Investigations on the reaction behaviour in the presence of depolymerization reactions. Investigation of copolymerizations with alpha-methylstyrene

For radical copolymerizations of alpha-methylstyrene (MS) with methacrylonitrile (MAN) and of MS with acrylonitrile (AN) studies were carried out to examine pos postulations of kinetic models known from literature, in particular the terminal model with chain-length-independent and chain-length-dependent depolymerization steps. The results of investigations were based on measurements of the sequence length distributions from C-13-NMR spectra. Analyses of MS/MAN copolymers with various compositions were carried out. Reaction parameters and depolymerization constants depending on temperature were calculated. The values of enthalpy and entropy of polymerization and the ceiling temperature were computed for MS to Delta H = 26,5 +/- 0,5 kJ mol(-1), Delta S = 95 +/- 5 J mol(-1) K-1, T-ceiling = 65 +/- 1 degrees C. The terminal model with depolymerization steps turned out to be wrong for the accurate description of the polymerization behaviour in case of the tested systems. Results clearly show important penultimate effects. At the point of knowledge, the description of the polymerization behaviour in terms of a penultimate model with depolymerization steps are suggested.