Several ferrocenium salts as efficient photoinitiators and thermal initiators for cationic epoxy polymerization

A study of the photoinitiated and thermally initiated cationic polymerizations of epoxy oligomers with three ferrocenium salt photoinitiators bearing different arene ligands had been conducted. These photoinitiators were cyclopentadienyl - Fe-carbazole hexafluorophosphate ([Cp-Fe-carbazole]+PF6-), cyclopentadienyl-Fe-N-ethylcarbazole hexafluorophosphate ([Cp-Fe-n-ethylcarbazole]+PF6-) and cyclopentadjenyl-Fe-aminonaphthalene hexafluorophosphate ([Cp-Fe-aminonaphthalene]+PF6-). They were synthesized by the reaction of ferrocene and the corresponding arenes. These ferrocenium salts were capable of photomitiating the cationic polymerization of epoxide directly on irradiation with long-wavelength UV light. Comparative Studies demonstrated that they were more effective photoinitiators than I-261 due to the strong absorption above 300 nm. Preliminary studies had shown that these photoinitiators could also be employed as thermal initiators for the cationic ring-opening polymerization of epoxides at moderate temperatures. (c) 2006 Elsevier B.V. All rights reserved.