EFFECT OF INTRAMOLECULAR INTERACTIONS ON THE MISCIBILITY WINDOWS OF PVC BLENDS WITH MODIFIED SAN COPOLYMERS

We investigated the miscibility windows in the blends of poly(vinyl ch loride) (PVC) with chemically modified styrene/acrylonitrile (SAN) cop olymers such as a-methyl styrene/acrylonitrile (alpha SAN), alpha-meth yl styrene/methacrylonitrile (MSMAN). The blends of PVC with alpha SAN were found to have the broader miscibility window. This enhanced misc ibility was interpreted in terms of intramolecular repulsion that orig inates from unfavorable interaction between counits of the copolymers and also intramolecular association of AN units. The intramolecular in teractions were studied by using Fourier transform infrared [FT-IR) sp ectroscopy. These interactions were reflected by a peak broadening in the nitrile stretching band in the acrylonitrile segments. The intermo lecular interactions governing the miscibility in the blends of PVC wi th the series of copolymers were also discussed.