Photomechanical Effects in Amorphous and Semicrystalline Polymers

This chapter focuses on photomechanical responses observed in photoresponsive polymeric materials that employ photochromic constituents to transduce light into macroscopic mechanical responses. It also focuses on photomechanical effects in amorphous and semicrystalline polymers that are polymers in the bulk solid states. In the numerous literature reports to date, photomechanical effects in amorphous and semicrystalline polymeric materials have shown strong dependence on the morphology, free volume, and other variables. Researchers at the Air Force Research Laboratory have recently completed a series of systematic investigations focused on elucidating the relationship of photomechanical effects in amorphous and semicrystalline polymeric materials to a variety of factors including crystallinity, segmental mobility, and cross-linking. Ordered crystalline regions have a denser molecular packing, leading to high bulk density of semicrystalline polymers versus amorphous polymers. In addition to the molecular packing effect, the proximity between polymer segments of crystalline region promotes stronger intermolecular secondary bonding, due to the reduction in intermolecular distance.