Effect of Crystallizability of Hard Segments in Polyether-Polyester Block Copolymers on the Segregation of a Soft Segment to Polymer Surface

Abstract

The present investigation was undertaken to clarify how variations in crystallizability of hard segments affect the extent of the segment-segregation by determining the polymer composition and wettability of the polymer surface layer. Poly (ethylene terephthalate) (T), poly (ethylene terephthalate-co-isophthalate) [T/iPh] and poly (butylene terephthalate) [PBT] were employed as hard segments and poly (ethylene glycol) [PEG] as a soft segment. Segregation of the PEG soft segment in the block copolymers with the T/iPh hard segment with low crystallizability was found to be suppressed because of the lowered exclusion effect by crystal domains of the hard segment. When the PBT hard segment with a high crystallization rate was used, no marked changes in the composition at the surface layer were observed. The PBT segment could be frozen rapidly from the melt, and therefore, the restraint of segment migration led to pool segregation of soft PEG.