Lower critical solution temperature and upper critical solution temperature phase behaviour in random copolymer blends: poly(styrene- co-acrylonitrile)/poly(methyl methacrylate) and poly(styrene- co-acrylonitrile)/poly(ε-caprolactone)

Abstract

The phase behaviour of blends of poly(methyl methacrylate) (PMMA) and poly(styrene- co-acrylonitrile) (SAN) is calculated as a function of copolymer composition from the data of the temperature dependence of all three segmental interaction parameters, χ i/ j ( T) of the system SAN/PMMA, i.e. χ S/MMA( T), χ AN/MMA( T) and χ S/AN( T). Using blends with different copolymer compositions might change the temperature dependence of the polymer-polymer interaction parameter χ AB( T) dramatically, from increasing to decreasing with temperature. In the copolymer composition range from ≈ 11 to 55 mol% of acrylonitrile in SAN the χ AB( T) parameter is increasing with temperature, leading to lower critical solution temperature behaviour, and in the copolymer composition range up to ≈ 10 mol% and > 56 mol% of AN in SAN the χ 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 oligomers. Similar conclusions can be obtained for blends of SAN with poly (ε-caprolactone).