Side-chain azopolymers

Figure 4.1. Chemical structure of poly(Disperse Red 1) acrylate, pdria, a pseu-dostilbene side-chain azopolymer that generates high quality surface relief structures.

Abstract Smart polymers based on photoresponsive azobenzene moieties have been extensively explored as potential materials for high capacity optical storage. This chapter reviews different strategies to incorporate azobenzenes into polymeric structures as well as their photoresponse properties. The potential of this type of materials as volume holographic media is summarized with special emphasis on block copolymers and blends. Although side-chain azopolymers has been the most investigated, new macromolecular architectures have been recently proposed and will be briefly presented. 

These modifications include variations on the length of the spacer which connects the azobenzene and the polymeric chain in side-chain azopolymers, or the electronic nature of substituents at the azobenzene moiety (Ruhmann, 1997). This requires the synthesis of appropriate monomers. Conventional techniques can be used for the polymerization of azobenzene monomers. For instance, step polymerization has been used by Hvilsted and co-workers to synthesize different series of liquid crystalline polyesters with potential applications in reversible optical data storage. These polyesters have a side-chain architecture, which synthesis is represented in Fig. 16.6 (Hvilsted et al, 1995). Being a modular synthetic approach, the influence of different structural parameters on the photoinduced optical properties can be evaluated in relatively simple manner. 

O. V. Yaroshchuk, A. D. Kiselev, Yu. Zakrevskyy, T. Bidna, J. Kelly, L.-C. Chien, and J. Lindau, Photo-induced three dimensional orientational order in side chain liquid crystalline azopolymers. Physical Review E, 68, 011803 (2003). 

---