Photopolymerization of methyl methacrylate with azo-containing polydimethylsiloxane as photoinitiator

Azo-containing polydimethylsiloxane (PDMS-ACP), prepared by the polycondensation reaction of hydroxybutyl-terminated polydimethylsiloxane (PDMS) with 4,4'-azobis-4-cyanopentanoyl chloride (ACPC), was used as the photoinitiator for the polymerization of methyl methacrylate (MMA) in bulk. Polymerization of MMA with azobisisobutyronitrile (AIBN) as the photoinitiator was conducted for comparison. The propagation and termination rate constants (k(p) and k(t)), and the fraction beta of primary radicals entering into termination were evaluated. The termination rate constant 4.5 x 10(7) mol . L(-1). s(-1) in the MMA/PDMS-ACP system was smaller than 9.1 x 10(7) mol . L(-1). s(-1) in the MMA/AIBN system. The photoinitiator efficiency Phi of PDMS-ACP was found to be smaller than that of AIBN. The ratio sigma k(t)/k(i) of the rate constants for chain termination and chain initiation by primary radicals were determined to be 7.9 x 10(7) and 5.8 x 10(7) for PDMS-ACP and AIBN, respectively.