title: Optical properties of light-sensitive liquid-crystal elastomers in the vicinity of the nematic-paranematic phase transition.
abstract: We investigate light-induced patterning of a monodomain side-chain liquid crystal elastomer (SC-LCE) doped with light-sensitive azobenzene moiety in the temperature region close to the nematic-paranematic phase transition. We show that a strongly nonlinear relationship between the concentration of the cis isomers of the azomesogens and the refractive index modification of the material, which is characteristic for the phase transition region, results in nonmonotonous time dependence of the diffraction efficiency of a probe beam. From this effect we determine the sensitivity of the nematic transition temperature on the molar fraction of the cis isomers. The relation between the cis isomer molar fraction and nematic order also provides a possibility for recording hidden holograms, which can be made visible by cooling the sample from the paranematic to the nematic phase.
authors.affiliation: Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI 1001 Ljubljana, Slovenia.
authors.forename: Marko
authors.initials: M
authors.lastname: Gregorc
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Valentina
authors.initials: V
authors.lastname: Domenici
authors.forename: Gabriela
authors.initials: G
authors.lastname: Ambrožič
authors.forename: Martin
authors.initials: M
authors.lastname: Čopič
authors.forename: Irena
authors.initials: I
authors.lastname: Drevenšek-Olenik
mesh_terms: D003198:Computer Simulation; D020724:Elastomers / Q000737:chemistry* / Q000528:radiation effects*; D008027:Light; D050866:Liquid Crystals / Q000737:chemistry* / Q000528:radiation effects*; D008956:Models, Chemical; D008958:Models, Molecular; D044367:Phase Transition / Q000528:radiation effects; D012031:Refractometry / Q000379:methods*
chemical_list: D020724:Elastomers