Rapid and reversible shape changes of molecular crystals on photoirradiation
Rapid and reversible shape changes of molecular crystals on photoirradiation
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DOI：
10.1038/nature05669
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发表时间：
2007-04-12
期刊：
影响因子：
64.8
通讯作者：
Irie, Masahiro
中科院分区：
文献类型：
--
作者：
Kobatake, Seiya;Takami, Shizuka;Irie, Masahiro
基于响应于外部刺激可逆地改变形状和/或尺寸的材料的致动器的开发已经吸引了一段时间的兴趣（1）。一个特别有趣的可能性是由光响应材料提供的，它允许远程操作，而不需要直接接触致动器。这些材料的光响应是基于组成分子的光异构化（通常是偶氮苯发色团的反-顺异构化），其引起分子运动并由此使本体材料变形。这种效应已被用于产生光可变形的聚合物膜和凝胶（2-10），但这些系统的响应相对较慢。在这里，我们报告的分子晶体的基础上二芳基乙烯发色团和尺寸范围从10至100微米表现出快速和可逆的宏观变化的形状和大小诱导的紫外线和可见光。我们发现，在紫外光照射下，（2-乙基-5-苯基-3-噻吩基）全氟环戊烯从正方形变为菱形，而1，2-双（噻吩基）全氟环戊烯的矩形单晶（5-甲基-2-苯基-4-噻唑基）全氟环戊烯收缩约5 - 7%。变形的晶体是热稳定的，并且在用可见光照射时切换回它们的原始状态。我们发现，我们的晶体响应时间约为25微秒（即比偶氮苯基聚合物系统的响应时间快约5个数量级（7-10）），并且它们可以移动微观物体，使它们成为可能的光驱动致动器应用的有前途的材料。
The development of actuators based on materials that reversibly change shape and/or size in response to external stimuli has attracted interest for some time(1). A particularly intriguing possibility is offered by light-responsive materials, which allow remote operation without the need for direct contact to the actuator. The photo-response of these materials is based on the photoisomerization of constituent molecules ( typically trans - cis isomerization of azobenzene chromophores), which gives rise to molecular motions and thereby deforms the bulk material. This effect has been used to create light-deformable polymer films and gels(2-10), but the response of these systems is relatively slow. Here we report that molecular crystals based on diarylethene chromophores and with sizes ranging from 10 to 100 micrometres exhibit rapid and reversible macroscopic changes in shape and size induced by ultraviolet and visible light. We find that on exposure to ultraviolet light, a single crystal of 1,2-bis(2-ethyl-5-phenyl-3-thienyl) perfluorocyclopentene changes from a square shape to a lozenge shape, whereas a rectangular single crystal of 1,2-bis(5-methyl-2-phenyl- 4-thiazolyl) perfluorocyclopentene contracts by about 5 - 7 per cent. The deformed crystals are thermally stable, and switch back to their original state on irradiation with visible light. We find that our crystals respond in about 25 microseconds ( that is, about five orders of magnitude faster than the response time of the azobenzene-based polymer systems(7-10)) and that they can move microscopic objects, making them promising materials for possible light-driven actuator applications.