Moving Polymers via Photoisomerization

Photoresponsive materials, which can adapt their states and shapes upon light irradiation, have attracted worldwide attention in the past decades. The development of azobenzene‐containing polymers (azopolymers) opens up an avenue for controlling their properties and functions with light. These polymers show shape changes and mechanical responses under the stimulation of light via photoisomerization of azobenzene groups. Herein, this report focuses on the growing research on moving polymers via photoisomerization, including their moving mechanisms and various applications.     

液晶高分子材料的新功能:微管执行器及其光控微量液体运动

微量液体的精确操控在生物医药、液体传输等领域具有广泛的应用价值.目前,基于光诱导的毛细作用力操控液体的方法引起了人们极大的兴趣,因为这类方法在操控过程中无需特殊的光学装置和复杂的微组装过程.但是目前报道的方法只适用于少数特定的液体,并且驱动距离短、运动速度慢、局限于直线运动.最近,俞燕蕾等设计了一种新型结构的侧链液晶高分子材料,以此制备了液晶高分子微管执行器,可以通过不对称光致形变诱导毛细作用力,实现了光控各种类型液体按照设计的速度和方向运动,有望在可控微流体传输、微反应系统、微机械系统、芯片实验室等领域展现出巨大的应用价值.     

Synthesis of an Azobenzene-containing Main-chain Crystalline Polymer and Photodeformation Behaviors of Its Supramolecular Hydrogen-bonded Fibers

The synthesis of a new azobenzene(azo)-containing main-chain crystalline polymer with reactive secondary amino groups in its backbone and photodeformation behaviors of its supramolecular hydrogen-bonded fibers are described. This main-chain azo polymer(namely Azo-MP6) was prepared via first the synthesis of a diacrylate-type azo monomer and its subsequent Michael addition copolymerization with trans-1,4-cyclohexanediamine under a mild reaction condition. Azo-MP6 was found to have a linear main-chain chemical structure instead of a branched one, as verified by comparing its ~1H-NMR spectrum with that of the azo polymer prepared via the polymer analogous reaction of AzoMP6 with acetic anhydride. The thermal stability, phase transition behavior, and photoresponsivity of Azo-MP6 were characterized with TGA,DSC, POM, XRD, and UV-Vis spectroscopy. The experimental results revealed that it had good thermal stability, low glass transition temperature,broad crystalline phase temperature range, and highly reversible photoresponsivity. Physically crosslinked supramolecular hydrogen-bonded fibers with good mechanical properties and a high alignment order of azo mesogens were readily fabricated from Azo-MP6 by using the simple melt spinning method, and they could show "reversible" photoinduced bending under the same UV light irradiation and good anti-fatigue properties.