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在不同刚性的聚合物基体聚甲基丙烯酸甲酯(PMMA)、聚乙烯咔唑(PVK)和聚苯乙烯(PS)薄膜基体中掺入相同质量分数(均为0.003)的分散红13(DR13)偶氮染料。以线偏振连续Ar+激光(514 nm)作为控制光,连续He-Ne激光(632.8 nm)作为信号光考察了具有相同厚度的三种样品在相同控制光功率(15 mW)下的光致双折射效应。实验发现刚性较大的聚乙烯咔唑基体样品的双折射效应最小,刚性最小的聚苯乙烯基体样品的双折射效应最大。在偶氮生色团光致异构的四能级模型基础上,建立一新的唯象的模型。在模型中引入描述聚合物基体刚性的参量s,通过数值计算描述了不同基体刚性参量s对偶氮生色团光致异构取向的影响。计算结果表明,基体的刚性越大,样品的光致双折射效应越小,定性地解释了实验现象。
Disperse red 13 (DR13) with the same mass fraction (all 0.003) was incorporated into different rigid matrix of polymer matrix PMMA, PVK and PS. ) Azo dyes. Continuous linearly polarized Ar + laser (514 nm) was used as control light and continuous He-Ne laser (632.8 nm) was used as signal light to investigate the photo-induced birefringence of the three samples with the same thickness at the same controlled power (15 mW) effect. It was found that the birefringence effect of the more rigid polyethylene carbazole matrix sample was the smallest, and the birefringence effect of the most rigid polystyrene matrix sample was the largest. Based on the four-level model of azo chromophore’s photoisomerization, a new phenomenal model is established. The parameter s, which describes the stiffness of the polymer matrix, is introduced into the model to describe the effect of the matrix parameters s on the photo-isomerism of azo chromophores. The calculation results show that the larger the rigidity of the matrix, the smaller the photorefractive birefringence effect of the sample, which qualitatively explains the experimental phenomenon.