Property-structure relationships in partially sulphonated poly(ethylene terephthalate)—I. Infrared studies

Abstract

Lightly sulphonated poly(ethylene terephthalate)s containing 1.9 to 10.1 mol.% of SO 3H or SO 3K groups were studied with infrared spectroscopy. Characteristic absorption bands of sulphonic acid or potassium sulphonate groups attached to the aromatic nucleus of the copolyester chain were analysed in detail. It has been shown that in the studied copolyesters sulphonic acid groups are extensively associated through hydrogen bonds. The process of association is complex. Interaction of sulphonic acid groups with other proton acceptor and proton donor groups existing in the polymer chain superimposes the self-association of these groups. Associated structures such as dimers and greater aggregates of sulphonic acid groups and hydrogen bonded complexes composed of SO 3H groups and C(O)O and CH 2CH 2OCH 2CH 2 residues of polymer chain are mainly formed.