Zhou Xiaorui, Jin Binjie, Zhu Zhan, Wu Jingjun, Zhao Qian, Chen Guancong
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China.
Institute of Emergent Elastomers, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China.
Angew Chem Int Ed Engl. 2024 Oct 24;63(44):e202409182. doi: 10.1002/anie.202409182. Epub 2024 Sep 17.
Dynamic covalent bonds endow liquid crystal elastomers (LCEs) with network rearrangeability, facilitating the fixation of mesogen alignment induced by external forces and enabling reversible actuation. In comparison, the bond exchange of supramolecular interactions is typically too significant to stably maintain the programmed alignment, particularly under intensified external stimuli. Nevertheless, remaking and recycling of supramolecular interaction-based polymer networks are more accessible than those based on dynamic covalent bonds, as the latter are difficult to completely dissociate. Thus, preparing an LCE that possesses both supramolecular-like exchangeability and covalent bond-level stability remains a significant challenge. In this work, we addressed this issue by employing metal-ligand bonds as the crosslinking points of LCE networks. As such, mesogen alignment can be repeatedly encoded through metal-ligand bond exchange and stably maintained after programming, since the bond exchange rate is sufficiently slow when the programming and actuation temperatures are below the bond dissociation temperature. More importantly, the metal-ligand bonds can be completely dissociated at high temperatures, allowing the LCE network to be dissolved in a solvent and reshaped into desired geometries via solution casting. Building on these properties, our LCEs can be fabricated into versatile actuators, such as reversible folding origami, artificial muscles, and soft robotics.
动态共价键赋予液晶弹性体（LCE）网络重排能力，有助于固定外力诱导的介晶排列，并实现可逆驱动。相比之下，超分子相互作用的键交换通常过于显著，以至于难以稳定维持程序排列，尤其是在强化的外部刺激下。然而，基于超分子相互作用的聚合物网络的重塑和回收比基于动态共价键的聚合物网络更容易实现，因为后者难以完全解离。因此，制备一种兼具超分子样交换能力和共价键级稳定性的LCE仍然是一项重大挑战。在这项工作中，我们通过使用金属-配体键作为LCE网络的交联点来解决这个问题。这样，介晶排列可以通过金属-配体键交换反复编码，并在编程后稳定维持，因为当编程和驱动温度低于键解离温度时，键交换速率足够慢。更重要的是，金属-配体键在高温下可以完全解离，使LCE网络能够溶解在溶剂中，并通过溶液浇铸重塑成所需的几何形状。基于这些特性，我们的LCE可以制成多功能致动器，如可逆折叠折纸、人造肌肉和软机器人。
