Synthesis of SBS thermoplastic block copolymers in cyclohexane in the presence of diethylether used as a structure modifier

Abstract

Diethylether (DEE) was used as a structure modifier during the synthesis of linear styrene-butadiene block copolymers of poly A-block-polyB-block-polyA type (SBS). The microstructures of synthesized polymers were analyzed, and the effect of DEE on polymerization kinetics was studied. Addition of DEE at 2 wt% concentration results in the highest styrene polymerization rate, while addition at 6 wt% concentration gives the highest butadiene polymerization rate. The vinyl content of the polybutadiene portion increases from 14 to 47% with an increase in the DEE concentration from 500 ppm to 10 wt% while thetrans- l,4 andcis-1,4 isomers decrease. For SBS polymer synthesized via a sequential method, the addition of DEE as a structure modifier minimizes the crossover deficiency which would otherwise result in a skewed molecular weight distribution with a higher polydispersity. For SBS polymers made via a coupling method, the coupling efficiency appears to be constant in a range of DEE concentration from 500 ppm to 1 wt% before declining with a further increase in DEE.