Title: A Reactive Azobenzene Liquid-Crystalline Block Copolymer as a Promising Material for Practical Application of Light-driven Soft Actuators

Author: Jiu-an Lv, Wei Wang, Wei Wu, Yanlei Yu*

Journal: J. Mater. Chem. C, 2015, 3(26), 6621-6626

Abstract:

Cross-linked liquid-crystalline polymers containing azobenzene have been drawing the great research interests of the scientists due to their significant values in design of light-driven soft actuators. However, poor processabilities due to the chemical cross-linking severely prevent their practical applications. Here, we designed and synthesized a novel reactive block copolymer PEO-b-PAZO bearing N-hydroxysuccinimide carboxylate substituted azobenzene groups. This copolymer is compatible with the traditional polymer processing methodology including melt and solution processing methods, providing a facile way to prepare the photoresponsive films and fibers, and enabling post-crosslinking after processing through a mild reaction between N-hydroxysuccinimide carboxylate substituents and a difunctional amine. Most importantly, the prepared fibers and films showed reversible photodeformation regulated by alternating irradiation of UV and visible light (365 nm/470 nm). We envision that this novel liquid crystalline polymer will open up new possibilities for low-cost fabrication of high performance photo-driven actuators on a large scale.

Fulltext Link: https://pubs.rsc.org/en/content/articlelanding/2015/TC/C5TC00595G#!divAbstract

We successfully synthesized a novel reactive block copolymer PEO-b-PAZO, and prepared the monodomain CLCP fiber and the polydomain CLCP film through the mild chemical crosslinking reaction between PEO-b-PAZO and 1,6-hexanediamine at room temperature. Both of the CLCP fiber and film showed reversible photoinduced bending and unbending behaviors in response to UV and visible light, respectively. The monodomain CLCP fiber bends toward the light source along the fiber axis as well as the alignment direction of mesogens; therefore the fiber is able to bend toward any direction when we change the irradiation direction of the incident UV light. On the other hand, the polydomain CLCP film underwent directional bending behaviors upon exposure to linearly polarized UV light. This reactive block copolymer with excellent processability allows fabrication of the freestanding CLCPs with good photomechanical properties and unlimited shape. Either the melt or the solution processing method also benefits the realization of widely practical applications of the CLCPs as light-driven actuators on a large scale.