Synthesis of novel cellulose mixesters for transparent responsive films with switchable mechanical properties

Abstract

Soft actuators have attracted much attention during the last decades due to their potentially broad applications ranging from sensors to artificial muscles. Up to now, most of such soft actuators are still based on synthetic polymers. Herein, we described a novel group of materials derived from sustainable cellulose as potential starting materials for the preparation of soft actuators. To be precisely, cellulose mixesters with acyl esters of distinct chain lengths and cinnamic ester were synthesized through a two-step synthesis and used for the preparation of responsive thin film actuators. These cellulose mixesters have degree of substitution ascribed to stearoyl groups (DSSt) of 1.51 or lauroyl groups (DSLa) of 1.48 and degree of substitution ascribed to cinnamoyl groups (DSCi) around 1.35. Furthermore, the influence of the chain lengths of the two different aliphatic esters as well as the switchable crosslinking of cinnamoyl moieties on the materials properties was further shown. Using these cellulose mixesters, transparent thin films with thickness of 4−15 μm were prepared via facile solvent casting. These films had light-responsive mechanical properties from rigid to elastic after illumination with UV light of distinct wavelengths (254 nm and 310−400 nm). Moreover, the thin films showed shape memory effect and the ability of self-healing.