Liquid crystals as solid-state templates

Liquid crystals (LCs) combine the anisotropy of crystals with the fast molecular dynamics of liquids. Controlling the molecular orientation of LCs is the key enabling feature of liquid crystal displays (LCDs), a technology that has played a pivotal role in ushering in the digital age of today. Here we review controlling molecular organization in LCs over large distances for a different application: the assembly of macroscopically organized solids. The traditional approach of controlling orientational order in organic solids is growing single crystals, a process limited by slow kinetics. In this article, we review an alternate approach: the generation of organized solids through the (i) polymerization, (ii) physical gelation, and (iii) vitrification of small-molecule LCs. The generation of solids through these routes is enabled by innovations in (i) molecular design, (ii) formulation chemistry, and (iii) macroscopic alignment of LCs. Controlling molecular orientation, defects, and deformations in the precursor LC phase enables the assembly of solids with unique properties such as programmable responses to stimuli. We discuss the "organize and solidify" approach for the preparation of materials with LC order for soft robotics, chemical sensing, and lithographic patterning. Finally, we outline future challenges and opportunities in the field of liquid crystalline solids.