1999 ANNUAL SCIENTIFIC MEETING 49 POLYMER-SURFACTANT INTERACTIONS STRUCTURE• RHEOLOGY• AND REACTION TEMPLATING Robert K. Prud'homme Princeton University, Princeton, NJ 08544 Mixtures of polymers and surfactants occur ubiquitously in consumer products applications. Polymers are often added to surfactant formulations to control rheology - sometimes with disastrous effects. While both the polymer and surfactant are water soluble their interactions can cause phase separation, gelation, or precipitation depending of the nature of the interactions, interaction strengths, and concentrations. We will begin by presenting the data on unmodified, or uniform polymers with surfactants. For repulsive interactions phase separation is the norm, and for attractive interactions again 'phase separation is the norm. But the equilibrium rules for both systems will be different. The rules for surfactants interacting with hydrophobically modified polymers are significantly different. The presence of hydrophobes on the polymer creates specific interaction sites with the surfactant micelles or mesophases. We will present three problems involving the interactions between surfactant structures and hydrophobically modified polymers. The first two involve association complexes between hydrophobically modified polymers in dilute and concentrated surfactant phases and the second involves polymerizations in surfactant mesophases. In several applications involving surfactant formulations it is desirable to have a fluid with tunable rheology. Adding polymers alone often results in phase separation and unstable formulation. Recently considerable work has gone into understanding hydrophobically modified polymers and their influence on formulation rheology. In the talk we will discuss how the control of surfactant morphology can be used to tune rheology. Neutron scattering under shear is used to clarify the structure of the association fluid in the case of hydrophobically modified polymers interacting with rod-like surfactant micelies. The second problem involves the miscibilization of polymers in concentrated surfactant phases. Polymers do not mix with surfactant lameliar or hexagonal phases because the polymer suffers too great a loss of configurational entropy if it were to be confined into the lameliar bilayers. However, with hydrophobically modified polymers it is possible to balance the entropy loss with the gain of hydrophobic interaction energy and, thereby, produce miscibile systems. Using neutron scattering we show the effect on the surfactant membrane stiffness of the interacting hydrophobically modified polymers. And we will show preliminary results on the use of these polymers to create stable multilamellar vesicles. For several oil/water/surfactant systems "cubic phases" can be obtained which are periodic, oil and water hi-continuous structures. We have successfully polymerized monomers in the aqueous phase to produce regular micro-porous gels with periodicity of 5 to 800 nm. These materials offer interesting opportunities for new classes of separation media, and media for controlled release and as separation media. ABSTRACTS abs.poly/surf SCS 12/99 RKP 7/99

50 JOURNAL OF COSMETIC SCIENCE POLYMER-STABILIZED LIPOSOMES: PREPARATION, CHARACTERIZATION AND APPLICATIONS Francoise M. Winnik, Ph.D. McMaster University, Hamilton, ON L8S 4M1 Canada Introduction Liposomes are spherical vesicles consisting of one or several bilayers of amphiphilic molecules surrounding an inner aqueous pool. This morphology enables the entrapment of lipophilic materials in the bilayer and of hydrophilic compounds in the aqueous compartment. This ability to transport substances soluble in either oil or water makes liposomes extremely attractive in cosmetics applications. • Other advantages offered by liposomes are their high affinity with biological membranes and their perceived ability to enhance the natural hydrating functions of skin'- and hair. Traditionally, the liposome membrane constituents were selected among natural phospholipids, such as lecithin (phosphatidylcholine), phosphatidylserine, and phosphatidylethanolamine. Unlike other tissues, the stratum comeurn is devoid of phospholipids) Therefore, the membrane of liposomes ideal for topical applications should be composed of amphiphiles similar to skin's lipid lamellae. Natural derivatives, such as ceramides and cerebrosides, when mixed with cholesterol and palmitic acid were shown to form liposomes. 4 More recently, it was reported that stable liposomes can be prepared from a large number of synthetic lipids. 5 These vesicles, known as non-phospholipid liposomes (NPL's), are obtained from a mixture of three types of lipids: (a) a main amphiphile, such as n- octadecyldiethylene oxide, (b) a modulator, usually cholesterol, and (c) an ionogen, such as dioctadecyldimethylammonimn bromide (DDAB) in the case of cationic vesicles or dioctadecyl phosphate (DP) in the case of anionic NPL's. A major shortcoming of liposomes as delivery agents in cosmetics formulations is the fragility of the bilayer membrane, especially in the presence of surfactants. A promising method to strengthen the liposome is to anchor or ligate polymers to the lipid bilayer. In addition, the outer surface of liposomes can be endowed with specific properties by further modifications, such as the attachment of polymers carrying specific receptors or responsive to changes in temperature, pH, or ionic strength. 6 The design and properties of complexes between non-phospholipid liposomes and polymers, such as Quatrisoft LM200 and its fluorescently-labeled derivatives, will be discussed. Techniques used to monitor the properties of liposomes and polymer/liposome complexes will be presented. They include fluorescence spectroscopy, dynamic light scattering, centrifugation assays and gel permeation chromatography. Materials and Methods Cholesterol, n-octadecyldiethylene oxide (EO2C•sH37), and dicetylphosphate (DCP) were purchased t¾om Aldrich Chemicals. Quatrisoft LM200 and (hydroxyethyl)cellulose (HEC, approximate MW 400 000) were gifts of Amerchol Inc. Pyrene-labeled Quatrisoft LM200 (LM200-Py) and HEC-N • PyC•2 were prepared as described previously. 7 It contains 2.9 x 10 -5 mol Py g-• of polymer or on average 1 Py per 190 glucose units. Instrumentation. Fluorescence spectra were recorded on a SPEX Industries Fluorolog 212 spectro•neter equipped with a GRAMS/32 data analysis system. UV spectra were recorded with a Hewlett Packard 8452 photodiode array spectrometer. Dynamic light scattering measurements were performed with a Brookhaven Instrument Corporation Particle Sizer Model BI-90. Liposomes were prepared by extrusion using a Lipofast extruder (Avestin, Canada) fitted with polycarbonate filters (200 nm pore size) obtained from Avestin. Liposome preparation. A solution in chloroform of EO2CtaH37, cholesterol, and DCP (75/20/5 w/w) was poured into glass vials. The solvent was evaporated under a stream of nitrogen. It was dried under high vacuum for at least 2 hr. The dry lipid film was hydrated with aqueous NaCI (I mmol) to give a 20 g L • lipid suspension. The lipid suspension was subjected to extrusion at 65 øC. Liposome/polymer mixtures were prepared by addition of an extruded liposome suspension (2.7 mL) to polymer solutions (0.3 ink) of various concentrations. The mixtures were allowed to equilibrate for at least 2 hr prior to spectroscopic measurements.