The solid state photobleaching and photocrosslinking of copolymers containing the anthracene chromophore

Abstract

Abstract Copolymers of methyl methacrylate with an anthracene derivative are photodegraded in the solid state to give crosslinked material. The mechanism of insolubilization is dependent on the nature of the substituents at both the 9 and 10 positions of the anthracene chromophore. Photodimerization is the primary and most efficient cause of insolubilization if one of these positions is unsubstituted. Photodimerization does not occur if both of these positions are substituted; instead crosslinking is caused by photolysis of the endoperoxide of the parent anthracene. Bromination can sensitize the initial photooxidation and subsequent crosslinking in a copolymer where photodimerization does not occur. As a consequence of the crosslinking the rate of photobleaching of the anthracene chromophore by 1 Δ g O 2 is severly curtailed. Poly(methyl methacrylate), a positive‐tone polymer when exposed to UV light, is made negative acting by the incorporation of bound anthracene chromophores.