Kinetics of surface-initiated photoiniferter-mediated photopolymerization

Surface-tethered poly(methyl methacrylate) films were synthesized by surface-initiated photoiniferter-mediated photopolymerization (SI-PMP), and the kinetics of film growth were followed by measuring layer thickness as a function of reaction time, monomer concentration, and light intensity using variable angle ellipsometry. The initial rate of photopolymerization had approximate first-order dependence on monomer concentration. However, the rate of photopolymerization decreased with reaction time, indicating the presence of termination reactions. To determine which termination reactions are prevalent, kinetic models accounting for bimolecular termination as well as chain transfer to monomer were developed for the photoiniferter-mediated photopolymerization reactions and used to analyze the experimental data. Comparisons of model predictions to experimental data as functions of reaction time and light intensity suggest that bimolecular termination is the dominant termination mechanism in these systems for the range of reaction conditions investigated.