With regard to polyesters based on biobased 2,5-furandicarboxylic acid (FDCA), our work presents a new strategy, heteroatom substitution, to adjust the thermal and gas barrier properties. The effects of nonhydroxyl oxygen heteroatoms in the diols on the properties of FDCA-based polyesters were first investigated by a combination of an experiment and molecular simulation. The results demonstrated that the introduction of oxygen heteroatoms significantly influenced the thermal and gas barrier properties. As for the two model polymers with a very similar skeleton structure, poly­(pentylene 2,5-furandicarboxylate) (PPeF) and poly­(diethylene glycol 2,5-furandicarboxylate) (PDEF), their T g exhibited an obviously increasing order. Moreover, they showed similar thermal stability and thermal oxidative stability. Dynamic mechanical analysis, positron annihilation lifetime spectroscopy, and molecular dynamics simulation indicated that the gas barrier properties followed the sequence of PDEF > PPeF mainly due to the decreased chain mobility and smaller fractional free volume. In-depth analysis of the effects of heteroatom substitution has an important directive significance for the design and preparation of new high glass transition temperature or novel excellent gas barrier materials. Through the manipulation of different heteroatoms in the diols, the polyesters with varied properties can be expected.

Synthesis of high molecular weight maleic acid-based polyesters via a green approach is of great significance but also a huge challenge. To date, it is still impossible to obtain high...

Based on the fact that the flexibility of the polymer backbone will affect the ion transport and sometimes enhance the ionic conductivity, copolymer electrolytes of 1,2,4,5‐benzene‐tetracarboxylic dianhydride (PMDA), 4‐aminophenyl ether (ODA), and aminopropyldimethyl‐terminated polydimethylsiloxane (PSX), with or without doping of lithium triflate, have been prepared and investigated by infrared spectroscopy and electrical conductivity measurements. The PSX was found to be incorporated into PMDA‐ODA polyimide to form block copolymers, and the best conductivity (10‐7 s/cm at 300°C) is observed in the lithium triflate‐doped PMDA‐ODA‐PSX copolymer with a composition of 4PMDA: 3DA: 0.6PSX: 2LiCF3SO3. This conductivity is about 100 times better than the result of the lithium‐doped PMDA, ODA, and 2,5‐diaminobenzene sulfonic acid (DABSA) copolymer (4PMDA: 3DA:1DABSA:1LiCF3SO3) recently reported by this group. © 1994 John Wiley & Sons, Inc.

The need for high-performance bioplastics brings new challenges to the design and preparation of next-generation sustainable bioplastics. With the emergence of a number of biobased monomers with a similar chemical structure in recent years, it is necessary to conduct a systematic and in-depth study on the effects of different isomers of monomers on the final material properties. Considering the potential barrier and bacteriostatic properties of emerging thiophene-based polyesters, this work systematically investigated the effects of different isomers of thiophenedicarboxylic acids (TFDCAs), 2,5-TFDCA and 3,4-TFDCA, on the synthesis and properties of polyesters by a combination of experiments and molecular simulations. A novel biobased polyester based on the 3,4-TFDCA isomer was synthesized and compared with its analogue. Theoretical studies modeled through population balances were performed to simulate the polymerization kinetics of these two polyesters. Contrary to expectations, we successfully prepared high-molecular-weight poly(1,4-butylene 3,4-thiophenedicarboxylate) (3,4-P14BTF) via melt polycondensation. As we know, for the polyesters based on the analogous phthalic acid, high molecular weights cannot be obtained by this strategy. Barrier properties were further systematically studied from both theoretical calculation and experimental perspectives. The superior gas and water vapor barrier properties of semicrystalline poly(1,4-butylene 2,5-thiophenedicarboxylate) (2,5-P14BTF) could be attributed to the decreased chain mobility and smaller fractional free volume. More intriguingly, they exhibited improved bacteriostatic effect compared to poly(lactic acid) (PLA), while no notable difference was observed between 2,5-and 3,4-isomers. 3,4-P14BTF could be degraded under milder conditions than 2,5-P14BTF enabled by methanolysis with the imidazole acetate ionic liquid catalyst. Therefore, in-depth analysis of the effects of different isomers of monomers should be considered for the design and preparation of new high-barrier and antibacterial polymeric materials for advanced applications such as biobased active food packaging and electronic encapsulation.

High molecular weight fully biobased poly(propylene succinate-co-2,5-thiophenedicarboxylate) (PPSTF) random copolyesters based on the emerging biobased aromatic diacid, 2,5-thiophenedicarboxylic acid (TFDCA), in full composition range were synthesized via melt polycondensation. Their crystallization behavior, thermal-mechanical, gas barrier, and biodegradable properties were systematically investigated. A certain level of comonomer cocrystallization was evidenced by XRD, and PTF units had stronger crystallization competitive capability compared to PS units due to the higher stiffness of TFDCA units. These copolyesters exhibited excellent thermal stability, and mechanical properties can be easily controlled by tuning the varied ratio of flexible to rigid segments. Gas barrier properties were studied from both theoretically calculated and experimental perspectives, and the copolyesters even with 50 mol % PS units still showed superior gas permeation resistance. The selected lipase from Aspergillus oryzae can degrade the copolyesters with up to 60 mol % PTF units. The nonbiodegradable-biodegradable transition was found to occur at the number-average sequence length of aromatic PTF units as low as about 3. Interestingly, 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 apparent degradation rate constant (k) and half period (t 1/2) of PPSTF60 were actually between them. These findings offer much promise for the application of polyesters containing odd-carbon diol monomers in green packaging and other fields.