Photopolymerization of methyl methacrylate with azo‐containing polydimethylsiloxane as photoinitiator: Effect of siloxane chain length

The kinetics of the free radical photopolymerization of methyl methacrylate (MMA) initiated by azo-containing polydimethylsiloxane (PSMAI) and azobisisobutyronitrile (AIBN) was investigated. The greater polymerization rate R-p in MMA/PSMAI systems may be due to the higher value of the initiation rate R-i and the lower value of the termination rate constant k(t) than that in MMA/AIBN system. The reaction orders with respect to initiators PSMAI decreased with an increase in polydimethylsiloxane chain length (SCL) in PSMAI. The observed deviations in polymerization rate from rate equation could be explained in terms of primary radical termination. The photoinitiator efficiency phi of initiators decreased with increase in SCL, while the ratio of the rate constants for chain termination and chain initiation by primary radical increased with SCL. The fraction beta of primary radicals entering into termination in MMA/PSMAI systems were larger than that in MMA/AIBN system. (C) 1996 John Wiley & Sons, Inc.