LOWER CRITICAL SOLUTION TEMPERATURE AND UPPER CRITICAL SOLUTION TEMPERATURE PHASE-BEHAVIOR IN RANDOM COPOLYMER BLENDS - POLY(STYRENE-CO-ACRYLONITRILE) POLY(METHYL METHACRYLATE) AND RENE-CO-ACRYLONITRILE)/POLY(EPSILON-CAPROLACTONE)/

The phase behaviour of blends of poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN) is calculated as a function of co polymer composition from the data of the temperature dependence of all three segmental interaction parameters, chi(i/j)(T) of the system SAN /PMMA, i.e. chi(S/MMA)(T), chi(AN/MMA)(T) and chi(S/AN)(T). Using blen ds with different copolymer compositions might change the temperature dependence of the polymer-polymer interaction parameter chi(AB)(T) dra matically, from increasing to decreasing with temperature. In the copo lymer composition range from similar to 11 to 55 mol% of acrylonitrile in SAN the chi(AB)(T) parameter is increasing with temperature, leadi ng to lower critical solution temperature behaviour, and in the copoly mer composition range up to similar to 10 mol% and > 56 mol% of AN in SAN the chi(AB)(T) parameter is decreasing with increasing temperature , predicting upper critical solution temperature behaviour when one or two components have relatively low molecular weight, i.e. for oligome rs. Similar conclusions can be obtained for blends of SAN with poly (e psilon-caprolactone).