338 JOURNAL OF COSMETIC SCIENCE Table II Results of a Six-Week, Room-Temperature, Emulsion-Stability Study of Various Oils and Solids Suspended in the Aqueous Polyquaternium-24/Amylose Complex Weight Week Week Week Week Week Week Emulsified component percent 1 2 3 4 5 6 Mineral oil Isononyl isononanoate Dimethicone Cyclomethicone Caprylic capric triglycerides Hydrogenated polybutene Titanium dioxide ]_ ß ß ß ß ß ß 5 ß ß ß ß ß SU 10 ß ß ß ß ß ß 1 ß ß SU SU SU SU 5 ß ß ß SU SU SU 10 ß ß ß ß ß ß 1 ß ß ß ß ß SU 10 ß ß ß ß ß ß 10 ß ß ß ß ß ß 1 ß ß SU U U U 5 ß ß SU U U U 10 ß ß SU U U U 5 ß ß ß ß ß SU 10 ß ß ß ß ß ß 1 ß ß ß SU SU U 5 ß ß ß ß ß ß 10 ß ß ß ß ß ß Slightly unstable (SU): Material is starting to separate. Unstable (U): Material has separated into two distinct phases. (*) indicates a stable emulsion. approximately 1% dimethicone, the droplets appearing as dark circles against the white TiO 2 particles. What is particularly intriguing is the apparent ability of the complex to prevent the TiO 2 and the oil from agglomerating. The TiO2 remains well dispersed in the mixture. PREPARATION OF SKIN LOTION FORMULATIONS USING THE POLYQUATERNIUM-24/ AMYLOSE COMPLEX Following the completion of the initial oil-suspending study, a prototype skin lotion formulation was developed using the polymer complex (Table III). The simple prototype formulation was developed by taking advantage of the functional attributes of various well-known skin conditioners. Hydroxylated milk glycerides and glycerin are excellent emollients and humectants, respectively. Dimethicone oil is the primary skin condi- tioner, but the polyquaternium-24 also has demonstrable feel properties. Methyl glu- ceth-10 was added to impart rheological control to the slightly pituitous polyquater- nium-24/amylose complex. These formulations impart a soft, lubricious feel to the skin with little tackiness during drying. Once dried, the formulations leave a soft afterfeel. The formulations showed no signs of pilling upon application, an occurrence sometimes noted in anionic poly(acry- late) thickeners. We investigated different application methods, including pump sprays

POLYQUATERNIUM-24/AMYLOSE COMPLEX 339 . : Figure 1. Photomicrograph of 10% suspension of cyclomethicone in a 1% aqueous solution of the polyquaternium-24/amylose complex (magnified 37.5 x). and pouring devices, and found that the shear-thinning complex allows for the lotions to be easily pumped or poured. PRESERVATIVE AND COMPATIBILITY STUDY OF SURFACTANT-FREE FORMULATIONS Polysaccharides, especially starch, are particularly susceptible to contamination, and dissolved starch is an excellent bacterial growth medium. Breakdown of the amylose component of the polyquaternium-24/amylose complex results in eventual collapse of the stabilizing matrix. To examine the coalescence stability of the formulation described in Table III, four similar samples were prepared. Two were stored at room temperature, and two were stored in a 45øC oven for six weeks to mimic accelerated aging. Diazo- lidinyl urea and DMDM hydantoin were examined as potential preservatives. The samples were visually inspected for signs of creaming or separation, and the viscosity was monitored weekly. The results of both the oven-accelerated and room temperature studies are summarized in Figures 3 and 4. After one week, all four samples showed a slight initial decrease in viscosity, which was