Synthesis, characterization, and photoresponsive behavior of new azobenzene‐containing polyethers

Two new polyethers, bearing azobenzene moiety in the side chain, were synthesized in excellent yields by means of anionic polymerization of 4-glycidyloxyazobenzene and 4-cyano-4′-glycidyloxyazobenzene (leading to azo-P1 and azo-P2 polymers, respectively) with the system polyiminophosphazene base t-Bu-P4/3,5-di-tert-butylphenol as initiator. The polymers were characterized with respect to their molecular weights, structure, and calorimetric features. The polyether bearing cyanoazobenzene group in the side chain was found to exhibit nematic phase up to 200 °C. E–Z isomerization of both polymers in tetrahydrofuran solution, after irradiating with UV light at 364 nm for 15 min, was investigated by means of UV–visible absorption spectroscopy. In the case of glycidylic monomers as well as the resulting polymers, E–Z isomerization was also investigated by means of 1H NMR, by direct irradiation in the NMR probe in deuterated 1,1,2,2-tetrachloroethane solution. By this technique, in the case of 4-cyano-4′-glycidyloxyazobenzene, it was found that irradiation led to a photostationary state corresponding to an amount of Z isomer equal to 25%. For azo-P1 polymer, Z–E or “reverse” isomerization was investigated at 60, 70, or 80 °C directly in the NMR probe; as expected, the process followed a first-order rate law. The kinetic constants as well as the activation energy for the process were determined in this temperature range. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5426–5436, 2009