title: Surface-relief gratings and photoinduced birefringence in layer-by-layer films of chitosan and an azopolymer.
abstract: Layer-by-layer (LBL) films of chitosan alternated with an azopolymer, PS119, have been used for optical storage and fabrication of surface-relief gratings. The optical properties stem from the trans-cis-trans isomerization cycles undergone by the azochromophore, with a kinetics for writing the birefringence pattern that is much slower than in the spin-coated or cast films of azopolymers. The long writing times, of the order of 100 s, are due to the electrostatic interactions between adjacent chitosan and PS119 layers. Such interactions are also responsible for other features in the LBL films, namely the increase in the amount of adsorbed material when the pH of the preparation solution is decreased and the large residual birefringence after the writing laser is switched off. Gratings could be inscribed with s-polarized but not with p-polarized light, indicating a mass transport process associated with photodegradation.
authors: Departamento de Físico-Química, Instituto de Química de São Carlos, Caixa Postal 780, 13560-970, São Carlos, SP, Brazil.
authors: C S
authors: CS
authors: Camilo
authors: D S
authors: DS
authors: dos Santos Júnior
authors: J J
authors: JJ
authors: Rodrigues Júnior
authors: M L
authors: ML
authors: Vega
authors: S P
authors: SP
authors: Campana Filho
authors: O N
authors: ON
authors: Oliveira Júnior
authors: C R
authors: CR
authors: Mendonça
mesh_terms: D001391:Azo Compounds; D001718:Birefringence; D002686:Chitin / Q000031:analogs & derivatives*; D048271:Chitosan; D016249:Optical Storage Devices; D011108:Polymers; D013499:Surface Properties
chemical_list: D001391:Azo Compounds; D011108:Polymers; D002686:Chitin; D048271:Chitosan