Optical storage and surface-relief gratings in azobenzene-containing nanostructured films Osvaldo N. Oliveira Jr. * , David S. dos Santos Jr., De ´bora T. Balogh, Valtencir Zucolotto, Cleber R. Mendonc ¸a Instituto de Fı ´sica de Sa ˜o Carlos, USP, CP 369-13560-970 Sa ˜o Carlos, SP, Brazil Available online 28 October 2005 Abstract This paper brings an overview of photoisomerization-derived properties in azobenzene-containing nanostructured films produced with the Langmuir – Blodgett (LB) and layer-by-layer (LbL) methods. Emphasis was placed on the optical storage and formation of surface-relief gratings (SRGs), where the distinctive properties of the nanostructured films were highlighted. For optical storage, in particular, a discussion was made of the higher birefringence induced in LB films from azopolymers due to their organized nature, and of the strong effects from ionic interactions on the photoisomerization of azochromophores in LbL films. The molecular-level control of film properties in the LbL films is described as being responsible for the varied behavior observed in the photoinscription of SRGs, which may involve considerable level of photodegradation depending on the film fabrication conditions and materials used. D 2005 Elsevier B.V. All rights reserved. Keywords: Azobenzene; Photoisomerization; Optical storage; Surface-relief gratings; Langmuir– Blodgett; Layer-by-layer Contents 1. Introduction ........................................................... 179 2. Synthesis of azopolymers .................................................... 180 3. Fabrication of nanostructured films ............................................... 182 4. Optical storage using nanostructured films ........................................... 182 4.1. Optical storage experimental setup ........................................... 182 5. Photoinscription of surface-relief gratings (SRGs) ....................................... 187 5.1. SRGs photoinscribed in LbL films ........................................... 188 5.2. SRGs photoinscription in LB films ........................................... 190 6. Final remarks and prospects .................................................. 190 Acknowledgements ......................................................... 191 References .............................................................. 191 1. Introduction Since the first reports on the preparation of synthetic azodyes in the 1850s [1], many applications have been developed for such dyes which in recent years overcame the simple use as colorants. The new uses of azodyes exploit their property of photoisomerization [2], whose process is illustrated in Fig. 1 for the non-substituted azobenzene [3,4]. Photoisomerization occurs when the chromophores are promoted from the lower-energy trans form to their cis form upon absorbing light. The reverse process is thermal 0001-8686/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cis.2005.05.008 * Corresponding author. Tel.: +55 16 33739825. E-mail address: chu@if.sc.usp.br (O.N. Oliveira). Advances in Colloid and Interface Science 116 (2005) 179 – 192 www.elsevier.com/locate/cis