Preparation and photo-responsive behavior of azobenzene decorated PEG single crystal

In this work, we prepared the azobenzene decorated PEG single crystal for the first time. The azobenzene terminated PEG was prepared by the nucleophilic substitution reaction between the tosylate ended PEG and 4-hydroxy-4 '-methoxy azobenzene. Uniform square-shaped crystals were obtained by a self-seeding approach. Due to the relatively large size of azobenzene, the azobenzene groups could only exist in the surface layer of the lamella crystals. The photo-responsive behavior of the azobenzene was studied by using UV-vis spectra. The photo-induced trans -cis isomerization of azobenzene could take place very well. The trans -cis isomerization rate was even similar with that in solution, which proved that the azobenzene groups attached on the single crystal had relatively loose surroundings.

Automated summary

In this study, we successfully prepared azobenzene decorated PEG single crystal for the first time. The azobenzene terminated PEG was synthesized through nucleophilic substitution reaction between tosylate ended PEG and 4-hydroxy-4'-methoxy azobenzene. Square-shaped crystals were obtained using self-seeding approach. The photo-responsive behavior of azobenzene was studied by UV-vis spectra, and the trans-cis isomerization of azobenzene occurred well, indicating that the attached azobenzene groups had loose surroundings in the single crystal.