Photo-regulated phase transition of poly(ethylene glycol) derivative containing azobenzene group.

A photo-responsive and thermo-responsive poly(ethylene glycol) derivative containing azobenzene group was synthesized. Its photoisomerization kinetics was investigated by the UV-vis spectra, and the pseudo-first-order rate constants ( k_t and k_c) were determined to be 1.5 × 10⁻² and 9.3 × 10⁻² s⁻¹, respectively. It is found that the phase transition behavior can be tuned theoretically through photoirradiation between 26.6°C and 36.7°C. Finally, it is worthy to note that the changes of the lower critical solution temperature occur repeatedly upon successive irradiation of UV and visible light. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]