Photo‐responsive Helical Motion by Light‐Driven Molecular Motors in a Liquid‐Crystal Network

Jiaxin Hou,Jiawen Chen,Dirk J Broer,Wei Zhao,Anirban Mondal,Ben L Feringa,Guiying Long,Danqing Liu,Guofu Zhou,Laurens De Haan

doi:10.1002/ange.202016254

Abstract

AbstractControlling sophisticated motion by molecular motors is a major goal on the road to future actuators and soft robotics. Taking inspiration from biological motility and mechanical functions common to artificial machines, responsive small molecules have been used to achieve macroscopic effects, however, translating molecular movement along length scales to precisely defined linear, twisting and rotary motions remain particularly challenging. Here, we present the design, synthesis and functioning of liquid‐crystal network (LCN) materials with intrinsic rotary motors that allow the conversion of light energy into reversible helical motion. In this responsive system the photochemical‐driven molecular motor has a dual function operating both as chiral dopant and unidirectional rotor amplifying molecular motion into a controlled and reversible left‐ or right‐handed macroscopic twisting movement. By exploiting the dynamic chirality, directionality of motion and shape change of a single motor embedded in an LC‐network, complex mechanical motions including bending, walking and helical motion, in soft polymer materials are achieved which offers fascinating opportunities toward inherently photo‐responsive materials.

Highlights

Facing the challenge to achieve multiple distinctive autonomous motions in a soft material powered by light we envisioned that our photochemical rotary motors[36,37] offer unique opportunities to achieve more complex mechanical movements
In our approach all the key parameters, that is, dynamic chirality, dopant function, shape change and photo-responsiveness, are embedded in a single rotary motor that acts as a cross-linker unit in a polymer LC network
The fast helical motion is due to several unique features of these molecular rotary motors that are able to act as chiral dopant, responsive cross-linker and photochemical -actuator in the liquid-crystal network (LCN) film

Summary

Introduction

The prospects of dynamic molecular systems,[1,2,3] using artificial molecular machines[4,5,6] to induce motion and perform complex mechanical tasks reminiscent of the omnipresent “machinery of life”,[7,8] has greatly stimulated scientists to design molecular motors and machines that can power specific movements or allow several distinct mechanical operations.[9,10] Molecular muscles,[11,12,13] chemical synthesizers,[14,15] multitasking catalysts,[16,17] self-sorting machines,[18] transporters,[19,20] pumps[21,22,23] and responsive surfaces[24,25] are illustrative of machine-like dynamic functions demonstrated in recent years. In our approach all the key parameters, that is, dynamic chirality, dopant function, shape change and photo-responsiveness, are embedded in a single rotary motor that acts as a cross-linker unit in a polymer LC network.

Results

Conclusion