How does the initial alignment of mesogens affect the photoinduced bending behavior of liquid-crystalline elastomers?
How does the initial alignment of mesogens affect the photoinduced bending behavior of liquid-crystalline elastomers?
复制标题
DOI：
10.1002/anie.200503684
复制
发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Ikeda, T
中科院分区：
文献类型：
--
作者：
Kondo, M;Yu, YL;Ikeda, T
显示弯曲运动的致动器的发展越来越受到关注。弯曲运动通常由材料中的不对称收缩或膨胀引起。[1-4]从精确的三维致动和由于弯曲动作的小变形而长的寿命的观点来看，这种类型的致动器比仅显示二维运动（例如膨胀和收缩）的致动器具有更多的优点。由于这些独特的性质，弯曲致动器有望用于微机械，微泵和许多其他微机械应用。各种材料已被报道作为弯曲致动器，如压电换能器，[5]形状记忆合金，[6]和聚合物。[2]与其他材料相比，聚合物致动器更柔软，更轻，并且高度可加工，这使得它们容易制成各种形状;因此，已经对聚合物材料的致动进行了研究，并且已经提出了许多应用。[7]此外，大多数聚合物致动器（例如导电聚合物）的弯曲是由电能驱动的;因此，这些材料需要电线来获得电力。[3]另一方面，弹性体聚合物，包括凝胶和形状记忆聚合物，可以响应于各种物理刺激而进行机械致动，例如pH，[8]溶剂成分，[9]热，[10-12]和光。[13光可以作为外部刺激被远程且快速地控制，因此在开发可以由光驱动的简单、高效且紧凑的弹性体聚合物致动器方面具有重要意义。已知液晶弹性体（LCE）在被加热到高于其双（N）-各向同性（I）相变温度时表现出沿指向矢轴沿着的自发收缩。[15-17]另一方面，当偶氮苯发色团掺入LCE中时，由于光引起的排列顺序的变化，它们可以等温收缩。[18-20]此外，作为偶氮苯部分在
The development of actuators that show bending movement is of increasing interest. The bending movement is usually induced by an asymmetric contraction or expansion in the materials.[1–4] This type of actuator has more advantages than the actuators that show only two-dimensional movements, such as expansion and contraction, from the viewpoint of precise three-dimensional actuation and long lifetime owing to small deformation for the bending action. Because of these unique properties, the bending actuators are expected to be used for cantilevers, micropumps, and many other micromechanical applications.Various materials have been reported as the bending actuators, such as piezoelectric transducers,[5] shape-memory alloys,[6] and polymers.[2] In comparison with other materials, the polymer actuators are much softer, lighter, and highly processible, which makes them easily made into various shapes; consequently, studies have been performed on the actuation of polymer materials and many applications have been proposed.[7] In addition, the bending of most polymer actuators, such as conducting polymers is driven by electrical energy; thus, these materials require wires to acquire electrical power.[3] On the other hand, elastomeric polymers, including gels and shape-memory polymers, can undergo mechanical actuation in response to various physical stimuli, such as pH,[8] solvent composition,[9] heat,[10–12] and light.[13, 14] Light can be controlled remotely and rapidly as an external stimulus, so it is of great importance in developing simple, efficient, and compact elastomeric polymer actuators that can be driven by light. It is known that liquid-crystalline elastomers (LCEs) exhibit a spontaneous contraction along the director axis when heated above their nematic (N)–isotropic (I) phase-transition temperatures.[15–17] On the other hand, when azobenzene chromophores are incorporated into LCEs, they can undergo the contraction isothermally because of the change in alignment order by light.[18–20] Furthermore, as the extinction coefficient of the azobenzene moieties at