The Effect of Polymer Chain Alignment and Relaxation on Force- Induced Chemical Reactions in an Elastomer
The Effect of Polymer Chain Alignment and Relaxation on Force- Induced Chemical Reactions in an Elastomer
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DOI：
10.1002/adfm.201302341
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发表时间：
2014-03-01
影响因子：
19
通讯作者：
Sottos, Nancy R.
中科院分区：
文献类型：
--
作者：
Beiermann, Brett A.;Kramer, Sharlotte L. B.;Sottos, Nancy R.
同时测量的机械响应，光学双折射，和荧光信号在原位获得在拉伸测试的机械连接的弹性体聚合物。机械应力、变形和聚合物链排列与力诱导的机械基团的化学反应相关。所研究的机械力化学响应聚合物是螺吡喃-（SP-）连接的聚（丙烯酸甲酯）（PMA）。SP向其汞（MC）形式的力驱动转化（活化）通过用入射在样品上的532 nm光的荧光信号的出现来指示。拉伸变形速率的增加导致应力和SP到MC的转化率的增加，表明宏观应力和活化之间的正相关性。同时收集的双折射测量结果表明，快速的机械基团激活时发生的最大聚合物链对齐。据发现，SP到MC转换PMA需要一个足够的水平的应力和足够的取向的聚合物链在施加的力的方向。
Simultaneous measurements of mechanical response, optical birefringence, and fluorescence signal are acquired in situ during tensile testing of a mechanophore-linked elastomeric polymer. Mechanical stress, deformation, and polymer chain alignment are correlated with force-induced chemical reaction of the mechanophore. The mechanochemically responsive polymer under investigation is spiropyran- (SP-) linked poly(methyl acrylate) (PMA). Force-driven conversion (activation) of SP to its merocyanine (MC) form is indicated by the emergence of a fluorescence signal with 532 nm light incident on the sample. Increasing rate of tensile deformation leads to an increase in both stress and SP-to-MC conversion, indicating a positive correlation between macroscopic stress and activation. Simultaneously collected birefringence measurements reveal that rapid mechanophore activation occurs when maximum polymer chain alignment is reached. It is found that SP-to-MC conversion in PMA requires both a sufficient level of stress and adequate orientation of the polymer chains in the direction of applied force.