Mai Jingjing, Pratt Steven, Laycock Bronwyn, Chan Clement Matthew
School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
Polymers (Basel). 2023 Jul 31;15(15):3257. doi: 10.3390/polym15153257.
Bacterially derived polyhydroxyalkanoates (PHAs) are attractive alternatives to commodity petroleum-derived plastics. The most common forms of the short chain length (scl-) PHAs, including poly(3-hydroxybutyrate) (P3HB) and poly(3-hydroxybutyrate--3-hydroxyvalerate) (PHBV), are currently limited in application because they are relatively stiff and brittle. The synthesis of PHA--PHA block copolymers could enhance the physical properties of PHAs. Therefore, this work explores the synthesis of PHBV--PHBV using relatively high molecular weight hydroxy-functionalised PHBV starting materials, coupled using facile diisocyanate chemistry, delivering industrially relevant high-molecular-weight block copolymeric products. A two-step synthesis approach was compared with a one-step approach, both of which resulted in successful block copolymer production. However, the two-step synthesis was shown to be less effective in building molecular weight. Both synthetic approaches were affected by additional isocyanate reactions resulting in the formation of by-products such as allophanate and likely biuret groups, which delivered partial cross-linking and higher molecular weights in the resulting multi-block products, identified for the first time as likely and significant by-products in such reactions, affecting the product performance.
细菌衍生的聚羟基脂肪酸酯（PHA）是商品石油衍生塑料的有吸引力的替代品。短链长度（scl-）PHA的最常见形式，包括聚（3-羟基丁酸酯）（P3HB）和聚（3-羟基丁酸酯-3-羟基戊酸酯）（PHBV），目前在应用中受到限制，因为它们相对坚硬且易碎。PHA-PHA嵌段共聚物的合成可以增强PHA的物理性能。因此，这项工作探索了使用相对高分子量的羟基官能化PHBV起始材料合成PHBV-PHBV，通过简便的二异氰酸酯化学方法进行偶联，得到具有工业相关性的高分子量嵌段共聚物产品。将两步合成方法与一步合成方法进行了比较，两种方法都成功制备出了嵌段共聚物。然而，两步合成法在增加分子量方面效果较差。两种合成方法都受到额外异氰酸酯反应的影响，导致生成副产物，如脲基甲酸酯和可能的缩二脲基团，这些副产物在所得的多嵌段产品中产生了部分交联并提高了分子量，首次确定这些副产物是此类反应中可能且重要的副产物，影响了产品性能。
