Recent trends in skin care polymers: new polymers and polymeric systems continue to drive skin care innovation. Here's a review of some of the most interesting chemistries available to cosmetic formulators.
Stimuli-responsive polymers are materials that exhibit a particular desired property that is triggered to change suddenly by a specific change (e.g. temperature, pH, ionic strength) in the physical environment. They can aid in processing and manufacturing of cosmetics and they allow the formulation of products that exhibit desired attributes in the storage container and a tunable change of properties when added to the substrate.
Thermally reversible viscosifying polymers exhibit a dramatic increase in solution viscosity when they are heated above a threshold temperature. One class of such polymers is prepared by end-capping poloxamers with poly (acrylic acid). (1) These polymers enable the preparation of multiple emulsions. (2) Water-in-oil-in-water (W0W) emulsions are systems in which small water droplets are dispersed inside larger oil droplets that are in turn dispersed in an aqueous continuous phase. They have been proposed as suitable formulation vehicles for two-component actives, or triggered actives in which the chemical properties of the internal aqueous phase and external aqueous phase are different. The objective of the ideal WOW formulation is stability in the container and then mixing of the internal and external phases to trigger the desired response when the emulsion is applied to the skin. Formulation of these emulsions is not trivial and their commercialization has been retarded by processing and stability constraints. Two mechanisms have been proposed for mixing of the actives in the internal and external aqueous phases: (2)
* Diffusion of the active agent through the oily barrier to the other aqueous phase; and
* Droplet-bursting either by dilution in a hypo-osmotic solution or by the application of a shear stress.
For droplet-bursting under shear, the droplets disrupt when the shear stress exceeds the droplets' cohesion stress.
The cohesion stress is given a capillary number Ca = [[eta].sub.c] Gr/[sigma], where [[eta].sub.c] is the continuous phase viscosity, G the shear rate, r the radius of the globule at rest and o the interfacial tension between oil and water. Bursting occurs when this capillary number exceeds a critical value [Ca.sub.cr] close to unity. Thus bursting is favored by a decrease in the oil/water interfacial tension or increases in shear rate, droplet size and continuous phase viscosity. The continuous phase viscosity can be easily increased with conventional thickeners to enhance probability of the droplet disruption. However, while droplet disruption is desirable on skin, it is not desirable during processing. There is a need, therefore, for thickeners that do not viscosify during processing but thicken under the conditions of application to skin. The thermally reversible viscosifying polymers described above can be designed to thicken at skin temperature as well as give lower continuous phase viscosity at room temperature. Thus, if the WOW emulsions are processed at room temperature, droplet disruption can be minimized. The triggered increase in viscosity upon application to skin will favor mixing of the internal and external aqueous phases (see Fig. 1, p. 64).
Cosmetics often depend on film-formers. Volatile solvents are included in these formulations to allow dissolution of the film-former in the product and good film formation on the skin upon evaporation of the solvent. However, as the polymeric film is formed in this mode, the applied film can shrink and penetrate wrinkles and blemishes on the skin surface. This opposes the objective of applying foundation to camouflage surface blemishes.
Ferrari and Tournilhac of L'Oreal have attempted to overcome this drawback by depositing polymers that increase in volume as the composition dries on the surface of skin. (3) They exploit the fact that polymer molecules adopt an expanded conformation when they are dissolved in a good solvent and a collapsed conformation in a poor solvent. By formulating polymers in a mixture of a nonvolatile good solvent and a volatile poor solvent, they are able to form deposits that increase in volume with time and keep the skin's defects camouflaged for a long time. The compositions are exemplified by poly (methylstyrene-co-2-ethylhexyl acrylate), and poly (styrene-co- 2-ethylhexyl acrylate/isobutyl methacrylate)--Pliolite AC3-H and AC5-G from Goodyear--and a mixture of kaolin and of poly(alkylstyrene) and (poly(alkylstyrene)--Imbiber Beads and Polymer 295 from Imbibitive Technologies--in the good, nonvolatile solvent isopropyl myristate and the poor, volatile solvent isododecane.
Heat-producing cosmetic compositions produce pleasant sensations when exposed to skin. Shaving creams, hand lotions, body lotions, lubricants and facial preparations (including masks and depilatories) all benefit from a warm sensation upon application to the skin. With this in mind, there have been regular attempts to introduce self-heating compositions. Methyl salicylate provides a sensation of warming, but it irritates skin. Heating can be caused by increasing blood circulation. This is the mechanism of L-Arginine. (4) Generally, the warm sensation is generated from heat of hydration of the product with water on the skin's surface and the products are necessarily anhydrous. Attempts have been made with finely divided solid absorbent materials such as silica gel, activated alumina and synthetic zeolites, (5,6) however, the amount of heat generation was small for compositions containing reasonable concentrations of these powders. Gott has introduced iron oxide redox systerns to generate sufficient heat. (7) This self-warming composition comprised a silicone oil or carboxylic ester as the skin conditioning agent, a redox system based on iron powder and a high surface area charcoal catalyst. A two-stage chemically heated liquid soap composition depended upon a novel double reductant and single oxidant redox systern of a hydrogen peroxide and a combination of sodium sulfite and ascorbic acid with a suitable catalyst. (8) Boron compounds, such as triethoxyboroxine, react exothermically with water and this has been used in self-heating shaying creams. (9) Polyols can heat by hydration upon topical application and are reportedly non-irritating to mucous membranes. (10) Self-warming compositions can be based on the heat of hydration of polyvinylamine or polyethyleneimine. (11)
An anhydrous silicone lotion containing 30% polyethyleneimine (Lupasol PR815 from BASF) produced a warm sensation a few seconds after topical application. One would expect the skin to be impermeable to polymers, especially polymers with a strong enthalpic interaction with stratum corneum.
Silicones for Skin Feel
Skin feel is extremely important and compositions based on silicones are often used for their good feel characteristics. Silicone resins give a silky feel to the skin when dried but they go through a tacky, draggy phase during dry down. This tacky stage can be eliminated by using a mixture of amorphous silica, such as Cabosil from Cabot or Aerosil from Degussa; silicone resin (dimethicone and trimethylsiloxysilicate) such as DC 593 Fluid from Dow Coming or KF-7312 from Shin Etsu; and a low oil-absorbing spherical powder, including Rubinate polyurethane powder from Huntsman of Belgium; DC 9506 powder from Dow Coming; BPA polymethylmethacrylate and MSS-500N silica both from Kobo Products. (12)
Silicone resins are typically made by hydrosilylation in which Sill groups are reacted with terminal olefinic groups to form crosslinked siloxane polymers. This limits the range of possible organofunctional groups that may be incorporated into the polymeric structure to create performance advantages in cosmetic formulations. Silicone epoxide chemistry overcomes these limitations and increases the diversity of polymeric silicone gels. This chemistry allows the synthesis of polyethersiloxane copolymer crosslinked networks in which certain cosmetic fluids are insoluble but are capable of swelling the network. (13,14) The desired fluids are silicone fluids, hydrocarbon fluids, esters, alcohols, fatty alcohols, glycols and organic oils. The copolymer network gels the fluid to confer the properties of a solid gel material at rest. The composition shows high stability and resistance to syneresis, yet the fluid may be released from the network by rubbing the composition on the skin to provide the sensory feel characteristic of the silicone fluid. Another approach to forming stable clear gels of volatile silicones is to use siloxane polymers with quadruple hydrogen bonding units. (15) The quadruple hydrogen bonding units are formed from nitrogen containing compounds that are reacted with isocyanates or thioisocyanates, or activated and reacted with primary amines to obtain a urea moiety that is part of the quadruple hydrogen bonding site on a polysiloxane molecule. These molecules are efficient thickeners of volatile silicones. Since the amount to form gels is tiny, the perceived tackiness on drying is reduced or eradicated.
Silicone resins have also been utilized to confer transfer resistance to color cosmetics such as lipsticks, (16) but the early products were perceived by some consumers to give a certain level of discomfort during wear. It has now been revealed that poly(alkyl, hydroxyalkylsiloxanes)--such as KF6104 from ShinEtsu--are capable of improved color fastness, while conferring satisfactory gloss and satisfactory comfort.
A skin protectant with good skin feel and easy application can be obtained by using a block copolymer having a linear polysiloxane-polyoxyalkylene block and an HLB less than six, in combination with a cosmetic oil, and with a low water content. (17)
Silicone emulsions confer good feel on skin, but they usually require special emulsifiers such as dimethicone copolyol. Non-aqueous emulsions of silicones are useful delivery systems for cosmetic applications, particularly when the presence of water initiates a process that changes the nature of the cosmetic composition. (18) The polyether-siloxane network copolymers can be used to enhance the properties of non-aqueous emulsions, oil-in-water emulsions or water-in-oil emulsions. (13)
Clear microemulsions can allegedly be formed spontaneously by combining water; a volatile siloxane, a long chain or high molecular weight silicone poly ether (such as DC 5329 as a high molecular weight silicone polyether and DC 5211 as a low molecular weight polyether from Dow Corning) and, optionally a cosurfactant such as a monohydroxy alcohol, organic diol, organic triol, organic tetraol, silicone diol, silicone triol, silicone tetraol and a nonionic organic surfactant. (19)
Glyceryl derivatives of dimethicone are claimed to provide better long-term emulsion stability than silicone copolyol and they spontaneously swell to absorb their own weight of silicone oil. (20)
Silicones can build up on skin with continued use, leading to a dull appearance. Esters of hydroxycarboxylic acids and alkyl and alkenyl oligoglycosides--such as Cognis' sodium laurylglucoside citrate, sodium laurylglucoside malate, or sodium cocoylglucoside tartrate--are said to permanently re-emulsify silicones, making them easy to remove after each use and preventing buildup. (21)
The thickening of oils, while achieving cosmetic efficacy, continues to be a challenge for the formulator. Useful compositions have been thickened by particulates such as clays (22, 23) or fumed silica, (24, 25) structuring waxes, (26) triglyceride gellants such as glyceryl tribehenate (27) and silicone elastomers. (28) Guenin et. al. (29) reveal that silicones thickened by elastomers tend to have unacceptably high viscosities and leave a film on the skin that occludes sweat glands. In order to overcome these deficiencies, they propose a thickener comprising dimethicone crosslinked with an alpha, omega diene--such as DC-9040 from Dow Corning--in combination with polyethylene beads.
Side-chain crystalline polymers reportedly thicken a wide range of oils. (30) These polymers comprise a water soluble (or polar) backbone with crystallizable long chains arranged along the polymer like teeth on a fine comb. The melting temperature can be tuned to distribute side-chain lengths and their content along the chain. These polymers are dispersed in the desired oil and heated above their melting point. Thickening occurs upon cooling below the melting point of the side-chains. These interesting stimuli-responsive copolymers have been used in agriculture to coat seeds. The coating is hydrophobic and protects the seed if the side chains are crystallized. When the side chains melt, water enters the seed and the seed germinates. By adjusting the coating to certain temperatures, the seeds can be planted early in spring or even in winter where they remain ready to grow when the ground reaches the triggering temperature.
Oil-in-water nanoemulsions are liquid/liquid dispersions in which the droplet size is less than 100nm. These small droplet size emulsions are transparent and the droplets can be stabilized by a shell of emulsifiers in lamellar phase that completely wraps each droplet. Nanoemulsions are distinctly different from microemulsions insofar as the latter are spontaneously-forming thermodynamically stable miceller phases in which the oil is solubilized. This requires large concentrations of surfactants which make these compositions feel sticky upon application to the skin. Moreover, microemulsions form only in a very limited range of compositions. Nanoemulsions, on the other hand, are similar to regular emulsions as they are thermodynamically unstable and the small droplet size is achieved by subjecting the system to enormous shear energies using homogenizers or dispersers. Nanoemulsions often must be thickened to be acceptable to consumer expectations. There are two conventional ways to thicken a nanoelmulsion:
* Increase the concentration of the dispersed oil phase. This is usually not an option for the formulator because it usually leads to compositions with an undesirable oily or greasy feel; and
* Add conventional polyionic thickeners. But these thickeners usually cause flocculation and/or coalescence of the nanoemulsion and destroy the transparency for which the nanoemulsion was made in the first place.
L'Alloret recently revealed that nanoemulsions can be thickened without loss of clarity, if the thickener is nonionic. (33) Exemplified thickeners are poly(ethylene oxide) (Carbowax 20M from Dow Chemical), hydroxypropyl guar (daguar HP-105 from Rhodia) and hydroxyethylcellulose (Natrosol 250HHR from Hercules).
Thickening alpha hydroxy acid (AHA) and beta hydroxy acid (BHA) formulas, especially low-pH compositions, is another challenge for the formulator. Complex thickening systems comprising xanthan gum (Kelco and Kelzan xanthan gums from Kelco), magnesium aluminum silicate (Veegum magnesium aluminum silicate from R.T. Vanderbilt) and polyacrylamide and C (13-14) isoparaffin and laureth-7 (Sepigel 305 thickener from Seppic) provide efficient thickening for these systems and also stabilize cosmetic oil-in-water emulsions. Compositions thickened with the latter crosslinked polyacrylamide have been recognized for improved skin feel, rub-in and absorption characteristics. Lorant explained that ultrafine oil-in-water emulsions, prepared by phase--inversion, are difficult to gel and stabilize with conventional thickeners but they could be stabilized by a cross-linked poly(2-acrylamido-2-methylpropanesulphonic acid) (Hostacerin AMPS from Clariant). This would be achieved at acid pH conditions under which conventional anionic thickeners would exhibit loss of viscosity. Unlike other polyelectrolyte thickener, these thickeners also resist dramatic viscosity loss in the presence of the UVA sunscreen 1,4-benzene[di(3-methylidene-10-camphorsulfonic)]acid. Copolymers of 2 acrylamido-2-methylpropanesulphonic acid and acrylic acid can thicken strongly acid solutions. If the molecular weight is higher than 6,000,000 and the 2-acrylamido-2-methylpropanesulphonate content is greater than 20%, then the polymer may confer yield stress and shear thinning characteristics on the composition. Acryloyl taurate/vinyl pyrrolidone copolymer (Aristoflex AVC from Clariant) is an efficient thickener and stabilizer for emulsions containing AHAs and BHAs.
Copolymers have now been made by polymerizing N-acryloyl taurate with commercially available macromonomers (Genapol LA-070 methacrylate). These polymers provide good thickening and emulsifying properties and clarity. (42, 43)
A new class of associative thickeners--thiocarbonate compounds--has been disclosed. (44) These multifunctional thickeners can be used as rheology modifiers, suspending and spreading agents, lubricants and film formers. Cationic versions can be used for acidic formulations such as AHA treatments.
Amphiphilic polymers may be used to prepare mini-emulsions that are essentially free of conventional surfactant. It has been disclosed (45) that a commercially available styrene/acrylic copolymer (Morez resin from Rohm and Haas) is appropriate for this purpose and a reactive hydrophobic comonomer (Luperox 256 from Atofina) may be combined with the amphiphilic polymer in order to confer mini-emulsion stability.
Other Rheology Modifiers
A block copolymer consists of at least two covalently linked polymer blocks in which the blocks are characteristically comprised of chemically different monomer units. In amphiphilic block copolymers, one of the blocks is hydrophilic and the other is hydrophobic. In recent years there has been a flurry of activity in the syntheses and applications of block copolymers (46) following the introduction of techniques for living free-radical polymerization. (47,48,49,50) Prior to the introduction of this technique, block copolymers could be obtained only by anionic or cationic "living" polymerization or by condensation methods that were applicable only to a small class of monomers. Free radical living polymerization has greatly increased the diversity of monomers that can be assembled into block copolymers.
Amphiphilic block copolymers can form a sequence of hierarchical morphologies that can be tailored to confer desired mechanical properties on the solid material and specific rheologies on solutions. (51) These polymers readily form micellar aggregates, just like surfactants, except that the dimensions are larger by one to three orders of magnitude. (52, 53) (see Fig. 2)
Thus the block copolymer of caprolactone and PEG 550 spontaneously form microemulsions and micelles ranging in size from 15 to 125nm. (54) Block copolymer micelles may solubilize oils such as sunscreens. (55) Solutions containing spherical micelles range from being non-viscous to having the properties of associative thickeners. (56) Amphiphilic block copolymers can be nanofabricated (57) to confer a wide range of rheologies. The amphiphilic block copolymer of acrylic acid, methyl acrylate and polystyrene (PA[A.sub.90]-b-PM[A.sub.80]-b-P[S.sub.98]) self-assembles in aqueous solution into stable nanostructures having spherical and cylindrical topologies (58) and A--B and A-B-A block copolymers of methacrylic and (A) and styrene (B) form stable micelles that are capable of solubilizing hydrophobic molecules. (59)
Easy dispersing triblock B-A-B amphiphilic block copolymers have been disclosed that gel the aqueous phase to obtain a broad range of textures and emulsifying properties and enable the preparation of cosmetic compositions with stable viscosity over wide ranges of pH and temperature. (60) It is also revealed that they make it possible to prepare homogeneous, nonflowing, non-runny products that are soft and slippery when applied and stable on storage. (14) Living free radical polymerization can also be used to synthesize hyperbranched polymers that may be useful in lipstick formulation. (61)
Soap has been used as a cleanser for thousands of years and became common during the Industrial Revolution. However, solid bar soap has a relatively slow time for dissolution and solubilization. This can be improved by providing the product as a liquid soap, but its high water and solvent content increases manufacturing and shipping costs. Recently, a solid, rapidly dissolving soap composition, suitable for predose dispensing, has been disclosed." The sheet-like product is prepared by combining soap with a water-soluble, film-forming polymer and introducing air bubbles. Suitable polymers are listed as polyamides, polyacrylates, polyamino acids, polyvinyl acetate, polyvinyl alcohol, polyethylene glycols, polyvinyl-pyrrolidones, pullulan, alginic acid, starch, cellulose and cellulose derivatives. Only poly(vinylalcohol) is exemplified in the patent application. Consistent with storage and dispensing, the product is designed to rebound to its original shape, like a sponge, after deformation under a slight external force but shows permanent deformation under greater forces.
Wipes and Skin Feel
Two types of cosmetic wipes are currently being marketed: moist wipes impregnated with a cleansing or skincare formulation and dry wipes that must be moistened before use. Wipes were originally directed toward cleaning and sanitization, but now cosmetic attributes such as skin feel and foam structure are becoming increasingly important. In recent years, major efforts have been spent to improve the softness and absorbency characteristics of wipe and pad materials to alleviate skin irritation upon prolonged or repeated use. (63)
Good foaming, cleansing and skin feel has been reported for wipes impregnated with an emulsifier mixture containing nonionic and amphoteric surfactants, a mixture of wax components containing wax esters, partial glycerides and fatty alcohol ethoxylates and a cationic polymer. (64) The preferred cationic polymer in this case is a cationic guar which is likely to confer the perceived skin feel benefits. Cationic galactomannans, such as guar hydroxypropyltrimonium chloride, are used as thickener deposition aids in skin care compositions. Most wipes are fragranced, but some consumers prefer wipes with a barely perceptible hint of fragrance or no perceivable fl'agrance at all. It is interesting in this context that Hercules recently developed a cationic guar with reduced odor. The cationic functionality of these polymers is conferred by quaternizing with trimethylamine and trace residuals of this amine can cause the product to have a fishy odor, which may be detectable in products formulated at neutral or basic pH values. Hercules has claimed that a cationic galactomannan with less than 25ppm of residual trimethy lamine has no discernible odor when formulated into personal care compositions. (65)
Cleansing and Moisturizing
The ideal time to deliver moisturization to the skin is during a shower or bath. However, deposition is challenging in these situations when there is a tendency for the moisturizer to be rinsed from the skin. There have been several attempts to meet the challenge. For example:
* High internal phase emulsions break easily on the skin and, if they are substantially free of surfactant, satisfactory deposition of moisturizer can be achieved. (66)
* Delivery of deodorants from spheroidal networks comprising wetting agents and emulsifiers such as stearic acid, cetyl alcohol, glyceryl monostearate and stearyl alcohol. (67-68)
* Patterned multi-phase systems that comprise a a cleansing phase, a benefit phase, and a non-lathering structured aqueous phase. (69)
* Oil-in-water emulsions in which the oil is structured by a stable network of finely divided particles such as silicas, clays or trihydroxystearin. (70) The structured oil has a high low-shear viscosity that favors adhesion and retention on the skin, and the network yields under stress when rubbed in. The viscosity of the system can be built with a polymeric stabilizer (71) such as the naturally-derived hydroxypropyl starch phosphate (Structure XL from National Starch). This is a pre-gelatinized esterified form of starch that fulfills several roles in skin care products, such as emulsion stabilization, improved sensory quality and viscosity build. Hydroxypropyl starch phosphate can enhance formulation aesthetics as a dispersed starch. This starch polymer gives body to formulations and leaves the skin feeling soft and it is a nonionic polymer that is compatible with most skin care ingredients. This polymer is easy to use and it can be added at virtually any point in production.
This starch derivative also addresses the desire of consumers for cosmetics and toiletries that contain naturally derived ingredients. Such ingredients are perceived favorably with respect to health, safety and environmental responsibility. However, consumers are not willing to sacrifice product performance to satisfy a preference for natural ingredients. Today's consumers actually demand products with increasingly sophisticated performance. This creates a formidable challenge for cosmetic scientists--to develop new products containing naturally derived raw materials that meet or exceed performance expectations. Hydrophobically-modified pre-gelatinized crosslinked starches are polymeric emulsifiers that yield emulsions that are salt-tolerant and do not exhibit tackiness. (72) Corn Starch Modified (Dry-Flo AF Pure from National Starch), provides unique smooth, velvety feel benefits. One of the more distinctive properties of this unique polymer is its ability to impart a pleasantly light, soft feel to a range of product forms (lotions, creams and pressed powders) both during application and after dry-down. It has the ability to mitigate greasiness, even in heavy formulations.
* Moisturizing compositions for adolescents usually require a sebum control agent. Liquid crystal/gel networks containing a sebum absorbing agent, preferably aluminum starch octenyl succinate (and) acrylates copolymer (and) magnesium carbonate (Natrasorb HFB from National Starch), have been proposed for this purpose. (73) Adding between 1% and 3% of this hydrophobically--modified starch polymer allows for a matte finish on skin, reducing unwanted shine.
Gelled alcohol hand sanitizers are commonplace. In early versions, alcohol solutions were thickened with hydroxypropylcellulose (Klucel HF and Klucel EF from Hercules) and the thickener increased the contact time of the antimicrobial alcohol by retarding the evaporation of the alcohol. (74) Later versions (75) were formulated with alcohol and a cationic antibacterial; they included a silicone wax for moisturizing properties and they were thickened using a Carbomer (Ultrez from Noveon) for better skin feel characteristics.
The inclusion of aromatic alcohols and quaternary antimicrobial compounds enhance the broad spectrum effectiveness of these products. (76) Polymeric antimicrobials are now being developed and there is a possibility that these could be included in hand sanitizers for more durable antimicrobial effectiveness.
In recent years there has been a consumer-driven trend, especially in Europe, to reduce the amount of preservatives in cosmetics. While no ethical manufacturer would inflict an inadequately preserved product on the consumer, manufacturers are interested in exploring alternative routes to preservation. Short peptides having antimicrobial activity have been discovered and are targeted toward reducing the microbial activity on or in skin with respect to conditions such as acne. (77) Polypeptides that contain sequences rich in amino acids with positively charged side groups enhance cell membrane penetration, which is believed to be essential step in the mechanism involved in the antibacterial functioning of these molecules. (23,78)
Polyhexamethylenebiguanide, (79) polyornithine, and polylysine are candidate polypeptides. Polypeptides may be an acceptable approach to personal care product preservation. In this context, epsilon polylysine is being advanced as a safe water-soluble preservative for skin care compositions.
UV Absorbing Polymers
UV absorbing, water-soluble polymers reportedly protect substrates from the effect of ultraviolet light wavelength of 200-420nm. (81) These polymers allow the delivery of a UV-absorber directly from an aqueous solution from a polymeric form that bodes well for deposition on the desired substrate (Solamer from Nalco). The polymers combine four monomer types: the first is a vinyl or acrylic monomer that absorbs ultraviolet light radiation of wavelength in the range 200-420nm; and the other three monomers are free-radical polymerization water-soluble monomers.
The UV absorbing monomers are selected from N-[3-(dimethylamino) propyl]methacrylamide-N-(3-bromopropyl)phthalimide quaternary salt (DMAPMA-PQ), N-[3-(dimethylamino)propyl] methacrylamide 1-chloromethylnaphthalene quaternary salt (DMAPMA-MNQ), (3-allyloxy-2-hydroxypropyl)-[3-(2-hydroxybenzoylamino)propyl]-dimethyl ammonium hydroxide, [(4-carboxy-3-hydroxyphenylcarbamoyl)methyl]-dimethyl -[3-(2-methylacryloylamino)propyl] ammonium hydroxide, and 4-methacrylamidosalicylic acid (4-MASA).
New Polymers Show Promise
New polymers and polymeric systems continue to drive innovation in skin care cosmetics. Stimuli-responsive advances promise to provide "smart" systems that formulators will be able to tune to provide desired attributes depending upon their physical environment. Strongly hydrating polymers will, perhaps, yield safe non-irritating self-warming compositions.
Precisely tailored block copolymers promise to yield new tunable rheologies, processing aids and thermodynamically-stable micro-emulsions with low skin irritation. Polymers with specific side groups may provide the basis for a new class of antimicrobial agents and sunscreens that can be delivered effectively from aqueous solution. Even soap and wipes may be revolutionized by water-soluble, film-forming, foam-boosting polymers.
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Robert Y. Lochhead The Institute for Formulation Science, The School of Polymers & High Performance Materials The University of Southern Mississippi Hattiesburg, MS
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|Author:||Lochhead, Robert Y.|
|Publication:||Household & Personal Products Industry|
|Date:||Apr 1, 2006|
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