Abstract
A series of poly(butylene terephthalate- co-cyclohexyanedimethylene terephthalate)- b-poly(ethylene glycol) segmented random copolymer (PBCG) with poly(cyclohexyanedimethylene terephthalate) moieties (PCT) molar fraction ( M PCT) varying from 10% to 60% were synthesized and characterized. The copolymers exhibit good symmetric peak in GPC chromatographs with the number average molecular weight more than 3.5×10 4 and polydispersity less than 1.70. It reveals that the two sorts of hard segment, PCT and poly(butylenes terephthalate) (PBT), take a random distribution along the copolymer chain and the number average block length of PBT decreases from 4.02 to 1.41, while that of PCT increases from 1.17 to 2.50 with the increasing M PCT by sequence distribution analysis. Micro-phase separation structure is validated for the appearance of two glass transition temperatures and one melting point in DSC thermograms. The minima of melting point, crystallinity as well as the discontinuous jump of glass transition temperature of hard segments at M PCT about 20–30% are derived from the crystal lattice transition from α-PBT to trans-PCT and discussed from the viewpoint of cohensive energy. The improved thermal stability is observed with ascending M PCT because of the high thermal stability of cyclohexylene group in the backbone. The mechanical testing results show that the lower crystallinity of hard segments imparts the copolymer higher elongation, while the higher one improves the elastic modulus, tensile strength and yield strength.
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