基于偶氮聚合物的智能膜/基系统：光调制的表面起皱/防皱/消皱与应用

How to effectively solve and make good use of the stress-relaxation-related material defects is a great challenge for modern composite materials. In the present project, a film/foundation system with an azo-containing polymer-based film is fabricated. The light-exposure-induced cis/trans isomerization will be utilized to drive the light-controlled stress-relaxation surface wrinkling/anti-wrinkling/wrinkle eliminating. Here we will investigate systematically the influences of the parameters (e.g., the composition and structure of the film/foundation system, the light-exposure conditions, the external stimuli, and the pre-formed wrinkle patterns) on the wrinkle evolution and the relation of them with the light-controlled surface anti-wrinkling/wrinkle eliminating effects. Furthermore, the selective light exposure of the azo-based system through a photo-mask is used to yield a variety of hierarchical wrinkle patterns. Based on this kind of novel light-sensitive stress-relaxation wrinkle morphologies, the azo-based system is explored for new applications in the fields of smartly light-tailored surface wettability, repetitious light-erasable patterns and confidential information, wrinkle-free-compatible flexible devices. Here the underlying physics for the light-controlled surface wrinkling/anti-wrinkling/wrinkle eliminating effects as well as the photo-softening will be revealed based on the experimental and theoretical results. A simple and new approach of light modulation will be developed for the large-scale surface wrinkling/anti-wrinkling/wrinkle eliminating as well as fine tailoring of the wrinkled microstructures. The project will direct the subsequent optimum design of the composites in theory, not only for elimination of the stress-relaxation-driven materials defects (e.g., wrinkling, delaminating, and cracking), but also for patterning of a surface via a non-lithographic method and fabrication of high-performance flexible devices.

如何有效解决和可控利用应力松弛相关的材料问题是现代复合材料学面临的一项前沿性挑战课题。本项目拟以偶氮聚合物为膜层的膜/基系统为对象，利用偶氮基光致顺反异构化反应来驱动应力松弛型表面起皱/防皱/消皱的光调制；系统研究膜/基结构组成、光照条件、外界刺激、预起皱形貌等参数对光照下皱纹形貌演变的影响，以及与光防皱/消皱的内在关系；结合光掩膜选区曝光，进一步实现多种高级表面皱纹化；基于该光响应松弛型皱纹形貌，探索其在润湿性光调控、多次光可擦写图案与信息、柔性无皱兼容的高性能器件等方面的新应用；结合理论计算模拟，揭示偶氮膜光防皱/消皱的物理机制以及光软化等效应；发展一种简单全新的光调控法，来大面积实现防皱/消皱和皱纹微结构的精细构筑。本研究不仅为表面防皱/消皱，以及抑制应力松弛导致的脱层开裂等材料问题而进行的材料设计优化奠定理论基础，而且为非刻蚀法的表面微结构化和高性能柔性器件构造等方面提供理论指导。

作为一种常见的应力失稳形式，表面起皱会影响材料结构与性能，是一种须极力避免的工程危害；另一方面，表面起皱在物性表征、功能化表面制备及柔性器件构筑等领域有独特的应用潜力。如何有效消除/抑制材料表面起皱，以及可控构筑特定形貌的皱纹图案，仍是一大急需解决的难题。在本项目中:1）通过表层膜引入偶氮苯组分来构建光响应的“硬”膜/“软”基系统，实现了该膜/基体系表面起皱形貌的动态光调控和光擦除。结合理论计算与模拟首次揭示了光致异构化反应触发的应力松弛消皱机制。借助选区曝光，构筑了其他方法难于获得的高级取向皱纹图案，由此开启了光响应起皱体系在光可擦写图案的全新应用。该光调制法很大程度上破解了大面积表面消皱的难题。2）利用偶氮苯基元的多重光响应特性，激光直写构筑了高纵横比和取向可控的表面皱纹图案，进而获得了全光控驱动下表面起皱态和消皱态间的可逆转换，并揭示了平行边界的表面起皱源于新颖的光致“软/硬”对比边界的形成机制。该智能光响应体系在软光子学等方面表现出优异的应用前景。3）借助光照下机械应变诱导表面起皱行为的研究，发展了基于表面起皱来测量偶氮苯膜光软化效应的一种简单新方法。借助偶氮苯光软化效应开发了一种光抑制表面起皱的新技术。所得结果在柔性与无皱兼容的高性能器件构造等方面具有重要的理论指导价值。4）该光响应起皱体系已分别拓展到基于光降解聚合物膜的光响应膜/基系统，基于偶氮超分子聚合物膜的膜/基系统，以及基于偶氮苯层/非光响应层共同形成表面多层膜的膜/基系统，深入研究了光降解物种类、偶氮苯种类、非光响应层种类和多层膜结构组成等参数与体系表面光起皱/消皱/防皱的内在关系，揭示了各体系表面形貌光调制的内在机制。5) 作为对比，基于偶氮苯的多重光响应特性，借助起皱模板作为新颖的相位掩模，结合简单的激光移动辐照，实现了偶氮膜/“硬基底”体系其表面未曾报道的高级微纳光栅结构（路径可控、单/双/三周期与单/双取向有机组合）的精细构筑。上述所得结果已成功应用于光可擦写信息存储、防伪、多功能表面和智能光学器件等领域，在Angew. Chem. Int. Ed., Adv. Funct. Mater., ACS Nano, ACS Appl. Mater. Interfaces, Langmuir等期刊发表SCI论文23篇，并获7项授权专利。