Effect of molecular architectures in photoinduced birefringence in films of azo-modified diblock copolymers

Abstract

Langmuir films of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) with an azo dye, 4-[4-(phenylazo)-1-naphthylazo]phenol (Disperse Orange 13, DO13), hydrogen-bonded to the pyridine group of P4VP blocks were investigated. Nonselective and selective solvents were used to spread the samples on the water surface. The spreading solvents showed large effect on the surface pressure-molecular area isotherms. The photoinduced birefringence of the Langmuir films were investigated and compared with those obtained using the traditional spin coating technique. The combination of the self-assembly of block copolymer and the nano-structured nature of the Langmuir films cooperated to lead to an enhancement of photoinduced anisotropy.