Study On Ionic Liquid And PAN/ Ionic Liquid Diluted Solution

Nowadays the traditional solvents of PAN for the industry have more or less disadvantages, such as high corrosion, volatilization and environment pollution. With the appearance of the conception of green chemistry, more and more attention has been paid to environment protection. Ionic liquids have been researched warmly as one kind of green solvents. Ionic liquids are organic salts that are liquids at room temperature, which contain organic cations and inorganic anions.In this paper, two-step method is used to synthesize ionic liquids. Infrared spectrum analysis (FTIR), nuclear magnetic resonance spectroscopy (NMR) and qualitative elementary analysis are employed to analyze the structure of l-butyl-3-methylimidazolium chloride ([BMIM]C1) and l-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) which are synthesized in our lab. The results are identical with theoretical structures.And then, the influence of water and acetone on the refraction indexof ionic liquid was studied. Discussion on the interaction fundamental of water/acetone and [BMIM]BF4 is performed, according to the relation of molar fraction of water/acetone and solution refraction index. It is shown that in the salt-rich region (molar fraction less than half), the solution refraction index changes smoothly for the hydrogen bonds between water/acetone and [BMIM]BF4; in the water/acetone-rich region (molar fraction more than half), the solution refraction index decreases remarkably for the free water/acetone.The variety of intrinsic viscosities of PAN in [BMIM]BF4 and DMF were studied. The result revealed that the curve of reduced viscosities (η_sp/C) vs. concentration was not linear but upward as the concentration below definite concentration. At the same time the results revealed that the intrinsic viscosity of PAN/DMF was higher than that of PAN/[BMIM]BF₄. The intrinsic viscosity of PAN/[BMIM]BF₄ was more sensitive to temperature. But the intrinsic viscosities of both solutions decreased with the increase of temperature.Meanwhile the molecular weights of the PAN samples were obtained by GPC and the Mark-Houwink constants of PAN in [BMIM]BF₄ were determined. The Mark-Houwink equation is: [η]= 5.87 X 10^-4 M_η⁰.6268 . The molecular weights of PAN were measured at different conditions. The results showed that only using DMF with NaNO₃ as eluant and using a PAN sample with known molecular weight and wide molecular weightdistribution as a standard sample, the final molecular weight was reliable. Finally the Z-average size and distribution of PAN in [BMIM]BF₄ and DMF were studied by the laser size detector and AFM. The results of the laser size detector showed that the size of PAN in [BMIM]BF₄ decreased with the decrease of concentration, while the size distribution increased accordingly. The size of PAN in DMF changed slightly which decreased first and then increased with the concentration. At the same time, the results obtained by the method of AFM were identical with the results which were obtained by the method of laser size detector.