Monodomain Liquid Crystal Elastomers Composed of Main-Chain Type Nematic Polyester Bonded to Rubbery Segments at Both Ends

Abstract

Monodomain liquid crystal elastomers (LCEs) are prepared using liquid crystal block copolymers (LCBCPs) comprised of a nematic liquid crystal (NLC) main-chain polyester linked to cross-linkable polymethacrylate (PMA) at both ends. LCBCPs at a PMA weight fraction of ≈30% are doped with a tetra-thiol compound, stretched in one direction, and then illuminated by UV light, yielding LCBCPs that formed microlamellae consisting of alternate stacking crosslinked PMA blocks and NLC polyester blocks. The LC director lay along the stretching direction (SD). Raising the temperature to the NLC isotropization temperature, the crosslinked LCBCP strips fixed at one end contracted reversibly by a factor of 1.2–1.4 along the SD, deforming the microlamellae. The strips fixed at both ends increased the tensile stress to ≈200 kPa while maintaining the microlamellae undeformed. Regardless of strip fixation at one or both ends, the NLC decreased the orientational order. The contraction amounts and the tensile stress of strips are well associated with decreased NLC orientational order.