Initiated Styrene Copolymerization with Polybutadiene Reaction Conditions on the Length of Polystyrene Graft Branches

Abstract

The specificity of styrene copolymerization with polybutadiene (PBD) is a heterogeneous polymerization. The creation of an exhaustive theory of this process must include regulation of all reactions which take place in both phases and take into account the propagation of graft polystyrene branches as well as the rubber macromolecule. Results obtained by Mori et al (1) showing that the length of the graft branches equals the length of homopolystyrene molecules (PS) -as well as difficulties of polymer fractionation to homopolystyrene (PS) in both graft copolymers, and selective degradation of copolymer polybutadiene backbone revealed the fact that the propagation of graft branches were not investigated. The researchers had identified the graft branches as free polystyrene using kinetic calculations in a better case (2), without taking into account polymerization specificity in the rubber phase, i.e. high viscosity of the media already at the initial stages, large monomer concentration when the system is near equilibrium (3), rubber and PS incompatibility in styrene solution, the presence of additional chain transfer, and unequal initiator distribution in both phases (4). All these factors may substantially affect reactions taking place in the rubber phase, even the change of elementary constants.