用~1H-和~(13)C-NMR方法研究聚对苯二甲酸乙二酯/聚一氧基苯甲酸酯共聚酯的序列分布

测定了PET/30PHB和PET/60PHB共聚酯的高分辨~1H和~(13)C谱,并采用INEPT方法和部分弛豫FT技术确定了季碳吸收峰,对NMR谱进行了归属.应用我们先前提出的方法对共聚酯的序列分布进行了表征.结果表明,两种共聚酯的无规度B_q值均小于1,序列分布不象Jackson等认为的那样为完全无规的.此外,文中还指出,某些研究者套用Flory公式判别PET/PHB共聚酯是否为无规的不妥之处.

A STUDY ON SEQUENCE DISTRIBUTION IN PET/PHB COPOLYESTERS BY ~1H AND ~(13)C-NMR

High resolution 1H and 13C-NMR spectra for PET/30PHB and PET/6 PHB copolyes-ters in solution have been measured. The 13C absorptions were assigned by the help of the determination of quaternary carbon absorption with INEPT and partially relaxed FT techniques. Our method previously proposed was applied to characterize the sequence distribution of the copolyesters. The degree of randomness Bq for PET/30PHB and PET/60PHB were found to be 0.87 and 0.81 respectively, the values which are both less than unity for the completely random copolyester. In addition, it has been pointed out to be improper to judge whether the chain structure of PET/PHB copolyesters is random by comparing their melting points with that predicted by Flory's equation, as some researchers have done.