Syndiotactic polystyrene/thermoplastic polyurethane blends using poly(styrene-b-4-vinylpyridine) diblock copolymer as a compatibilizer

The effect of adding diblock copolymer poly(styrene-b-4-vinylpyridine) (P(S -b-4VPy), to immiscible blends of syndiotactic polystyrene (sPS)/thermoplas tic polyurethane (TPU) on the morphology, thermal transition, crystalline s tructure, and rheological and mechanical properties of the blends has been investigated. The diblock copolymer was synthesized by sequential anionic c opolymerization and was melt-blended with sPS and TPU. Scanning electron mi croscopy (SEM) showed that the added block copolymer reduced the domain siz e of the dispersed phase in the blends. Differential scanning calorimetry ( DSC) and wide-angle X-ray diffraction (WAXD) revealed that the extent of co mpatibility between sPS and TPU affected the crystallization of the sPS in the blends. Tensile strength and elongation at break increased, while the d ynamic modulus and complex viscosity decreased with the amount of P(S-b-4VP y) in the blend. The compatibilizing effect of the diblock copolymer is the result of its location at the interface between the sPS and the TPU phases and penetration of the blocks into the: corresponding phases, i.e. the pol ystyrene block enters the noncrystalline regions of the sPS, and the poly(4 -vinylpyridine) block interacts with TPU through intermolecular hydrogen bo nding. (C) 1999 Elsevier Science Ltd. All rights reserved.