Photoisomerization of azobenzene moiety in crosslinking polymer materials

In this study, a series of acryloyloxy-substituted azobenzene derivatives, 3-(tert-butyl)-4,4'-bisacryoloxy-azobenzene (tBu-Azo-AO), 3-(tert-butyl)-4,4'-bis[3-(acryoloxy) propoxy]-azobenzene (tBu-Azo-AO3) and 3-(tert-butyl)-4,4'-bis[6-(acryoloxy) hexyloxy]-azobenzene (tBu-Azo-AO6) were synthesized and employed as monomers to prepare polymer films by copolymerizing dipentaerythritol hexaacrylate (DPE-6A) and methyl methacrylate (MMA), respectively. When exposed to a nanosecond laser beam at the wavelength of 355 nm, ultraviolet-visible (UV-Vis) absorption spectra of the resultant polymer films with different irradiation time were monitored. On the basis of the absorbance of the pi-pi* electronic transition, the kinetics of trans-to-cis photoisomerization of three kinds of azobenzene moieties were demonstrated and found to be influenced by both the pump energy and azobenzene concentration.