Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA.
BOTTLE Consortium, Golden, CO 80401, USA.
Sci Adv. 2023 Nov 24;9(47):eadi1735. doi: 10.1126/sciadv.adi1735. Epub 2023 Nov 22.
Cross-linked elastomers are stretchable materials that typically are not recyclable or biodegradable. Medium-chain-length polyhydroxyalkanoates (mcl-PHAs) are soft and ductile, making these bio-based polymers good candidates for biodegradable elastomers. Elasticity is commonly imparted by a cross-linked network structure, and covalent adaptable networks have emerged as a solution to prepare recyclable thermosets via triggered rearrangement of dynamic covalent bonds. Here, we develop biodegradable and recyclable elastomers by chemically installing the covalent adaptable network within biologically produced mcl-PHAs. Specifically, an engineered strain of was used to produce mcl-PHAs containing pendent terminal alkenes as chemical handles for postfunctionalization. Thiol-ene chemistry was used to incorporate boronic ester (BE) cross-links, resulting in PHA-based vitrimers. mcl-PHAs cross-linked with BE at low density (<6 mole %) affords a soft, elastomeric material that demonstrates thermal reprocessability, biodegradability, and denetworking at end of life. The mechanical properties show potential for applications including adhesives and soft, biodegradable robotics and electronics.
交联弹性体是一种具有拉伸性能的材料，但通常不可回收或生物降解。中链长度聚羟基烷酸酯（mcl-PHA）柔软且具有延展性，使其成为生物基弹性体的良好候选材料。弹性通常通过交联网络结构赋予，而共价适应性网络的出现为通过动态共价键的触发重排来制备可回收热固性材料提供了一种解决方案。在这里，我们通过在生物合成的 mcl-PHA 中化学引入共价适应性网络来开发可生物降解和可回收的弹性体。具体来说，我们使用经过工程改造的菌株来生产含有末端烯基的 mcl-PHA，作为后功能化的化学接头。硫醇-烯点击化学用于引入硼酸酯（BE）交联剂，从而得到基于 PHA 的热塑性弹性体。在低密度（<6mol%）下交联 BE 可得到柔软的弹性材料，该材料具有热再加工性、生物降解性和使用寿命结束时的解交联性。其机械性能显示出在包括粘合剂和柔软、可生物降解的机器人技术和电子学在内的应用中的潜力。
