Cationic photopolymerization of tetrahydrofuran: A mechanistic study on the use of a sulfonium salt-phenothiazine initiation system

The kinetics aspects of the photoinitiated polymerization of tetrahydrofura n with triphenylsulfonium hexafluoroarsenate and sensitized by phenothiazin e was studied under visible-light irradiation. A photosensitizer mechanism was proposed involving electron transfer from phenothiazine to the tripheny lsulfonium salt, forming a cation radical, the true precursor of the polyme rization. An initial complex in the ground state between the phenothiazine and the triphenylsulfonium was formed prior to the excitation, and this com plex actually activated the photopolymerization rate. The polymerization co nversion presented an S-shaped curve, suggesting an induction period caused by the existence of two pathways responsible for the beginning of the poly merization. (C) 2000 John Wiley & Sons, Inc.