ . The radius of gyration and the molecular mass can be measured by any method known to those skilled in the art, for example by size exclusion chromatography. A water soluble polymer is distinguished from microgel particles: for example microgel particles can be identified by atomic force microscopy (AFM) observation of a film made by drying an aqueous dispersion of microgel particles. On the contrary, no particle can be detected by AFM observation of films which are made by drying a solution of the water soluble polymer. The expression "between" excludes in the meaning of the invention the numerical limits which follow it. On the other hand, the expression "from ... to" includes the cited limits.

Detailed description of the invention

The first object of the invention relates to a composition, in particular a cosmetic composition, a pharmaceutical composition, or a medical device, comprising a polymer soluble in water and particles of microgels, said particles of microgels having an average diameter from 100 nm to 1000 nm in the dry state, wherein the microgel particles and the water soluble polymer can be independently obtained, or are independently obtained, by aqueous phase precipitation polymerization of at least the three following monomers, in the presence of a crosslinking agent:

- di (ethylene glycol) methyl ether methacrylate,

- an oligo (ethylene glycol) methyl ether methacrylate,

- a vinyl monomer comprising a carboxyl group, where at least one of the two crosslinking agents (that is to say at least the crosslinking agent used to prepare the particles of microgels or at least the crosslinking agent used for preparing the water soluble polymer), is N, N'-methylenebisacrylamide and where the ratio between the mass of the water soluble polymer and the mass of the particles of microgels in the dry state is between 0% and 100 % by mass.

In the case where the composition constitutes or forms part of a medical device, this device includes a mixture consisting of the water-soluble polymer, the microgels and optionally water.

The solid content of the cosmetic composition, the solid content of the pharmaceutical composition, and the solid content of the mixture included in the medical device is preferably 1.5% to 100% by mass. The solid content may be greater than a percentage selected from the group consisting of 2%; 3%; 4%; 5%; 10%; 15%; 20%; 25%; 30 % ; 35%; 40%; 45% and 50% by mass. The solid content of the composition of the invention can be defined as the percentage by weight of the solid elements that it contains, in particular as equal to the sum of the percentage by weight of the microgels in the dry state, of the percentage by weight of the polymer soluble in water, and optionally a percentage of any other solid compound which would be present in the composition. In the case of a medical device, the solid content can be the sum of the percentage of microgels in the dry state and the percentage of polymer which are contained in the mixture.

According to one embodiment, the microgel particles and the water-soluble polymer comprise chains having monomer units of diethylene glycol methacrylate, monomer units of oligoethylene glycol methacrylate comprising from 6 to 10 ethylene glycol units, methacrylic acid monomer units, and crosslinks. The oligo (ethylene glycol) methyl ether methacrylate preferably comprises from 7 to 8 ethylene glycol units.

The oligo (ethylene glycol) methyl ether methacrylate may have a number-average molar mass (Mn) of 400 g / mole to 600 g / mole, preferably 450 to 500 g / mole.

The vinyl monomer can be a monomer of formula CR1R2 = CR3R4 in which RI, R2, R3 and R4 represent a hydrogen, a halogen or a hydrocarbon group, provided that at least one of the four groups comprises a -COOH group or -COO-M ⁺ , M ⁺ representing a cation. The vinyl monomer is preferably a (meth) acrylic acid monomer.

The microgel particles and the water-soluble polymer can be independently obtained by polymerization by aqueous phase precipitation of three monomers in the presence of a crosslinking agent. The precipitation polymerization step comprises contacting, in an aqueous phase, the three monomers described above and the crosslinking agent, at a temperature between 40 ° C and 90 ° C, preferably of the order 70 ° C. The process does not require the presence of a surfactant, such as SDS (sodium dodecyl sulfate), and the Polymerization can be initiated by the addition of a water soluble free radical initiator, for example potassium persulfate (KPS).

According to one embodiment, the mole fraction of di (ethylene glycol) methyl ether methacrylate is 80 mole% to 90 mole%, the mole fraction of oligo (ethylene glycol) methyl ether methacrylate is 5% by mole to 15% by mole, the mole fraction of the vinyl monomer bearing a carboxyl group is from 2% by mole to 8% by mole, and the mole fraction of the crosslinking agent is from 0.5 to 10% by mole , the sum of the four mole fractions being equal to 100 mole%. In the present description, the mole fractions can be defined as the mole fractions of the monomers which are used to prepare the microgel or the water soluble polymers. Alternatively, mole fractions can be defined as the mole fractions of the monomer units in the microgel or in the water soluble polymer which have been obtained from the reaction between the monomers.

The mole fraction of the crosslinking agent can be from 0.5 mole% to 10 mole%, from 0.5 mole% to 8 mole%, from 1 mole% to 7 mole% or from 1.5 mole% to 6 mole%.

The molar ratio (a: b) between the di (ethylene glycol) methyl ether methacrylate (a) and the oligo (ethylene glycol) methyl ether methacrylate (b) is preferably between 1: 1 and 20: 1, for example between 5: 1 and 10: 1.

The (meth) acrylic acid monomer can have the formula CR1R2 = CR3R4 in which RI, R2, R3 and R4 represent a hydrogen, a halogen or a hydrocarbon group, at least one of the four groups comprising a -COOH group or -COO-M ⁺ , M ⁺ representing a cation.

The (meth) acrylic acid monomer can be selected from the group consisting of methyl acrylic, methyl methacrylic, ethyl acrylic, ethyl methacrylic, n-butyl acrylic, and n-butyl methacrylic, methacrylic, itaconic or acrylic acids. Methacrylic acid is preferred. The oligo (ethylene glycol) methyl ether methacrylate can have a molecular mass between 200 g / mole and 600 g / mole, or between 300 g / mole and 550 g / mole or between 450 g / mole and 500 g / mole.

In a particular embodiment, the mole fraction of monomer units of di (ethylene glycol) methacrylate is 80 mole% to 90 mole%, preferably 82 mole% to 86 mole%, the mole fraction of oligo (ethylene glycol) methyl ether methacrylate monomer units is 5 mole% to 15 mole%, preferably 7 mole% to 11 mole%, the mole fraction of monomer units of (meth) acrylic acid is 2 mole% to 8 mole%, preferably 3 mole% to 7 mole%, and the mole fraction of the crosslink is 1 mole% to 6 mole% or 1 mol% to 3 mol%.

According to another embodiment, the crosslinked polymer comprises copolymer chains having monomer units of diethylene glycol methacrylate, monomer units of oligoethylene glycol methacrylate comprising from 4 to 10 ethylene glycol units, and acid monomer units. methacrylic. The monomer units are preferably: oligo (ethylene glycol) methyl ether methacrylate having 7 or 8 ethylene glycol units; and methacrylic acid. The monomer units of oligo (ethylene glycol) methyl ether methacrylate can also have 9 ethylene glycol units.

The microgel is obtained by polymerization of at least three monomers, in the presence of a first crosslinking agent, and the water-soluble polymer is obtained from a polymerization of at least three monomers, in presence of a second crosslinking agent. The first crosslinking agent and / or the second crosslinking agent is N, N'-methylenebisacrylamide.

According to one embodiment, one of the two crosslinking agents has di (meth) acrylate end groups and a unit chosen from the group consisting of - (CH ₂ -CH ₂ -0) _m -CH ₂ -CH ₂ - where n is 0 to 6, -NH-CH ₂ -NH- and mixtures thereof. The number m is preferably 3 to 6.

One of the crosslinking agents is for example N, N'-methylenebisacrylamide (MBA) while the other is (ethylene glycol) dimethacrylate (EGDMA) or an oligo (ethylene glycol) diacrylate (OEGDA). According to one embodiment, the first crosslinking agent and the second crosslinking agent are both N, N'-methylenebisacrylamide.

According to a preferred embodiment, the cosmetic composition, the pharmaceutical composition and the mixture included in the medical device are in the form of a film comprising microgels which are obtained with 1.8-2.2% by mole of N, N'-methylenebisacrylamide as a crosslinking agent. These films are advantageous because they are very flexible.

[0060] In a particular embodiment, the cosmetic composition, the pharmaceutical composition or the mixture which is included in the medical device is in the form of a film which has a thickness of 500 microns to 1000 microns.

The ratio between the mass of the water-soluble polymer and the mass of the microgel particles is greater than 0% and less than 100%. The ratio may have a lower value which is chosen from the group consisting of 5%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% , 70%, 75%, 80%, 85%, 90% and 95%. The ratio may have a higher value which is chosen from the group consisting of 5%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% , 70%, 75%, 80%, 85%, 90% and 95%.

In one embodiment, the ratio between the mass of the water-soluble polymer and the mass of the microgel particles is between 0% and 35%. In a second embodiment, the ratio between the mass of the water-soluble polymer and the mass of the microgel particles is between 35% and 100%.

The cosmetic composition and the pharmaceutical composition can be a liquid, a gel or a solid.

The cosmetic composition, the pharmaceutical composition or the mixture consisting of the polymer soluble in water, the microgels and optionally water which is included in the medical device may contain from 50% to 100% by mass of a mixture consisting of particles of microgels and polymer soluble in water, and from 0% to 50% by mass of water, the percentages being relative to the mass of the composition and the mass of the microgel particles being the mass of the particles in the dry state. The solid content of the cosmetic composition, the solid content of the pharmaceutical composition, and the solid content of the mixture consisting of the water soluble polymer, the microgels and optionally water which is included in the medical device, can be from 50% to 100% by mass. In the case where the composition of the invention is liquid, it can be spread on the skin or on the mucous membranes, and can form a transparent film adhering to the skin or to the mucous membranes by simple evaporation of the water. It is known that the skin has a low elastic modulus and that the product applied must have a modulus comparable to that of the skin so as not to be felt by the user. In this invention, the free polymer is a lever for adjusting the modulus according to the intended application. When formulating a product, the addition of components, such as gelling agents or bioactants, can increase the modulus: it is then possible to add the proportion of free polymer agreed to reduce it to a target value. The films have a high elongation at break whatever the level of free polymer, which is essential for application to the face for example.

The composition can comprise from 1% to 100% by mass of the microgels. The composition comprises according to one embodiment from 1% to 50% by mass of microgels relative to the mass of the composition, and from 0.9% to 100% by mass of water relative to the mass of the composition.

The composition can be in the form of a dispersion of microgels in water. The aqueous dispersion may comprise from 1% to 50% by mass of a mixture consisting of microgels and water soluble polymer based on the mass of the composition, and from 50% to 99% by mass of water, based on the mass of the composition.

The composition can be in the form of a film having a thickness of 1 micron to 10 millimeters comprising from 50% to 100% by mass of a mixture consisting of microgels and water-soluble polymer, and 0 % to 50% by mass of water, the percentages being expressed relative to the total mass of the composition. The films can be produced from an aqueous dispersion comprising the microgel and the water-soluble polymer, by evaporation of the water. The aqueous dispersion is for example spread on a rigid or flexible substrate, where the substrate has a temperature between 20 ° C and 60 ° C, even better a temperature of 30 ° C to 40 ° C, much better still a temperature equal to 35 ° C. ° C.

The films can be formed by a step of placing in a mold a dispersion of particles of microgels in water and the water-soluble polymer, and by a step of drying the dispersion. Drying can be achieved by placing the mold at a temperature above room temperature, for example a temperature of 30 ° C to 60 ° C.

The cosmetic composition can comprise at least one component chosen from the group consisting of preservatives, perfumes, emollients, surfactants, oils, biologically active products, pigments and dyes.

According to the second object of the invention, the method of the invention comprises a first step of preparing microgels, a second step of preparing the water-soluble polymer and a third step of mixing the two.

The method for the preparation of a cosmetic composition, of a pharmaceutical composition or of a medical device as described above, can comprise a step of preparing a mixture of particles of microgels and of a soluble polymer. in water, said step comprising a first step and a second step which may be successive, in any order, or simultaneous:

- said first step being a step of preparing microgel particles, and comprising a step (i) of polymerization by precipitation in aqueous phase of at least the following three monomers, in the presence of a first crosslinking agent: di (ethylene glycol) methyl ether methacrylate, an oligo (ethylene glycol) methyl ether methacrylate, a vinyl monomer bearing a carboxyl group, and a purification step (ii) to recover the microgel particles which were obtained at the end of step (i),

- said second step of preparing the water-soluble polymer comprising a step (a) of polymerization by precipitation in aqueous phase of at least the following three monomers, in the presence of a second crosslinking agent: di (ethylene glycol) methyl ether methacrylate, an oligo (ethylene glycol) methyl ether methacrylate, a vinyl monomer bearing a carboxyl group, and a purification step (b) to recover the water-soluble polymer which was obtained at the end of the step (a), in which at least the first or the second crosslinking agent is N, N'-methylenebisacrylamide,

a third step which follows said first step and said second step, said third step being a step of mixing a mass of particles of purified microgels which have been obtained at the end of said first step, and a mass of water-soluble polymer which is obtained at the end of said second step, where the ratio between the mass of the water-soluble polymer and the dry mass of the microgel particles is between 0% and 100%.

[0073] Step (ii) can comprise at least one centrifugation / redispersion cycle to separate the precipitate and the supernatant, and a step of recovering the microgel particles in the precipitate.

[0074] Likewise, step (b) can include at least one centrifugation / redispersion cycle to separate the precipitate and the supernatant, and a step of recovering the water-soluble polymer from the supernatant.

According to one embodiment, the first step and the second step are a single step, so that particles of microgels and a water-soluble polymer are produced at the same time from the same monomers, in which the single step comprises at least one centrifugation / redispersion cycle to separate the precipitate and the supernatant which has been obtained from the aqueous phase precipitation polymerization of the monomers, said microgel particles being recovered in the precipitate, and said water soluble polymer being recovered in the supernatant.

In the case where the first step and the second step are a single step - the ratio between the mass of the water soluble polymer in the supernatant, and the mass of the microgel particles in the precipitate is a first ratio and, in the third step, the ratio between the mass of the water soluble polymer and the mass of the microgel particles is a second ratio which is between 0% and 100% and which is different from the first ratio.

The first crosslinking agent and the second crosslinking agent are preferably both N, N'-methylenebisacrylamide, although one of them may be different from this.

The invention also relates to a method of topical cosmetic or pharmaceutical treatment of the skin, nails, lips, mucous membranes or hair of a person, said method comprising a first step of application to the person. of a composition or a medical device as described above. The method may include a second step of drying the composition or device that has been applied to the person to obtain a flexible, cohesive and adhesive film.

Examples

Poly (oligo- (ethylene glycol) methacrylate) microgels, water-soluble polymers, and films comprising the mixture of these microgels and water-soluble polymers were prepared according to the following protocol. Their rheology (linear and non-linear) was studied and their structure observed by atomic force microscopy (AFM).

A) Preparation of microalites ÎMG1, Dolvmères soluble in water and films comprising these We bought the di (ethylene glycol) methyl ether methacrylate (ME02MA, 95%), oligo (ethylene glycol) methyl ether methacrylate (OEGMA, terminated by 8 EG units with Mn = 475 g. Mol ¹ ), methacrylic acid (MAA), poly (ethylene glycol) diacrylate (OEGDA, Mn = 250 g. Mol ¹ ), N, N-methylenebisacrylamide (MBA) and potassium persulfate (KPS) from Sigma Aldrich and were used as receipts. Water purified from a Millipore Milli-Q system was used.

ME02MA (92.6 mmol), OEGMA (10.3 mmol) and a crosslinker (OEGDA or MBA) were dissolved in 930 g of water. The crosslinker ratios are set either at 2.0% by mole or at 8.0% by mole depending on the total of the vinyl molecules, corresponding respectively to 2.12 mmol and 9.42 mmol. The mixture is introduced into the 2 L reactor and the stirring is set at 150 rpm. The reactor is purged with nitrogen for 45 min to remove oxygen at room temperature. MAA (5.41 mmol) is dissolved in 30 g of water and added to the reactor. The mixture is then heated to 70 ° C. Finally, KPS (0.958 mmol) is dissolved in 40 g of water and inserted into the reactor to start the reaction. The reaction is finally maintained at 70 ° C for 6 hours.

A first part of the aqueous suspension comprising MG and WSP is obtained and the films (F6, F6 ', F7 and F7') are formed.

A second part of the aqueous suspension is separated by 3 cycles of centrifugation (20,000 rev / m, 20 min), where WSP is maintained in the aqueous supernatant while MG is found in the precipitate. Films with WSP alone (F5 and F5 ') and films with MG alone (Fl and Fl') are formed as comparative films.

Films comprising a mixture of WSP and MG in a predetermined ratio are also prepared (F2, F2 ', F3, F3', F4 and F4 ').

Films were formed by the direct evaporation of water from solutions of microgels in a glass bell oven heated to 37 ° C. It has been shown that the formation temperature does not influence the properties of the film. We used silicone molds as containers for easy removal of films after drying. For rheological experiments, the final film thicknesses are between 500 microns and 1000 microns. All thicknesses less than and greater than these values are nevertheless technically feasible, for example as low as 500 nm.

B) Determination of the molar mass of water-soluble polymers by size exclusion chromatography

- Method: The steric exclusion chromatography (SEC) apparatus consists of a set of aqueous columns from Shodex and an Agilent 1260 Iso pump from Agilent technologies. The device is coupled with a Multi Angle Light Scattering (MALS) and a differential refractometer (RI) detector. The MALS detector used is a Dawn Heleos detector from WYATT Technology. The RI detector is an Optilab T-rEX from WYATT Technology operating at a laser wavelength of 664 nm. The flow rate is set during the experiment at 0.5 mL / min and the column temperature is set at 30 ° C. The mobile phase consists of a solution of NaNCh at 0.1 g / mole (8.2 g / L), and sodium azide NaN ₃ (0.1 mol / L) as eluent, stabilized with a buffer at pH 8. The mobile phase is filtered at 0.1 μm before use. The water-soluble polymer solutions are prepared at a concentration of 200 ppm in a buffer of pH 8, of which a volume of 100 µL is injected. The solutions are filtered before use at 250 nm to remove any impurities and possible microgels.

To interpret the SEC results, the value of the refractive index increment (dn / dc) is experimentally measured on an Optilab T-rEX refractometer from WYATT Technology with a laser wavelength of 532 nm. Five WSP solutions are prepared with Milli-Q water at different concentrations (0.97 gL ¹ ; 0.75 gL ¹ ; 0.51 gL ¹ and 0.11 gL ¹ ).

- Results: The size exclusion chromatography makes it possible to determine the molar mass of WSP from a synthesis of 2 mol% OEGDA and a synthesis of 2 mol% MBA. This technique has the advantage of measuring both molecular mass and radius of gyration. It thus provides more information about the structure of WSP. OEGDA-WSP and MBA-WSP are compared to a linear PEG with an average molecular weight of 35,000 g. mol ¹ . Molar mass and radius of gyration are related by Flory's theory.

With a SEC technique, the separation is made by size: larger objects will pass through the set of columns earlier (= in a lower elution volume) than smaller objects.

[0090] FIG. 1 represents the graph of conformity that is to say the radius of gyration as a function of the molecular mass for OEGDA-WSP, MBA-WSP and PEG 35K. Figure 2 summarizes the molecular weights and polydispersity index of OEGDA-WSP, MBA-WSP and PEG 35K. PEG 35K exhibits an average Mw at 34,000 g. mol ¹ which validates the reliability of the method used. As the polymer has a very narrow mass distribution, it is not possible to observe the change in the radius of gyration as a function of molecular weight. OEGDA-WSP and MBA-WSP share a similar population of molecular weights from 1 x 10 ⁴ to 1 x 10 ⁵ g. mol ¹ . These polymer chains have a radius of gyration of around 15-20 nm on average, which shows that they have a very dense structure. MBA-WSP has a significant and significant proportion of much higher molecular weights of ^{1 x 10 5} to 1 x 10 ⁶ g. mol ¹ , which does not appear in the chromatogram of OEGDA. These masses reach radii of gyration of up to 30 nm. The detection limit of the equipment corresponds to Rg equal to approximately 10 nm and explains the scattered value for the weakest rays. As mentioned, linear PEG 35K (black dots) has such a narrow mass distribution that it is not possible to adjust the radius of gyration by a power law. The black line drawn from Rg = 0.6 Mw was thus added to represent a theoretical linear polymer in a good solvent. Only MBA-WSP was adjusted by a power law since it is the population with the sharpest and largest variation. The value of the power law exponent was found to be a = 0.27, which is very close to the theoretical value for dendrimers. The last result confirms the initial hypothesis consisting in that the water-soluble polymer formed during the synthesis is for the two crosslinkers a hyperbranched polymer with a diameter of 30 to 60 nm. C) Soectromechanical characterization of films comprising microaels alone (comparative), water-soluble polymers alone (comparative) and films comprising microaels and WSP (invention)

Some films are formed from the aqueous suspension comprising MG and WSP which is obtained from the aqueous precipitation polymerization process, before any centrifugation step.

F6 - 2% by mole OEGDA: (32% by mass WSP - 68% by mass MG);

F7 - 8 mol% OEGDA: (22% by mass WSP - 78% by mass MG);

F6 '- 2% by mole MBA: (29% by mass WSP - 71% by mass MG);

F7 '- 8% by mole MBA: (20% by mass WSP - 80% by mass MG);

Other films are formed by mixing with a controlled ratio of a microgel (MG) and a water soluble polymer (WSP) which have been recovered from the precipitate and the supernatant, after the centrifugation step.

Fl - 2% by mole Comparative OEDGA (0% by mass WSP - 100% by mass MG);

Fl '- 2 mol% comparative MBA (0 mass% WSP - 100 mass% MG);

F2 - 2% by mole OEDGA (25% by mass WSP - 75% by mass MG);

F2 '- 2 mole% MBA (25 wt% WSP - 75 wt% MG);

F3 - 2% by mole OEDGA (50% by mass WSP - 50% by mass MG);

F3 '- 2 mole% MBA (50 wt% WSP - 50 wt% MG);

F4 - 2% by mole OEDGA (75% by mass WSP - 25% by mass MG);

F4 '- 2 mole% MBA (75 wt% WSP - 25 wt% MG);

F5 - 2% by mole Comparative OEDGA (100% by mass WSP - 0% by mass MG);

F5 '- 2% by mole Comparative MBA (100% by mass WSP - 0% by mass MG). 1. Spectromechanical characterization method

To study the mechanical properties, the films are characterized by linear oscillatory rheology and non-linear extensional rheology on an MCR 302 rheometer from Anton Paar.

Oscillatory rheology is carried out on films approximately 1 mm thick with parallel 8 mm plates at controlled temperature. Frequency sweeps are performed at 20 ° C from 0.01 to 600 rad / s at constant 1% elongation which ensures linear speed.

Extension rheology is performed using SER (Sentmanat Extension Rheometer) geometry which consists of paired winding drums moving in equal but opposite rotation. The tests are carried out at 20 ° C. The film dimensions are in the following range: 0.5-1mm x 1-2mm x 15-20mm. The thickness and the width are before the test respectively measured by optical microscopy and compass. Films are stretched to break with a constant elongation rate, also cited as the Hencky eH elongation rate. A minimum of fifty samples are tested for each type of film. The extensional viscosity hE is measured as a function of time. The logarithmic elongation in the sample, also cited as the Hencky elongation eH, is a function of e, of the constant rate of elongation; t, time; L is the sample length at time t and L0 is the initial sample length. In order to calculate the elongation at break cR, the constant elongation rate is multiplied by the time at break.

2. Spectromechanical characterization of comparative films fFl: 0% WSP and 100% MG)

The impact of the formation temperature was evaluated by forming films purified at 20 ° C, 32 ° C, 37 ° C and 60 ° C. In this field, the object was to evaluate whether the state of the microgels, that is to say collapsed or swollen, impacts the quality of the assembly during the formation of the film. Indeed, during the liquid-to-solid transition, one can imagine that the state of the microgel can play an important role, that is to say that the microgels inflated under the VPTT would create more intra-tangles than microgels collapsed above the VPTT. The extensional viscosity was measured at 20 ° C with a constant elongation rate of 0.5 s ¹ .

Figure 10 shows the average extensional viscosity for four different formation temperatures. It is clearly observed that the formation temperature does not impact the extensional viscosity or the elongation at break. It is not a parameter controlling the mechanical properties of films. If the microgels are under the VPTT (20 ° C), in the range (32 ° C, 37 ° C) or above (60 ° C), the elongation at break remains equal to 133 plus or minus 2 %. The microgel bark appears to retain some mobility at 60 ° C which allows the microgels to interpenetrate each other in their collapsed state. In addition, the microgel films, once formed, are maintained at 20 ° C and tested at 20 ° C. The chains thus have time to relax and reach a similar state of interpenetration regardless of the formation temperature.

3. Electromechanical characterization of films (F6 and F7)

The following four systems were studied: 2 mol% OEGDA, 2 mol% MBA; 8 mol% OEGDA and finally 8 mol% MBA. Figure 4 shows the ratio of water soluble polymer and microgels of the different films that were prepared.

3.1 Linear rheology: results

The dynamic rheological response is compared for the different films in FIG. 3. Frequency sweeps, with fixed elongation in the linear domain, were carried out at 20 ° C.

[0100] All the films generally behaved like viscoelastic solids since G 'is greater than G "at low frequency values. Films plateau at low frequency values, which is characteristic of chain entanglements in films. (elastic network) The transition to the vitreous region is observed in all cases by a point of intersection of G 'and G "at higher frequencies. The storage moduli of 2 mol% OEGDA and 2 mol% MBA are approximately 1 x 10 ⁵ Pa at 1 Hz (6 rad / s). The films thus have a very low tack. Indeed, the Dahlquist criterion quotes that G 'would be less than 1 x10 ⁵ Pa at 1 Hz for the material to exhibit rapid and measurable tack. [0101] The modulus of films of 8 mol% of MBA increases considerably compared to 2 mol% of crosslinking agent, respectively approximately 1.5 x 10 ⁶ Pa and 1 x 10 ⁵ Pa at 1 Hz (6 rad / s) . The increase in modulus of preservation, resulting from the higher crosslinker density, leads to a less flexible film, which does not exhibit any tacky property at all.

[0102] An 8 mol% OEGDA film surprisingly demonstrates moduli very similar to 2 mol% films. This particular behavior could be explained by a higher quantity of water in the film at the time of the test, due to the environment of uncontrolled hygrometry or to incomplete drying of the film.

3.2 Extensional rheology: results

Extension rheology consists of the elongation of materials in the non-linear domain of deformations, at a constant rate of elongation. Uniaxial extension can produce a much higher degree of molecular orientation and stretch than a simple tear. Therefore, extension rheology is more sensitive to polymer long chain branching and may be more descriptive than other types of bulk rheology tests. Extensional rheology makes it possible to establish a relationship with adhesive behavior.

The extensional viscosity of films of OEGDA and MBA for 2% by mole and 8% by mole of crosslinking agent was measured at 20 ° C. at a constant rate of elongation: 0.5 s ¹ . The logarithm of the mean elongation at break c _{R as} well as the LR / L ₀ ratio were calculated with the following formula: c _R = ext _R = In (LF / LO).

[0105] FIG. 5 (photograph on the right) shows the mean extensional viscosity as a function of time of MBA and OEGDA for the two levels of crosslinking agent. First, the extensional viscosity increases permanently following the linear viscoelastic envelope defined by the slope of 3 times the complex viscosity: 3.rf.

[0106] For elongation values greater than 40%, the extensional viscosity begins to deviate upwards from the shear viscosity. at zero speed. This upward deflection is referred to as elongation-cure and conventionally occurs in chemically crosslinked or physically well-entangled polymers. It is an indicative aspect of the branching chain architecture. The chain entanglements begin to resist extension whenever the chain extensibility limit is approached and cause the network to stiffen. Therefore, the extensional viscosity follows an upward deviation. The appearance of elongation-hardening was expected since the films contained 2 mole% and 8 mole% of crosslinker, respectively. Elongation-cure has been considered a desirable property for better adhesive performance. It fulfills the typical requirement for an adhesive that fails without leaving a sticky residue on the surface by providing cohesion to the network at high strain.

[0107] OEGDA and MBA films exhibit similar behavior in the linear region. The elongation at break is however significantly higher for MBA than OEGDA regardless of the crosslinker density, FIG. 5 (image on the left). This indicates that the MBA network resists higher stress before failure, although it does not differentiate the influence of water soluble polymer and microgels. The increased crosslink density leads to a lower elongation at break for both crosslinkers. Indeed, a more reticulated network cannot stretch as much to adapt to the stress, and break at a less advanced stage. More dense and more crosslinked particles also tend to interpenetrate less with each other, thus creating a weaker lattice.

4. Spectromechanical characterization of films (Fl to F5)

[0108] The formulation consisting in the formation of films with a controlled ratio of WSP and MG was carried out for films of 2 mol% MBA and 2 mol% OEGDA. The method of linear oscillatory rheology and linear extensional rheology is identical to that described above.

4.1 Linear rheology: results For the two crosslinking agents OEGDA and MBA, frequency scans at 20 ° C. were carried out on the five different formulated films, that is to say with an MG content of 0% by mass to 100% by mass. .

[0110] The dynamic rheology response is compared for the different MG contents for OEGDA and MBA in FIG. 6. It is first of all important to note that all the films, independently of the MG content, behaved like solids. viscoelastic since G 'is greater than G "at low frequency values. Regardless of MG content, all microgel films plateaued at low frequencies, indicating the presence of a polymer network. flow is not observed, even for films made of 100% WSP. This important result indicates crosslinking and / or branching in the water soluble polymer. Thus, WSP is not linear and does not break down. not flow like thermoplastic polymers (in the parameter scales explored in this work, frequency, temperature ...). The glass transition is observed in all films by an intersection of G 'and G "at high frequencies. For the two crosslinkers, the crossing does not vary significantly with the addition of WSP. The glass transition thus appears at approximately the same frequency regardless of the amount of WSP. This is not surprising since the glass temperature of a polymer is determined by its molecular structure. As observed in Figure 7, the storage and loss moduli (taken from the rubbery plateau at w = 0.01 rad.s ¹ ) increase significantly with increasing MG content. MG particles increase shear modulus, similar to fillers that consolidate a composite. In addition, tan d, the ratio of G "to G 'decreases for an increasing MG content which indicates that the dissipative response of the films is less and less pronounced. The possibility of deviation of the shear modulus towards higher values or lower by controlling the MG / WSP ratio is extremely valuable since it provides a simple lever to adjust the sticky or adhesive properties of films depending on the targeted application. For both systems, G 'is just about 1 x 10 ⁵ Pa at 1 Hz: 8.5 x 10 ⁴ Pa and 1.5 x 10 ⁵ Pa respectively for OEGDA-MG and MBA-MG. It is indicated that the films have a very fine tack at 20 ° C when they are completely purified. 4.2 Extensional rheology: results

The extensional viscosity was measured for films of 2 mol% OEGDA and MBA with a different MG content at 20 ° C. for the constant elongation rate: 0.5 s ¹ . FIG. 8 shows the mean extensional viscosity as a function of time of MBA and OEGDA for different MG contents.

[0112] For elongation values greater than 40%, the extensional viscosity begins to deviate upward from the zero speed shear viscosity for all formulations. As previously mentioned, this upward deflection is called elongation-hardening. The appearance of elongation-cure for 100% MG films is expected since the films contained 2 mole% crosslinker providing crosslinked spots to the network. More surprisingly, however, all films, including 100% WSP, exhibit elongation-cure. We can therefore assume that network stiffening is much more related by chemical crosslinking points than physical branching chain entanglements. As expected, the microgel content has a large impact on the extensional viscosity values. This is because microgels act as matrix stiffening fillers, and increase the G ’and G’ moduli. As a direct consequence, the higher moduli increase the extension viscosity value.

However, it follows that the microgel content has no impact on the elongation / hardening, nor the elongation at break. In the field of future applications, this result is extremely positive since it indicates that the proportion of water-soluble polymer can be modified to adjust the desired modulus according to the application but without losing in all cases the capacity of stretching of the film. As observed in Figure 9, the log elongation at break is significantly higher for MBA films than for those of OEGDA regardless of microgel content. This initially confirms that the MBA microgel network resists higher stress before breaking than OEGDA particles. This reinforces the supposition of a higher capacity of MBA to form a more solid network, this being surely due to a "looser bark" architecture for the latter than for OEGDA-MG. The second An important result of Fig. 9 is that the MBA films made from 100% WSP also exhibit a higher elongation at break than the OEGDA-WSP films. This corroborates the SEC results which show a more branched structure in the case of MBA-WSP.

D). Assembly of micro-gel films (Fl to F5)

[0114] Method: Topographic images were captured by AFM (Bruker Multi mode 8 apparatus) in order to analyze the assembly of microgels on the film surface. Peak Force QNM Air mode and ScanAsyst Air probes (mean spring constant k of 0.4 Nm ¹ ) were used for all scans. Clean cross sections of microgel films were also prepared to visualize the assembly within the film, with a Leica EM UC7 ultra cryo-microtome apparatus, using a Leica EM-FC7 cryo-chamber, cooled to -80 ° C. Finally, the films were manually subjected to unidirectional stretching and images were formed in the stretched state. The elongation corresponded to 30%.

Comparative results for Fl and Fl ^{1 films}

[0115] Atomic force microscopy was performed on the top surface of films made with 100% microgels (no water soluble polymer). The microgel particles self-assemble in a perfect close-to-hexagonal settlement as seen on the topographic contrast images in Figure 11 (image on the right) for 2 mol% OEGDA-crosslinked microgels and (image at left) for 2 mol% MBA-crosslinked microgels. Unlike a conventional latex, the particles do not coalesce but maintain their spherical shape with some interpenetration with each other. AFM topographic contrast images showed the slightly larger size of the MBA-crosslinked microgels.

The cross sections of films were surface treated by ultra cryomicrotomy and observed by AFM. The topographic contrast images in Figure 12 show the settlement of spherical particles with localized hexagonal settlement. In contrast to the deformation of particles having dropped and dried on a hard wafer, the several layers of MG stacking during the evaporation of the solvent has not flattened out and remains spherical. A contrast difference of about 15 nm between core and bark is observed for most microgels in both types of crosslinkers. Even after being formed, the microgel films contain and absorb water from their surroundings. As a result, it can be suggested that the bark, which is much more swollen, is loosely reticulated and the core, which is more hollow, is more reticulate than the bark.

Microgel films were stretched to obtain 30% elongation and their upper surfaces were observed by AFM. Figure 13 shows a 5mm topographic contrast image of OEGDA-crosslinked and MBA-crosslinked microgel films. The direction of stretching is parallel to the X axis. Stretching causes loss of hexagonal compact settlement and deformation of the particle network. Gaps appear between the microgels in the direction of deformation. However, it seems that the microgels are not significantly deformed and maintain their spherical shape. It is suggested that at this elongation most of the tangled chains of the microgel bark stretch to accommodate the stress and the dense core is not yet deformed.

Results of the assembly of WSP-MG films according to the invention F2 to F4 '

The cross sections of reformulated films were observed with a microgel content controlled by AFM. Figure 14 shows the 2 micron topographic contrast image (a) and logDMT modulus (b) of 2 mol% MBA-MG to 25 mass% MG films. The logDMT module channel has the steepest regions in lighter color and the softer regions in darker color. As you would expect, the microgels are much denser than the water soluble polymer and look like fillers dispersed in a flexible composite matrix. They do not form aggregates but are not perfectly dispersed homogeneously. Figure 14 shows the 2 micron topographic contrast image (c) and logDMT modulus (d) of 2 mol% MBA-MG to 50 mass% MG films. The microgels start to come into contact with each other but no structured arrangement is observed. In some areas, microgel depletion is observed. In figure 14 is presented the topographic contrast image of 500 nm (e) and logDMT modulus (f) of MBA-MG films for 75% by mass of MG. Similar conclusions can be expressed, the microgels are closer but no hexagonal packing arrangement is observed.

Once again, the core / shell structure is clearly observed with a clear modulus gradient between the core relative to the WSP matrix. The denser and less swollen hearts are characterized by hollows, the rinds are more swollen than the hearts but slightly denser than the water soluble polymer which is characterized by the lower modulus. A very gradual transition is observed between the microgel shell and the water soluble polymer, suggesting a similar structure as well as some interpenetration between the two phases.

E) Conclusion

Linear rheology on 2 mol% OEGDA and MBA-crosslinked microgel films demonstrates that the shear modulus value can vary and be adjusted via the water soluble polymer content, from 0% to 100%. As a result, it is possible to form a range of very tacky films up to films not exhibiting tackiness on any substrate by the simple evaporation of water. Microgel films exhibit interesting mechanical properties at high strain. The elongation at break is up to 60%, demonstrating that these films exhibit strong cohesion for a simple and spontaneous self-assembled particle network. In addition, the variation of the water-soluble polymer makes it possible to vary the rheological properties without modifying the stretch properties of the films. Indeed, all films, regardless of the microgel content, exhibit elongation-cure, which is known to be a valuable property for adhesives since it allows the cohesion of a film during peel. The latest finding suggests that a water soluble polymer is conspicuously branched and / or crosslinked since films completely composed of the latter also exhibit elongation-cure. The elongation at break of MBA-crosslinked films is significantly higher than OEGDA-crosslinked films for 2 mole% of crosslinker. This correlates with the results on suspension viscosities which show that MBA-crosslinked particles exhibit higher interaction and tend to create a more solid network. These stronger interactions, possibly due to the higher number of chains suspended on the surface, lead to a higher elongation at break when the film is formed since the microgels are more interpenetrated with each other. In addition, the elongation at break decreases for a higher crosslinker ratio similarly to the viscosity decreases for dispersions. More dense particles tend to have less interpenetration and to form a weaker network than looser crosslinked particles.

Claims

[Claim 1] Cosmetic composition, pharmaceutical composition, or medical device each comprising a water-soluble polymer and microgel particles, said microgel particles having an average size of 100 nm to 1000 nm in the dry state, characterized in that the microgel particles and the water-soluble polymer can be independently obtained by aqueous phase precipitation polymerization of at least the following three monomers, in the presence of a crosslinking agent:

- di (ethylene glycol) methyl ether methacrylate,

- an oligo (ethylene glycol) methyl ether methacrylate having a number-average molar mass of 400 g / mole to 600 g / mole,

- a vinyl monomer comprising a carboxyl group, where at least one of the two crosslinking agents is

N, N'-methylenebisacrylamide, and where the ratio of the mass of the water soluble polymer to the mass of the microgel particles in the dry state is between 0% and 100% by mass, where the medical device includes a mixture consisting of the polymer soluble in water, microgels and optionally water, and wherein the solid content of the cosmetic composition, the solid content of the pharmaceutical composition, and the solid content of said mixture is from 1.5% to 100% by mass.

[Claim 2] Cosmetic composition, pharmaceutical composition or medical device according to claim 1, characterized in that the composition or mixture contains from 50% to 100% by mass of a mixture consisting of particles of microgels and polymer soluble in the water, and from 0% to 50% by mass of water, the percentages being relative to the mass of the composition, and the mass of the microgel particles being the mass of the particles in the dry state.

[Claim 3] Cosmetic composition, pharmaceutical composition, or medical device according to claim 1 or 2, characterized in that the solid content of the cosmetic composition, the solid content of the pharmaceutical composition, and the solid content of said mixture are 50% at 100% by mass.

[Claim 4] A cosmetic composition, pharmaceutical composition, or medical device according to any preceding claim, being in the form of a film which has a thickness of 500 microns to 1000 microns.

[Claim 5] Cosmetic composition, pharmaceutical composition or medical device according to any one of the preceding claims, characterized in that the radius of gyration of the water-soluble polymer measured by size exclusion chromatography at 20 ° C is 5 nm to 80 nm.

[Claim 6] Cosmetic composition, pharmaceutical composition or medical device according to any one of the preceding claims, characterized in that the water-soluble polymer has an average molecular mass measured by size exclusion chromatography at 20 ° C of 1 x 10 ⁵ g. mol ¹ to 1 x 10 ⁶ g. mol ¹ .

[Claim 7] Cosmetic composition, pharmaceutical composition or medical device according to any one of the preceding claims, characterized in that the mole fraction of di (ethylene glycol) methyl ether methacrylate is 80 mole% to 90 mole%, the mole fraction of oligo (ethylene glycol) methyl ether methacrylate is 5 mole% to 15 mole%, the mole fraction of the vinyl monomer bearing a carboxyl group is 2 mole% to 8 mole%, and the mole fraction of the crosslinking agent is 0.5 to 10 mole%, the sum of the four mole fractions being equal to 100 mole%.

[Claim 8] Cosmetic composition, pharmaceutical composition or medical device according to any one of the preceding claims, characterized in that the ratio between the mass of the water soluble polymer and the mass of the microgel particles is between 0% and 35%.

[Claim 9] Cosmetic composition, pharmaceutical composition or medical device according to any one of claims 1 to 7, characterized in that the ratio between the mass of the water-soluble polymer and the mass of the microgel particles is between 35% and 100%.

[Claim 10] A method of cosmetic topical treatment of the skin, nails, lips, mucous membranes or hair of a person, said method comprising a first step of applying to the person a cosmetic composition according to l any of claims 1 to 9.

[Claim 11] A method of preparing a cosmetic composition, a pharmaceutical composition or a medical device according to any one of claims 1 to 9, said method comprising a step of preparing a mixture of microgel particles and a water-soluble polymer, said step comprising a first step and a second step which may be successive in any order, or simultaneous:

- said first step being a step of preparing microgel particles, and comprising a step (i) of polymerization by precipitation in aqueous phase of at least the following three monomers, in the presence of a first crosslinking agent: di (ethylene glycol) methyl ether methacrylate, an oligo (ethylene glycol) methyl ether methacrylate, a vinyl monomer bearing a carboxyl group, and a purification step (ii) to recover microgel particles which were obtained at the end of the step (i),

- said second step of preparing the water-soluble polymer, and comprising a step (a) of polymerization by precipitation in aqueous phase of at least the following three monomers, in the presence of a second crosslinking agent: di (ethylene glycol) methyl ether methacrylate, an oligo (ethylene glycol) methyl ether methacrylate, a vinyl monomer bearing a carboxyl group, and a purification step (b) to recover the water-soluble polymer which was obtained at the end of step (a), characterized in that at least the first or the second crosslinking agent is N, N'-methylenebisacrylamide,

a third step which follows the first step and said second step, said third step being a step of mixing a mass of purified microgel particles which are obtained at the end of said first step, and a mass of polymer soluble in the water which is obtained at the end of said second step,

- in which the ratio between the mass of the water-soluble polymer and the dry mass of the microgel particles is between 0% and 100%.

[Claim 12] A method according to claim 11, characterized in that step (ii) comprises at least one centrifugation / redispersion cycle to separate the precipitate and the supernatant, and a step of recovering the particles of microgels in the precipitate. .

[Claim 13] A method according to claim 11 or claim 12, characterized in that step (b) comprises at least one centrifugation / redispersion cycle to separate the precipitate and the supernatant, and a step of recovering the soluble polymer. in water in the supernatant.

[Claim 14] A method according to claim 11, 12 or 13, characterized in that the first step and the second step are a single step, so that particles of microgels and a water-soluble polymer are produced at the same time. from the same monomers, where the single step comprises at least one centrifugation / redispersion cycle to separate the precipitate and the supernatant which have been obtained from the aqueous phase precipitation polymerization of the monomers, said microgel particles being recovered in the precipitate, and said water soluble polymer being recovered in the supernatant.

[Claim 15] A method according to claim 14, characterized in that - in the single step - the ratio between the mass of the water soluble polymer in the supernatant, and the mass of the microgel particles in the precipitate is a first ratio and - in the third step - the ratio between the mass of the water soluble polymer and the mass of the microgel particles is a second ratio which is between 0% and 100% and which is different from the first ratio.

[Claim 16] A method according to claim 11, characterized in that the first crosslinking agent and the second crosslinking agent are N, N'-methylenebisacrylamide.