Poly(ether/ester)s based on poly(butylene terephthalate) and poly(ethylene glycol), 2. Effect of polyether segment length

Abstract

Abstract Structure‐properties relationships of poly(ether/ester)s (PEEs) 1 based on poly(butylene terephthalate) (PBT) and poly(ethylene glycol) (PEG) are studied. By varying the length of the soft segments (PEG) of molecular weights 600, 1000 and 2000) two series of PEEs are obtained, (i) with constant mole ratio PBT:PEG (the PBT block length being approximately the same) and (ii) with constant weight ratio PBT:PEG (different PBT segment length). The block structure is proved by 1 H nuclear magnetic resonance and differential scanning calorimetry studies. A three‐phase morphology is established, i.e. two amorphous phases (polyether and polyester) and a crystalline phase (PBT), each one distinguished by its own transition temperature. At low temperatures (between −60 and 20°C) a fourth phase (crystalline PEG) appears. Small angle X‐ray scattering intensity and long spacing increase abruptly for the compositions with PEG 2000. The mechanical characteristics of the studied PEEs depend on the weight ratio of the two types of blocks.