Dialkoxy functionalized quaternary ammonium ionic liquids as potential electrolytes and cellulose solvents
作者:Zhengjian Chen、Shimin Liu、Zuopeng Li、Qinghua Zhang、Youquan Deng
DOI:10.1039/c1nj20062c
日期:——
A series of new ionic liquids, based on dialkoxy-functionalized quaternary ammonium cations side chains: 1 = CH3, 1O1 = CH3OCH2, 1O2 = CH3OC2H4, 2O2 = C2H5OC2H4; cations: [N11,1O1,1O2], [N11,1O1,2O2], [N11,1O2,1O2], [N11,1O2,2O2] and [N11,2O2,2O2]}, with BF4−, (CF3SO2)2N− (NTf2) and CH3CO2− (OAc) as counteranions, have been prepared and characterized. Their basic properties, such as spectroscopic characteristics, melting point, glass transition temperature, thermal stability, electrochemical window, density, refractive index, viscosity and conductivity, were measured and comparatively studied. The incorporation of two flexible alkoxy chains makes the quaternary ammonium salts highly qualified to be low-viscous and high-conductive room temperature ILs, and even some of them have significantly better fluidity than the popular imidazolium ILs with a similar molecular weight, e.g.[N11,1O1,2O2]BF4 (151 cP and 2.11 mS cm−1, Mw: 249) vs.[HMIm]BF4 (220 cP and 1.2 mS cm−1, Mw: 256) at 25 °C. The electrochemical windows of these ILs were evaluated up to 5.5 V. In addition, the dialkoxy OAc ILs were found to have excellent solvent power for cellulose under mild conditions, e.g. a solution of 18 wt% microcrystalline cellulose in [N11,2O2,2O2]OAc at 80 °C. By precipitation with water, the dissolved cellulose (I crystal structure) was regenerated as nanosized cellulose II particles with increased surface area and decreased crystallinity, determined by FE-SEM and XRD.
一系列新型离子液体,基于二烷氧基功能化季铵阳离子侧链:1=CH3、1O1=CH3OCH2、1O2=CH3OC2H4、2O2=C2H5OC2H4;阳离子:[N11,1O1,1O2]、[N11,1O1,2O2]、[N11,1O2,1O2]、[N11,1O2,2O2] 和 [N11,2O2,2O2]},含 BF4−、(CF3SO2)已制备并表征了 2N− (NTf2) 和 CH3CO2− (OAc) 作为抗衡阴离子。对它们的光谱特性、熔点、玻璃化转变温度、热稳定性、电化学窗口、密度、折射率、粘度和电导率等基本性能进行了测量和比较研究。两条柔性烷氧基链的引入使得季铵盐非常适合作为低粘度和高导电性的室温离子液体,甚至其中一些季铵盐的流动性明显优于相似分子量的流行咪唑离子液体,例如[N11] ,1O1,2O2]BF4(151 cP 和 2.11 mS cm−1,Mw:249)与 [HMIm]BF4(220 cP 和 1.2 mS cm−1,Mw:256),25 °C。这些离子液体的电化学窗口高达 5.5 V。此外,发现二烷氧基 OAc 离子液体在温和条件下(例如在室温下)对纤维素具有优异的溶解能力。 80 °C 下 18 wt% 微晶纤维素的 [N11,2O2,2O2]OAc 溶液。通过用水沉淀,溶解的纤维素(I 晶体结构)再生为纳米纤维素 II 颗粒,其表面积增加,结晶度降低(由 FE-SEM 和 XRD 测定)。