Rhodia and Procter & Gamble researchers have come up with block copolymers that enhance foam in detergent systems.1 These are block copolymers comprising a cationic block and a nonionic block. A broad range of chemistries are disclosed, but the exemplified polymers consist of blocks of dimethylaminoethyl methacrylate and hydroxyethylmethacrylate and triblock copolymers that also contain acrylic or methacrylic acids.
Block copolymers offer the amphipathic properties of surfactants but on a larger scale. We can expect an increase in the prominence and diversity of block copolymers as a direct result of the introduction of living free radical polymerization techniques. It might be interesting to speculate on the mechanism whereby these polymers enhance foam. Foams are formed when surfactant molecules diffuse to and adsorb at an expanding liquid/air interface. Polymer molecules diffuse slowly—too slowly to adsorb at the expanding interface in the instant before it collapses. Therefore, it is reasonable to deduce that these polymers stabilize foam that is initially formed by adsorption of surfactant at the interface. Foams collapse by two main mechanisms; draining of the liquid and puncture of the lamellae. The foam lamellae are the junctions between two foam bubble cells and the Plateau Border is situated at the triple-cell junction. The Laplace pressure in the liquid components of the foam is inversely proportional to the curvature of the interface. The higher curvature of the plateau border results in a lower pressure in that region, causing the liquid in the foam to drain preferentially from the lamellae to the plateau borders. Based upon this reasoning, it can be understood that drainage can be hindered in two ways, namely by blockage of the lamellae or by blockage at the plateau border.
About two decades ago, Des Goddard carefully measured the drainage from foam films and he deduced that polyquaternium-24 adsorbed across the lamellar interface and hindered the drainage of liquid from the foam. About 30 years ago, Stig Friberg concluded that certain liquid crystals blocked the plateau border region and thus delayed foam drainage and conferred longer-term stability on surfactant foams.
In the case of the Rhodia polymers, hindered drainage of the lamellar liquid could be caused by adsorption of the cationic entities at the lamellar surface with the nonionic and/or anionic blocks in the lamellar liquid. Alternatively, formation of phase-separated coacervates between the cationic polymer and the anionic surfactant could result in blockage of the plateau border. Of course, if the interaction of the cationic polymer is strong enough to form “inverse micellar” structures, then the phase-separated particles could cause a local reversal of the curvature in the lamellae, resulting in breakage of the lamellar film and subsequent foam destabilization. This limit could be a reason for the specified maximum cationic charge density in the written description and in claims of the patent application. This type of foam destabilization mechanism has been extensively reported by Peter Garrett. It would be interesting to conduct careful film drainage and phase studies on these systems to understand precisely how they work.
One of our previous articles included P&G’s revelation of easily dissolvable, porous solid shampoos. This line of research has been extended to provide delivery of cationic conditioners that would normally be incompatible with liquid shampoos and enhanced delivery of these actives to the keratin substrate. Another claimed advantage of porous solids is the ability to have one scent for the solid and then to allow a second different fragrance to bloom when the solid was wetted by water.2 The porous solids are made by mixing the surfactants, glycerin as plasticizer and water in the presence of a water soluble polymer. The working example shows poly(vinyl alcohol) as this water-soluble polymer, but the invention is not restricted to this polymer; a wide range of synthetic and natural polymers may be used. After a heating and mixing cycle, the porous solid is formed by aeration.
The aroma of fragrance can be prolonged by encapsulation. It has now been claimed that certain cationic capsules are retained to a larger extent than nonionic capsules.3 The cationic urethane capsules are prepared by reacting 2-hydrazino-N,N,N- trimethyl-2-oxoetanammonium chloride with a solvent –free di-isocyanate base on hexamethylene diisocyanate. The capsules are prepared to consist of a core of a urethane protected aqueous phase dispersed in a continuous fragrance oil phase that is surrounded by a crosslinked polyurethane shell.
Isethionates have been known as mild surfactants for at least three decades; they have been the basis of non-soap detergent bars such as Dove. Recently, Unilever researchers discovered that the mildness can be enhanced by including mildness benefit agents that can be flocculated by cationic polymers present in the formulation and delivered as flocs upon dilution of the formulation.4 The preferred benefit agent in this case is petrolatum and the cationic polymers are well known polymers like polyquaternium-10 and guar hydroxypropyltrimonium chloride. This could form the basis of shampoos that are mild to the skin.
Cationic guar has been a known additive for 2-in-1 shampoos for more than three decades. However, it has now been shown that improved post-shampoo detangling times are achieved by including a small degree of hydrophobic substitution in the cationic guar derivatives.5 The hydrophobe is added by the well-known ring opening of the appropriate glycidyl ether.
A conditioning shampoo that contains a conditioning gel phase in the form of vesicles is described by Unilever researchers.6Cationic conditioners are usually incompatible with anionic shampoos and, as a consequence, conditioners based upon cationic surfactants are usually applied as separate post-shampoo products. The Unilever researchers prepared a conditioning gel phase by combining a small amount of water, fatty alcohol, a long-chain secondary anionic surfactant (sodium cetostearyl sulfate) and a long-chain cationic surfactant (behenyltrimethylammonium chloride) and subjecting the mixture to high shear to form a stable vesicular gel phase. Prolonged shear causes the lamellar gel phase to “roll-up” into an array of multilamellar vesicles. The gel phase was added to a dilute primary surfactant solution (sodium laureth sulfate) to form a conditioning shampoo, which conferred good wet smoothness on hair.
Freeze-Thaw stability can still be a problem for concentrated or vesicular phases. The subject of freeze-thaw stability in this context is addressed by Rhodia researchers who have developed new hydrophobically modified alkali swellable (HASE) in which the hydrophobes are specially designed macromonomers.7
Rhodia also revealed HASE thickeners with improved clarity and improved resistance to salt. These polymers, based upon the conventional methacrylic acid/ethylacetate system have “associative” monomers that are bicycloheptyl polyethers and long chain polyethers.8 It has also been shown that mixtures of certain cationic polysaccharides and anionic HASE polymers can give systems with enhanced viscosity stability with respect to increased ionic strength and also to elevated temperatures.9
Acryloyl taurate thickeners have improved resistance to salt but, according to Shiseido scientists, these polymers have a sticky feel which can be ameliorated by copolymerizing acrylamidomethylpropane sulfonate with hydroxyethyl methacrylate and an appropriate crosslinker.10 Carbomers are crosslinked polyacrylic acid prepared by precipitation polymerization. Carbomer technology was developed by BF Goodrich (now Lubrizol). It is interesting that a BASF patent application is directed to the preparation of carbomers using the same monomer, same crosslinker, and same solvent mixture as the BF Goodrich technology. The BASF patent application reveals a quicker process can be realized by the use of two initiators in sequence with a deliberate temperature change during the reaction.11
There are many rheology modifiers available to the personal care formulator, but a recent trend has been directed toward multifunctional polymers, especially to rheology modifiers with film-forming fixative properties. BASF has contributed to this trend by revealing copolymers of acrylic acid, N-vinylpyrrolidone, a cationic monomer (preferably N-vinylimidazole), and a hydrophobic monomer which may be an long chain ester of methacrylic acid having an ethoxylated spacer chain, preferably PEG-25 methacrylate.12 Such rheology modifiers disperse rapidly in aqueous systems of pH 6-8 to yield gels with hair fixative properties.
Whipped emulsions are divulged by a L’Oréal researcher to provide all the benefits of a pomade but with improved elasticity.13 The products are formed by using two polysaccharide emulsifiers and a gelling agent. One of the emulsifiers is xanthan gum and the other is a mannan polymer (this includes a wide range of polymers including guar, locust bean gum and pectin). The gellant may be carbomer or an acryloyl taurate thickener.
Longer-lasting conditioning silicone quaternaries have long been known as hair conditioning compounds. A recent patent application from Evonik Goldschmidt is directed to silicone quats that confer conditioning with longer lasting conditioning through several shampoo cycles.14 The premise is that long-term substantivity to hair requires the conditioning agent to contain a string of cationic charges. Evonik Goldschmidt achieved this by polymerizing cationic monomers and grafting them to silicone backbones. In general, water-soluble monomers polymerized in the presence of silicones yield a mixture of water-soluble polymers and unsubstituted silicones because the two ingredients are incompatible and attachment of the polymer chain to the silicone would require appropriate “coupling groups.” Evonik Goldschmidt researchers rose to the challenge by polymerizing the cationic monomers in the presence of silicone polyethers. The ether groups are compatible with the quat monomers and they readily chain transfer to give graft copolymers. Once grafted, the copolymers are quaternized to confer permanent positive charges with enhanced substantivity to hair. The grafts are obtained by polymerizing the readily available monomers, dimethylaminoethylmethacrylate or 3-trimethylammoniopropyl methacrylamide.
Biopolymer latex may be produced by crosslinking starch with glyoxal (for example in an extruder) followed by cryogenic grinding. Such biopolymer latexes are revealed by Honeywell to be suitable hair fixatives with the benefit that the polymers are derived from natural and sustainable resources.15
Conventional conditioning agents are incompatible with hair dye formulations. Dow researchers have revealed that they have resolved the need to simultaneously color and condition the hair by the addition of ethylene acrylic acid copolymers optionally in combination with a metallocene polymerized polyolefin.16 The addition of one percent polymer provided advantages in wet combing benefits. The oxidizing agents used in hair colorants damage hair fibers. Moreover, the rapid kinetics of oxidation can cause uneven coloring of the hair, especially when long preparation procedures are involved such as in selective highlighting. Encapsulating the oxidation precursors with polymethacrylates, poly(vinylacetate)s or shellacresults in a more uniform coloring process.17
Our review of recent patent applications revealed interesting advances in technologies relating to the use of polymers in hair care:
1. Block copolymers continue to make inroads into personal care products. In this case we identified the proposed use of cationic/nonionic block copolymers to stabilize surfactant foams.
2. Solid, easily dispersible foams offer advantages with respect to improved 2-in-1 conditioning over conventional liquid systems and the capability to build in stimuli-responsive fragrance attributes.
3. Super-mild detergent systems are claimed from the inclusion of cationic polymer induced flocs of petrolatum in isethionate-based systems.
4. Vesicular gel phase conditioners can be included in anionic shampoos for 2-in-1 cleaning and conditioning.
5. There are some advances in rheology modifiers mainly around the inclusion of complex hydrophobes within the associative thickeners.
6. The trend toward multi-purpose thickeners continues with a rheology modifier that contains vinylpyrrolidone monomer to confer additional film-forming characteristics.
7. Longer-lasting silicone conditioning of colored hair is claimed from graft copolymers of dimethylaminomethacrylate on a silicone ether backbone.
8. Encapsulation of hair coloring precursors is advanced as a way to achieve more consistent coloring and to mitigate hair damage due to the coloring process.
1. Yeung, Dominic Wai-Kwing; Bergeron, Vance; Bodet, Jean-Francois; Sivik, Mark Robert; Kluesener Bernard William; Scheper, William Michael; “Polymers, compositions and methods for use for foams, laundry detergents, shower rinses and coagulants,” US Patent Application 20110257015, Oct. 20, 2011, Assignee Rhodia Inc.
2. Glenn, JR., Robert Wayne; Kaufman, Kathleen Mary; Dunbar, James Charles; Gardlik, John Michael; Murphy; Bryan Patrick; “Porous, Dissolvable Solid Substrate and Surface Resident Coating Comprising Water Sensitive Actives,” US Patent Application 20110195098, Aug. 11, 2011; US Patent Application 20110189247, Aug. 4, 2011; US Patent Application 20110189246, Aug. 4, 2011; US Patent Application 20110182956, July 28, 2011;US Patent Application 20110182956, July 28, 2011.
3. Ouali, Lahoussine; Jacquemond, Marlene; “Microcapsules and uses thereof,” US Patent Application 20110230390, Sept. 22, 2011.
4. Tsaur, Liang Sheng; Ananthapadmanabhan, Kavssery P.; “Personal Wash Cleanser Comprising Defined Alkanoyl Compounds, Defined Fatty Acyl Isethionate Surfactant Product and Skin or Hair Benefit Agent Delivered in Flocs Upon Dilution,” US Patent Application 20110245125, Oct. 6, 2011, assignee Conopco, Inc., dba Unilever.
5. Baldaro, Eva; Bouzeloc, Sylvie; Postiaux, Stephanie; Schirosi, Esterina; Soontjens, Dirk; Ugazio, Stephane; “Home And Personal Care Compositions,” US Patent Application 20110189248, Aug. 4, 2011.
6. Cooke, Michael James; Pham, Thuy-Anh; Murray, Andrew Malcolm; “Conditioning shampoo comprising an aqueous conditioning gel phase in the form of vesicles,” US Patent Application 20110243870, Oct. 6, 2011.
7. Hough, Lawrence Alan; Bzducha, Wojciech; Herve, Pascal; Hennaux, Pierre; O’Rourke, Mary; Park, Ericka; “Compositions with freeze thaw stability;” US Patent Application 20110223125; assignee Rhodia Operations
8. Houg,; Lawrence; Bzducha, Wojciech; Herve, Pascal; Hennaux, Pierre; Douglass, Andrew; Adamy, Monique; Gonzalez, Inigo; Rheology modifier polymer; US Patent Application 20110243873, Oct. 6, 2011; assignee Rhodia Operations
9. Talingting Pabalan, Ruela; Martinez-Castro, Nemesio; Kesavan, Subramanian; Labeau, Marie Pierre; “Rheology modifier compositions and methods of use,” US Patent App. 20110256085, Oct. 20, 2011; assignee Rhodia Operations.
10. Sogabe, Atsushi; Kaneda, Isamu; “Water Soluble Thickener And Cosmetic Preparation Containing Same;” US Patent Application 20110237752, Sept. 29, 2011; assignee Shiseido Company, LTD
11. Nguyen Kim Son; Jahnel, Wolfgang; “Method for producing cross-linked acrylic acid polymers;” US Patent Application 20110158929, June 30, 2011; assignee BASF SE.
12. Nguyen, Kim Son; Fast, Ina; Werner, Rolf; “Anionic associative rheology modifiers,” US Patent App. 20110218295, US Patent App.20110218296, Sept. 8, 2011; assignee BASF SE
13. Hunter, Nikisha; “Whipped composition for the treatment of keratin fibers,” US Patent App. 20110224309, Sept. 15, 2011; assigned to L’Oréal.
14. Kuppert, Dirk; Ferenz, Michael; Schwab, Peter; Knott, Wilfried; Silber, Stefan; “Nitrogen-Containing Organosilicon Graft Copolymers,” US Patent Application 20110230619, Sept. 22, 2011. Assignee Evonik Goldschmidt GMBH
15. Wheeler, Mark Richard; Orawski, Philip; Higuera, Malena; Mores, Lee; “Hair fixatives comprising cross linked starches,” US Patent App. 20110212145, Sept. 1, 2011, assignee Honeywell International Inc.
16. Jordan, Susan L; Schwartz, Curtis; “Personal care compositions for coloring hair,” US Patent Application 20110236334, Sept. 29, 2011.
17. Welz, Carolin; Manneck, Hartmut; Kleen, Astrid; Akram, Mustafa, “Coated Coloring Agents,” US Patent App. 20110247149, Oct. 13, 2011.