Bianchi Enrico, Soccio Michelina, Siracusa Valentina, Gazzano Massimo, Thiyagarajan Shanmugam, Lotti Nadia
Civil, Chemical, Environmental and Materials Engineering Department, University of Bologna, Via Terracini 28, 40131 Bologna, Italy.
Interdepartmental Center for Industrial Research on Advanced Applications in Mechanical Engineering and Materials Technology, CIRI-MAM, University of Bologna, Bologna 40126, Italy.
ACS Sustain Chem Eng. 2021 Sep 6;9(35):11937-11949. doi: 10.1021/acssuschemeng.1c04104. Epub 2021 Aug 21.
High-molecular-weight poly(butylene 2,4-furanoate) (2,4-PBF), an isomer of well-known poly(butylene 2,5-furanoate) (2,5-PBF), was synthesized through an eco-friendly solvent-free polycondensation process and processed in the form of an amorphous film by compression molding. Molecular characterization was carried out by NMR spectroscopy and GPC analysis, confirming the chemical structure and high polymerization degree. Thermal analyses evidenced a reduction of both glass-to-rubber transition and melting temperatures, as well as a detriment of crystallization capability, for 2,4-PBF with respect to 2,5-PBF. Nevertheless, it was possible to induce crystal phase formation by annealing treatment. Wide-angle X-ray scattering revealed that the crystal lattices developed in the two isomers are distinct from each other. The different isomerism affects also the thermal stability, being 2,4-PBF more thermally inert than 2,5-PBF. Functional properties, such as wettability, mechanical response, and gas barrier capability, were tested on both amorphous and semicrystalline 2,4-PBF films and compared with those of 2,5-PBF. Reduced hydrophilicity was determined for 2,4-isomer, in line with its lower average dipole moment, suggesting better chemical resistance to hydrolysis. Stress-strain tests have evidenced the higher flexibility and toughness of 2,4-PBF with respect to those of 2,5-PBF and the possibility of improving its mechanical resistance by annealing. Finally, the different isomerism deeply affects the gas barrier performance, being the O- and CO-transmission rates of 2,4-PBF 50 and 110 times lower, respectively, than those of 2,5-PBF. The gas barrier properties turned out to be outstanding under a dry atmosphere as well as in humid conditions, suggesting the presence of interchain hydrogen bonds. The gas blocking capability decreases after annealing because of the presence of disclination associated with the formation of crystals.
高分子量聚（2,4 - 呋喃二甲酸丁二醇酯）（2,4 - PBF）是著名的聚（2,5 - 呋喃二甲酸丁二醇酯）（2,5 - PBF）的异构体，通过环保的无溶剂缩聚工艺合成，并通过压缩模塑加工成非晶薄膜形式。通过核磁共振光谱和凝胶渗透色谱分析进行分子表征，证实了化学结构和高聚合度。热分析表明，相对于2,5 - PBF，2,4 - PBF的玻璃化转变温度和熔点均降低，结晶能力也受到损害。然而，通过退火处理可以诱导晶相形成。广角X射线散射表明，两种异构体中形成的晶格彼此不同。不同的异构性也影响热稳定性，2,4 - PBF比2,5 - PBF具有更高的热惰性。在非晶和半结晶的2,4 - PBF薄膜上测试了润湿性、机械响应和气体阻隔能力等功能特性，并与2,5 - PBF的进行了比较。确定2,4 - 异构体的亲水性降低，这与其较低的平均偶极矩一致，表明其对水解具有更好的化学抗性。应力 - 应变测试表明，相对于2,5 - PBF，2,4 - PBF具有更高的柔韧性和韧性，并且通过退火可以提高其机械抗性。最后，不同的异构性深刻影响气体阻隔性能，2,4 - PBF的氧气和二氧化碳透过率分别比2,5 - PBF低50倍和110倍。气体阻隔性能在干燥气氛以及潮湿条件下都表现出色，表明存在链间氢键。由于与晶体形成相关的位错的存在，退火后气体阻隔能力降低。
