Stress-responsive polymers containing cyclobutane core mechanophores: reactivity and mechanistic insights.
Stress-responsive polymers containing cyclobutane core mechanophores: reactivity and mechanistic insights.
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DOI：
10.1021/ja4075997
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发表时间：
2013-09-11
影响因子：
15
通讯作者：
Craig SL
中科院分区：
文献类型：
--
作者：
Kean ZS;Niu Z;Hewage GB;Rheingold AL;Craig SL
共价机械化学的主要目标是开发聚合物结合的机械载体，其响应于破坏性力而经历建设性转化。环丁烷机械载体的[2+2]环化逆转已经成为一个通用的框架，以开发广泛的应力激活功能。在此，我们报告了一类环丁烷轴承双环[4.2.0]辛烷机械载体的发展。使用碳二亚胺聚酯化，这些应力响应单元被掺入到每个聚合物链含有多达700个机械基团的高分子量聚合物中。在暴露于脉冲超声波的破坏性拉伸力下，这些机械载体以每个单体单元约7 μ m的量散开，形成α，β-不饱和酯，其通过硫醇-烯共轭加成进行建设性反应，形成硫化物官能化共聚物和交联聚合物网络。为了探索机械化学开环的动力学，合成并活化了一系列在立体化学、取代和对称性方面不同的双环[4.2.0]辛烷衍生物。通过1H NMR分析反应活性和产物立体化学，这使我们能够询问机械化学[2+2]环化逆转的机制。这些结果支持开环不是协同的，而是通过1，4双自由基中间体进行的。双环[4.2.0]辛烷有望作为新型应力响应聚合物材料中的活性官能团。
A primary goal of covalent mechanochemistry is to develop polymer bound mechanophores that undergo constructive transformations in response to otherwise destructive forces. The [2+2] cycloreversion of cyclobutane mechanophores has emerged as a versatile framework to develop a wide range of stress-activated functionality. Herein, we report the development of a class of cyclobutane bearing bicyclo[4.2.0]octane mechanophores. Using carbodiimide polyesterification, these stress-responsive units were incorporated into high molecular weight polymers containing up to 700 mechanophores per polymer chain. Under exposure to the otherwise destructive elongational forces of pulsed ultrasound, these mechanophores unravel by ~7 Å per monomer unit to form α,β-unsaturated esters that react constructively via thiol-ene conjugate addition to form sulfide functionalized copolymers and cross-linked polymer networks. To probe the dynamics of the mechanochemical ring opening, a series of bicyclo[4.2.0]octane derivatives that varied in stereochemistry, substitution, and symmetry were synthesized and activated. Reactivity and product stereochemistry was analyzed by 1H NMR, which allowed us to interrogate the mechanism of the mechanochemical [2+2] cycloreversion. These results support that the ring opening is not concerted, but proceeds via a 1,4 diradical intermediate. The bicyclo[4.2.0]octanes hold promise as active functional groups in new classes of stress-responsive polymeric materials.
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影响因子：
5.5
作者：
Berkowski, KL;Potisek, SL;Moore, JS
通讯作者：
Moore, JS
影响因子：
21.8
作者：
Klukovich, Hope M.;Kouznetsova, Tatiana B.;Craig, Stephen L.
通讯作者：
Craig, Stephen L.
影响因子：
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作者：
Black, Ashley L.;Orlicki, Joshua A.;Craig, Stephen L.
通讯作者：
Craig, Stephen L.
影响因子：
56.9
作者：
HOFFMANN, R;WOODWARD, RB
通讯作者：
WOODWARD, RB
影响因子：
4.4
作者：
Beyer, MK
通讯作者：
Beyer, MK