INFLUENCE OF POLARITY OF NON PHOTOACTIVE ORGANIC CRYSTALS ON OPTICAL PROPERTIES OF AZO-NETWORKS

OROFINO, A. B.; GALANTE, M. J.; OYANGUREN, P. A.

Bahía Blanca

Simposio; IX Simposio Argentino de Polímeros (SAP 2011); 2011

Comité Organizador - CRIBABB Centro Regional de Investigaciones Básicas y Aplicadas de Bahía Blanca

In recent years, azo polymers have attracted increasing attention because of their potential uses in various photonic applications. Ideal materials for optical switching and image storage should possess a large induced birefringence, high writing-erasing rate, long term stability and high sensitivity (Yager and Barrett, 2009). Even polymers containing azo moieties can fulfill those requirements, to achieve a good performance in practical applications, further improvement must be done towards these objectives.The mechanism for photoinduced anisotropy involves the photochemical trans-cis-trans isomerization of azo moieties, and the alignment of the molecular polarization vector perpendicular to the electric vector of the polarized actinic light. If present, nonphotoactive moieties can undergo alignment together with azobenzene groups by cooperative motion (Natansohn et al., 1994; Buffeteau et al., 1996).Thus, the photoinduced birefringence can be enhanced by improving the intrinsic molecular birefringence of the azobenzene moiety as well as increasing the order parameter of the birefingent moiety.On the other hand, the optical response is strongly affected by the mobility of the azo groups and any supramolecular order of the polymer (Wu et al., 1998). Rigidity and order in the structure favour the stability of the recorded information, so the glass transition temperature and crystallinity of the material are key factors that should be carefully designed and adjusted.In this work, the azobenzene units are introduced as photoalignment triggers with good optical response and the organic crystals provide large birefringence, a high order parameter and good stability of the aligned state.