Mechanically Gated Degradable Polymers
Mechanically Gated Degradable Polymers
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DOI：
10.1021/jacs.9b13359
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发表时间：
2020-02-05
影响因子：
15
通讯作者：
Craig, Stephen L.
中科院分区：
文献类型：
--
作者：
Lin, Yangju;Kouznetsova, Tatiana B.;Craig, Stephen L.
可降解聚合物是替代在环境中持续存在的传统有机聚合物的理想选择，但它们经常遭受聚合物主链上的可降解功能的无意破坏，这在储存和常规使用期间降低了聚合物的性能。在这里，我们报告了一种策略，通过结合两种常见的降解刺激-机械和酸触发器-以“与门”的方式来对抗聚合物的意外降解。环丁烷（CB）机械基团作为一种机械门来调节酸敏酮，这种酸敏酮已广泛应用于酸降解聚合物中。这种门控酮进一步并入聚合物主链中。在仅存在酸触发的情况下，原始聚合物保持其主链完整性，并且通过超声波单独提供高机械力将聚合物降解到明显的极限分子量为28 kDa。然而，连续的超声处理和酸处理，导致分子质量进一步降低11倍至2.5 kDa。实验和计算证据进一步表明，未门控酮具有与常规聚合物骨架相当的机械强度。单分子力谱（SMFS）表明，在100 ms的时间尺度上激活CB分子门所需的力约为2nn。
Degradable polymers are desirable for the replacement of conventional organic polymers that persist in the environment, but they often suffer from the unintentional scission of the degradable functionalities on the polymer backbone, which diminishes polymer properties during storage and regular use. Herein, we report a strategy that combats unintended degradation in polymers by combining two common degradation stimuli-mechanical and acid triggers-in an "AND gate" fashion. A cyclobutane (CB) mechanophore is used as a mechanical gate to regulate an acid-sensitive ketal that has been widely employed in acid degradable polymers. This gated ketal is further incorporated into the polymer backbone. In the presence of an acid trigger alone, the pristine polymer retains its backbone integrity, and delivering high mechanical forces alone by ultrasonication degrades the polymer to an apparent limiting molecular weight of 28 kDa. The sequential treatment of ultrasonication followed by acid, however, leads to a further 11-fold decrease in molecular weight to 2.5 kDa. Experimental and computational evidence further indicate that the ungated ketal possesses mechanical strength that is commensurate with the conventional polymer backbones. Single molecule force spectroscopy (SMFS) reveals that the force necessary to activate the CB molecular gate on the time scale of 100 ms is approximately 2 nN.