Photopolymerization of Cyclohexene Oxide--A Visible Light Initiating System and Mechanistic Investigations.

摘要

A visible light initiator system for the photoinduced cationic polymerization of epoxides is reported. It uses free radical promoted cationic polymerization the radical being generated from a visible light absorber. The developed system consists of an iodinated xanthene dye a coinitiator and a diaryliodonium salt. Aromatic amines having low basicity and containing alpha-hydrogens are the preferred coinitiators for the polymerization of cyclohexene oxide. The system can efficiently photoinitiate the polymerization of certain cyclic ethers and can function at any wavelength of the visible spectrum depending on the dye's absorption spectrum and its oxidation/reduction potentials. Studies on photochemical reactions between each two of the three components and characterization of the polymer formed from cyclohexene oxide indicate that both the oxidative bleaching of the dye by the diaryliodonium salt and the reductive bleaching of the dye by the aromatic amine contribute to alpha amino radical formation and oxidation of the (x-amino radicals by diaryliodonium salts produces (alpha-aminocarbocations which initiate the ring opening polymerization. Dye molecules are incorporated into the polymer in chain terminating processes.