Semiaromatic polyesters with a high glass transition temperature (T_g) are promising materials in demanding fields. Herein, a highly rigid diester, diethyl-2,3-diphenyl-1,4-benzenedicarboxylate (DDB), was synthesized from naturally occurring citric acid and cinnamaldehyde. DDB was used to synthesize a series of biobased polyesters by melt polymerization with linear and cyclic diols. Single-crystal X-ray diffraction analysis revealed that DDB crystallized in the monoclinic crystal system with the pendant phenyl groups almost orthogonal to the central benzene ring. The DDB polyesters based on alkanediols (abbreviated as PD-ms) exhibited high number average molecular weights (M_n) in the range of 10,700–39,800 g mol^–1. Thermogravimetric analysis (TGA) demonstrated their excellent thermostability that was comparable to petroleum-based polyesters. The crystallization of the PD-ms series was partially caused due to the π–π stacking of DDB units. The DDB homopolyester based on 1,10-decanediol showed a combination of high modulus, high tensile strength, and high ductility of 762, 17 MPa, and 153%, respectively. This was achieved due to the synergistic effects of the rigid DDB and the flexible 1,10-decanediol units. Lastly, DDB imparted inherent UV-blocking properties to polymers, which made them applicable in UV-protective and transparent films. In view of the fertile chemistry of biobased aromatic aldehydes, this work paves a path to DDB derivatives that are attractive precursors for semiaromatic polyesters.

中文翻译：

---

由刚性对苯二甲酸二苯酯制备的半芳族聚酯：从合成到性能

具有高玻璃化转变温度 ( T _g ) 的半芳族聚酯是在要求苛刻的领域中很有前途的材料。在此，一种高刚性二酯，二乙基-2,3-二苯基-1,4-苯二甲酸酯 (DDB)，是由天然存在的柠檬酸和肉桂醛合成的。DDB 用于通过与线性和环状二醇的熔融聚合合成一系列生物基聚酯。单晶X射线衍射分析表明，DDB在单斜晶系中结晶，苯基侧基几乎与中心苯环正交。基于烷二醇的 DDB 聚酯（缩写为 PD- ms ）表现出 10,700–39,800 g mol ^–1范围内的高数均分子量 ( M _{n )}. 热重分析 (TGA) 证明了它们出色的热稳定性，可与石油基聚酯相媲美。PD- ms系列的结晶部分是由于DDB单元的π-π堆积引起的。基于 1,10-癸二醇的 DDB 均聚酯表现出高模量、高拉伸强度和高延展性的组合，分别为 762、17 MPa 和 153%。这是由于刚性 DDB 和柔性 1,10-癸二醇单元的协同作用而实现的。最后，DDB 赋予聚合物固有的紫外线阻隔性能，使其适用于防紫外线和透明薄膜。鉴于生物基芳香醛的丰富化学性质，这项工作为 DDB 衍生物铺平了道路，这些衍生物是半芳香族聚酯的有吸引力的前体。