A novel class of recyclable thermoset has been developed from cis-3,4-diphenylcyclobutane-1,2-dicarboxylic acid (CBDA-4) due to its thermocleavability at high temperature. This key CBDA-4 building block was synthesized from β-trans-cinnamic acid using a [2+2] photocycloaddition reaction. CBDA-4 was subsequently linked with glycerol via esterification to give a thermoset with T_g of 68 °C. The thermoset was heated to 300 °C to analyze its degradation. A key intermediate was successfully obtained after purification of the degraded polymer. NMR, FT-IR, HRMS, and single crystal X-ray diffraction confirmed the intermediate was glycerol cinnamate, which was the result of splitting cyclobutane in the polymer backbone at high temperature. Glycerol cinnamate was readily hydrolyzed reforming the starting materials glycerol and trans-cinnamic acid to complete the recycling loop.

中文翻译：

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由顺式-环丁烷-1,2-二羧酸开发的具有内置热裂解基团的可回收热固性材料

由于顺式-3,4-二苯基环丁烷-1,2-二羧酸（CBDA-4）在高温下具有热裂解性，已开发出一类新型可回收热固性材料。使用 [2+2] 光环加成反应从 β-反式-肉桂酸合成了这个关键的 CBDA-4 结构单元。CBDA-4 随后通过酯化与甘油连接，得到具有T _{g的热固性材料}68°C。将热固性塑料加热至 300 °C 以分析其降解情况。降解后的聚合物纯化后成功获得关键中间体。NMR、FT-IR、HRMS和单晶X射线衍射证实中间体为肉桂酸甘油酯，是聚合物骨架中的环丁烷在高温下裂解的结果。肉桂酸甘油酯很容易水解，重整原料甘油和反式肉桂酸以完成循环回路。