Exploring Photo-Alignment of Liquid Crystals by Guest-Host Interactions: Toward Bulk-Mediated Photo-Alignment of Liquid Crystal Elastomers

Liquid crystal elastomers (LCEs) combine rubber elasticity with liquid crystal (LC) order. It is well-known that elastomers in which the LC constituents are aligned can experience significant reversible shape changes due to order-disorder transitions driven by stimuli (e.g. thermal energy or light). Well controlled LC alignment is a critical requirement for harnessing the desired response. Typically, alignment is achieved by command surfaces within a polymerization cell or by a two-step mechanical stretching and photo crosslinking technique. However, the mechanisms required for simultaneous alignment and polymerization of LCEs without enclosed cells or mechanical stretching, which would facilitate fabrication of complex 2D and 3D structures, are not well understood. In this work we investigate the alignment of low molecular weight liquid crystals by guest-host interactions with poly(vinyl cinnamate) dopants that have been cross-linked with polarized uv light. The LCs examined are similar in structure to the common LCE monomer RM257. We investigate and report on conditions required for in situ, bulk mediated alignment in preparation for simultaneous alignment and polymerization of thiol-acrylate based LCEs. Challenges and future steps will be discussed.