CHROMISM OF PARTIALLY SAPONIFIED POLY(VIN YL ALCOHOL) IN ORGANIC-SOLVENTS

The chromism of partially saponified poly(vinyl alcohol) (P-PVA) in or ganic solvents has been investigated. P-PVA was colored in organic sol vents having a refractive index close to that of P-PVA. As the amount of residual vinyl acetate unit in P-PVA increased, the coloration of P -PVA became clear, and the maximum of the transmitted light shifted to the long wavelength side. The color of the transmitted light was comp lementary to that of the scattered light. This indicates that an inter secting point of the dispersion curve of P-PVA and that of organic sol vent was in the visible region, and that the light at the intersecting point transmitted P-PVA and the other was reflected by P-PVA. As the refractive index of organic solvent decreased, the maximum of the ligh t transmitted P-PVA shifted to the short wavelength side. When methano l having a low refractive index was added to an organic solvent having a high refractive index, the maximum of the light transmitted P-PVA w as shifted from the short wavelength side to the long wavelength side with a small amount of methanol, and was conversely shifted from the l ong wavelength side to the short wavelength side with a large excess o f methanol. These interesting phenomena were attributed to the competi tion between the decrease in the refractive index of P-PVA due to a se lective adsorption of methanol from the mixed solvents and the decreas e in the refractive index of the mixed solvents by the addition of met hanol.