应用化学 ›› 2021, Vol. 38 ›› Issue (10): 1226-1237.DOI: 10.19894/j.issn.1000-0518.210381

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液晶聚合物的表面形貌光调控研究进展

纪宇帆, 蔡锋, 于海峰()   

  1. 北京大学材料与科学工程学院与教育部高分子化学与物理重点实验室,北京 100871
  • 收稿日期:2021-07-30 接受日期:2021-08-26 出版日期:2021-10-01 发布日期:2021-10-15
  • 通讯作者: 于海峰
  • 基金资助:
    国家自然科学基金(51773002)

Research Progress on Photoswitchable Surface Topography of Liquid Crystalline Polymer

Yu-Fan JI, Feng CAI, Hai-Feng YU()   

  1. School of Materials Science and Engineering,and Key Laboratory of Polymer Chemistry and Physics of Ministry of Education,Peking University,Beijing 100871,China
  • Received:2021-07-30 Accepted:2021-08-26 Published:2021-10-01 Online:2021-10-15
  • Contact: Hai-Feng YU
  • About author:yuhaifeng@pku.edu.cn
  • Supported by:
    National Natural Science Foundation of China(51773002)

摘要:

光响应液晶聚合物具有良好的自组装特性与光调控性能,被广泛地应用于表面微纳结构的研究中。通过改变液晶分子的取向方式和有序参数,可以得到复杂多样的表面形貌,这在光学、生物学和机械控制等领域有较高的研究价值与应用前景。表面形貌调控的关键在于对其机理的深刻理解与把握:从液晶分子指向矢的角度来说,当液晶分子的有序参数减小时,会沿指向矢方向收缩,垂直指向矢方向膨胀,利用相邻域之间分子取向差异产生的侧向剪应力,可以构建具有表面起伏的微纳结构;从液晶聚合物产生自由体积的角度来说,紫外光照射时产生的自由体积会使薄膜密度下降,在偶氮苯可逆的反-顺-反异构化的动态过程中,会形成宏观表面起伏;从光诱导聚合物质量迁移的角度来说,光场的光强分布、偏振态以及光束的波前均会对材料的定向质量迁移产生影响;从光照使薄膜表面稳定性改变的角度来说,可以利用光聚合时薄膜的各向异性收缩产生褶皱,也可以通过应力释放对薄膜的表面褶皱形貌进行调控。因此,基于光诱导产生表面形貌变化的4种不同机理,对光控表面形貌的相关研究进展进行了回顾和总结,并展望了未来可能的发展方向,为后续进一步研究液晶聚合物的表面形貌调控及其功能化提供了参考。

关键词: 光响应, 液晶聚合物, 表面形貌调控, 功能应用

Abstract:

Light-responsive liquid crystalline polymer has been widely used in the study of micro/nanostructures on the surface because of its self-organization and photoresponsive properties. Complex and diverse topographical deformation with different orientation modes and order parameters in various systems is important for applications in the fields of optics, biology and mechanics. The key to achieving the manipulation of surface topography lies in a deep understanding and grasp of the mechanism behind phenomena: From the perspective of the liquid crystal director, when the order parameter decreases, molecules will shrink in the direction of the director and expand in the direction perpendicular to the director. The lateral shear stress generated by the difference in molecular orientation between adjacent domains can be used to construct a type of micro/nanostructure. As for the free volume of liquid crystalline polymer, it can be generated by ultraviolet light irradiation and the density of the film will decrease. In the dynamic process of the reversible trans-cis-trans isomerization of azobenzene, macroscopic surface reliefs will be formed. Another principle is light-induced polymer mass transport. The light intensity distribution, polarization state of the light field, and the wavefront of the beam all have an impact on the directional mass transport of the material. Last but not least, light can change the stability of the surface. The anisotropic shrinkage of the film during photopolymerization can be used to produce wrinkles, and the surface wrinkling of the film can be manipulated by stress release. Therefore, based on the four different mechanisms of light-induced topographical deformation, the research processes in the development of light-controlled surface topography are reviewed. Accordingly, the possible future directions in this field are outlooked, and some guidelines for further research on the surface topography control and functional applications of liquid crystalline polymer are provided.

Key words: Light-responsive, Liquid crystalline polymer, Surface topography control, Functional application

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