ACS Appl Mater Interfaces. 2018 Sep 5;10(35):29909-29917. doi: 10.1021/acsami.8b08025. Epub 2018 Aug 9.
It is highly challenging to achieve an optically deformable polymer with good controllability, stability, and self-healability for fabricating an optically controlled microrobotics. Here, we present a photo-responsive self-healing supramolecular assembly cross-linked by 3,3',5,5'-azobenzenetetracarboxylic acid (t-Azo) enabling the controllable and stable deformation. The network (PAA-u) of polyacrylic acid (PAA) grafted with 2-ureido-4[1 H]-pyrimidinone (UPy) is formed via multiple intermolecular hydrogen bonds (H-bonds) between UPy and t-Azo moieties. Molecular H-bonds stabilize the cis-isomer, enables stress transfer at the interface, and also contributes to fast healability. The PAA-u/t-Azo assembly shows a green-light-induced bending deformation, which recovers its shape under the irradiation of UV light. On the basis of this controllable and reversible deformation, the PAA-u/t-Azo "hand" realizes reversible light-driven grabbing and releasing of an object by optimizing bending and recovery. The assembly also shows a fast and excellent self-healing performance irradiated by green light during deformation. The multiple-H-bonding-cross-linked assembly with stable deformation and fast self-healability can be used for the development of a multitude of advanced microrobotics.
对于制造光控微机器人来说，具有良好可控性、稳定性和自修复性的光学可变形聚合物极具挑战性。在这里，我们提出了一种光响应自修复超分子组装体，由 3,3',5,5'-偶氮苯四羧酸（t-Azo）交联，实现了可控且稳定的变形。通过 2-脒基-4[1 H]-嘧啶酮（UPy）与 t-Azo 部分之间的多个分子间氢键（H-bonds）形成了聚丙烯酸（PAA）接枝的聚丙交酯网络（PAA-u）。分子 H-bonds 稳定了顺式异构体，实现了界面上的应力传递，也有助于快速修复。PAA-u/t-Azo 组装体表现出绿光诱导的弯曲变形，在紫外光照射下可恢复其形状。基于这种可控且可逆的变形，PAA-u/t-Azo“手”通过优化弯曲和恢复，实现了对物体的可逆光驱动抓取和释放。组装体在变形过程中用绿光照射也表现出快速和优异的自修复性能。这种具有稳定变形和快速自修复性能的多重氢键交联组装体可用于开发多种先进的微机器人。
