Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States.
Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, Swiss Federal Institute of Technology (ETH) Zurich , 8092 Zürich, Switzerland.
J Am Chem Soc. 2018 Jan 24;140(3):963-973. doi: 10.1021/jacs.7b10173. Epub 2018 Jan 16.
Chemically cross-linked elastomers are an important class of polymeric materials with excellent temperature and solvent resistance. However, nearly all elastomers are petroleum-derived and persist in the environment or in landfills long after they are discarded; this work strives to address these issues by demonstrating the synthesis of renewable, enzymatically hydrolyzable, and mechanically competitive polyester elastomers. The elastomers described were synthesized using a novel bis(β-lactone) cross-linker and star-shaped, hydroxyl-terminated poly(γ-methyl-ε-caprolactone). Using model compounds, we determined that the bis(β-lactone) cross-linker undergoes acyl bond cleavage to afford β-hydroxyesters at the junctions. The mechanical properties of the cross-linked materials were tunable and competitive with a commodity rubber band. Furthermore, the elastomers demonstrated high thermal stability and a low glass transition (-50 °C), indicating a wide range of use temperatures. The polyester networks were also subjected to enzymatic hydrolysis experiments to investigate the potential for these materials to biodegrade in natural environments. We found that they readily hydrolyzed at neutral pH and environmentally relevant temperatures (2-40 °C); complete hydrolysis was achieved in all cases at temperature-dependent rates. The results presented in this work exemplify the development of high performance yet sustainable alternatives to conventional elastomers.
化学交联弹性体是一类具有优异的温度和耐溶剂性的高分子材料。然而，几乎所有的弹性体都是石油衍生的，在被丢弃后很长一段时间内都会存在于环境中或垃圾填埋场中；这项工作努力通过展示可再生、可酶解和机械性能有竞争力的聚酯弹性体的合成来解决这些问题。所描述的弹性体是使用新型双（β-内酯）交联剂和星形、末端羟基聚（γ-甲基-ε-己内酯）合成的。使用模型化合物，我们确定双（β-内酯）交联剂经历酰基键断裂，在连接处提供β-羟基酯。交联材料的机械性能可调，与商品橡皮筋具有竞争力。此外，弹性体表现出高的热稳定性和低的玻璃化转变温度（-50°C），表明其使用温度范围很广。聚酯网络还进行了酶水解实验，以研究这些材料在自然环境中生物降解的潜力。我们发现它们在中性 pH 值和环境相关温度（2-40°C）下很容易水解；在所有情况下，在温度相关的速率下都能完全水解。本工作中提出的结果例证了开发高性能但可持续的传统弹性体替代品的发展。
