J. Cosmet. Sci., 62, 251–258 (March/April 2011) 251 Polymer/surfactant interactions and nanostructures: Current development for cleansing, release, and deposition of actives P. SOMASUNDARAN and P. PUROHIT, Center for Particulate and Surfactant Systems and Langmuir Center for Colloids and Interfaces, Columbia University, New York, NY 10027. Synopsis Nature exhibits a variety of remarkable phenomena that are useful but diffi cult to be imitated in real life. Examples are a “touch me not” plant folding up upon being attacked or microbes depositing on ocean vessels even under hostile conditions. Understanding of mechanisms governing these phenomena can prove powerful for developing new classes of cosmetic products. Systems based on polymer/surfactant colloid chemistry are being developed for achieving transport and release of cosmetic and pharmaceutical molecules at desired rates and desired sites. Modifi cations of the surfactants and polymers provide cleansing properties such as scaveng- ing of odor and sebaceous body excretions and controlled delivery and deposition of sensory/hygienic attrib- utes. New surfactants (sugar based and bio surfactants), hybrid polymers (silicone based and hydrophobically modifi ed) and nanogels have been recently synthesized which may have applications in fi elds of cosmetics/ fragrances/drugs etc. Due to the associative nature of the hydrophobic groups, hybrid polymers can form intramolecular nanodomains at all concentrations of the polymer and inter-molecular aggregates at high concentrations. New hybrid polymers and nano-gel particles can be developed with ability to extract and deliver actives by varying such properties as swelling/shrinking capacity and sensitivity to temperature, shear and dilution. Control of such properties as size, shape and cross linking of nanohybrid particles offer maxi- mum opportunity for producing families of nanovehicles in personal and homecare industry. This review ar- ticle provides an insight into current developments in fi eld of nano-surfactant science, comprising discussions on nanogel particles, hybrid polymer and liposomes. INTRODUCTION Nano-sized systems are currently fi nding increasing applications in personal care (1-4) and pharmaceutics (5,6). Potential advantages of these nano systems include homoge- neous distribution in the formulation, better encapsulation and the ability to release en- capsulates at targets in a controlled fashion. The delivering agents as nanogel particles/ emulsions, hybrid polymers, and liposomes are discussed in this paper. Innumerable ac- tive nanostructures exist in nature in different forms, exhibiting a variety of sensory phenomena. A most intriguing example is that of the nodes of plant ‘Mimosa pudica’ that is responsive to the stimulus of touch (7). When the plant is touched, the liquid in the nano and microgels in the nodes apparently get squeezed out leading to the folding of the leaves and dropping of the braches. This principle can conceivably be used in designing

JOURNAL OF COSMETIC SCIENCE 252 nanogel materials for the controlled delivery of fl avors (8), fragrances (4), drugs (9), vita- mins (10), steroids (10), proteins (11), or enzymes (12). Ideally these materials should be capable of prolonged activity, protect actives against adverse conditions and release them at desired site with desired stimulus. The polymers can be modifi ed with functionalized groups that are responsive to external stimuli. Such nanoparticles, owing to their submi- cron size, can also be well dispersed in the cosmetic and personal care products Hybrid polymers are another nano-sized system which can be employed for effective de- livery of cosmetic ingredients. In hybrid polymers, the polymeric chains are associated with hydrophobic and hydrophilic moieties. In order to avoid unfavorable contacts be- tween the solvent and moieties of different polarity, they form nano-domains. These do- mains can grow and shrink depending on the enviromental conditions and hence can be utilized to encapsulate and release actives. Also hybrid polymers such as modifi ed sili- cones can be used as an oil phase for oil-in-water nanoemulsions where the nanodroplets can act as carriers of actives. Liposomes can be used for encapsulation and release of cos- metic attributes. Liposomes are nanocapsules with hydrophobic domains, but with differ- ent permeation properties. Correspondingly the cleansing agents such as conventional surfactants are produced from petroleum, or from seed oils such as palm or coconut oil. Production from petroleum contributes to the release of atmospheric CO2 while there is a limit to the amount of palm and coconut oil that can be manufactured responsibly, while preserving the rainforest. Hence there is a need for sustainable manufacturing of surfactants and development of greener surfactants is necessary for cosmetic industry for moving forward. Developement and use of the above systems for cleansing, con- trolled extraction and release of fragrance, fl avors and other attributes are explored in the following: NANOGEL PARTICLES Nanoparticles can be organic, inorganic or hybrid type. The organic nanoparticles include particles made out of organic polymers, e.g. poly(acrylic acid) and poly(acrylamide) (32). Inorganic nanoparticles are particles of inorganic elements and their compounds, e.g. gold nanoparticles. The third and a very novel class of nanoparticles are hybrid - organic/inorganic nanoparticles, e.g. silicone nanoparticles. There is very little work done on such hybrid nanoparticles. Somasundaran’s group had initiated the synthesis and characterization of functionalized silicone nanoparticles using the reactions between amino silicones and acid modifi ed silicones in a microemulsion system. It was observed that cyclic silicones can sol- ubilize skatole, an odor molecule, an order of magnitude higher than water. Clearly these hybrid silicone nanoparticles can be very effective for odor control (13,14). Currently mostly organic nanoparticles are employed as nano-delivery systems for cosmetic applications. EXTRACTION AND RELEASE OF ATTRIBUTES Controlled extraction and release of attributes can be achieved by using nanoparticles systems based on selective interaction. Use of nanoparticles as carriers of fragrance was tested by monitoring extraction of linalyl acetate from methanol solution by poly(acrylic acid) (PAA) and hydrophobically modifi ed poly(acrylic acid) nanoparticles. It was found