REDOX BEHAVIOR IN PHOTOCHROMIC POLYMERS OF THIAZINE SERIES

The photochromic redox behavior of the thiazine polymers prepared by the condensation reactions of the N‐hydroxymethylacrylamido components of vinyl polymers with four thiazine compounds, i.e., thionine and asym‐dimethyl‐, trimethyl‐, and mono‐methylthionine chloride, in combination with various electron‐donating components, including hydroxyl, amino, and sulfhydryl groups and ferrous ion, were investigated. The reversible color fading (at ca. 600 mμ) of the thiazine polymers under illumination in the solid state was found to be largely dependent upon the moisture content in the polymer. This, together with other evidence, suggests that water molecules adsorbed on the active groups in the polymer also participate in the reduction of the thiazine components. Polyvinyl alcohol, cellulose, and enzymes such as papain, when incorporated in the photochromic compositions, induce remarkable improvements of the photochromism, in both the sensitivity to light and the rate of color recovery in dark; the incorporation of the ferrous–ferric ion system into the polymers in the form of acrylates also improves photochromism remarkably, especially the rate of recovery. Copyright © 1969 John Wiley & Sons, Inc.