Morphology and phase behaviour of poly(propylene oxide) containing copoly(ether ester)s

Abstract

Abstract The morphology and phase behaviour of six different copoly(ether ester) elastomers, based on poly(butylene terephthalate) (PBT) hard blocks and poly- (ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b- PPO-b-PEO) soft blocks, differing in soft-block content and molecular weight of the soft block, have been investigated using various analytical techniques such as DSC, dynamic mechanical thermal analysis, dielectric spectroscopy, 13C CP-MAS NMR, AFM, TEM, and optical microscopy. The PBT blocks were found to crystallize in lamellar structures that form a continuous highly interconnected architecture. No crystalline regions for the PEO-b-PPO-b-PEO triblock could be observed, whereas no indications of a separate pure amorphous PBT phase were found. It is further shown that the amorphous phase is not a homogeneous mixture of amorphous PBT and soft segments. Based on the combined results of the analytical techniques used it is concluded that the PPO segments form an almost pure amorphous phase, whereas the PEO segments form a mixed phase with amorphous PBT. It is believed that the presence of this pure amorphous PPO phase provides the PEO-b-PPO-b-PEO containing copoly(ether ester)s with their excellent coldtemperature properties.