Abstract
Herein, the synthesis of ten tetra-branched tetra-cationic ionic liquids, which consist of a pentaerythritol-based core, alkylene or ethylenedioxy spacers, imidazolium cationic units, and short alkyl tails, is described. The physical properties of the tetra-cations, including their glass transition and thermal decomposition temperatures, densities, viscosities, and ionic conductivities, were investigated. The tetra-cations were analyzed to determine the effects of the spacer and tail structure on the above-mentioned physical properties. The spacer unit located between the pentaerythrityl core and cationic unit was confirmed to be the key for improving ionic conductivity. A maximum ionic conductivity of 2.8 × 10−4 S cm−1 (25 °C under anhydrous conditions) and a minimum viscosity of 1.6 Pa s (25 °C) were observed. While the physical values of the tetra-cationic ionic liquids are close to those of di-cationic ionic liquids, their structure-property relationship is similar to that of poly-cations rather than di-cations.
摘要
本文介绍了由季戊四醇为核心、亚烷基或亚乙二氧基间隔物、咪唑阳离子单元和短烷基尾部组成的十种四分支四阳离子离子液体的合成。研究了四阳离子的物理性质,包括玻璃转化温度和热分解温度、密度、粘度和离子电导率。通过分析四阳离子,确定了间隔单元和尾部结构对上述物理性质的影响。结果表明,位于季戊四醇核心和阳离子单元之间的间隔单元是提高离子电导率的关键。观察到的最大离子电导率为 2.8 × 10-4 S cm-1(25 °C,无水条件下),最小粘度为 1.6 Pa s(25 °C)。虽然四阳离子离子液体的物理值接近二阳离子离子液体,但其结构-性质关系类似于多阳离子而非二阳离子。