GRAFTING OF STYRENE ONTO POLYBUTADIENE - CALCULATION OF THE MOLECULARMACROSTRUCTURE

The radical-induced grafting of styrene onto polybutadiene at 60-degre es-C and in dilute solution is theoretically investigated, with the ai m of estimating the detailed molecular macrostructure of the evolving polymer mixture. To this effect, the kinetic mechanism proposed by Bry don et al. [J. Polym. Sci. Polym. Chem. Ed., 11, 3255 (1973) and 12, 1 011 (1974)] was extended to evaluate the bivariate weight chain-length distribution (WCLD) for each of different copolymer topologies genera ted along the polymerization. Each molecular topology is characterized by two integers: the number of grafted styrene chains and the number of incorporated butadiene chains. Apart from the bivariate WCLDs for e very topology and for the total copolymer, the molecular weight distri butions of the accumulated polystyrene and of the unreacted polybutadi ene are calculated. The model predictions of global variables (monomer conversion, polymer production, average molecular weights, grafting e fficiencies, and average number of graft sites per reacted polybutadie ne molecule) closely match the experimental measurements in the cited publications. (C) 1993 John Wiley & Sons, Inc.