可白光编程主链聚二硫液晶弹性体的制备及可控变形

Preparation and Controllable Deformation of White-Light-Programmable Main-Chain Poly(disulfide)-Based Liquid Crystalline Elastomer

摘要

动态共价键的引入解决了传统共价交联液晶体系固化后难以再加工和回收的问题，其中二硫键因对热、光和氧化还原刺激的多重响应性而备受关注。通过在巯基封端液晶低聚物（SH-LCO）末端进行1,2-二硫戊环官能团修饰，并结合白光介导的开环聚合反应与拉伸诱导液晶取向，成功制备了一种主链型聚二硫液晶弹性体（PDS-LCE）薄膜。在初始聚合时间为4 h、预拉伸应变为200%、SH-LCO的摩尔分数为20%的最优制备条件下，PDS-LCE薄膜的驱动应变为35.2%、做功能力（Work capacity）为340 kJ/m³。聚二硫网络的热可逆性赋予材料可重构、自修复（恢复率94.3%）和可回收（回收率92.4%）等性能，同时白光编程特性可以构建复杂的形状变换模式，为高性能液晶弹性体驱动器件的开发提供了新思路。

Abstract

The introduction of dynamic covalent bonds addresses the challenge of difficult reprocessing and recyclability after curing in traditional covalently crosslinked liquid crystal systems. Disulfide bonds have attracted considerable attention due to their multi-responsive behavior to thermal, light, and redox stimuli. A main-chain poly(disulfide)-based liquid crystalline elastomer (PDS-LCE) film was successfully prepared by terminal modification of thiol-terminated liquid crystalline oligomers (SH-LCO) with 1,2-dithiolane functional groups, followed by white-light-mediated ring-opening polymerization combined with stretch-induced liquid crystal alignment. The distinctive white-light response enables spatially resolved programming of the resulting PDS-LCE. Optimal fabrication conditions were identified as an initial polymerization time of 4 h, a pre-stretching strain of 200%, and an SH-LCO molar ratio of 20%, yielding an aligned film with an actuation strain of 35.2% and a work capacity of 340 kJ/m³. By employing photomasks during irradiation, localized alignment can be selectively locked, generating internal stress fields that drive out-of-plane deformations. For example, a rectangular film programmed with an H-shaped mask adopts a twisted configuration at room temperature. Owing to stress relaxation during the stretching process, the programmed regions retain a longer equilibrium length than the unprogrammed regions. Upon heating, this length mismatch creates internal stresses that reshape the film into a saddle-like morphology, allowing room-temperature and high-temperature shapes to be programmed simultaneously. A regular octagonal film subjected to sequential masking and stretching steps spontaneously forms a double-arch morphology at room temperature, which reversibly switches to a saddle-shaped polyhedron upon heating. Furthermore, dynamic disulfide exchange under thermal stimulation imparts macroscopic reconfigurability. Thermal erasure resets the material to its isotropic state, enabling subsequent thermal reprogramming into new geometries such as a folded triangle or a rolled cylinder. The dynamic disulfide network also provides excellent self-healing capability, achieving 94.3% recovery of mechanical properties after thermal healing, as well as complete chemical recyclability via reductive depolymerization with a recovery yield of 92.4%.

关键词

聚二硫材料 / 液晶弹性体 / 可控变形 / 自修复 / 可回收

Key words

poly(disulfide) materials / liquid crystalline elastomer / controllable deformation / self-healing / recyclability

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基金资助

国家自然科学基金(52373121)

国家自然科学基金(52573143)

国家重点研发计划(2022YFA1305100)