Quinn Ethan C, Westlie Andrea H, Sangroniz Ainara, Caputo Maria Rosaria, Xu Shu, Zhang Zhen, Urgun-Demirtas Meltem, Müller Alejandro J, Chen Eugene Y-X
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States.
POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizábal 3, Donostia-San Sebastián 20018, Spain.
J Am Chem Soc. 2023 Mar 15;145(10):5795-5802. doi: 10.1021/jacs.2c12897. Epub 2023 Mar 3.
Stereo-defects present in stereo-regular polymers often diminish thermal and mechanical properties, and hence suppressing or eliminating them is a major aspirational goal for achieving polymers with optimal or enhanced properties. Here, we accomplish the opposite by introducing controlled stereo-defects to semicrystalline biodegradable poly(3-hydroxybutyrate) (P3HB), which offers an attractive biodegradable alternative to semicrystalline isotactic polypropylene but is brittle and opaque. We enhance the specific properties and mechanical performance of P3HB by drastically toughening it and also rendering it with the desired optical clarity while maintaining its biodegradability and crystallinity. This toughening strategy of stereo-microstructural engineering without changing the chemical compositions also departs from the conventional approach of toughening P3HB through copolymerization that increases chemical complexity, suppresses crystallization in the resulting copolymers, and is thus undesirable in the context of polymer recycling and performance. More specifically, syndio-rich P3HB (-P3HB), readily synthesized from the eight-membered -dimethyl diolide, has a unique set of stereo-microstructures comprising enriched syndiotactic [] and no isotactic [] triads but abundant stereo-defects randomly distributed along the chain. This -P3HB material is characterized by high toughness ( = 96 MJ/m) as a result of its high elongation at break (>400%) and tensile strength (34 MPa), crystallinity ( = 114 °C), optical clarity (due to its submicron spherulites), and good barrier properties, while it still biodegrades in freshwater and soil.
立构规整聚合物中存在的立构缺陷通常会降低其热性能和机械性能，因此抑制或消除这些缺陷是实现具有最佳或增强性能聚合物的主要目标。在此，我们通过向半结晶可生物降解聚（3-羟基丁酸酯）（P3HB）中引入可控的立构缺陷来实现相反的效果，P3HB是半结晶等规聚丙烯的一种有吸引力的可生物降解替代品，但它易碎且不透明。我们通过大幅增韧P3HB并使其具有所需的光学透明度，同时保持其生物降解性和结晶度，从而提高了P3HB的特定性能和机械性能。这种不改变化学组成的立构微观结构工程增韧策略也不同于通过共聚增韧P3HB的传统方法，后者会增加化学复杂性，抑制所得共聚物的结晶，因此在聚合物回收和性能方面是不可取的。更具体地说，由八元环二甲基二内酯易于合成的富含间同立构的P3HB（-P3HB）具有一组独特的立构微观结构，包括富集的间同立构[ ]且无等规[ ]三联体，但沿链随机分布有大量立构缺陷。这种-P3HB材料具有高韧性（ = 96 MJ/m），这归因于其高断裂伸长率（>400%）和拉伸强度（34 MPa）、结晶度（ = 114 °C）、光学透明度（由于其亚微米球晶）以及良好的阻隔性能，同时它仍能在淡水和土壤中生物降解。
