偶氮染料掺杂液晶中分子重新取向对入射光方向依赖关系的机理研究

Mechanism of the Dependence of Molecular Reorientation on the Direction of Incident Light in Azo dye Doped Liquid Crystals

研究了发生在偶氮染料掺杂液晶中的光诱导重新取向问题,并解释增强因子与光入射方向存在依赖关系的物理机制。文章所用理论是建立在对偶氮染料光致异构化过程分析的基础上。对于这个特殊的系统而言,入射光方向的变化会改变系统的有序参数,进而影响到分子间的相互作用势能。为了描述顺式染料分子与液晶分子间的相互作用,利用有序参数与顺式染料分子数密度之间的关系,给出了梅尔邵普势能与顺式染料分子数密度关系的具体表达式。从二能级耦合方程出发,得到了系统中增强因子的微观表达式并给出了掺R4偶氮染料的E63液晶样品增强因子对角度Ψ的依赖图样。最后,给出了旋转扩散常数对增强因子η的影响。通过与已有实验的比较,验证了增强因子微观形式的有效性。

This paper investigates an optical reorientation process of azo dye doped liquid crystals and explains the dependence of the enhancement factor on the incident light direction. Because the order parameters of the guest host liquid crystal system depend on the direction of the incident light, the intermolecular orientational interaction potential is also related with the incident light direction. To describe the interaction between the cis isomer and the LC molecules, Maier Saupe potential expression was re written by means of the order parameters of the doped liquid crystal system. Beginning with a two level coupling equation, this paper investigated a microscopic formula and an angular dependence of the enhancement factor with liquid crystals E63 doped with R4 azo dye, and obtained the relation of the enhancement factor with the rotational diffusion constants. The comparison of computational results with the existent experimental results verified the enhancement factors microscopic form.