Birefringent Control of Photo-Oriented Polymeric Films by in situ Exchange of Functional Moieties

Abstract

Thermally stimulated photoinduced molecular reorientation with high dichroism ( D >0.6) is explored in liquid crystalline (LC) copolymerthacrylate films comprising of 4-methoxy- N-benzylideneaniline (MNBA) and benzoic acid (BA) side groups. Thermal hydrolysis of MNBA side groups induces free phenyl aldehyde (PA) side groups in the oriented film. Birefringence of the oriented films is adjusted by introducing 2,7-diaminofluorene (FL) to form new imine bonds with free PA side groups. Meanwhile, in situ exchange from MNBA to FL-based imine also controls the birefringence of the oriented film. The initial birefringence of the oriented copolymer film increases up to 0.22 after introducing oriented FL moieties.