Sequence Structures of Poly(Ethylene Terephthalate-Co-Ethylene 2,5-Furandicarboxylate) via 1 H-NMR and 13 C-NMR / 分析化学

ABSTRACT

A series of poly(ethylene terephthalate-Co-ethylene 2,5-furandicarboxylate) (PEFT) copolyesters were synthesized with different terephthalic acid (PTA) /2,5-furandicarboxylic acid (FDCA) molar ratios by direct esterification method. In order to investigate their chain structures, 1 H-NMR and 13 C-NMR spectra of these copolyesters were recorded. The average length ( L) , the degree of randomness ( B) and composition of copolyesters were calculated from the intensities of four kinds of signals, which corresponding to the chemical shifts of hydrogen and carbon atoms in ethylene glycol unit in PEFT copolyesters chains. It was shown that the degree of randomness B of all purified copolyesters reached to 1 by the formula of Yamadera and Murano, which indicated that they were random copolymers. Comparatively, the PEF-block-PET of B value was 0. 577, and the PEF-blend-PET of B value was 0 . It was also consistent with the previous results of differential scanning calorimeter ( DSC) that each of the PEFT copolyesters had only one glass transition temperature and the copolyesters were random copolymers. The randomness B of PEFT-50 was the greatest of all, the value was 1. 012 based on the result of 1 H-NMR, and the value was 1. 028 based on the result of 13 C-NMR. Furthermore, the results above displayed that the activity of 2,5-furandicarboxylic acid and terephthalic acid was similar in this nucleophilic substation reaction with ethylene glycol.