An Azotolane Liquid‐Crystalline Polymer Exhibiting Extremely Large Birefringence and Its Photoresponsive Behavior
An Azotolane Liquid‐Crystalline Polymer Exhibiting Extremely Large Birefringence and Its Photoresponsive Behavior
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DOI：
10.1002/adma.200501783
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发表时间：
2006-02
影响因子：
29.4
通讯作者：
K. Okano;A. Shishido;T. Ikeda
中科院分区：
文献类型：
--
作者：
K. Okano;A. Shishido;T. Ikeda
Polymers containing azobenzene on their side chains are promising materials for optical applications because a change in birefringence ( D n ) can be induced by photoisomerization. [1,2] A large change in D n enables a large change in the phase of incident light, which is very useful and effective for optical applications. To develop a high-performance optical material using azobenzene polymers, it is necessary to induce a large change in D n by pumping light. In azobenzene polymers, two processes for the change in D n have been reported: reorientation of azobenzene moieties upon irradiation of isotropic films with polarized pumping light (disorder–order change) [3–5] and destruction of homogeneous alignment of mesogenic azobenzenes by photochemical phase transition (order–disorder change). [6] Atwater and co-workers have shown that a large D n , of up to 0.56 at 660 nm, is induced by the reorientation of an azobenzene moiety. [7] In addition, Hagen and Bieringer focused on high-density optical data storage by using an amorphous azobenzene polymer. [8] We have performed, so far, systematic studies on the nematic–isotropic phase transition of azobenzene liquid-crystalline polymers (LCPs). An advantage of the azobenzene LCPs is the fact that a large change in D n is induced quickly by photo-isomerization of the azobenzene moieties. Herein, we have synthesized a highly birefringent LCP containing a long mesogenic core in which an azobenzene group is directly connected to a two-ring tolane moiety (azotolane moiety). Figure 1a shows the chemical structure, molecular weight, and phase-transition temperature of the LCP, P4TA .
