Deformation of a Polydomain, Smectic Liquid Crystalline Elastomer

A main-chain, polydomain, smectic liquid crystalline elastomer (LCE) was prepared by reacting the LC epoxy monomer, diglycidyl ether of 4,4′-dihydroxy-R-methylstilbene, with the aliphatic diacid, sebacic acid. When deformed in uniaxial tension, a “polydomain-to-monodomain” transition took place leading to bulk, macroscopic orientation. With this process was associated a plateau in the nominal stress-versus-strain curve and a dramatic change in optical properties from opaque to translucent. Polarized optical microscopy showed that the transition took place by an elongation of the LC domains and a rotation of the local director orientations along the stress axis. The strain and orientation of the deformed samples were retained upon unloading, even after annealing above Tg for extended periods. Upon heating, the oriented LCEs disordered at the same temperature as the undeformed polydomains and “remembered” their original polydomain microstructure and sample dimensions when subsequently cooled from the isotropic state.