title: Effects of block copolymer self-assembly on optical anisotropy in azobenzene-containing PS-b-PMMA films.
abstract: Polystyrene-b-polymethylmethacrylate (PS-b-PMMA) was selected as the host for 4-(4-nitrophenylazo)aniline (Disperse Orange 3, DO3) based on a previous study of DO3/PMMA and DO3/PS binary blends. Selective location of DO3 into the PMMA block of the copolymer was expected during self-assembly of the block copolymer since a preferential interaction of DO3 with PMMA has been demonstrated. However, surface segregation of DO3 was found during the thermal annealing used to nanostructure the copolymer. To avoid this, a thermoplastic polymer (Azo-TP) was synthesized from the bulk reaction of DO3 and diglycidyl ether of bisphenol A (DGEBA). The choice of DGEBA as a co-reactant was an attempt to encourage the selective location of azo groups in the PMMA phase of PS-b-PMMA. An inspection of solutions of Azo-TP in PS and PMMA, corroborates the preferential affinity of Azo-TP for PMMA. The Azo-TP could be satisfactorily dissolved in PS-b-PMMA. We have investigated the growth and decay processes of the optically induced birefringence in films of PS-b-PMMA containing 12 wt% Azo-TP. The resulting materials showed a good photoinduced time response, high maximum birefringence and an elevated fraction of remnant anisotropy.
authors.affiliation: Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J B Justo 4302, 7600 Mar del Plata, Argentina.
authors.forename: A B
authors.initials: AB
authors.lastname: Orofino
authors.forename: M F
authors.initials: MF
authors.lastname: Camezzana
authors.forename: M J
authors.initials: MJ
authors.lastname: Galante
authors.forename: P A
authors.initials: PA
authors.lastname: Oyanguren
authors.forename: I A
authors.initials: IA
authors.lastname: Zucchi