WO2003086342A1

WO2003086342A1 - Cosmetic, esp. anti-wrinkle compositions containing water-soluble or -dispersible lcst polymers

Info

Publication number: WO2003086342A1
Application number: PCT/IB2003/001308
Authority: WO
Inventors: Florence L'alloret
Original assignee: L'oreal
Priority date: 2002-04-12
Filing date: 2003-04-04
Publication date: 2003-10-23
Also published as: AU2003216593A1

Abstract

The invention relates to the use of water-soluble or water-dispersible polymers comprising water-soluble or water-dispersible units and units with an LCST, the said units with an LCST having in water a demixing temperature of from 5 to 40°C at a mass concentration of 1%, as a tensioning agent in a cosmetic composition, especially an anti-wrinkle composition, and to the manufacture of a dermatological composition for smoothing out wrinkles and/or fine lines on the skin.

Description

COSMETIC , ESP . ANTI-WRINKLE COMPOSITIONS CONTAINING WATER-SOLUBLE OR -DISPERSIBLE LCST POLYMERS

DESCRIPTION

TECHNICAL FIELD

The present invention relates to cosmetic compositions , and in particular anti-wrinkle compositions , comprising a tensioning agent .

PRIOR ART

In the course of the process of ageing of the skin, various signs appear that are ^'especially reflected by a change in the structure and function of the skin. One of these main signs is the appearance of fine lines and deep wrinkles, the size and number of which increase with age. The microrelief of the skin becomes less uniform and is of anisotropic nature.

It is common practice to treat these signs of ageing with cosmetic compositions containing active agents capable of combating ageing, such as α-hydroxy acids and retinoids. These active agents act especially on wrinkles by removing the dead cells from the skin and by accelerating the process of cell ageing. However, these active agents have the drawback of being effective in treating wrinkles only after application for a certain amount of time.

Compositions comprising agents for obtaining immediate smoothing of the skin have also been developed in the prior art. These agents are referred to more specifically by the term tensioning agents.

The term "tensioning agent" means compounds capable of having a tensioning effect, i.e. capable of making the skin taut and, by means of this tensioning effect, smoothing out the skin and causing the wrinkles and fine lines thereon to be reduced or even disappear immediately.

The tensioning agents used in the compositions of the prior art are generally agents of natural or synthetic origin.

Thus, patent application FR-A-2 758 083 [1] mentions the use of tensioning agents such as polymers of plant origin, for instance proteins extracted from maize, from rye, etc., polymers of animal origin, such as chitin and its derivatives, and egg proteins such as albumin. However, these agents have the drawback of resulting in tensioning agents that are mild and not particularly long-lasting. Moreover, the use of certain natural derivatives is not without risk to the consumer.

Patent application FR-A-2 758 084 [2] mentions the use of tensioning agents of synthetic origin introduced into anti-wrinkle compositions in the form of aqueous dispersions of synthetic polymers such as polyurethanes, polyureas, acrylic derivatives or sulphonated isophthalic acid polymers.

Patent application FR 2 791 257 [3] also describes the use of tensioning agents of synthetic origin such as grafted silicone polymers comprising a siloxane portion and a portion consisting of a non-silicone organic chain. The introduction of gelling agents into such compositions is necessary in order to obtain textures that are easy to apply. Such is the case for the examples of sera and creams in the said patent application citing the use of gelling agents such as the polyacrylamide/Cι₃-ι isoparaffin/Laureth-7 system. By way of example, the main aqueous gelling agents used in the care formulations are the following:

crosslinked polymeric gelling agents such as carboxylated derivatives (Carbopols sold by Goodrich) or sulphonated derivatives (Hostacerin AMPS sold by Clariant) ;

natural polymers such as xanthan and guar gums or cellulose derivatives, starches and alginates.

These gelling agents undergo a reduction in their viscosity on increasing the temperature. Thus, any composition that is fluid at 20 °C remains fluid at skin temperature (32°C), which does not lead to good application properties. Moreover, compositions that are gelled at skin temperature, which are easier to apply, must also be gelled at 20°C. The range of textures available for the prior-art compositions with a tensioning effect is thus limited.

Investigations have thus been conducted to find compounds that offer an immediate tensioning effect, without risk to the consumer, and which can broaden the range of textures available for compositions with a tensioning effect. It is also desired to obtain all these properties using a single compound so as to simplify the formulation of these compositions. DESCRIPTION OF THE INVENTION

As a result of these investigations, the Applicant has discovered, surprisingly, that certain water-soluble or water-dispersible polymers comprising water-soluble or water-dispersible units and units with an LCST ("Lower Critical Solution Temperature") have an immediate tensioning effect and furthermore allow access to various textures.

Thus, one subject of the present invention is the use of at least one water-soluble or water-dispersible polymer comprising water-soluble or water-dispersible units and units with an LCST, the said units with an LCST having in water a demixing temperature (or cloud point) from 5 to 40°C at a mass concentration of 1%, as a tensioning agent in a cosmetic composition.

More particularly, a subject of the invention is also the use of polymers of this type in an anti-wrinkle composition.-

A subject of the invention is also the use of at least one water-soluble or water-dispersible polymer comprising water-soluble or water-dispersible units and units with an LCST, the said units with an LCST having in water a demixing temperature from 5 to 40 °C at a mass concentration of 1%, for the manufacture of a dermatological composition for smoothing out wrinkles and/or fine lines on the skin by means of a tensioning effect. ^'

The demixing temperatures are determined by visible UV spectroscopy by measuring, at a wavelength equal to 500 nm, the absorbence of aqueous solutions comprising 1% by weight of the said units with an LCST. The demixing temperature is identified as the temperature at which the absorbence of the solution is equal to 2.

The polymers thus mentioned have the particular feature of having, preferably, a tensioning effect such that they can produce a retraction of stratum corneum of at least 0.5% at 30 °C under a relative humidity of 40%.

Water-soluble or water-dispersible polymers comprising water-soluble or water-dispersible units and units with an LCST have already been described in the following documents: D. HOURDET et al., Polymer, 1994, vol. 35, No. 12, pages 2624 to 2630 [4]; F. L'ALLORET et al., Coll. Polym. Sci., 1995, vol. 273, No. 12, pages 1163- 1173 [5]; F. L'ALLORET et al., Revue de 1' Institut Frangais du Petrole [Review of the French Petroleum Institute], 1997, vol. 52, No. 2, pages 117-128 [6]; EP-A-0 583 814 [7] and EP-A-0 629 649 [8].

Thus, as described in these documents, these water- soluble or water-dispersible polymers comprise water- soluble or water-dispersible units and units with an LCST which have in water a lower critical solution temperature. These units with an LCST are units whose solubility in water is modified above a certain temperature. They are units which have a heat-induced demixing temperature (or cloud point) that defines their region of solubility in water. The minimum demixing temperature obtained as a function of the polymer concentration is referred to as the "LCST" ("Lower Critical Solution Temperature") . For each polymer concentration, a heat-induced demixing temperature is observed; it is higher than the LCST, which is the minimum point on the curve. Below this temperature, the polymer is soluble in water; above this temperature, the polymer loses its solubility in water.

Furthermore, these polymers have gelling properties in water caused by an increase in temperature. These properties are observed above the demixing temperature of the units with an LCST and are due to the association of the units with an LCST within hydrophobic microdomains, thus forming crosslinking nodes between the main chains.

These properties may be exploited for applications in the petroleum field, as described in documents [7] and [8], especially for their anti-sedimentation properties on suspensions.

Document WO-A-95/24430 [9] describes copolymers comprising units with an LCST and pH-sensitive units, which also have temperature-induced gelling properties, for applications in the controlled release of active principles in the pharmaceutical field and in the cosmetics field. These polymers have a heat-induced demixing temperature (LCST) and produce opaque gels when the temperature increases. This differentiates them from the polymers of the present invention, which remain soluble in water irrespective of the temperature. Moreover, among the documents mentioned above, none of them mentions the use of polymers comprising units with an LCST as tensioning agents.

According to the invention, polymers with a gel point from 5 to 50 °C and preferably from 15 to 40 °C, for a mass concentration in water of 2%, are preferably used. This characteristic is particularly advantageous since it offers access to a broad range of textures for cosmetic compositions. These polymers have, as has been stated previously, gelling properties in aqueous phase stimulated by an increase in temperature. Thus, by means of the polymers according to the invention, it is possible to gain access to cosmetic compositions, and especially anti-wrinkle compositions, which have an immediate tensioning effect and a broad range of textures, which is not the case for the compositions of the prior art, which require, besides the standard tensioning agents, the addition of gelling agents.

The gelling properties of water-soluble or water- dispersible polymers comprising units with an LCST are observed when the concentration is sufficient to allow interactions between units with an LCST borne by different macromolecules . The minimum concentration required, known as the critical aggregation concentration or CAC, is evaluated by rheological measurements: it is the concentration at and above which the viscosity of an aqueous solution of the polymers becomes higher than the viscosity of an aqueous solution of the equivalent polymer not comprising_, units with an LCST.

Above the CAC, the polymers used in the context of the invention have gelling properties when the temperature becomes higher than a critical value, known as the gel point or T_geι. According to the literature data, there is good agreement between the gel point and the demixing temperature of the units with an LCST, under the same concentration conditions. The gel point of an aqueous solution of a polymer of the invention is determined by rheological measurements: it is the temperature at and above which the viscosity of the polymer solution becomes higher than the viscosity of a solution of the equivalent polymer not comprising units with an LCST.

The gel points are determined in the following manner. It is considered that the gel point has been reached when the difference between the viscosity of the polymer solution and the viscosity of a solution of the equivalent polymer not comprising units with an LCST is greater than 5%. The viscosity of the composition is measured using a Haake RS150 rheometer equipped with a 3.5 cm/2° or 6 cm/2° cone/plate geometry and a temperature control system. The viscosity measurements are performed in the flow mode by imposing a shear rate equal to 10^"1 s^-1.

Polymer networks that may be stimulated to reversible gelation comprising a sensitive component capable of aggregating in response to a change in an • external stimulus and a structural component have been described in US-A-5 939 485 [10] and WO 97/00275 [11] . The external stimulus may be the temperature. The sensitive component may be a block copolymer such as a Poloxamer, for example a Pluronic®, which undergoes microscopic aggregation above a critical temperature not corresponding to an LCST. A nonionic surfactant may also be used as sensitive component. These polymer networks have heat-induced gelling properties that are used in the pharmaceutical field for delivering medicinal products and in many other fields, including the cosmetics field. The polymer networks described in reference [10] are different from the polymers of the present invention since they consist of two oligo eric or polymeric compounds not linked via covalent bonds. These gelling systems correspond to interpenetrating polymer networks, also known as IPNs.

Moreover, in these formulations, the sensitive component of the polymer system behaves differently to that of units with an LCST on heating. Thus, when the said component is heated to about 30-40 °C, it has a micellization temperature, i.e. a temperature at which microscopic aggregation takes place, and when it is heated further, it then has a higher LCST temperature. This LCST corresponds to a macroscopic aggregation between the macromolecules . It is explained in WO-A-97/00275 [11] on pages 16 and 17 that the gelation and the LCST are observed at temperatures that differ by about 70 °C. This shows that these polymer networks are different from the polymers of the present invention.

Cosmetic compositions using a polymer system which undergoes reversible heat-induced gelation, comprising polyacrylic acid and a poloxamer, are also disclosed in document WO-A-98/48768 [12] . This polymer system is thus different from the polymers of the invention.

The polymer networks which undergo reversible gelation described in documents [10], [11] and [12] are different from the polymers used in the invention. Firstly, the temperature-sensitive units do not have a demixing temperature in the range from 5 to 40 °C. Secondly, in contrast with the polymers used in the invention, in which the demixing temperature of the chains with an LCST corresponds substantially to the gel point under the same concentration conditions, the heat-sensitive units of these polymer networks have a demixing temperature that is very remote from the gel point.

Furthermore, it is not envisaged in any of the said documents to use these polymer networks to obtain a tensioning effect in cosmetic compositions.

The polymers used in the context of the invention may be in the form of block polymers comprising water- soluble or water-dispersible units alternating with units with an LCST, or in the form of grafted polymers consisting of an optionally crosslinked skeleton formed from water-soluble or water-dispersible units and bearing grafts consisting of units with an LCST, or vice-versa.

The water-soluble or water-dispersible units of these polymers according to the invention are preferably units that are soluble in water, from 5°C to 80°C, to a proportion of at least 10 g/L and preferably of at least 20 g/L.

However, it is also possible to use, as water-soluble or water-dispersible units, units not necessarily having the solubility mentioned above, but which, in aqueous solution at 1% by weight, from 5°C- to 80°C, allow the production of a macroscopically homogeneous and transparent solution, i.e. a solution having a maximum light transmittance value, irrespective of the wavelength of between 400 and 800 nm, through a sample 1 cm thick, of at least 85% and preferably of at least 90%. These water-soluble or water-dispersible units do not have a heat-induced demixing temperature of LCST type.

These water-soluble or water-dispersible units may be obtained by free-radical polymerization of vinyl monomers, or by polycondensation, or alternatively may consist of existing natural polymers or modified natural polymers.

Examples that may be mentioned include the following water-soluble monomers and the salts thereof, which are capable of being used to form, partially or totally, by polymerization the said water-soluble or water- dispersible units, alone or as a mixture:

(meth) acrylic acid;

- vinylsulphonic acid;

(meth) allylsulphonic acid;

- vinylphosphonic acid;

- methylvinylimidazolium chloride;

(meth) acrylamide;

- 2-vinylpyridine or 4-vinylpyridine;

- maleic acid and anhydride;

- crotonic acid;

- itaconic acid;

- vinyl alcohol of formula CH=CHOH;

- N-vinyllactams comprising a cyclic alkyl group of 4 to 9 carbon atoms, such as N-vinylpyrrolidone, N-vinylcaprolactam and N-butyrolactam;

- water-soluble styrene derivatives, especially styrene sulphonate;

- dimethyldiallylammonium chloride; - N-vinylacetamide and N-methyl-N-vinylacetamide;

- N-vinylformamide and N-methyl-N-vinylformamide;

- the vinyl monomers of formula (I) below:

H₂C=C _(|) _?0 X

in which:

- R is chosen from H, -CH₃, -C₂H₅ or -C₃H₇, and

- X is chosen from:

- alkyl oxides of -OR' type in which R' is a linear or branched, saturated or unsaturated hydrocarbon-based radical containing from 1 to 6 carbon atoms, substituted with at least one group chosen from halogen atoms (iodine, bromine, chlorine or fluorine) ; a sulphonic (-S0₃ ^") , sulphate (~S0₄ ^~) , phosphate (-P0₄H₂ ^~) ; hydroxyl (-0H) ; ether (-0-) ; primary amine (-NH₂) ; secondary amine (-NHRi) , tertiary amine (-NR_XR₂) or quaternary amine (~N⁺RιRR₃) group with Ri, R₂ and R₃ being, independently of each other, a linear or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, with the proviso that the sum of the carbon atoms of R' + Ri + R₂ + R₃ does not exceed 7; and

- -NH₂, -NHR₄ and -NR₄R₅ groups in which R₄ and R₅ are, independently of each other, linear or branched, saturated or unsaturated hydrocarbon-based radicals containing 1 to 6 carbon atoms, with the proviso that the total number of carbon atoms of R₄ + R₅ does not exceed 7, the said R₄ and R₅ being substituted with at least one group chosen from halogen atoms (iodine, bromine, chlorine or fluorine) ; a hydroxyl (-OH) ; ether (-0-) ; sulphonic (-S0₃ ^~) ; sulphate (-S0₄ ^~) ; phosphate (-P0₄H₂ ^~) ; primary amine (-NH₂) ; secondary amine (-NHRi) , tertiary amine (-NRιR₂) and/or quaternary amine (- N⁺RχR₂R₃) group with Ri, R₂ and R₃ being, independently of each other, a linear or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, with the proviso that the sum of the carbon atoms of R₄ + R5 + Ri + R + R₃ does not exceed 7.

Examples of water-soluble monomers of formula (I) that may be mentioned include glycidyl (meth) acrylate, hydroxyethyl methacrylate, ethylene glycol

(meth) acrylate, diethylene glycol or polyalkylene glycol (meth) acrylate, N,N-dimethylacrylamide, acrylamido-2-methylpropanesulphonic acid (AMPS) ,

(meth) acrylamidopropyltrimethylammonium chloride (APTAC and MAPTAC) and quaternized dimethylaminoethyl

(DAMEMA) .

Among the monomers that may be used to constitute, partly or totally, the water-soluble or water- dispersible units by polymerization, mention may also be made of hydrophobic monomers, the said monomers being copolymerized with at least one water-soluble monomer in an amount such that the resulting units are water-soluble or water-dispersible, the said hydrophobic monomers being chosen from the following monomers :

- styrene and its derivatives such as 4-butylstyrene, α-methylstyrene and vinyltoluene;

- vinyl acetate of formula CH₂= -H-0C0CH₃; - vinyl ethers of formula CH₂=CHOR6, in which R₆ is a linear or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms;

- acrylonitrile;

- caprolactone;

- vinyl chloride and vinylidene chloride;

- silicone derivatives such as methacryloxypropyl- tris (trimethylsiloxy) silane and silicone-based methacrylamides ;

- the hydrophobic vinyl monomers of formula (II) below:

H₂C =CR₇

in which:

- R is chosen from H, -CH₃, -C₂H₅ and C₃H₇,

- Xi is chosen from:

- alkyl oxides of the type -OR₈ in which R₈ is a linear or branched, saturated or unsaturated hydrόcarbon-based radical containing 1 to 22 carbon atoms;

- groups NH₂, -NHRg and -NR₉R₁0 in which R₉ and Rio are, independently of each other, linear or branched, saturated or unsaturated hydrocarbon-based .radicals containing 1 to 22 carbon atoms, with the proviso that the total number of carbon atoms in R₉ + Rio does not exceed 22. Examples of such monomers that may be mentioned include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, cyclohexyl acrylate, isobornyl acrylate and 2-ethylhexyl acrylate.

The water-soluble or water-dispersible units may be neutralized, where appropriate, partially or totally, with a mineral or organic base chosen from sodium, ammonium, lithium, calcium and magnesium salts, salts of ammonium substituted with 1 to 4 alkyl groups bearing from 1 to 15 carbon atoms, or alternatively from monoethanolamine, diethanolamine, triethanolamine, aminoethylpropanediol, N-methylglucamine, basic amino acids such as arginine and lysine, and mixtures thereof.

It may also be noted that the skeleton of the grafted polymers may be crosslinked by the action of at least one crosslinking agent chosen from the compounds containing olefinic polyunsaturation commonly used for crosslinking polymers obtained by free-radical polymerization. Examples of such agents that may be mentioned include divinylbenzene, diallyl ether, dipropylene glycol diallyl ether, polyglycol diallyl ethers, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetrallyl-oxethanoyl, polyfunctional alcohol allyl or vinyl ether derivatives, tetraethylene glycol diacrylate, triallylamine, trimethylolpropane diallyl ether, tetraallyloxyethane, methylenebis- acrylamide, allyl ethers of alcohols of the sugar series, allyl methacrylate and trimethylolpropane triacrylate (TMPTA) , and mixtures thereof.

A non-crosslinked grafted polymer skeleton is preferably used. Among the polycondensates and the natural polymers or modified natural polymers capable of constituting, partially or totally, the water-soluble or water- dispersible units, mention may be made of:

- water-soluble polyurethanes,

- xanthan gum, especially the products sold under the names Keltrol T and Keltrol SF by Kelco, or Rhodigel SM and Rhodigel 200 from Rhodia;

- alginates (Kelcosol from Monsanto) and derivatives thereof such as propylene glycol alginate (Kelcoloid LVF from Kelco) ;

- cellulose derivatives and especially carboxymethylcellulose (Aquasorb A500 from Hercules) , hydroxy- propylcellulose, hydroxyethylcellulose and quaternized hydroxyethylcellulose;

- galactomannans and derivatives thereof, such as konjac gum, guar gum, hydroxypropyl guar, hydroxypropyl guar modified with sodium methylcarboxylate groups (Jaguar XC97-1 from Rhodia) and guar hydroxypropyl- trimethylammonium chloride; and

- polyethyleneimine.

The water-soluble or water-dispersible units preferably have a molar mass from 1000 g/mol to 10 000 000 g/mol when they constitute the water-soluble skeleton of a grafted polymer.

These water-soluble or water-dispersible units preferably have a molar mass from 500 g/mol to 500 000 g/mol when they constitute a block of a multiblock polymer or when they constitute the grafts of a grafted polymer. The units with an LCST in the polymers used in the invention may be defined as units whose water solubility is modified beyond a certain temperature. They are units with a heat-induced demixing temperature (or cloud point) defining their region of solubility in water. The minimum demixing temperature obtained as a function of the polymer concentration is referred to as the "LCST" (Lower Critical Solution Temperature) . For each polymer concentration, a heat-induced demixing temperature is observed; it is higher than the LCST, which is the minimum point of the curve. Below this temperature, the polymer is soluble in water; above this temperature, the polymer loses its solubility in water.

The expression "soluble in water at a temperature T" means that the units have a solubility at T of at least 1 g/1 and preferably of at least 2 g/1.

The measurement of the LCST may be performed visually: the temperature at which the cloud point of the aqueous solution appears is determined visually, since, at this temperature, opacification of the solution, or loss of transparency, takes place.

In general, a transparent composition will have a maximum light transmittance value, irrespective of the wavelength of between 400 and 800 nm, through a sample 1 cm thick, of at least 85% and preferably of at least 90%.

The transmittance may be measured by placing a sample 1 cm thick in the light beam of a spectrophotometer working at the wavelengths of the light spectrum. The units with an LCST in the polymers used in the invention may consist of one or more of the following polymers :

- polyethers such as polyethylene oxide (PEO) , polypropylene oxide (PPO) and random copolymers of ethylene oxide (EO) and of propylene oxide (PO) ,

- polyvinyl methyl ethers,

- polymeric and copolymeric N-substituted acrylamide derivatives with an LCST,

- polyvinylcaprolactam and vinylcaprolactam copolymers.

Preferably, the units with an LCST consist of random copolymers of ethylene oxide (EO) and of propylene oxide (PO) , represented by the formula:

(EO)_m(PO)_n

in which m is an integer ranging from 1 to 40 and preferably from 2 to 20, and n is an integer ranging from 10 to 60 and preferably from 20 to 50.

The molar mass of these units with an LCST is preferably from 500 to 5300 g/mol and preferentially from 1500 to 4000 g/mol.

It has been found that the random distribution of the EO and PO units is reflected by the existence of a lower critical solution temperature, above which a macroscopic phase separation is observed. This behaviour is different from that of the block EO PO copolymers, which undergo micellization above a critical temperature known as the micellization temperature (microscopic aggregation) . The units with an LCST may thus especially be in the form of amino, especially monoa ino, diamino or triamino, random copolymers of ethylene oxide and of propylene oxide. Among the commercially available units with an LCST that may be mentioned are the copolymers sold under the name Jeffamine by Huntsman, and especially Jeffamine XTJ-507 (M-2005) , Jeffamine D-2000 and Jeffamine XTJ-509 (or T-3000) .

The units with an LCST may also be in the form of random EO/PO copolymers containing OH end groups, such as those sold under the name Polyglycols P41 and Bll by Clariant .

Advantageously, it is possible according to the invention to use polymers containing units with an LCST, such as polymeric and copolymeric N-substituted acrylamide derivatives with an LCST and also poly-N- vinylcaprolactam and vinylcaprolactam copolymers.

Examples of N-substituted acrylamide derivatives that may be mentioned include poly-N-isopropylacrylamide, poly-N-ethylacrylamide and copolymers of N-isopropyl- acrylamide or of N-ethylacrylamide and of a vinyl monomer corresponding to formula (I) or (II) given above or of a monomer chosen from (meth) acrylic acid, vinylsulphonic acid, (meth) allylsulphonic acid, maleic acid and anhydride, vinylphosphonic acid, crotonic acid, itaconic acid, (meth) acrylamide, vinylpyridine, vinyl alcohol, N-vinyllactams such as N-vinylpyrrolidone, styrene and its derivatives, dimethyldiallylammonium chloride, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methyl- vinylformamide, vinyl ethers and vinyl acetate derivatives, acrylonitrile, caprolactone, vinyl chloride and vinylidene chloride.

The molar mass of the polymeric or copolymeric N- substituted acrylamide derivatives is preferably from 1000 g/mol to 500 000 g/mol.

These polymers may be synthesized by free-radical polymerization using a pair of initiators such as aminoethanethiol hydrochloride in the presence of potassium persulphate, so as to obtain oligomers with an amino reactive end group.

Examples of N-vinylcaprolactam copolymers that may be mentioned include copolymers of N-vinylcaprolactam and of a vinyl monomer corresponding to formula (I) or (II) given above, or of a monomer chosen from (meth) acrylic acid, vinylsulphonic acid, (meth) allylsulphonic acid, maleic acid, maleic anhydride, vinylphosphonic acid, crotonic acid, itaconic acid, (meth) acrylamide, vinyl- pyridine, vinyl alcohol, N-vinyllactams such as N-vinylpyrrolidone, styrene and its derivatives, dimethyldiallylammonium chloride, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methyl- vinylformamide, vinyl acetate, vinyl ethers, acrylonitrile, caprolactone, vinyl chloride and vinylidene chloride.

The molar mass of these polymers is preferably from 1000 g/mol to 500 000 g/mol.

These polymers may be synthesized by free-radical polymerization using a pair of initiators such as aminoethanethiol hydrochloride in the presence of azobisisobutyronitrile, so as to obtain oligomers with an amino reactive end group.

The mass proportion of units with an LCST in the final polymer is preferably from 5% to 70%, especially from 20% to 65% and particularly from 30% to 60% by weight relative to the final polymer.

As defined above, the heat-induced demixing temperature of the units with an LCST is from 5 to 40 °C and preferably from 10 to 35 °C for a mass concentration of the units with an LCST in water of 1%.

The polymers used in the context of this invention may be readily prepared by a person skilled in the art by various methods, such as grafting, copolymerization, coupling or living polymerization processes.

For example, when the final polymer is in the form of a grafted polymer especially having a water-soluble skeleton with side units with an LCST, it is possible to prepare it by grafting the units with an LCST containing at least one reactive end group, for example an amino group, onto a water-soluble polymer forming the skeleton, the said skeleton bearing at least 10 mol% of reactive groups such as carboxylic acid functions. This reaction may be performed in the presence of a carbodiimide such as dicyclohexylcarbo- diimide or 1- (3-dimethylaminopropyl) -3-ethylcarbo- diimide hydrochloride, in a solvent such as N-methyl- pyrrolidone or water.

Another possibility for preparing grafted polymers consists in copolymerizing, for example, a macromonomer with an LCST (unit described previously with an unsaturated end group) and a water-soluble vinyl monomer such as acrylic acid or vinyl monomers having the formula (I) mentioned above.

When the final polymer is in the form of a block polymer, it may be prepared by coupling between water- soluble or water-dispersible units and units with an LCST having complementary reactive sites at each end.

It is also possible to prepare such polymers by living polymerization of anionic or cationic type, or by controlled free-radical polymerization. The latter synthetic process may be performed by various methods, for instance the atom-transfer method (Atom Transfer Radical Polymerization or ATRP) , the method with free radicals such as nitroxides, or via the method by reversible chain transfer with addition-fragmentation (Radical Addition-Fragmentation Chain Transfer) such as the MADIX process (Macromolecular Design via the Interchange of Xanthate) . These processes may be used to obtain the water-soluble blocks and the blocks with an LCST of the polymers used in the context of the invention. They may also be used to synthesize only one of the two types of polymer block used according to the invention, the other block being introduced into the final polymer via the initiator used, or alternatively by coupling reaction between the water-soluble blocks and the blocks with an LCST.

According to the invention, the polymers described above are used in cosmetic compositions, which will find applications in the field of care, makeup and antisun products. Generally, the compositions comprise an aqueous phase containing the polymer having a tensioning effect at a suitable mass concentration. The mass concentration of polymer in the composition is preferably from 0.01% to 20% and better still from 0.1% to 15%.

The compositions also generally comprise an oily phase, the said phase comprising, for example, constituents chosen from oils of alkane, ester, triglyceride and ether type, which contain silicone and fluorine, and optionally lipophilic gelling agents, surfactants, waxes, organic or mineral particles and/or organic or mineral lipophilic or lipodispersible sunscreens. The polymer having a tensioning effect according to the invention may also be dispersed in the oily phase.

These compositions may also comprise one or more adjuvants that are common in cosmetics, such as glycols, for instance dipropylene glycol, glycerol, surfactants, organic and mineral water-soluble ϋV- screening agents, active agents, salts, fillers, organic, particles, hydrophilic polymers such as carboxyvinyl polymers (carbomers) , polymers derived from 2-acrylamido-2-methylpropanesulphonic acid, synthetic neutral polymers such as poly-N-vinyl- pyrrolidone, polysaccharides, for instance guar gum, xanthan gum and cellulose derivatives, water-soluble or water-dispersible silicone derivatives, for instance acrylic silicones, polyether silicones and cationic silicones .

The active agents may be chosen especially from vitamins, for example A, C, K or PP, alone or as a mixture, keratolytic and/or desquamating agents such as salicylic acid and its derivatives, α-hydroxy acids, anti-inflammatory agents, calmants, depigmenting agents, matting agents, agents for preventing hair loss and/or agents for promoting hair regrowth, and anti- wrinkle agents, and mixtures thereof.

The compositions using polymers as described above may also comprise, if necessary, an additional gelling agent chosen from crosslinked polymers such as carbopols and 2-acrylamido-2-methylpropanesulphonic acid derivatives, and natural polymers such as xanthan, and mixtures thereof.

The compositions using polymers according to the invention may also comprise additional tensioning agents .

Examples of conventional tensioning agents that may be mentioned include synthetic polymers, polymers of natural origin, plant proteins and plant protein hydrolysates; mixed silicates; colloidal particles and microgels .

The synthetic polymers may be chosen especially from polyurethane polymers and copolymers, acrylic polymers and copolymers, sulphonated isophthalic acid polymers and grafted silicone polymers.

Examples of grafted silicone polymers are given in patent application EP-1 038 519 [13] , which is incorporated herein by reference. A preferred example of a grafted silicone polymer is polysilicone-8 (CTFA name) , which is a polydimethylsiloxane onto which are grafted, via a connecting chain of thiopropylene type, mixed polymer units of the poly (meth) acrylic acid type and of the polyalkyl (meth) acrylate type. A polymer of this type is especially available under the trade name VS 80 (at 10% in water) or LO 21 (in pulverulent form) from the company 3M. It is a copolymer of polydimethyl- siloxane containing propylthio groups, of methyl acrylate, of methyl methacrylate and of methacrylic acid.

Polymers of natural origin that may be mentioned include polyholosides, for example in starch form. This may especially be starch of natural origin, obtained from rice, from maize, from potato, from cassava, from pea, from Triticum aestivum wheat, from oat, etc. The polymer of natural origin may also be chosen from latices consisting of shellac resin, sandarac gum, dammar resins, elemi gums, copal resins and cellulose derivatives, and mixtures thereof.

Examples of plant proteins that may be used as additional tensioning agents consist of proteins extracted from maize, from rye, from Triticum aestivum wheat, from buckwheat, from sesame, from spelt, from pea, from bean, from lentil, from soybean and from lupin.

Another category of additional tensioning agents that may be used according to the invention consists of mixed silicates. This expression means any silicate of natural or synthetic origin containing several types of cations chosen from alkali metals (for example Na, Li or K) or alkaline-earth metals (for example Be, Mg or Ca) and transition metals.

Phyllosilicates are preferably used, i.e. silicates having a structure in which the Si0₄ tetrahedra are organized into leaflets between which the metal cations are enclosed.

One family of silicates that is particularly preferred as additional tensioning agents is the laponite family. Laponites are magnesium lithium sodium silicates with a layer structure similar to that of montmorillonites. Laponite is the synthetic form of the natural mineral known as "hectorite". The synthetic origin of this family of silicates has a considerable advantage over the natural form since it affords good control of the composition of the product. It is possible to use, for example, the laponite sold under the name Laponite XLS or Laponite XLG by the company Rockwood.

Another category of tensioning agents that may be used in the present invention consists of colloidal particles. The term "colloidal particles" means particles with a mean number-average diameter of between 0.1 and 100 nm and preferably between 3 and 30 nm.

They may be colloidal particles of mineral fillers or waxes .

Examples of mineral fillers comprise: silica, cerium oxide, zirconium oxide, alumina, calcium carbonate, barium sulphate, calcium sulphate, zinc oxide and titanium dioxide, in the form of particles with a diameter ranging from 0.1 to 100 nm and preferably from 3 to 30 nm. A mineral filler that is particularly preferred is silica. Colloidal silica particles are especially available in the form of an aqueous dispersion from the company Catalysts & Chemicals under the trade names Cosmo S-40 and Cosmo S-50. The microgels that may be used as other additional tensioning agents in the present invention have gel particle sizes of less than one micron. They may be particles of wax or of polyholoside . Thus, it is possible to use wax microparticles with a diameter generally less than 5 μm and consisting essentially of a wax or a mixture of waxes chosen, for example, from carnauba wax, candelilla wax or esparto wax. The melting point of the wax or of the mixture of waxes is preferably between 50°C and 150°C.

Finally, the colloidal polyholoside particles generally have a size of between 0.5 and 100 μm and may consist of carrageenans, alginates, agars, gellans, cellulose polymers or pectins.

As regards the formulations, the compositions may be in various forms, such as a lotion, a serum or a cream.

Another subject of the present invention is a cosmetic process for treating wrinkled skin, which consists in applying to the said skin, for example, around the contour of the eyes, a composition comprising an aqueous phase, and at least one polymer comprising water-soluble or water-dispersible units and units with an LCST, the said units with an LCST having in water a demixing temperature from 5 to 40 °C at a mass concentration of 1%, and the polymer having a gel point from 5 to 40°C for a mass concentration of 2%. The application is made according to the usual techniques, for example by applying creams, gels, sera, lotions, etc. to the skin intended to be 'treated. In the context of this process, the composition may be, for example, a care composition, a makeup composition or an antisun product.

Other characteristics and advantages of the invention will emerge more clearly on reading the examples which follow, which are given as non-limiting illustrations.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Various formulations were prepared, incorporating polymers as defined above, and tested so as to demonstrate the tensioning effect induced by the use of such polymers.

The evaluation of the tensioning effect is performed using a dermometer.

The measurement by dermometer is made on a device as described in the publication by L. Rasseneur et al. in the article entitled "Influence des differents constituants de la couche cornee sur la mesure de son elasticity [Influence of various constituents of the horny layer on the measurement of its elasticity] ", International Journal of Cosmetic Science, 4, 247-260, 1982 [14].

The principle of the method consists in measuring the length of a sample of stratum corneum isolated from human skin obtained from a surgical operation, before and after treatment with the test compositions. To do this, a sample is placed between the two jaws of the device, one of which is fixed and the other is mobile, in an atmosphere at 30°C and 40% relative humidity. A tensile force is exerted on the sample and the curve of the force as a function of the length is measured, the zero length corresponding to the contact between the two jaws of the device.

The tangent to the curve in its linear part is then plotted. The intersection of this tangent with the x-axis corresponds to the apparent length Lo of the sample at zero force.

The sample is placed at rest; 2 mg/cm² of the test composition, for which the mass content of polymer is greater than 1%, are then applied thereto. After drying for 15 minutes, the above steps are again performed to determine the length Li of the sample after treatment.

The percentage of retraction is defined by:

% retraction = 100 x (Lι~L₀) /L₀

A tensioning effect is obtained when this percentage is negative; the tensioning effect is proportionately greater the larger the absolute value of the percentage of retraction.

Example .1 : Anti-wrinkle lotion

This lotion has the composition below:

Sodium polyacrylate 450 000 g/mol bearing Jeffamine M-2005 grafts (random copolymer of ethylene oxide (6) and of propylene oxide (39) ) ; molar degree of grafting = 2% 7 g

Glycerol 1 g

Preserving agents 0.2 g

Demineralized water 91.8 g The demixing temperature at 1% in water of the units with an LCST Jeffamine M-2005 is 25°C.

The results obtained relative to this composition are as follows:

Tensioning effect Retraction power on stratum corneum = -0.9% + 0.3%

Gelling power Viscosity at 20°C (10 s^"1) = 0.03 Pa.s Viscosity at 35°C (10 s^"1) = 1 Pa.s

Gel point for a mass concentration of polymer in water equal to 2%: 33°C.

This composition has a tensioning effect; it is fluid at 20 °C and gels on application to the skin. This type of texture is novel and improves the application properties .

Example 2 : Anti-wrinkle serum

This serum has the composition below:

Sodium polyacrylate 550 000 g/mol bearing poly-N-iso- propylacrylamide (pNIPAM) grafts (10 000 g/mol) ; molar degree of grafting = 0.9% 1.75 g

Glycerol 1 g

Preserving agents 0.2 g

Demineralized water 96.85 g

The demixing- temperature at 1% in water of the units with an LCST (pNIPAM) is 33°C. The results obtained relative to this composition are as follows:

Tensioning effect Retraction power on stratum corneum = -0.9% '± 0.2%

Gelling power Viscosity at 20°C (10 s^"1) = 0.7 Pa.s Viscosity at 35°C (10 s^"1) = 1.8 Pa.s

- Gel point for a mass concentration of polymer in water equal to 2%: 27 °C.

This composition has a tensioning effect; it is slightly thickened at 20 °C, and its viscosity increases on application to the skin. The texture obtained is novel and pleasant.

Example 3 : Anti-wrinkle lotion

This lotion has the composition below:

Sodium polyacrylate 750 000 g/mol bearing Jeffamine M-2005 grafts (random copolymer of ethylene oxide (6) and of propylene oxide (39) ) ; molar degree of grafting = 3.1% 1.75 g

Glycerol 1 g

Fillers 0.2 g

Preserving agents 0.2 g

Demineralized water 96.85 g

The demixing temperature at 1% in water of the units with an LCST Jeffamine M-2005 is 25°C.

The results obtained relating to this composition are as follows: Tensioning effect Retraction power on stratum corneum = -1.1% ± 0.3%

Gelling power Viscosity at 20°C (10 s^"1) - 1.4 Pa.s Viscosity at 35°C (10 s^"1) = 3.5 Pa.s

Gel point for a mass concentration of polymer in water equal to 2%: 15°C.

This composition may be used as an anti-wrinkle lotion since it has a tensioning effect. It is thickened at 20°C, and its viscosity increases on application to the skin. The heat-induced gelling properties improve the stability of the formulation at 45°C.

Example 4 : Anti-wrinkle cream

This cream has the composition below:

Aqueous phase:

Sodium polyacrylate 750 000 g/mol bearing Jeffamine M-2005 grafts (random copolymer of ethylene oxide (6) and of propylene oxide (39) ) ; molar degree of grafting = 3.1% 2 g

Glycerol 1.5 g

Preserving agent 0.2 g

Carbopol 980 0.1 g

Neutralizer 0.05 g

Demineralized water 81.15 g

Demixing temperature at 1% in water of the units with an LCST Jeffamine M-2005 is 25°C. Gel point for a mass concentration of polymer in water equal to 2%: 15°C.

Oily phase:

Parleam oil 9 g

Cyclohexadimethylsiloxane 6 g

The aqueous phase is prepared by dissolving the polymer of the invention in 60 g of demineralized water containing the preserving agent and glycerol, with stirring for 2 hours. The carbopol 980 is hydrated with stirring in 21 grams of demineralized water and is then neutralized; it is then introduced into the aqueous solution comprising the polymer of the invention. The oily phase is then introduced slowly into the aqueous phase with stirring using a mixer of Moritz type, at a speed of 4000 rpm for 20 minutes.

The polymer makes it possible by itself to emulsify all of the oil phase. The formulation obtained is an attractive emulsion with a tensioning agent, which may be used as an anti-wrinkle cream. Its texture is novel since gelation takes place on application to the skin.

List of references cited

[I] FR A-2 758 083 [2] FR A-2 758 084 [3] FR 2 791 257

[4] D. HOURDET et al., Polymer, 1994, vol. 35, No. 12, pages 2624 to 2630; [5] F. L'ALLORET et al., Coll. Polym. Sci., 1995, vol. 273, No. 12, pages 1163-1173; [6] F. L'ALLORET et al., Revue de l'Institut Franςais du Petrole [Review of the French Petroleum

Institute], 1997, vol. 52, No. 2, pages 117-128; [7] EP-A-0 583 814; [8] EP-A-0 629 649 [9] WO-A-95/24430; [10] US-A-5,939,485;

[II] WO-A-97/00275; [12] WO-A-98/48768"; [13] EP-1 038 519; and

[14] International Journal of Cosmetic Science, 4, 247-260, 1982.

Claims

1. Use of at least one water-soluble or water- dispersible polymer comprising water-soluble or water- dispersible units and units with an LCST, the said units with an LCST having in water a demixing temperature from 5 to 40 °C at a mass concentration of 1%, as a tensioning agent in a cosmetic composition.

2. Use according to Claim 1, in which the cosmetic composition is an anti-wrinkle composition.

3. Use of at least one water-soluble or water- dispersible polymer comprising water-soluble or water- dispersible units and units with an LCST, the said units with an LCST having in water a demixing temperature from 5 to 40 °C at a mass concentration of 1%, for the manufacture of a dermatological composition for smoothing out wrinkles and/or fine lines on the skin by means of a tensioning effect.

4. Use according to any one of Claims 1 to 3, in which the said polymer has a tensioning effect such that it leads to a retraction of stratum corneum of at least 0.5% at 30°C under a relative humidity of 40%.

5. Use according to any one of Claims 1 to 4, in which the polymer has a gel point from 5 to 50°C for a mass concentration in water of 2%.

6. Use according to any one of Claims 1 to 5, in which the polymer is in the form of a block polymer comprising water-soluble or water-dispersible units alternating with units with an LCST, or in the form of a grafted polymer consisting of an optionally crosslinked skeleton formed from water-soluble or water-dispersible units and bearing grafts consisting of units with an LCST, or vice-versa.

7. Use according to any one of Claims 1 to 6, in which the water-soluble or water-dispersible units of the polymer are obtained, partially or totally, by polymerization of at least one water-soluble monomer or a salt thereof chosen from:

(meth) acrylic acid;

- vinylsulphonic acid;

(meth) allylsulphonic acid;

- vinylphosphonic acid;

- methyl inylimidazolium chloride;

(meth) acrylamide;

- 2-vinylpyridine or 4-vinylpyridine;

- maleic acid and anhydride;

- crotonic acid;

- itaconic acid;

- vinyl alcohol of formula CH₂=CH0H;

- water-soluble styrene derivatives, especially styrene sulphonate;

- dimethyldiallylammoniu chloride;

- N-vinylaceta ide and N-methyl-N-vinylacetamide;

- N-vinylformamide and N-methyl-N-vinylformamide;

- the vinyl monomers of formula (I) below: H₂C=CR _(|) 0 X

in which:

- R is chosen from H, -CH₃, -C₂H₅ or -C₃H₇, and

- X is chosen from:

- alkyl oxides of -OR' type in which R' is a linear or branched, saturated or unsaturated hydrocarbon-based radical containing from 1 to 6 carbon atoms, substituted with at least one group chosen from halogen atoms (iodine, bromine, chlorine or fluorine) ; a sulphonic (-S0₃ ^~) , sulphate (-S0₄ ^~) , phosphate (-Pθ₄H₂ ^~) ; hydroxyl (-OH) ; ether (-0-) ; primary amine (-NH₂) ; secondary amine (-NHRi) , tertiary amine (-NRιR₂) or quaternary amine (-N⁺RιR₂R₃) group with Ri, R₂ and R₃ being, independently of each other, a linear or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, with the proviso that the sum of the carbon atoms of R' + Ri + R₂ + R₃ does not exceed 7; and

- -NH₂, -NHR₄ and -NR₄R₅ groups in which R₄ and R₅ are, independently of each other, linear or branched, saturated or unsaturated hydrocarbon-based radicals containing 1 to 6 carbon atoms, with the proviso that the total number of carbon atoms of R₄ + R₅ does not exceed 1 , the said R₄ and R₅ being substituted with at least one group chosen from halogen atoms (iodine, bromine, chlorine or fluorine) ; a hydroxyl (-OH) ; sulphonic (-S0₃ ^~) ; sulphate (-S0₄ ^~) ; phosphate (-P0₄H₂ ^~) ; primary amine (-NH₂) ; secondary amine (-NHRx) , tertiary amine (~NRιR₂) and/or quaternary amine (-N⁺RιR₂R₃) group with Ri, R₂ and R₃ being, independently of each other, a linear or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, with the proviso that the sum of the carbon atoms of R₄ + R_s + Ri + R₂ + R₃ does not exceed 7.

8. Use according to any one of Claims 1 to 6, in which the water-soluble or water-dispersible units of the polymer are obtained, partially or totally, by copolymerization of at least one hydrophobic monomer with at least one water-soluble monomer, the said hydrophobic monomer being in an amount such that the resulting units are water-soluble or water-dispersible, the said hydrophobic monomer being chosen from:

- vinyl acetate of formula CH₂=CH-OCOCH₃;

- vinyl ethers of formula CH₂=CH0R_s, in which R₆ is a linear or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms;

- acrylonitrile;

- caprolactone;

- vinyl chloride and vinylidene chloride;

- silicone derivatives such as methacryloxypropyl- tris (trimethylsiloxy) silane and silicone-based methacrylamides;

- the hydrophobic vinyl monomers of formula (II) below:

in which:

- R₇ is chosen from H, -CH₃, -C₂H₅ and C₃H₇,

- X₁ is chosen from:

- alkyl oxides of the type -OR₈ in which R₈ is a linear or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 22 carbon atoms;

- groups NH₂, -NHR₉ and -NR9R10 in which R₉ and Rχ₀ are, independently of each other, linear or branched, saturated or unsaturated hydrocarbon-based radicals containing 1 to 22 carbon atoms, with the proviso that the total number of carbon atoms in Rg + Rio does not exceed 22.

9. Use according to Claim 7 or 8, in which the water- soluble or water-dispersible units of ^' the polymer are neutralized, partially or totally, with a mineral or organic base chosen from sodium, ammonium, lithium, calcium and magnesium salts, salts of ammonium substituted with 1 to 4 alkyl groups bearing from 1 to 15 carbon atoms, or from monoethanolamine, diethanolamine, triethanolamine, aminoethylpropanediol, N-methylglucamine, basic amino acids such as arginine and lysine, and mixtures thereof.

10. Use according to any one of Claims 7 to 9, in which the water-soluble or water-dispersible units of the polymer are crosslinked by the action of at least one compound chosen from divinylbenzene, diallyl ether, dipropylene glycol diallyl ether, polyglycol diallyl ethers, triethylene glycol di inyl ether, hydroquinone diallyl ether, tetrallyl-oxethanoyl, polyfunctional alcohol allyl or vinyl ether derivatives, tetraethylene glycol diacrylate, triallylamine, trimethylolpropane diallyl ether, tetraallyloxyethane, methylenebis- acrylamide, allyl ethers of alcohols of the sugar series, allyl methacrylate and trimethylolpropane triacrylate (TMPTA) , and mixtures thereof.

11. Use according to any one of Claims 1 to 6, in which the water-soluble or water-dispersible units of the polymer consist partially or totally of one or more of the following components:

- water-soluble polyurethanes,

- xanthan gum,

- alginates and derivatives thereof such as propylene glycol alginate,

- cellulose derivatives and especially carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose and quaternized hydroxyethylcellulose,

- galactomannans and derivatives thereof, such as konjac gum, guar gum, hydroxypropyl guar, hydroxypropyl guar modified with sodium methylcarboxylate groups and guar hydroxypropyltrimethylammonium chloride, and

- polyethyleneimine.

12. Use according to any one of Claims 1 to 11, in which the water-soluble or water-dispersible units have a molar mass ranging from 1000 g/mol to 10 000 000 g/mol when they constitute the water-soluble skeleton of a grafted polymer, or a molar mass ranging from 500 g/mol to 500 000 g/mol when they constitute a block of a multiblock polymer or when they constitute the grafts of a grafted polymer.

13. Use according to any one of Claims 1 to 12, in which the units with an LCST consist of one or more of the following polymers:

- polyethers such as polyethylene oxide (PEO), polypropylene oxide (PPO) and random copolymers of ethylene oxide (EO) and of propylene oxide (PO) ,

- polyvinyl methyl ethers,

- polymeric and copolymeric N-substituted acrylamide derivatives with an LCST,

- N-polyvinylcaprolactam and N-vinylcaprolactam copolymers .

14. Use according to Claim 13, in which the units with an LCST consist of random copolymers of ethylene oxide (EO) and of propylene oxide (PO) , represented by the formula:

(EO)_m(PO)_n

15. Use according to Claim 14, in which the molar mass of the units with an LCST is from 500 to 5300 g/mol and preferably from 1500 to 4000 g/mol.

16. Use according to Claim 13, in which the units with an LCST are polymeric or copolymeric N-substituted acrylamide derivatives with an LCST, such as poly-N- isopropylacrylamide, poly-N-ethylacrylamide and copolymers of N-isopropylacrylamide or of N-ethyl- acrylamide and of a vinyl monomer corresponding to formula (I) or (II) given in Claim 7 or 8, or of a monomer chosen from (meth) acrylic ^"acid, vmylsulphonic acid, (meth) llylsulphonic acid, maleic acid and anhydride, vinylphosphonic acid, crotonic acid, itaconic acid, (meth) acrylamide, vinylpyridine, vinyl alcohol, N-vinyllactams such as N-vinylpyrrolidone, styrene and its derivatives, dimethyldiallylammonium chloride, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methylvinylformamide, vinyl ethers and vinyl acetate derivatives, acrylonitrile, caprolactone, vinyl chloride and vinylidene chloride.

17. Use according to Claim 16, in which the said the polymeric or copolymeric N-substituted acrylamide derivatives have a molar mass ranging from 1000 g/mol to 500 000 g/mol.

18. Use according to Claim 13, in which the units with an LCST consists of a poly-N-vinylcaprolactam or a copolymer of N-vinylcaprolactam and of a vinyl monomer corresponding to formula (I) or (II) given in Claim 7 or 8, or of a monomer chosen from (meth) acrylic acid, vmylsulphonic acid, (meth) allylsulphonic acid, maleic acid, maleic anhydride, vinylphosphonic acid, crotonic acid, itaconic acid, (meth) acrylamide, vinylpyridine, vinyl alcohol, N-vinyllactams such as N-vinylpyrrolidone, styrene and its derivatives, dimethyldiallylammonium chloride, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methylvinylformamide, vinyl acetate, vinyl ethers, acrylonitrile, caprolactone, vinyl chloride and vinylidene chloride.

19. Use according to Claim 18, for which the molar mass of the units with an LCST is from 1000 g/mol to 500 000 g/mol.

20. Use according to any one of Claims 1 to 19, in which the mass proportion of the units with an LCST in the polymer is from 5% to 70%, preferably from 20% to 65% and better still from 30% to 60% relative to the final polymer.

21. Use according to any one of Claims 1 to 20, in which the demixing temperature of the units with an LCST is from 10 to 35 °C for a mass concentration of the units with an LCST in water of 1%.

22. Use according to any one of Claims 1 to 21, for which the mass concentration of polymer in the composition is from 0.01% to 20% and preferably from 0.1% to 15%.

23. Use according to any one of Claims 1 to 22, in which the composition also comprises at least one gelling agent chosen from crosslinked polymers such as carbopols, 2-acrylamido-2-methylpropanesulphonic acid derivatives and natural polymers such as xanthan, and mixtures thereof.

24. Use according to any one of Claims 1 to 23, in which the composition also comprises one or more adjuvants that are common in cosmetics, such as glycols, for instance dipropylene glycol, glycerol, surfactants, organic, and mineral water-soluble UV- screening agents, active agents, salts, fillers, organic particles, hydrophilic polymers such as carboxyvinyl polymers (carbomers) , polymers derived from 2-acrylamido-2-methylpropanesulphonic acid, synthetic neutral polymers such as poly-N-vinyl- pyrrolidone, polysaccharides, for instance guar gum, xanthan gum and cellulose derivatives, water-soluble or water-dispersible silicone derivatives, for instance acrylic silicones, polyether silicones and cationic silicones .

25. Use according to Claim 24, in which the active agents are chosen from vitamins, alone or as a mixture, keratolytic and/or desquamating agents such as salicylic acid and its derivatives, α-hydroxy acids, ascorbic acid and its derivatives anti-inflammatory agents, calmants, depigmenting agents, matting agents, agents for preventing hair loss and/or agents for promoting hair regrowth, and anti-wrinkle agents, and mixtures thereof.

26. Use according to any one of Claims 1 to 25, in which the composition comprises an oily phase.

27. Use according to Claim 26, for which the oily phase comprises constituents chosen from oils of alkane, ester, triglyceride and ether type, which contain silicone and fluorine, and lipophilic gelling agents, surfactants, waxes, organic or mineral particles and organic or mineral lipophilic or lipodispersible sunscreens.

28. Use according to any one of the preceding claims, in which the composition is in the form of a ^'lotion.

29. Use according to any one of Claims 1 to 27, in which the composition is in the form of a serum.

30. Use according to any one of Claims 1 to 27, in which the composition is in the form of a cream.

31. Cosmetic process for treating wrinkled skin, which consists in applying to the said skin a composition comprising at least one water-soluble or water- dispersible polymer comprising water-soluble or water- dispersible units and units with an LCST, the said units with an LCST having in water a demixing temperature from 5 to 40 °C at a mass concentration of 1%, and the polymer having a concentration such that the gel point in water is from 5 to 40 °C.

32. Process according to Claim 31, in which the composition is applied around the contour of the eyes.

33. Process according to claim 31 or 32, in which the composition is a care composition, a makeup composition or an antisun product.