Ordering processes in polyester thermoplastic elastomers

Synthesis of thermoplastic elastomers derived from poly-tetramethylene glycol (PTME glycol), dimethylterephthalate and different mixtures of ethylene and butylene glycol is described. Extended heating near the crystalline melting point of these systems leads to a measurable increase in the melting point of 15–20°C. This ordering process can be reversed by heating at 250°C or well above the melting point. These results are interpreted in terms of sequence ordering within existing crystallites via interchain transesterification on heating near the melting point. Heating at 250°C is best explained as randomization of the ordered ester units.