Hair Care Polymer Trends
A close look at recent patent activity reveals increasing emphasis on color, conditioning and styling applications.
Robert Y. Lochhead
The Institute for Formulation Science and The School of Polymers & High Performance Materials
The University of Southern Mississippi
This article samples recently published patent applications and identifies trends in the use of polymers for hair care. Major trends are directed toward more durable products, from color to conditioning to styling. Innovative ap- proaches to reduce VOCs are apparent too. There appears to be a move toward new cationic polymers as ac- tives for conditioning shampoos and also formulations for better deposition of antimicrobial actives, including antidandruff shampoos. During this period there has also been intense IP activity reflecting innovations in hair coloring, mainly from two companies. Clearly, hair care innovation continues unabated.
Traditionally, hair styling is achieved by applying film formers to the hair surface where they fix the hair matrix in a desired shape. Cationic film-forming polymers coat the hair and provide conditioning benefits such as ease of combing, hair alignment, antistatic effects and improved gloss. One challenge for the modern hair fixative polymer producer is compatibility with the formulation vehicle. This challenge is amplified by environmental regulations that limit the amount of volatile organic compounds (VOC) in finished goods such as hairsprays. Reduction of VOC content is usually achieved by replacing organic solvents in the formulation with water. But water in the formulation can reduce polymer solubility and impair their film-forming qualities. Alternatively, water can plasticize the polymer films, resulting in a degradation of mechanical properties and a loss of hold. In order to address these challenges, BASF researchers have prepared anionic, ampholytic copolymers designed to meet the constraints of low VOC formulations.1 The polymers are prepared by free-radical initiated polymerization of methacrylic acid ester(s), methacrylic acid, acrylic acid and a monomer containing amino groups. The copolymer composition is exemplified by a copolymer of methyl methacrylate, methacrylic acid, acrylic acid and dimethylaminoethylmethacrylate. This polymer conferred good curl retention, even when the hair swatch is styled by water-waving, and low tackiness (measured by capacity to prevent “blocking”).
VP/methacrylamide/N-vinyl imidazole copolymer is the polymer in new Thermafuse Control—a crystal clear, easy-to-apply gel that creates a very firm, humidity resistant hold without flakiness or the tacky/sticky feel of traditional extra firm hold styling gels. It promises long-lasting strong hold, yet easily washes out without buildup.
Polyurethanes can be prepared to be easily dispersed in water and this provides another route to effective low VOC hair fixatives. It is claimed that polyurethane dispersions provide setting and high humidity style retention, good feel and shine without sticky feel. According to a Bayer patent application2 hair fixative polyurethanes can be prepared from (a) prepolymers having the formula show below in Fig. 1. (b) chain extenders of type H2N-R4-NH2 in which R4 is alkylene or alkylene oxide, and (c) chain extenders of type H2N-R5-NH2 in which is an alkylene containing an ionic group.
Another way to address VOC issues is to eliminate the solvents entirely by introducing new product concepts. One example of an innovative approach is the introduction of hair fixative foils.3 These foils are thin strips of material that can be dissolved in small quantities of water by rubbing between the hands, then applying to hair. The foils are constructed of pullulan and can contain a wide variety of conventional hair fixative polymers.
However, styling hair by externally applying polymer fixatives has several disadvantages:
• Hair style is not necessarily durable and it is lost as the adhesive bonds between hairs are ruptured due to hair movement or plasticization due to humidity;
• Conditioning agents often work against hair fixatives; and
• The hair has a stiff, unnatural feel.
These disadvantages are reportedly overcome by conducting the polymerization inside the hair shaft.4 This can be achieved from a two-part kit comprising the monomers in one part and the polymerization initiator in the other. Thus, a sulfopropyl(meth)acry- late and alpha methylene lactone are applied to the hair and allowed to diffuse into the internal hair structure, both the cuticle and the cortex. The monomers are dissolved in a dermatologically-acceptable carrier, usually a cosmetically-acceptable oil and, optionally, a compound such as ammonium thioglycollate is included to break the disulfide bonds of hair to allow easier ingress of the monomers. Treated hair is exposed to a suitable light source to photopolymerize the monomers.
The resulting polymer forms complexes with the keratinous proteins and these complexes are stable over long periods of time. Due to the stability of these complexes, the style imparted to the hair persists through multiple washings. This treatment alleviates the adverse effects of humidity on hair, such as frizziness or limpness.
Durable coatings on hair fibers can be produced by applying two polymers with complementary groups that react on the hair surface to produce coatings that are sufficiently thick to obscure the cuticle.5 The layer persisted, although it thinned, for 10 washes. The complementary polymers are, for example starburst PAMAM Den-drimers (Dendritech Corporation) and PVM/MA copolymer.
One way to eliminate VOCs from hairstyling formulation is to apply the formulation to the hair as a powder. Powders prepared by pulverizing mixtures of hair-fixative polymers and hydrophized silica have been advanced for this purpose.6 These powders are distributed throughout the hair and then rubbed in to form bonds precisely at the fiber junction points.
Alkoxysilanes can also provide lasting desired feel to the hair, especially thin, frizzed hair that needs volume.7 Organosilicones have been used to achieve styling effects that endure through several shampoo cycles but repeated application of these compounds causes buildup which makes the hair feel dry or coarse. However, compositions that include one alkoxysilane having a solubilizing group, offer the prospects of volumizing while preventing deterioration in the feel of the hair. The compositions are exemplified by a styling lotion that contains aminopropyltriethoxysilane and DC 939 emulsion (Dow Corning).
Rheology modifiers that are easily incorporated into aqueous formulations and which confer good sensory properties can be prepared as copolymers containing silicone groups, at least one ionic monomer and a crosslinker.8 For example such a thickener could be a copolymer comprising silicone-urethane-polyallyl, vinyl pyrrolidone methacrylic acid, vinylimidazole and ethylene glycol dimethacrylate prepared by precipitation polymerization in butyl acetate as solvent.
It is well known that cationic species tend to adsorb to hair if the pH is above about a value of 5. An interesting development that builds on this effect is the preparation of cationic latexes for application to hair. These latexes are exemplified by a polymer latex comprising methacrylamidopropyltri- methyl ammonium chloride, styrene, methyl methacrylate, lauryl methacrylate and hydroxyethyl methacrylate.9 These latexes can be used as conditioning pretreatments or they can be applied directly from shampoo, presumably as a polymer-surfactant complex as, for example, a fragrance deposition aid.
Conditioning of hair is best done under acid pH conditions but thickeners for acidic pH are relatively sparse compared to the diverse range of anionic rheology modifiers that are available. An interesting development in this respect is the disclosure of cationic amphipathic copolymers that can thicken and also form films on the hair under acid conditions.10 These polymers contain an amino-substituted vinyl monomer, a nonionic vinyl monomer, an associative vinyl monomer, a semihydrophobic monomer and, optionally, a hydroxy-substituted nonionic vinyl monomer.
Hydrophobically-modified polylysine adsorbs to hair and confers better wet combing and hair alignment. The adsorption is strong and the treatment can last through several washes.11
“Esterquats” are becoming well-established conditioning and softening agents. They continue to displace traditional quaternary ammonium surfactants because of their better eco-toxicological properties especially with regard to biodegradation. Esterquats are prepared by reacting mono- or difunctional carboxylic acids (adipic acid is preferred) with alkanolamines and quaternizing the reaction product. Polymeric esterquats are especially useful because they exhibit both polymeric and surfactant properties. However, for symmetrical polymeric esterquats, the surfactant properties and especially the emulsifying properties are dominated by the polymeric behavior of the molecules. Now it has been discovered that esterquats with asymmetric chains have a better balance of surfactant to polymer behavior and this improves their conditioning performance on hair.12
The asymmetric esterquats are prepared by reacting alkanolamines with mixtures of C6-C10 monocarboxylic acids, C12-C22 monocarboxylic acids and dicarboxylic acids followed by quaternization of the resulting esters.
Conventional conditioning shampoos work by a mechanism in which cationic polymers interact with the anionic detersive surfactants to phase separate as a coacervate during the rinse stage. The coacervate deposits on the hair and also co-deposits beneficial agents such as silicones or other conditioning oils.13 For decades, the cationic polymers of choice have been Polyquaternium-10 and Guar hydroxypropyltrimonium chloride. However, during actual use, most of the coacervate is rinsed down the drain rather than deposited on the hair. In order to compensate for the inefficiency of deposition, formulators increase the concentration of cationic polymer in the system. This increases raw material costs, reduces foaming and takes the product closer to instability boundaries. Improved conditioning and lather performance is achieved by using a synthetic random copolymer of acrylamide and a tri-quaternary monomer having the general formula shown in Fig. 2.14
Dendritic polymers are beginning to appear in the cosmetic patent literature. For example the inclusion of dendritic polymers in conditioning shampoos is claimed to decrease the volume of hair and to produce better hair alignment.15 An example of the dendritic polymer is the hydroxy-functional Boltorn H60 Dendritic Polymer (from Perstrop).
For the past 50 years, oxidative “permanent” dyes have dominated hair-coloring systems. Oxidative hair dyes are usually two-part kits in which one part is the alkaline composition that contains the dye precursors and the other part is the oxidizer. These two components are mixed directly before application to the hair. The dyeing process takes between 5-45 minutes. Oxidative dye precursors, called “oxidative bases” (for example, ortho- or para-phenylenediamines, ortho- or para-aminophenols) are uncolored. They diffuse into the hair and there they undergo oxidative coupling with couplers such as metaphenylenediamine, to produce color inside the hair.
Conventional chemical coloring treatments for hair require careful preparation of both the coloring product and the hair and the process of coloring hair is difficult because the final color achieved depends on the physical state of the hair. Damaged, chemically-processed or bleached hair introduces variations that affect the coloring performance. Moreover, it is widely accepted that conventional coloring causes hair damage. The differences observed in coloring results from differences in the penetration of the dyestuffs into the fibers; damaged fibers are easier to penetrate. Not surprisingly, there have been research efforts directed toward protecting and normalizing the hair by surface treatment in order to bring uniformity and predictive quality to the dyeing process. Thus, over the years there have been a number of approaches directed to placing barrier substances on the surface of hair to try to achieve uniform dyeing.
Cationic polymers have been included to improve the hair condition but these can cause instability in the dyeing compositions and they can be removed by shampoo leading to a lack of durability of color in the hair. It has been found that the inclusion of an associative polymer and an aminosilicone in oxidative dyeing compositions can alleviate the detrimental properties of conventional oxidative dyes.16 Treatment with these improved compositions results in improved hair softness and pliability, good shampoo fastness and more uniform dyeing along the length of each hair fiber. The function of the associative polymer is to thicken the dyeing composition to keep it on the hair and to prevent it from running into the eyes and onto the scalp. However, the compositions with associative thickeners are essentially aqueous and they can react prematurely. This premature reaction causes the color to remain in the cream instead of being transferred into the hair. It has now been found that the inclusion of titanium oxide or mica-titanium pearling agents can improve the performance of associatively-thickened dyeing compositions making it possible to obtain intense shades.17 Moreover, the creamy texture conferred by the pearling agents is esthetically favored by users.
Unfortunately, most “permanent” colors are relatively transient; they tend to fade with time. This loss of color intensity depends on the condition of hair and damaged hair tends to lose color more rapidly. The situation is exacerbated by the fact that the process of dyeing hair tends to cause hair damage. Thus, those consumers with most need of dyeing must resist the urge to increase the frequency with which they undergo the process. Over the years many attempts have been made to produce products that resist fading. Direct dyes have been added to the permanent dyes to improve the wash-fade profile. These products confer intense color immediately, but it does not persist long term. Furthermore, direct dyes are not taken up uniformly from root to tip and this results in undesirable variations in color along the lengths of the fibers. Attempts have been made to seal the color into the hair by surface treatment. It has now been found that treatment with certain silicones allows the color to be maintained longer.18
Surprisingly, the detailed chemistry of these functionalized silicones appears to be less important than their physical characteristics. The desired performance is achieved most preferentially by functionalized silicone polymers with interfacial tensions from 1 to 4 mN/m and viscosities in the range 4000 to 25,000 mPas. If these interfacial tension and viscosity limitations are met, then the functional group of the silicone could be polyoxyalkylene(polyether), primary and secondary amine, amide, quaternary ammonium, carboxyl, sulfonate, sulfate, carbohydrate, phosphate, or hydroxyl. The proposed mechanism by which these silicones function is twofold:
1. Enhancement of the hair’s condition leads to less inter-fiber friction and less mechanical damage, which slows the diffusion of dyes from the hair and
2. The silicone alters the surface properties of the hair, restoring some of the hydrophobicity to the surface and this in turn slows the rate at which water can diffuse into the hair and leach the oxidative dyes. In addition, the restoration of hydrophobicity from root to tip leads to more uniform dyeing along the fibers. Cationic polymers have been added to these functionalized silicone compositions to further improve the hair condition.19
It has been discovered that acid pre-treatment of hair with Polysilicone-9 mediates the penetration of color into damaged hair and results in more consistent coloring across different hair types and leads to more intense and even coloration.20 Furthermore, the color is durable.
There is a need for coloring processes that are simpler to apply for consistent results while causing little or no damage to the hair. L’Oréal researchers have attempted to achieve this goal by applying colored polymers to the hair.21 The polymers are precisely colored by the attachment of chromophores as side groups to the polymer backbone. The preferred chromophores are shown in Tables 1 and 2.
Another simple process is direct dyeing of hair by heat transfer printing.22 In this process, a dye-impregnated wipe is wound around selected strands and heat is applied. The heat causes evaporation or sublimation of the dye, which consequently diffuses into the hair. The advantages of this approach are that it does not require any solvent and this allows the use of a very wide range of direct dyes, including those that are insoluble. Direct heat transfer dyeing also avoided the use of liquid bases that could drip into the eyes and spread onto the scalp. In essence it is a consumer-friendly approach that requires little training to perfect.
Hair highlighting involves the segregation of some strands of hair that are then treated with peroxides or persulfates. Highlighting requires considerable skill and it usually falls in the realm of professional salon operators. “High-lift” powdered bleaches combine sodium, potassium and ammonium persulfate with hydrogen peroxide at high pH to give rapid bleaching of hair. Originally, hair was segregated by placing a plastic cap over the head and pulling strands through the cap. Alternatively, strands of hair are woven and placed inside aluminum foils that are painted with the highlighting composition. The foils must be opened frequently for observation during the process. It would be desirable to have transparent closures to allow facile observation of the highlighting process. Devices have been patented to address these challenges.23 The devices are made of material that can be easily closed around segregated hair strands.
The material of construction can be transparent and it can also be water soluble (for example poly(vinyl alcohol) to allow easy rinsing from the hair after treatment. It may also contain pH indicators to follow the progress of the bleaching reaction. One object of this invention is to provide at-home highlighting kits. These kits can be made safer by trapping the hydrogen peroxide and alkali separately in fangible Consumer Activated Rupturable Multi-cell Applicators (CARMA) bubbles that are frangible under finger pressure and which rupture to deliver the bleaching components to the hair surface. These bubbles are usually constructed of polyethylene or polypropylene.
Heat treatments damage hair. The extent of damage can be evaluated by measuring the amount of alpha crystallinity in the cortex proteins.24 Treatment with low molecular weight glucosamines helps maintain alpha crystallinity and alleviates the extent of heat-induced damage.
A method for determining the amount of damage includes placing hair into a solution containing at least one metal ion so that an amount of the metal ion is adsorbed to the hair.25 For example, 400ppm solution of Ni was prepared in a tris buffer and hair was soaked for an hour in 20ml of this nickel solution. It was rinsed six times with a pH 7 buffer (20 minutes per rinse). The hair was dried overnight in an oven at 105°C. The hair was then incinerated and the amount of nickel determined by a simple strip test.
Zinc pyrithione has been incorporated as the active ingredient in antidandruff shampoos since the 1960s. Now it has been revealed that the deposition of zinc salts from shampoos can be improved by including a cationic polymer, preferably poly(methacrylamido-propyl trimethylammonium chloride), in the anionic surfactant base, especially if the polymer interacts with the anionic surfactant base to form discrete particles of liquid crystals.26
Odor-causing skin bacteria, yeasts and fungi can adhere to fibers and cause unpleasant odors even after washing if the bacteria continue to adhere to the fiber surface. A clever way of preventing this is to treat the fibers with anti-adhesive polymers that prevent the bacteria from sticking in the first place. It has been disclosed that some PEG polymers have the capability to adsorb to fibers and prevent the adhesion of bacteria to these fibers.27 PEG polymers are widely used as anti-fouling surface treatments for “in-body” therapeutics and they usually function by a steric-stabilization mechanism that prevents the close approach of micro-organisms to the treated surface. The invention is directed mainly to laundry treatment, but this could be a treatment that could alleviate odors from treated hair. Good anti-adhesive action could be demonstrated in the simulated washing experiment for PEG 600, PEG 12,000, a graft copolymer of PEG 6000 and vinyl acetate, and polyurethanes obtainable by reaction of, for example, PEG 12,000. The graft copolymer and the polyurethanes exhibited better action than the free polyethylene glycols.
Cationic copolymers comprising styrene, butyl acrylate, butadiene, laurylmethacrylate, N-methyloylacrylamide and quaternized dimethylaminoethylmethaacrylate are proposed to confer both antibacterial and antistatic action on hair. These polymers can be included in shampoos. 28
In recent months, marketers and suppliers have made advances in the prevention of damage, as well as in ease-of -use in hair coloring. There continues to be continued emphasis on achieving improvements in low VOC products, and the formulation of conditioners, colors and styling products that endure through many shampoo cycles.
1. Kim, Son Nguyen; Laubender, Matthias; Pierobon, Marianna; Winter, Gabi; Anionic, Ampholytic Copolymers for Low-Voc-Compositions, United States Patent Application 20080219934; September 11, 2008; assigned to BASF Aktiengesellschaft
2. Berezkin, Yuliya; Schmitt, Peter D.; Unal, Serkan; Polyurethane dispersions for use in personal care products, United States Patent Application 20080226569, September 18, 2008, assigned to Bayer MaterialScience LLC.
3. Maillefer, Sarah; Zenhaeusern, Benedikt; Doepner-Reichenbach, Ute; Moenks, Monika; Steinbrecht, Karin; Hair-Styling Foil and Method For Preparing Hair-Fixing Products in Foil Form, United States Patent Application 20080223395; September 18, 2008.
4. Carballada, Jose Antonio; Nijakowski, Timothy Roy; Murphy, Bryan Patrick; Huyghues –Despointes, Alexis M.J.A.; Hair care composition, United States Patent Application 20080210253, September 4, 2008, The Procter & Gamble Company.
5. Samain, Henri; Rollat-Corvol, Isabelle; Vic, Gabin; Livoreil, Aude; Cosmetic compositions comprising polymers comprising complementary chemical functional groups, United States Patent Application 20080226578, September 18, 2008, assigned to L’Oreal S.A.
6. Hentrich, Dirk; Richters, Bernd; Pulverulent styling composition; United States Patent Application 20080233071; September 25, 2008.
7. Benabdillah, Katarina; Lerda, Patrice; Rollat-Corvol, Isabelle; Samain, Henri; Hair shaping compositions comprising at least one silicone and at least one alkoxysilane having solubilizing functional groups, United States Patent Application 20080226576, September 18, 2008.
8. Kim, Son Nguyen; Garcia Castro, Ivette; Mathauer, Klemens; Ampholytic Copolymer, Production Thereof, and Use of the Same, United States Patent Application 20080227871; September 18, 2008, assigned to BASF AG.
9. Baxter, Steven Michael; Brown, James T.; Creamer, Marianne Patricia; Kohr, Alan Wayne; Manna, Joseph; Reeve, Paul Francis David; Suleiman, Halla Ahmad; Cationic polymer latex; United States Patent Application 20080216978; September 11, 2008; Rohm & Haas Company.
10. Tamareselvy, Krishnan; Barker, Thomas A.; Mullee, James E; Greenslade, Charles T.; Schmucker-Castner, Julie F; Filla, Deborah; Multi-Purpose Polymers, Methods and Compositions, United States Patent Application 20080233069, September 25, 2008, Lubrizol Advanced Materials.
11. Philippe, Michel; Metois, Alexandra; Cosmetic Composition Comprising at Least One Fatty-Chain Polylysine, Which is Intended to Improve the Surface State of Keratin Fibers, United States Patent Application 20080213206, September 4, 2008.
12. Bigorra Llosas, Joaquin; Behler, Ansgar; Amela Conesa, Cristina; Polymeric esterquats with asymmetric side chains, United States Patent Application 20080214776; September 4, 2008, Cognis Corporation.
13. Peffly, Marjorie Mossman; Hall, Nicole Alane; Personal Care Composition Comprising a Silicone Elastomer, United States Patent Application 20080206185, August 28, 2008, The Procter & Gamble Company.
14. Peffly, Marjorie Mossman; Brown, Mark Anthony; Staudigel, James Anthony; Zhang, Jun Ji; Personal Care Compositions Containing Cationic Synthetic Copolymer and a Detersive Surfactant, United States Patent Application 20080206179, August 28, 2008, The Procter & Gamble Company.
15. Bjornberg, Hakan Claes; Derici, Leo; Haggman, Bo Henrik;; Harcup, Jason Peter; Khoshdel, Ezat; Hair Care Compositions Comprising a Dendritic Polymer, United States Patent Application 20080247980, October 9, 2008, Unilever.
16. Cottard, Francois; Rondeau, Christine; Composition for the oxidation dyeing of keratin fibers, comprising at least one oxidation dye, at least one associative polymer, and at least one aminosilicone, United States Patent 7,410,505, August 12, 2008; assigned to L’Oreal S.A.
17. Cottard, Francois ; Rondeau, Christine; Oxidation dyeing composition for keratinous fibers comprising an associative polymer and a pearling agent, United States Patent 7,431,740, October 7, 2008; assigned to L’Oreal S.A.
18. Errey, Pauline Jane; Haas, Christine Lee; Hille, Vera; Stephens, Tracy; Hair coloring kits and methods of use thereof, United States Patent 7,431,742, October 7, 2008, assigned to The Procter & Gamble Company.
19. Bureiko, Andrei Sergeevich; Godfrey, Simon Paul; Raineau, Olivier Charles; Process and Kit-of-Parts for Improved Hair Conditioning After Coloring, Bleaching or Perming, United States Patent Application 20080233072, September 25, 2008, The Procter & Gamble Company.
20. Noecker, Bernd; Ghiasi, Fariba; Pre-treatment composition for colouring hair, United States Patent 7,402,181, July 22, 2008, assigned to KPSS - KAO Professional Salon Services GmbH.
21. De Boni, Maxime; Laguitton, Bruno, Debain, Jean-Daniel, Leave-in hair dyeing process using a composition comprising a colored polymer and an active cosmetic agent, WO 2008/032003, 20 March, 2008.
22. Guerin, Frederic; Gourlaouen, Luc; Simon, Pascal; Simon, Josselyne Raymonde Jacqueli; Cosmetic article and process for dry dyeing keratin materials, United States Patent Application 20080244837, October 9, 2008.
23. Barrass, Paul Leslie; Davies, Philip; James, Delyth Angharad; Pixley, Dale P.; McManus, Richard L.; Murphy, Bryan P.; Jones, Stevan David; Method for the cosmetic treatment of hair and implement for carrying out the same, United States Patent 7,425,220, September 16, 2008, assigned to The Procter & Gamble Company.
24. Cannell, David W.; Fadeeva, Natalya; Van Nguyen, Nghi; Compositions comprising at least one aminated C5-C7 saccharide unit, and their use for the protection and/or repair of keratinous fibers, United States Patent 7,431,937; October 7, 2008, assigned to L’Oreal S.A.
25. Shmuylovich, Gregory; Kalinoski, Henry T.; Picone, Robert;; Rosen, Jacob;; Kravetz, Michael A.; Kits and methods for evaluating hair, United States Patent Application 20080241854, October 2, 2008, assigned to L’Oreal S.A.
26. Schwartz, James Robert; Johnson, Eric Scott; King, Bonnie Theresa; Margraf, Carl Hinz; Tomos, Gregory V.; Warnke, David Thomas; Chang, Deborah W.; Dunlop, David Scott; Labitzke, Kevin M.; Murawski, Sandra Lou; Gore, William Jeffrey; Verbrugge, Theodore Jay; Brown, Mark Anthony; Coffindaffer, Timothy Woodrow; Asante, Afua Asiedua; Wells, Robert Lee; Manuel, Teresa Cuasay; Geary, Nicholas William; Asare, Martin; Composition comprising a particulate zinc material, a pyrithione or a polyvalent metal salt of a pyrithione and a synthetic cationic polymer, United States Patent Application 20080206355, August 28, 2008, assigned to the Procter & Gamble Company.
27. Bockmuhl, Dirk; Hohne, Heide-Marie; Wrubbel, Noelle; Heidemeter, Dorothee; Dahlmann, Doris; Plantenberg, Thomas; Jonke, Hermann; Bayersdorfer, Rolf; Schafer, Andre; Breves, Roland; Antiadhesive polymers for prevention of adhesion of microorganisms to textiles and for prevention of laundry odor, United States Patent Application 20080220034, September 11, 2008, assigned to Henkel KGaA.
28. Krishnan, Venkataram; Antimicrobial and antistatic polymers and methods of using such polymers on various substrates, United States Patent Application, 0080226584, September 18, 2008.