Synthesis of monomer and polymer-bound photosensitizers

A series of electron-transfer photosensitizers covalently bound to cationically polymerizable epoxy groups through siloxane spacer moieties were prepared. Novel synthetic methodology was employed for the preparation of these compounds that involves conducting a regioseleetive hydrosilation reaction at one end of a alpha, omega-difunctional Si-H terminated siloxane to introduce an epoxide group. Thereafter, the resulting adduct is further reacted with an electron-transfer photosensitizer,,such as N-vinyl carbazole or N-allyl carbazole (ACZ) or 9-vinyl anthracene, to produce the monomer-bound photosensitizer. Using this method, three monomer-bound photosensitizers were prepared. Ring-opening photopolymerizations of the monomer-bound photosensitizers were carried out to generate polymer-bound photosensitizers. The reactivities of both the monomer- and polymer-bound photosensitizers were investigated in various ring-opening cationic photopolymerizations using Fourier transform real-time infrared (FT-RTIR) spectroscopy and optical pyrometry (OP). A marked accelerating effect on the rates of the photopolymerizations was observed in the presence of monomer-bound photosensitizers.