Blends of Syndiotactic Polystyrene with SBS Triblock Copolymers

Blending of polystyrene-block-polybutadiene-block-polystyrene (SBS) triblock copolymers with syndiotactic polystyrene (PSsyn) has been performed in a Brabender mixer above the glass transition temperature of the triblock copolymer but below the melting point of PSsyn. The presence of a large excess of amorphous SBS (at least 70 wt.-%) as well as of the amorphous PSsyn phase (about 60 wt.-%, also above its Tg) allowed the easy mixing of the components. In contrast, the presence of unmelted PSsyn crystallites affects both the final morphology of the blend as well as its dynamic behavior. Indeed, according to the dynamic thermomechanical analysis (DMTA) data it is possible to suggest that such solid particles act to reinforce the overall blend structure (as in composite materials filled with inorganic solid particles). Similar behavior is also observed for the SBS copolymer alone below the Tg of the styrene blocks, Tg (PS). This conclusion is supported by both the compatibility of the blends, and the thermal and dynamic thermomechanical behavior at T > Tg (PS) as investigated by means of Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and DMTA. The results obtained are tentatively compared with those of similar blends obtained from toluene solution.