Synthesis And Photophysical Properties Of Triphenylimidazole Substituted Vinyl Polymer

Triarylimidazole derivatives with unique molecular structures have been widely used in optics, biomedicine, and other fields due to their excellent optical properties and biological activities. However, most of the studies only concern small triarylimidazole molecules, and few reports have derived from the research of triarylimidazole-based polymers. This paper thus proposes a novel strategy for preparing the vinyl polymer containing triphenylimidazole side groups, which possesses the characteristic of temperature-dependent absorption in near-UV spectral region (250-350 nm) and has a potential application for temperature sensors.The vinyl monomer,2-(4'-((4'-vinylbenzyl)oxyl)phenyl)-4,5-diphenylimidazole, was synthesized and characterized by 1H NMR,13C NMR, FTIR. Homopolymer of this monomer was obtained by conventional radical polymerization. The number average molecular weight (Mn) and molecular weight distribution (PDI) of the polymer were determined by gel permeation chromatography (GPC).Photophysical properties of the as-prepared polymer were studied, including the effect of solvent, temperature, and metal irons on its ultraviolet and fluorescence spectroscopy. The results indicate that the absorbances of monomer and polymer decrease (increase) with increasing (decreasing) temperature reversibly between 30 and 85℃. Both the absorbances of polymer solution and film showed a similar sensitivity to temperature changes.Density functional theory (DFT) combined with time-dependent density functional theory (TD-DFT) in Gaussian 09 was used to simulate the electronic spectra of monomer at different temperatures. It is demonstrated that the linear relationship between the UV absorbance of monomer and temperature can be attributed to the conformational equilibrium shift under different temperature circumstances.