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

340 JOURNAL OF COSMETIC SCIENCE Figure 2. Photomicrograph of a 1% suspension ofdimethicone and 0.5% titanium dioxide in a 1% aqueous solution of the polyquaternium-24/amylose complex (magnified 75x). Table III Prototype Skin Lotion Formulation Employing Polyquaternium-24/Amylose Complex a Dimethicone (Amerchol) 5.00% PQ-24/amylose complex b 91.50% Hydroxylated milk glycerides (Amerchol) 2.00% Glycerin (Mallinckrodt) 0.50% Methyl gluceth-10 (Amerchol) 0.50% Titanium dioxide (Aldrich) 0.50% Preservative c q.s. • Procedure: Disperse micronized titanium dioxide into previously prepared pQ-24/amylose complex at room temperature, followed by dispersion of the dimethicone oil into the complex. Add molten hydroxylated milk glycerides (previously melted in a 45øC oven prior to use). Stir 15 minutes, add glycerin and methyl gluceth-10, and stir for an additional 15 minutes. Add preservative and stir for one hour. b Complex comprises approximately 0.9% Quatrisoft and 0.2% amylose. c DMDM hydantoin at 0.40% or diazolidinyl urea at 1%.