Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
J Am Chem Soc. 2012 Jun 13;134(23):9577-80. doi: 10.1021/ja302996n. Epub 2012 May 31.
Epoxidized polybutadiene and epoxidized polynorbornene were subjected to pulsed ultrasound in the presence of small molecules capable of being trapped by carbonyl ylides. When epoxidized polybutadiene was sonicated, there was no observable small molecule addition to the polymer. Concurrently, no appreciable isomerization (cis to trans epoxide) was observed, indicating that the epoxide rings along the backbone are not mechanically active under the experimental conditions employed. In contrast, when epoxidized polynorbornene was subjected to the same conditions, both addition of ylide trapping reagents and net isomerization of cis to trans epoxide were observed. The results demonstrate the mechanical activity of epoxides, show that mechanophore activity is determined not only by the functional group but also the polymer backbone in which it is embedded, and facilitate a characterization of the reactivity of the ring-opened dialkyl epoxide.
环氧化聚丁二烯和环氧化聚降冰片烯在能够被羰基叶立德捕获的小分子存在的情况下经受脉冲超声处理。当对环氧化聚丁二烯进行超声处理时，聚合物中没有观察到可检测到的小分子添加。同时，也没有观察到明显的异构化（顺式到反式环氧化物），这表明在实验条件下，沿主链的环氧环没有机械活性。相比之下，当环氧化聚降冰片烯受到相同条件的处理时，观察到叶立德捕获试剂的添加和顺式到反式环氧化物的净异构化。结果表明了环氧基团的机械活性，表明机械基团的活性不仅取决于官能团，还取决于其嵌入的聚合物主链，并且有助于对开环二烷基环氧化物的反应性进行特征描述。
