Toshchevikov Vladimir, Petrova Tatiana, Saphiannikova Marina
Leibniz-Institut für Polymerforschung, Hohe Str. 6, 01069 Dresden, Germany.
Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi pr. 31, Saint-Petersburg 199004, Russia.
Polymers (Basel). 2018 May 15;10(5):531. doi: 10.3390/polym10050531.
Azobenzene-containing polymer networks are unique compounds that are able to change their shape in response to light, which makes them prospective materials for photocontrollable nano-templates, sensors, microrobots, artificial muscles, etc. In present work, we study the kinetics of light-induced ordering and deformation in two-component polymer networks containing optically inert liquid crystalline (LC) mesogens and azobenzene chromophores. By this, we generalize our previous theory [J. Phys. Chem. Lett. 2017, 8, 1094⁻1098] devoted to the kinetics of photoizomerization in one-component azo-polymers without mesogenic inclusions. The kinetic equations of photoisomerization are used, taking into account the angular selectivity of the photoisomerization with respect to the polarization direction of the light . After multiple trans-cis-trans photoisomerization cycles, the azobenzenes are reoriented preferably perpendicular to the vector . This changes the ordering of the mesogens due to the orientational LC interactions between the components. The light-induced reordering is accompanied by network deformation. Time evolution of ordering and deformation is found as a function of the intensity of light and structural parameters of the LC azo-networks, which define the viscosity, the strength of the LC interactions between the components, the volume fraction of the azobenzene moieties, and the angular distribution of azobenzenes in polymer chains. Established structure-property relationships are in agreement with a number of experimental data.
含偶氮苯的聚合物网络是一类独特的化合物，能够响应光而改变其形状，这使其成为用于光控纳米模板、传感器、微型机器人、人造肌肉等的潜在材料。在当前工作中，我们研究了包含光学惰性液晶（LC）介晶和偶氮苯发色团的双组分聚合物网络中光诱导有序化和变形的动力学。借此，我们推广了我们之前关于不含介晶夹杂物的单组分偶氮聚合物中光异构化动力学的理论[《物理化学快报》2017年，8卷，1094 - 1098页]。使用了光异构化的动力学方程，同时考虑了光异构化相对于光偏振方向的角度选择性。经过多次反式 - 顺式 - 反式光异构化循环后，偶氮苯优先重新取向至垂直于该矢量的方向。这由于各组分之间的取向液晶相互作用而改变了介晶的有序性。光诱导的重新排序伴随着网络变形。发现有序化和变形的时间演化是光强度以及LC偶氮网络结构参数的函数，这些结构参数定义了粘度、各组分之间LC相互作用的强度、偶氮苯部分的体积分数以及聚合物链中偶氮苯的角度分布。所建立的结构 - 性能关系与许多实验数据一致。
