Azo-Containing Polymer Brushes Prepared By AGET-ATRP And Its Photo-responsive Behavior

Polymer brush is one of the most important modification approaches to solid surface.It also plays a key role on polymer chemistry including novel synthesis method, as well aspolymer physics such as the transition between random coils to stretched chains.Firstly, an azobenzene monomer was synthesized and confirmed by Fourier transforminfrared and nuclear magnetic resonance spectra. Secondly, amino-and bromo-groupswere successively grafted to the hydroxylation silicon substrate. Finally, thepolyazobenzene brush was grafted to the brominated silicon by a novel polymerizationmethod, i.e., activator generated by electron transfer atom transfer radical polymerization(AGET-ATRP). The composition, morphology, and film thickness of the brush wascharacterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy(AFM), and ellipsometry, respectively.XPS result indicated that polyazobenzene chains had been successfully grafted to thesilicon surface. AFM result showed that the root-mean-square roughness of polymer brushincreased with polymerization time linearly. The film thickness result strongly suggestedthat the brush was a mushroom at the early stage of polymerization and a stretched state atthe late stage, respectively. With the increase of polymerization time, the contact angle ofthe brush decreased initially and increased later. Compared with the irradiation of visiblelight, the contact angle under365-nm ultra-violet irradiation reduced3~5°and restoredunder visible light again. Obviously, this brush showed good photo-isomerizationbehavior.In the future, this brush has potential applications on information storage,photo-actuator, etc.