Balancing Compatibility and Gelability for High-Performance Cholesteric Liquid Crystalline Physical Gels

Abstract

Liquid crystalline physical gels (LCPGs) have attracted increasing interest because of their mechanical properties and stimulus-response behaviors. However, due to their gelator properties such as thermal stability, gelation capability, and compatibility in liquid crystals, development of LCPGs with high performances still remains a huge challenging task. Herein, four novel gelators ((l)-PH, (d)-PH, (l)-P2H, and (d)-P2H) based on 1,4-benzenedicarboxamide phenylalanine derivatives containing one or two ethylene glycol groups have been designed and synthesized. It is found that the ethylene glycol group plays a significant role in improving the compatibility between the gelator and the liquid crystal. All of the prepared compounds can form stable LCPGs in P0616A. In particular, the storage modulus of LCPG with 9.0 wt % of (l)-PH with one ethylene glycol unit is higher than 106 Pa, which is similar to SmC gels and advantageous over previously reported nematic LCPGs. Furthermore, the prepared gels display a strong Cotton effect with hand-preferred twisted fiber networks and the self-assembled aggregates of (l)-PH can induce P0616A to form a cholesteric fingerprint structure. Thus, these low molecular weight gelators provide a strategy to construct high-performance cholesteric LCPGs for the realization of LC device applications.