Toshchevikov Vladimir, Saphiannikova Marina
Leibniz-Institut für Polymerforschung , Hohe Str. 6, 01069 Dresden, Germany.
J Phys Chem B. 2014 Oct 23;118(42):12297-309. doi: 10.1021/jp5063226. Epub 2014 Oct 13.
We study light-induced deformation of azobenzene elastomers which can display liquid-crystalline (LC) order. It is shown that photomechanical behavior of azobenzene elastomers is determined by the strength of the LC interactions, which is proportional to the density of rodlike azobenzene chromophores. At weak LC interactions, a uniaxial order and uniaxial deformation of azobenzene elastomers along the polarization vector of the light E is observed. At strong LC interactions, the light is able to induce a phase transition from the uniaxial to the biaxial state, with two axes being related to the vector E and to a preferable alignment of the chromophores in the plane perpendicular to E. The phase transition can be of either the first or the second order. Azobenzene elastomers can demonstrate elongation or contraction along the polarization vector E, depending on the orientation distribution of chromophores around the main chains of network strands. The results of the theory are in a qualitative agreement with experiments and computer simulations, which demonstrate biaxial ordering in azo-containing polymers.
我们研究了偶氮苯弹性体的光致变形，这种弹性体能够呈现液晶（LC）有序态。结果表明，偶氮苯弹性体的光机械行为由液晶相互作用的强度决定，该强度与棒状偶氮苯发色团的密度成正比。在弱液晶相互作用下，观察到偶氮苯弹性体沿光的偏振矢量E发生单轴有序和单轴变形。在强液晶相互作用下，光能够诱导从单轴态到双轴态的相变，其中两个轴与矢量E以及发色团在垂直于E的平面中的择优取向有关。该相变可以是一级相变或二级相变。偶氮苯弹性体可以沿偏振矢量E表现出伸长或收缩，这取决于发色团围绕网状链主链的取向分布。理论结果与实验和计算机模拟在定性上是一致的，实验和模拟均表明含偶氮聚合物中存在双轴有序。
