Block copolymer self-assembly effects on optical anisotropy in azobenzene-containing PS-b-PMMA films

ANTONELA B. OROFINO; MARIA F. CAMEZZANA; MARÍA J. GALANTE; PATRICIA A. OYANGUREN; ILEANA A. ZUCCHI

NANOTECHNOLOGY

IOP PUBLISHING LTD

Año: 2012 vol. 23 p. 115604 - 115611

0957-4484

Polystyrene-b-polymethylmethacrylate (PS-b-PMMA) was selected as the host for4-(4-nitrophenylazo)aniline (Disperse Orange 3, DO3) based on a previous study ofDO3=PMMA and DO3=PS binary blends. Selective location of DO3 into the PMMA block ofthe copolymer was expected during self-assembly of the block copolymer since a preferentialinteraction of DO3 with PMMA has been demonstrated. However, surface segregation of DO3was found during the thermal annealing used to nanostructure the copolymer. To avoid this, athermoplastic polymer (Azo-TP) was synthesized from the bulk reaction of DO3 anddiglycidyl ether of bisphenol A (DGEBA). The choice of DGEBA as a co-reactant was anattempt to encourage the selective location of azo groups in the PMMA phase ofPS-b-PMMA. An inspection of solutions of Azo-TP in PS and PMMA, corroborates thepreferential affinity of Azo-TP for PMMA. The Azo-TP could be satisfactorily dissolved inPS-b-PMMA. We have investigated the growth and decay processes of the optically inducedbirefringence in films of PS-b-PMMA containing 12 wt% Azo-TP. The resulting materialsshowed a good photoinduced time response, high maximum birefringence and an elevatedfraction of remnant anisotropy.