EXPERIMENTAL BRANCHING RESULTS FOR DIENE POLYMERS BY USE OF GEL-PERMEATION CHROMATOGRAPHY

Branching analyses in SBR and polybutadiene rubbers have revealed large differences in branching between rubbers polymerized in different ways. The functionalities of several star-branched solution-polymerized SBR were calculated and compared to their expected structures. Emulsion-polymerized polybutadiene rubber and a series of solution-polymerized polybutadienes made with different catalysts had different degrees of random branching, and evidence is presented, indicating that the different available catalyst systems provide some latitude in making rubbers of different branching contents. Random branching analyses on a series of emulsion-polymerized SBR revealed the dependency of branching on mol. wt and MWD. The influence of polymerization temperature on the branching of emulsion-polymerized SBR was also studied.