Novel pyridinium salts as cationic thermal and photoinitiators and their photosensitization properties

Novel pyridinium salts [N-(alpha-phenylbenzyl)-, N-(1-naphthylmethyl)-, or N-cinnamyl p- or o-cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of p- or o-cyanopyridine and the corresponding bromides followed by anion exchange with KSbF6. These pyridinium salts polymerized epoxy monomers at lower temperatures than previously reported for N-benzyl-2-cyanopyridinium hexafluoroantimonate. The o-substituted pyridinium salts showed higher activity than the p-substituted ones, and the crosslinked epoxy polymers cured with these initiators showed higher glass-transition temperatures. These pyridinium salts photoinitiated radical polymerization as well as cationic polymerization. The photopolymerization was accelerated by the addition of aromatic ketones as photosensitizers. (C) 2002 Wiley Periodicals, Inc.