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

The kinetics of the radical polymerization of 3-[tris(trimethylsilyloxy)sil yl]propyl methacrylate was studied in benzene and dioxane/hexane solutions at different conditions of temperature, monomer and initiator concentration s by using ultraviolet and electron paramagnetic resonance spectroscopic te chniques. The values of the ratios between the propagation rate constant an d the square root of the termination rate constant (k(p)/k(t)(1/2)) were de termined by W 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 k(p)/k(t)(1/2), in the temperatu re interval 50-70 degreesC, lie in the range 0.40-0.53 l(-1/2)s(-1/2). Meas urements of the radical concentrations, the efficiency factor of the initia tor and of the absolute rate constants k(p) and k(t) were carried out using electron paramagnetic resonance techniques. The values of k(p) are in the range 500-1000 l mol(-1) s(-1) in the temperature interval 50-70 degreesC, in fair agreement with those extrapolated from results obtained by pulsed-l aser/ size-exclusion chromatography at lower temperatures. (C) 2001 Elsevie r Science Ltd. All rights reserved.