Block copolymers based on nylon 6 and poly(propylene glycol). I. Structure and thermal properties

Abstract

The structure and the thermal properties of nylon 6-poly(propylene glycol) block copolymers have been studied using DSC, WAXD, SAXS, POM and DMA measurements and compared with those of nylon 6 homopolymer. The soft segment was found to be compatible with the hard segment in the armorphous region of block copolymers. The hard segment can partially crystallize and forms the same crystal structure as nylon 6. The melting point depression might be predicted by using Flory's model for random copolymers but the heat of fusion for crystals of the block copolymer with a large amount of soft segment (PAE-48) was much reduced than the value expected from the hard segment content. On annealing, the second lower melting temperature which increased linearly with the annealing temperature appeared in addition to the constant high melting temperature. The d 200 spacing of the intermolecular hydrogen-bonded plane approached that of the ideal crystal at relatively low annealing temperatures in the block copolymers. The soft segment of block copolymer was suggested to exist in the amorphous layers between the stacked lamellar crystals.