2-Oxazoline based photo-responsive azo-polymers. Synthesis, characterization and isomerization kinetics

New azo-polymer structures, with azo content ranging from 15% to approximate to 100%, are prepared by attaching a side-chain azo-moiety onto poly(isopropenyloxazoline-co-styrene)s and poly(isopropenyloxazoline). Postcoupling conditions are determined by kinetic investigations. Polymer compositions are evaluated from UV, H-1 NMR, titrimetry and elemental analysis. Chemical modification of polymers is evidenced by FTIR and H-1 NMR spectroscopy. Thermal analysis sustain that azobenzene loads up to 0.67 M ratio result in an increase of T(g)s, and that the azo dye content dictates the thermal stability of the modified copolymers. Both solution and solid-state trans-cis-trans isomerization kinetics are conducted. Cis-to-trans thermal relaxation rate constants of azo-polymers increase compared to the model compound used in solution measurements. Also, distinct relaxation mechanisms are assessed, as a function of solvents polarity and temperature for both polymers and model compound. For the azo-polymer thin films, the lifetime of cis isomers is tuned from polymer composition (dye load) to exhibit slow or fast relaxation. (c) 2012 Elsevier Ltd. All rights reserved.