Polarized photoluminescence of the polymer networks obtained by in situ photopolymerization of fluorescent monomer in a nematic liquid crystal

Abstract

Reported herein are the in situ creation and characterization of crossed-linked copolymer networks with a polarized photoluminescence. The π-extended fluorene-based reactive mesogen with photopolymerizable acrylate groups has been copolymerized with conventional reactive mesogen RM-257 in a uniformly aligned nematic LC host. Networks are localized at surfaces as thin films. The copolymer networks exhibit a strong optical anisotropy with a uniaxial orientation of the mesogens, templated by nematic order of the host LC. As a result, the network shows dichroic absorption for excitation and polarized photoluminescence. The degree of the orientational order of the fluorophore has been decreased during the polymerization process. The order parameter of the fluorophore has been curtailed from S = 0.57 for the reaction mixture prior to polymerization to S = 0.32 for the bare polymer networks after polymerization and removal of unreacted LC molecules.