Structure/property relationships in polystyrene–polyisobutylene–polystyrene block copolymers

Structure/property relationships of polystyrene–polyisobutylene–polystyrene (PS–PIB–PS) triblock copolymer made by different processes were studied using dynamic mechanical analysis (DMA). The PS–PIB–PS films were composed of approximately 30% polystyrene end-blocks. Small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) confirm that a self-assembled, segregated cylindrical morphology forms in the copolymer. DMA was used as a tool to investigate the structure–property relationships in these polymers. Modified PS–PIB–PS copolymers were also characterized. Modifications of the copolymers were carried out by conversion of approximately 20 mol% of the polystyrene end-blocks to styrene sulfonic acid. The modified copolymers exhibited distinctly different thermal characteristics than the unmodified copolymers, which were most notable in the storage modulus and tan δ data. The presence of sulfonic acid groups disrupted the morphology and solvent sorption characteristics of the copolymers. Dynamic mechanical behavior is discussed as it relates to the morphology of the PS–PIB–PS copolymers formed via different processing methods and chemical modification.