Abstract
Organic molecules can transform photons into Angstrom-scale motions by undergoing photochemical reactions. Ordered media, for example, liquid crystals (LCs) or molecular crystals, can align these molecular-scale motions to produce motion on larger (micron to millimeter)-length scales. In this chapter, we describe the basic principles that underlie organic photomechanical materials, starting with a brief survey of molecular photochromic systems that have been used as elements of photomechanical materials. We then describe various options for incorporating these active elements into a solid-state material, including dispersal in a polymer matrix, covalent attachment to a polymer chain, or self-assembly into molecular crystals. Particular emphasis is placed on semiordered systems like liquid crystal elastomers (LCEs) and fully ordered systems like molecular crystals. The ability to design materials that convert light into motion may eventually lead to the development of photon-fueled micromachines.