The Composition, Sequence Analysis, and Crystallization Characterization of Poly(Trimethylene‐co‐Butylene Terephthalate) Copolymer

Abstract

A series of poly(trimethylene‐co‐butylene terephthalate) (PTBT) copolymers were prepared by direct esterification followed by polycondensation. The composition and sequence distribution of the copolymers were investigated by nuclear magnetic resonance (NMR). The results demonstrate that the synthesized PTBT copolymers are block copolymers and the content of poly(butylene terephthalate) (PBT) units incorporated into the copolymers is always less than that in the polymerization feed. The 1,4‐butanediol consumption by a side reaction leads to a relatively lower content of PBT units in the resultant copolymers. At the same time, the PBT and poly(trimethylene terephthalate) (PTT) sequence length distributions in the copolymers are different. The PBT segments favor a longer sequence length than do the PTT segments in their corresponding enriched copolymers. The crystallization rate of the copolymers becomes lower than the homopolymers, especially for PTT‐enriched copolymers. Compared with the PTT segment, the presence of PBT segments in the copolymers seems to accelerate crystallization. A wide‐angle X‐ray diffraction (WAXD) analysis indicates PTT and PBT units do not co‐crystallize. The reduced melting temperatures of the copolymers may be attributed to a smaller lamellar thickness and lateral size due to short sequence lengths.