346 JOURNAL OF COSMETIC SCIENCE '-E"-CH2 CH--•CH2 • H•-CH2 I Jn L I m c5 -o Scheme 4. Vinyl caprolactam/PVP/dimethylaminoethyl methacrylate copolymer (VCL/VP/DMAEMA). '-•- CH2'-- OCH 3 C=O C=O OH OR Scheme 5. Butyl ester of PVM/MA copolymer (PVM/MA). _•CH2__ • H3 • H3 ell3 0=% C=O CU 3 0=% ,/C=O CH2CH3 CH2CH2OH Scheme 6. Isobutylene/ethylmaleimide/hydroxyethylmaleimide copolymer (IEHC). hair. As indicated in the previous section for oil treatments, the Nickerson contrast gloss parameter appears to be rather insensitive to the polymeric treatments of hair, as sug- gested by only minimal increases in the values of this parameter for modified fibers. In terms of peak intensity, we observed an increase for VCL/VP/DMAEMA-treated hair relative to untreated hair. On the other hand, hair treated with PVM/MA and IEHC resulted in peak intensities similar to or slightly less than that found for untreated dark brown hair. DULLING OF HAIR In order to examine the effect of hair dulling by surface deposits, we applied various amounts of a formulation containing 1.5% micronized ZnO. The micronized ZnO particles, ca. 50 nm in diameter, typically provide light absorption and scattering centers

LUSTER QUANTIFICATION OF HAIR 347 untreated PVP/VCL/DMEAMA Butyl Ester of IEHC PVM/MA Copolymer Figure 10. Images of hair treated with vinyl caprolactam/PVP/dimethylaminoethyl methacrylate copoly- mer, butyl ester of PVM/MA copolymer, and isobutylene/ethylmaleimide/hydroxyethylmaleimide copoly- mer (IEHC). Exposure values: f8, 1/6 s. 2õ0 I Vinyl Caprolactam/PVP/ 200 '] Dimethylaminoethyl Methacrylate Copolymer 1 õ0 untreated 100 50 0 , , 0 10 20 30 40 50 Distance (ram) Figure 11. Light distribution curves for untreated hair and hair treated with vinyl caprolactam/PVP/ dimethylaminoethyl methacrylate copolymer. in sunscreen products, hence resulting in an increase in diffuse reflection. ZnO is, however, frequently employed in formulations because its light-scattering efficacy in the visible range is lower than in the case of other pigments such as titanium dioxide. Thus,