POLYMERIZATION OF STYRENE BY PHOTOEXCITED SAFRANINE-T WITHOUT ADDITIVES

Styrene can be photopolymerized with methanolic solutions of safranine T (STH+) in the absence of any additives. Under these conditions the monomer acts as an electron donor for the excited singlet state of STH+, and after electron transfer an initiating semireduced STH. radical is produced. The experimentally determined monomer exponent of alpha = 2 indicates additional deactivation reactions of the primary radicals. The polymerization rate depends on the dye concentration also in those regions, in which all light is already absorbed. Presumably, this dependence is caused by a comproportionation reaction between STH+ and substituted leuco-safranine T formed in the course of polymerization.