Polymer-bound S-benzoyl O-ethyl xanthate: a new heterogeneous photoinitiator

Abstract

Ethyleneglycol dimethacrylate crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA) has been prepared by a reported procedure. A photodissociable chromophore, S-benzoyl O-ethylxanthate has been synthesized on the crosslinked PHEMA beads and used as a heterogeneous photoinitiator. The photopolymerization efficiency of this photoinitiator has been compared with that of the corresponding soluble photoinitiator, S-benzoyl O-ethyl xanthate. The rate of photopolymerization, using the polymer-bound initiator is higher than that for the soluble photoinitiator for longer irradiation times. For shorter irradiation times, the rate of polymerization is lower for the polymer-bound initiator than for the soluble material. During photopolymerization of methyl methacrylate, a sharp increase in the rate is observed after an initial delay, whereas, for the soluble initiator, the rate of polymerization is constant with time. Comparison of the rate of homopolymerization and that of the accompanying graft polymerization reveals that the latter process is more efficient.