| Summary: | 碩士 === 國立成功大學 === 化學系碩博士班 === 95 === 1-butyl-3-methylimidazole tetrafluoroborate (BMIBF4) was mixed firstly with various diluents such as propylene carbonate (PC)、ethylene carbonate (EC)、N-methylpyrrolidone (NMP) and tetrahydrofuran (THF). Nuclear Magnetic resonance techniques were then applied to investigate the influences of diluent content and temperature variations (300-340 K) on the chemical shift, diffusion coefficient and the relaxation time of 1H，11B and 19F species. The macroscopic properties, like viscosity, density and conductivity of the mixture were also measured to understand further the ionic diffusion and conductivity.
It’s known from the experiment that the diluent utilizes its lone electron pairs to form hydrogen bond with the H atom of BMI+ ring. The 1H chemical shift difference is closely related to the distance between BMI+ and BF4- ions. It’s also found from the NOESY spectra that hydrogen bond is also formed between the alkyl hydrogen of the diluent and the 19F atom of BF4- with an order of the interaction energy of EC＞PC＞NMP＞THF. As diluent content increases, the viscosity of solution falls, relaxation time rises, the movement of the ions and conductivity increase thereupon.
At a constant temperature and diluent concentration the hydrodynamic radius of BMI+ and BF4- ions, based on the Stokes - Einstein model, all follow the order THF＞NMP＞PC＞EC.
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