DIRECT AND SENSITIZED PHOTOINITIATED CATIONIC POLYMERIZATION USING PYRIDINIUM SALTS

Results of polymerization and laser flash photolysis studies concerning the direct and indirect photoinitiation of cationic polymerizations using N-alkoxy pyridinium and N-alkoxy quinolinium salts are presented. The indirect action can be based on (a) the generation of carbocations via the oxidation of photochemically produced free radicals and (b) the generation of radical cations via the reaction of electronically excited sensitizers with pyridinium or quinolinium ions. With respect to (a) substituted vinyl bromides were found be an effective source of oxidizable free radicals (vinyl radicals), and regarding (b) singlet or triplet excited states of thioxanthone, anthracene, perylene and phenothiazine, which, in the ground state, strongly absorb light in the 300 to 400 nm range, were found to react rapidly with pyridinium salts.