PTT-PBT共聚酯的核磁共振分析

利用直接酯化法合成了一系列不同配比的PTT-PBT（简称PTBT）共聚酯。采用核磁共振（NMR）和固体^13C-NMR研究了共聚酯的化学组成、序列结构和结晶性能。^1H-NMR和13C-NMR表明：PTBT为无规嵌段聚合物,而且共聚酯链段中PBT链段的实际含量都要小于投料比,可能归因于生成四氢呋喃的副反应消耗了部分丁二醇。共聚酯中各链段的序列长度与其含量成正比,即含量高的组份具有更长的平均序列长度,但PTT序列长度较短,PTT链段比PBT链段更倾向于发生交替反应。固体13C-NMR表明：PTBT共聚酯结晶主要是富集相对应的链段参与完成。

Study on PTT-PBT Copolymers by Nuclear Magnetic Resonance

A series of PTT-PBT （PTBT） copolyesters were prepared through direct esterification followed by polycondensation. The chemical composition and sequence distribution of the copolyesters were investigated by ^1H-NMR and ^13C-NMR. The results demonstrate that the obtained PTBT copolyesters are block copolyesters and the content of PTT units incorporated is always greater than that feeded. The extra consumption of BD owing to the side reaction of the formation of tetrahydrofuran （THF） may lead to a relatively lower content of PBT units in PTBT copolyesters. It was found that the number-average sequence lengths of the block in the copolyesters are in proportion to their respective content, i.e., the higher the content of the component, the longer its sequence length is. At the same time, compared with PIT and PBT segments, PIT shows a shorter sequence length in the copolyesters, i.e., PTT units are more susceptible to alternative copolymerization, Solid ^13C-NMR analysis deduce that PTT and PBT units do not co-crystallize and the enrich units develop the crystallization in the copolyesters.