具有多样化三维可逆驱动的智能液晶弹性体复合材料

Liquid crystal elastomers (LCE), recognized as smart materials, could produce reversible responsive actuation induced by the external stimuli, such as light and heat. The most studied actuations are elongation-contraction and bending-unbending. While the smart materials with 3D reversible actuation show great potential applications in many fields, especially in the application of biomimetic materials. But it is hard to prepare LCEs with 3D reversible actuation now, and there are only two reported methods to prepare them. The first method is resorting to liquid crystal box to align mesogens and obtain monodomain LCE. This method costs highly and can only produce very thin film. The second method is using dynamic ester bond. The mesogens alignment resulted from tensile force could be fixed by the exchangeable reaction triggered by catalyst at high temperature. Even though this method is very simple and highly successful, the deformation is small and the alignment is easily damaged by exchangeable reaction triggered by catalyst at high temperature. So based on the second method, this project proposes a simple improved method: introducing carbon nanotubes and not using catalyst. We will develop a new and simple method to produce LCEs with 3D reversible actuation by deforming with external force and irradiating with IR light. When irradiating, the strong photo-thermal effect of carbon nanotubes induces fast exchangeable reaction, which fixes the mesogens alignment caused by external-force induced deformation. This method is very simple, not only avoids the disadvantages of above two methods, but also can produce diverse and complex 3D reversible actuation with large deformation. It would not only widen the application range of LCE, but also pave the way for the development of biomimetic application.

液晶弹性体（LCE）在光、热等外界刺激下可产生可逆响应驱动。目前研究较多的只有伸长-缩短和弯曲-变直两种简单的驱动。而三维可逆驱动智能材料在很多领域应用前景广阔，尤其在仿生材料应用上。但目前的工艺很难制备出三维可逆驱动LCE，已被报道的工艺只有两种。一种是借助液晶盒使液晶基元取向来获得，该工艺成本高、只能制备非常薄的膜；另一种是利用动态酯键在催化剂条件下的交换反应将外力拉伸所致的液晶基元取向固定来获得，该工艺简单、成功率高，但形变较小、取向易被高温下催化剂催化的交换反应破坏。本项目拟针对第二种工艺，提出简单的改进方法：无需催化剂并引入碳纳米管，利用碳纳米管的强光热效应诱导交换反应，开发一种只需外力变形（无需拉伸）、再局部光照将变形处新液晶基元取向固定来获得可逆驱动LCE的方法。此方法很简单，避免了上述工艺的缺点，还可设计多样、复杂、形变大的三维可逆驱动，拓宽LCE的应用，为其仿生应用铺路。

本项目试图通过合理的分子设计，制备新型、含动态共价键、掺杂碳纳米管的液晶弹性体复合材料，旨在开发一种无需催化剂、无需外力拉伸、只需外力变形再局部光照变形处即可使液晶弹性体具有三维可逆驱动的简单制备工艺。项目执行期间，主要研究内容有：.①用AIE-分子探针技术探究含动态共价键的高分子网络的动态性质，检测含动态共价键的高分子（vitrimer）的拓扑网络凝固转变温度（Tv），这部分工作已发表在Nature Communications上；.②用传统热固性材料（环氧树脂）构建无需催化剂的液晶弹性体和3D柔性驱动器，打破了过去热固性材料无法再次加工和重塑形的观念，这部分工作已发表在Angewandte Chemie International Edition上；.③掺杂碳纳米管至上述传统热固性材料（环氧树脂）中，构建无催化剂的、无需外力拉伸、只需外力变形再局部光照变形处即可有三维可逆驱动的液晶弹性体复合材料，此工作实验部分已完成，目前在撰写文章，待投出和发表，预计在项目结题后半年内可完成。.本项目的研究内容颇多，但执行时间较短，仅一年（2019.1.1-2019.12.31）。在执行过程中，本项目的所有参与人员尽可能地多想多思、少走弯路，以期尽快全部完成各项研究内容。.具有三维可逆驱动的智能材料是一个具有重大应用价值但目前研究较少的前瞻性领域，在各类仿生材料中举足轻重。液晶弹性体是该领域里最具潜在应用的材料之一。本项目的进行极有可能为更多具有可逆驱动仿生材料的开发和利用带来新突破。这是国内外尚未开展但具有巨大潜在影响力的工作。