Photochromism and thermochromism of phenanthrospirooxazine in poly(alkylmethacrylates)
Photochromism and thermochromism of phenanthrospirooxazine in poly(alkylmethacrylates)
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DOI：
10.1021/jp9843151
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发表时间：
1999-03-18
影响因子：
3.3
通讯作者：
Aramendía, PF
中科院分区：
文献类型：
--
作者：
Levitus, M;Aramendía, PF
之后形成的光色花青(MC)的衰变。研究了聚(甲基)-、聚(乙基)、聚(甲基)丙烯酸异丁酯聚合物膜中邻菲螺恶嗪(SO)的闪光辐照，并与苯并吡喃(SP)的类似数据进行了比较。黑暗中的衰变偏离了单指数行为。数据采用高斯分布模型和矩阵松弛模型进行分析。高斯分布中心的速率常数在所有聚合物中都是相等的，并且等于在非极性液体中报告的单分子速率常数。这可能与聚合物不能溶剂化过渡态有关。聚合物基质影响激活能分布的宽度；在刚性较大的介质中，这种分布更宽。松弛模型能够提供与衰变相关的矩阵的松弛时间的平均值。在每个聚合物中，对于SO和SP的MC形式，该弛豫时间的阿累尼乌斯活化能是相似的，并且与聚合物的β松弛活化能相似。这表明局部运动是松弛的原因，这也解释了所有动力学参数在包括玻璃化转变温度在内的温度范围内都表现出Arrhenius类型的行为的事实。研究了可逆阿罗MC转变在聚甲基丙烯酸乙酯和聚甲基丙烯酸乙酯中的热致变色性。在流体介质中，平衡常数偏离正常行为。这种偏离可以通过假设两种形式的SO之间的能量差为高斯分布来解释。由动力学数据和平衡数据得到的分布宽度非常相似。
The decay of the photomerocyanine (MC) formed after. flash irradiation of a phenanthrospirooxazine (SO) was studied in polymer films of poly(methyl-), poly(ethyl-), and poly(isobutyl methacrylate) and compared with similar data of a benzospiropyran (SP). The decays in the dark depart from monoexponential behavior. The data were analyzed by a Gaussian distribution model and by a matrix relaxation model. The rate constant at the center of the Gaussian distribution is equal in all polymers and equal to the unimolecular rate constant reported in nonpolar liquids. This may be related to the inability of the polymer to solvate the transition state. The polymer matrix affects the width of the activation energy distribution; this distribution is broader in more rigid media. The relaxation model is able to provide a mean value for the relaxation time of the matrix, which is relevant for the decay. The arrhenius activation energy of this relaxation time is similar in each polymer for the MC forms of SO and of SP and is similar to the activation energy of the beta-relaxation of the polymers. This indicates that local movements are responsible for the relaxation, which also explains the fact that all kinetic parameters show an Arrhenius-type behavior in temperature ranges including the glass transition temperature. The thermochromism of SO reversible arrow MC transformation was studied in poly(methyl-) and in poly(ethyl methacrylate). The equilibrium constants depart from the normal behavior in fluid media. This departure is interpreted by assuming a Gaussian distribution of energy difference between the two forms of SO. The widths of the distributions obtained from kinetic and equilibrium data are very similar.