EPR study of the radical polymerization of 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate

The kinetics of the radical polymerization of 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate was studied in benzene and dioxane/hexane solutions at different conditions of temperature, monomer and initiator concentrations by using ultraviolet and electron paramagnetic resonance spectroscopic techniques. The values of the ratios between the propagation rate constant and the square root of the termination rate constant (kp/kt1/2) were determined by UV spectroscopy by measuring the changes of absorbance with time at several wavelengths in the range 275–285 nm, where appropriate changes in absorbance were observed. The values of kp/kt1/2, in the temperature interval 50–70°C, lie in the range 0.40–0.53 l−1/2mol−1/2s−1/2. Measurements of the radical concentrations, the efficiency factor of the initiator and of the absolute rate constants kp and kt were carried out using electron paramagnetic resonance techniques. The values of kp are in the range 500–1000 l mol−1 s−1 in the temperature interval 50–70°C, in fair agreement with those extrapolated from results obtained by pulsed-laser/size-exclusion chromatography at lower temperatures.