336 JOURNAL OF COSMETIC SCIENCE such assaults by replacing the lost oils and proteins (10). However, sometimes the body is not able to respond as expected and the normal healthy appearance of the skin becomes red and irritated (11-13). One response to this deficiency has been to employ polymeric thickhers that help to stabilize emulsions by imparting a yield point to the aqueous continuous phase. Two excellent examples of such polymers are the naturally occurring, marine-derived poly- saccharide, xanthan, and the synthetically derived, hydrophobically modified poly(acry- lates) (14,15). Both of these polymers can suspend oil droplets indefinitely when used at low concentration with or without additional surfactants. Both of these polymeric species, and in fact, most polymers that function in this capacity, are typically artionic polymers. They generally require the addition of base to promote their thickening and suspending characteristics. Because they are artionic in use, these polymers have little desire to interact with the proteins of the skin and hair. Cationic polymers, on the other hand, are very well known for their unique conditioning benefits because these polymers do have a natural attraction for the skin and hair (16-18). However, there are very few cationic polymers that can also be used to impart a yield point to the aqueous continuous phase of an emulsion. Some cationic polymers are capable of thickening aqueous mixtures, but they are not necessarily efficient rhe- ology modifiers and they are rarely used as conditioning polymers (19,20). On the other hand, some unique, hydrophobically modified cationic conditioning polymers, while showing some thickening abilities, do not impart a yield point to aqueous solutions. In particular, polyquaternium-24 has demonstrable hair and skin conditioning benefits but does not impart a yield point to aqueous solutions (21). Recently, we reported a unique, synergistic polysaccharide/polysaccharide blend wherein polyquarternium-24, when carefully blended with amylose, a linear, naturally occurring polysaccharide available from normal potato starch, affords an unusually thickened, aqueous, three-dimensional polymer network complex (22). This network creates a yield point in aqueous solutions when the polyquaternium-24 and amylose are used at low concentrations in very specific weight ratios. We wish to expand on the properties of this unique polymer blend by demonstrating that by employing the polyquaternium-24/ amylose complex, stable surfactant-free formulations can be developed. The aqueous complex can suspend a variety of oils and finely ground solid materials such as titanium dioxide. The combined use of the cationic conditioning polymer to also stabilize sur- factant-free emulsions shows that this hydrophobically modified cationic polymer is quite versatile. EXPERIMENTAL MATERIALS The preparation of the complex formed between polyquaternium-24 and amylose is described elsewhere (22). In summary, a hot aqueous solution of polyquaternium-24 is carefully blended with a hot aqueous solution of potato amylose, such that the resultant mixture is composed of 1.0 part polyquaternium-24, 0.25 part amylose, and 98.75 parts deionized water. The hot mixture is then carefully cooled, which allows the polymer complex to form, building aqueous viscosity. Additional raw materials used in the study

POLYQUATERNIUM-24/AMYLOSE COMPLEX 337 are summarized in Table I. The emulsion samples were made using a Talboy overhead stirrer at 15 rpm, and the viscosity of the samples was measured using a standard Brookfield DV-II+ viscometer, using spindle # 3 at 25øC. The oven samples were placed in a Blue M © Stabil-Therm oven, and the photos of formulations were taken via a Polaroid camera attached to an Olympus AH-2 model microscope. RESULTS AND DISCUSSION FORMATION OF OIL SUSPENSIONS An initial study was done to examine the ability of the aqueous polyquaternium-24 and amylose blend to suspend water-insoluble oils and solids by using various conditioning and emollient oils as well as titanium dioxide at 1, 5, and 10 wt % concentrations. The oils and solids were directly dispersed without strict control of biological conditions into 1% aqueous mixtures of the complex at 25øC (the complex itself must be created at higher temperatures) (22). The samples were then left undisturbed for six weeks at room temperature. The samples were visually inspected weekly for signs of incompatibility. The results of this initial study appear in Table II. Several of the emulsified samples remained clearly suspended at room temperature for six weeks. In particular, the emulsified silicon oils showed good resistance to oil and water partitioning. Microscopic examination after two weeks of one such 10% emulsion con- taining cyclomethicone is shown in Figure 1. The appearance of the various-sized oily droplets is evident in the photo. Samples of emulsions prepared using polyquaternium- 24 without the carefully blended amylose separate in a matter of days. The combination of the hydrophobic, cationic cellulose ether and amylose is clearly needed to maintain stable suspensions. It appears that the polyquaternium-24/amylose complex can suspend oils at room temperature at oil concentration levels at least as high as 10% without separation between the oil and water phases even after a six-week time period. We also examined the suspension of micronized TiO 2 in the complex. Figure 2 shows the fine dispersion of micronized TiO2 in the complex. This suspension also contained Table I Experimental Raw Materials INCI name Trade name Company Dimethicone Amersil © OSi Cyclomethicone Amersil VS © OSi Hydroxylated milk glycerides Cremerol HMG © Amerchol Polyquaternium-24 Quatrisoft © Polymer LM-200 Amerchol Isononyl isononanoate Salacos © 99 Nisshin Caprylic captic triglyceride Myritol © 318 Henkel Hydrogenated polyisobutene Panalene © Amoco Chemical Methyl gluceth- 10 Glucam © E- 10 Amerchol Diazolidinyl urea Germaben © II-E Sutton Laboratories DMDM hydantoin Glydant © Lonza Glycerin Glycerin Mallinckrodt Titanium dioxide Titanium dioxide Aldrich Amylose Amylose Sigma Chemical