Mechanism of thermal decolorization of benzospirans in some amorphous polymeric matrices
Mechanism of thermal decolorization of benzospirans in some amorphous polymeric matrices
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DOI：
10.1002/pol.1973.170111002
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发表时间：
1973-10
期刊：
影响因子：
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通讯作者：
M. Kryszewski;D. Łapienis;B. Nadolski
中科院分区：
文献类型：
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作者：
M. Kryszewski;D. Łapienis;B. Nadolski
本文研究了苯并螺兰基团的三种化合物在非晶态聚合物中的光致变色效应：聚甲基丙烯酸甲酯、聚甲基丙烯酸正丁酯、聚醋酸乙烯酯和聚正丁酸乙烯酯。热漂反应的动力学在基体Tg以上，由于在粘弹性状态下与扩散段有关的自由体积分布的平均，其动力学服从一阶方程。从光致变色分子存在于玻璃基质中的不均匀、离散分布的角度出发，考虑了低于Tg的脱色机理。通过Tg后活化能的变化和颜色衰减机理不是一个规律（PVB），这表明对于具有长而柔性链的聚合物，二次玻璃化转变现象起决定性作用。在玻璃聚合物（PMMA）的情况下，苯并螺酯的光致变色效应可用于测定Tβ。在脱色过程中，除了对反式异构化的空间限制外，还必须考虑光致变色分子与基质的相互作用以及它们的化学性质。
The photochromic effect has been investigated for three compounds of the benzospiran group dissolved in amorphous polymers: poly(methyl methacrylate), poly(n-butyl methacrylate), poly(vinyl acetate), and poly(vinyl n-butyrate). The kinetics of the thermal bleaching reaction above Tg of the matrix follow a first-order equation due to the averaging of free volume distribution related to the diffusion of segments in viscoelastic state. A more complex mechanism of decolorization below Tg has been considered from the point of view of unequal, discrete distribution of environments in which the photochromic molecules exist in the glassy matrix. A change of the activation energy and the mechanism of color decay on passing through Tg is not a rule (PVB), which shows, that for a polymer having long, flexible chains, secondary glass transition phenomena play a decisive role. In the case of glassy polymers (PMMA), the photochromic effect of benzospirans may be employed to determine Tβ. It seems, that in addition to steric restrictions for trans–cis isomerization in the decolorization process one must consider the interactions of photochromic molecules with the matrix as well as their chemical nature.