The optical behavior of different azopolymers based on epoxy-isocyanate and DR19

SÁIZ LUCIANA; OYANGUREN PATRICIA; GALANTE M. JOSÉ

Lyon

Simposio; 2nd International Symposium Frontiers in Polymers Science; 2011

Polymers containing azobenzene units are of special interest due to the reversibility of their photo-orientation. Applications of these materials are in the fields of optical information storage, information processing, optical switching devices, and others. The photoresponse of these polymers is based on cis/trans photoisomerization of azobenzene groups and is affected by the mobility of the groups. Studies on photoorientation processes in amorphous polymers have addressed the role of Tg and polymer structural effects, including the main chain rigidity, the nature of the connection of the chromophore to a rigid, semirigid or a flexible main chain, the free volume or a combinations of these. In this study, the photoinduced behaviour of the polymers is investigated in terms of dichroism and birefringence for epoxy- isocyanate based azo polymers. The difficult in controlling the synthesis of this kind of polymers in order to obtain materials with the best properties combination deals with the competition among the diverse reactions that could take place in an epoxy-isocyanate blend. The relative proportion of different groups will depend on factors such as: structure and concentration of monomers, type and concentration of catalyst and cycles of curing and postcuring. To elucidate the influence of these factors, in a first step, azo prepolymers (TAZ) were synthesized by reaction between a chromophore Disperse Red 19 (DR19) with different diisocyanate, using an appropriate stoichiometric relation to generate reaction products with reactive groups (isocyanate) in the extreme of chains. In a second step, these reactive groups were bonded to polymer precursors (epoxy, amine) to generate different types of networks. The resulting polymers were characterized using several techniques (DSC, GPC, FTIR, NMR), and their optical properties evaluated and discussed in terms of their structures. The high Tg and the great remaining birefringence fraction make these materials promising for optical storage applications.