PHASE-BEHAVIOR IN MIXTURES OF A HOMOPOLYMER AND A BLOCK-COPOLYMER .1.FTIR AND DSC STUDIES

Miscibility in blends of three styrene-butadiene-styrene and one styre ne-isoprene-styrene triblock copolymers containing 28%, 30%, 48%, and 14% by weight of polystyrene, respectively, with poly(vinyl methyl eth er) (PVME) were investigated by FTIR spectroscopy and differential sca nning calorimetry (DSC). It was found from the optical clarity and the glass transition temperature behavior that the blends show miscibilit y for each kind of triblock copolymers below a certain concentration o f PVME. The concentration range to show miscibility becomes wider as t he polystyrene content and molecular weight of PS segment in the tribl ock copolymers increase. From the FTIR results, the relative peak inte nsity of the 1100 cm-1 region due to COCH3 band of PVME and peak posit ion of 698 cm-1 region due to phenyl ring are sensitive to the miscibi lity of SBS(SIS)/PVME blends. The results show that the miscibility in SBS(SIS)/PVME blends is greatly affected by the composition of the co polymers and the polystyrene content in the triblock copolymers. Molec ular weights of polystyrene segments have also affected the miscibilit y of the blends. (C) 1995 John Wiley & Sons, Inc.