Ig. Popovic et al., THE HOMOGENEOUS PHOTOPOLYMERIZATION OF METHYL-METHACRYLATE BY COLLOIDAL CADMIUM-SULFIDE, Macromolecular chemistry and physics, 195(3), 1994, pp. 889-904
A completely new method of initiating the homogeneous radical polymeri
zation of methyl methacrylate in bulk or in solution via the photogene
ration of an electron hole pair in colloidal cadmium sulfide is presen
ted. A polymerization mechanism involving an excited cadmium sulfide p
article in both the initiation and termination steps is proposed. In t
he initiation a methyl methacrylate molecule is oxidized by a positive
hole photogenerated in a CdS particle, which results in a novel chain
-end structure of the poly(methyl methacrylate) (PMMA). Degradative ch
ain transfer to reduced excited cadmium sulfide particles is responsib
le for chain termination. Thus, for the first time, a detailed polymer
ization mechanism in which all states of the polymerization, i. e., in
itiation, propagation, chain transfer and termination, is presented fo
r the polymerization of vinyl monomers initiated by semiconductors. Th
ermogravimetry (TG) showed that the newly synthesized PMMA has greatly
enhanced thermal stability when compared to normal radically prepared
PMMA. In fact, the thermal stability approaches that of anionically p
repared PMMA but is experimentally much easier to prepare. This techni
que enables the homogeneous embedding of CdS particles in a polymer ma
trix.