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首页> 外文期刊>ACS Macro Letters >Effect of Mechanical Stress on Spiropyran-Merocyanine Reaction Kinetics in a Thermoplastic Polymer
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Effect of Mechanical Stress on Spiropyran-Merocyanine Reaction Kinetics in a Thermoplastic Polymer

机译：机械应力对热塑性聚合物中螺吡喃-花菁反应动力学的影响

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摘要

Mechanical force alters the potential energy surface of a mechanophore reaction by modifying the activation energy for conversion. The effects of force on the rate constants and activation energies are not well characterized for mechanophores in bulk polymers. In this work, spiropyran-linked polyurethanes are synthesized and the kinetics of the spiropyran-merocyanine transition in the bulk polymer measured under different values of a macroscopic tensile stress. Above a critical threshold stress, the forward rate constant (spiropyran to merocyanine transition) increases, while the reverse rate constant (merocyanine to spiropyran transition) decreases with applied stress. A tensile stress of 50 MPa enhances the forward rate constant by 110% and lowers the forward activation energy by 1.8 kJ/mol compared to the unstressed condition. Also, this same amount of stress reduces the reverse rate constant by 65% and increases the reverse activation energy by 2.5 kJ/mol.
机译：机械力通过改变转化的活化能来改变机械反应的势能表面。力对速率常数和活化能的影响对于本体聚合物中的机械发色团没有很好地表征。在这项工作中，合成了螺并吡喃连接的聚氨酯，并在不同的宏观拉伸应力值下测量了本体聚合物中螺并吡喃-硫氰酸的转变动力学。高于临界阈值应力时，正向速率常数（螺吡喃向花菁过渡）增加，而反向速率常数（硫氰酸向螺吡喃过渡）随着施加的应力而减小。与无应力条件相比，50 MPa的拉伸应力可使正向速率常数提高110％，并使正向活化能降低1.8 kJ / mol。同样，相同量的应力将反向速率常数降低了65％，并使反向活化能提高了2.5 kJ / mol。

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