Polymer nanoparticles self-assembled from photo-, pH- and thermo-responsive azobenzene-functionalized PDMAEMA

A series of amphiphilic azobenzene-functionalized poly(dimethylaminoethyl methacrylates) have been synthesized by quaternization between [3-(4-(4-bromo-butyloxy)phenyl)-trifluoromethyl]-diazene and the dimethylaminoethyl units of poly(dimethylaminoethyl methacrylate) (PDMAEMA). The azobenzene-functionalized polymers could self-assemble into micellar nanoparticles in water. Upon UV light irradiation, the spherical nanoparticles could only swell a little. Although the loaded nile red could not be released from the nanoparticles under UV light irradiation, the fluorescence intensity of nile red changed reversibly when altering UV and visible light irradiation. At pH 3, the nanoparticles could be swelled greatly and the loaded nile red could be released completely. At pH 10, the nanoparticles could be shrunk and the loaded nile red could be released a little. At high temperature, the nanoparticles could be shrunk, where little nile red could be released from the nanoparticles, while the fluorescence intensity of nile red could change reversibly during the heating and cooling processes.