生物基高分子材料正处于一个蓬勃发展的时期，2,5-噻吩二甲酸（2,5-TFDCA）作为一种新兴的生物基芳香族二元酸，以其为单体合成的聚酯有望部分替代石油基的对苯二甲酸基聚酯，并与其它芳香族聚酯形成重要互补。本论文围绕着基于2,5-噻吩二甲酸的生物基聚酯的合成及其结构性能关系，通过设计合成化学结构非常相似的聚（2,5-呋喃二甲酸1,5-戊二醇酯）(PPeF)和聚（2,5-呋喃二甲酸二甘醇酯）(PDEF)或者聚（2,5-噻吩二甲酸1,5-戊二醇酯）(PPeTF)、聚（2,5-噻吩二甲酸二甘醇酯）(PDETF)和聚（2,5-噻吩二甲酸硫代二甘醇酯）(PTDTF)作为模型聚合物，并采用实验与分子动力学模拟相结合的方法对其结构性能关系进行对比研究，发现了呋喃基聚酯和噻吩基聚酯的二元醇中的非羟基氧杂原子会增强聚酯的分子间相互作用，进而显著提升材料的玻璃化转变温度和气体阻隔性能。基于上述策略，我们设计合成了一系列高性能的生物基聚酯：聚（2,5-噻吩二甲酸1,4-丁二醇-共-二甘醇酯）（PBDETF）无规共聚酯，该共聚酯表现出了相比于聚对苯二甲酸乙二醇酯（PET）和聚（2,5-呋喃二甲酸1,4-丁二醇酯）（PBF）以及文献中报道的其它2,5-噻吩二甲酸基聚酯更优的气体阻隔性能。 为改善聚（2,5-噻吩二甲酸1,3-丙二醇酯）（PPTF）的生物降解能力，合成了全组成范围内的具有较高分子量的全生物基聚（2,5-噻吩二甲酸-共-丁二酸1,3-丙二醇酯）（PPSTF）无规共聚酯。该共聚酯中存在一定程度的共聚单体共结晶。相比于丁二酸1,3-丙二醇酯单元，2,5-噻吩二甲酸1,3-丙二醇酯单元具有更强的结晶竞争能力。不可降解-可降解的转变点发生在芳香族单元的数均序列长度低至大约3时，该规律具有一定的通用性。在相同芳香单体含量的条件下，聚（2,5-噻吩二甲酸-共-丁二酸1,3-丙二醇酯）的生物降解性能要优于聚（对苯二甲酸-共-丁二酸1,3-丙二醇酯），逊于聚（2,5-呋喃二甲酸-共-丁二酸1,3-丙二醇酯）。 最后，通过实验和分子模拟相结合的方法，系统研究了噻吩二甲酸的不同异构体对噻吩基聚酯合成、性能及其化学回收的影响。特别需要注意的是，我们通过熔融聚合的方法成功合成了高分子量的聚（3,4-噻吩二甲酸1,4-丁二醇酯）（3,4-P14BTF），这与传统预期相反。
The development of biobased polymer materials is in a booming period. Polyesters based on 2,5-thiophenedicarboxylic acid (2,5-TFDCA), an emerging biobased aromatic diacid, are expected to partially replace petroleum-based terephthalic acid-based polyesters and form an important complement to other aromatic polyesters. Herein, we focus on the synthesis and structure-property relationships of biobased polyesters based on 2,5-TFDCA. Poly(pentylene 2,5-furandicarboxylate) (PPeF) and poly(diethylene glycol 2,5-furandicarboxylate) (PDEF) or poly(pentylene 2,5-thiophenedicarboxylate) (PPeTF), poly(diethylene glycol 2,5-thiophenedicarboxylate) (PDETF), and poly(thiodiethylene glycol 2,5-thiophenedicarboxylate) (PTDTF) with very similar chemical structure were designed and synthesized as model polymers and their structure-property relationships were investigated comparatively by a combination of an experiment and molecular dynamics simulation. It was found that the nonhydroxyl oxygen heteroatoms in the diols of furan-based polyesters and thiophene-based polyesters could enhance the intermolecular interactions of polyesters, which in turn significantly improved the glass transition temperature and gas barrier properties. Based on the aforementioned strategy, we designed and synthesized a series of high-performance biobased polyesters, poly(1,4-butylene-co-diethylene glycol 2,5-thiophenedicarboxylate) (PBDETF) random copolyesters. They behaved superior gas barrier properties than poly(ethylene terephthalate) (PET), poly(butylene 2,5-furandicarboxylate) (PBF) and other thiophene-based polyesters in literature. High molecular weight fully biobased poly(propylene succinate-co-2,5-thiophenedicarboxylate) (PPSTF) random copolyesters in full composition range were synthesized to improve the biodegradation of poly(propylene 2,5-thiophenedicarboxylate) (PPTF). A certain level of comonomer cocrystallization was evidenced, and PTF units had stronger crystallization competitive capability compared to PS units. The nonbiodegradable-biodegradable transition was found to occur at the number-average sequence length of aromatic PTF units as low as about 3, which is somewhat generic. When compared with their terephthalic acid-based (TA-based) and 2,5-furandicarboxylic acid-based (FDCA-based) analogues with the same content of aromatic units, the biodegradability of PPSTF copolyesters was between those of them. Finally, the effects of different isomers of TFDCAs on the synthesis, properties, and chemical recovery of TFDCA-based polyesters were systematically investigated by a combination of an experiment and molecular simulation. Notably, we successfully prepared high molecular weight poly(1,4-butylene 3,4-thiophenedicarboxylate) (3,4-P14BTF) via melt polycondensation, which is contrary to traditional expectations.
