HYPERCRITICALLY ENHANCED DISTORTION OF A PHASE-DIAGRAM - THE (POLYSTYRENE PLUS ACETALDEHYDE) SYSTEM

We report new experimental evidence of the existence of double critica l points in a binary system. Pressure-temperature data on the solubili ty of (polystyrene + acetaldehyde) were obtained using a low-angle lig ht-scattering technique. Phase diagrams change from an UCST/LCST confi guration showing a marked double maxima to an hour-glass shape with a ''window of miscibility'' as pressure decreases. Successful modeling o f these unusual shapes was achieved by using a computation algorithm w hich incorporates a temperature- and concentration-dependent interacti on parameter. (C) 1997 John Wiley & Sons, Inc.