Effect of molecular parameters on thermomechanical behavior of side-on nematic liquid crystal elastomers

We investigated the structure–property relationship of liquid crystal elastomers (LCEs) obtained from a series of nematic side-on monomers. A new synthetic strategy was developed to obtain the acrylate monomers (n-ADBB), which gave us the opportunity to easily modify the spacer lengths of the monomers. Through magnetic field alignment, well-defined LCE micropillars were fabricated from the monomers by a method combining soft lithography and photopolymerization/photocrosslinking of the monomers and a crosslinker. The influence of structural parameters on the thermomechanical deformation of the microstructures was studied through microscopic observations. The study quantitatively revealed the correlation of thermomechanical behavior of the microstructured LCEs with the crosslinking density and length of the flexible spacer linking the mesogenic core to the backbone. With a proper control of the structural parameters, optimized performances such as large reversible contraction, good elasticity and mechanical robustness were demonstrated for this type of LCEs.