Ribeiro Mauro C C, Pádua Agílio A H, Gomes Margarida F Costa
Laboratório de Espectroscopia Molecular, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05513-970, SP, Brazil.
Institut de Chimie de Clermont-Ferrand, UMR 6296, CNRS/Université Blaise Pascal, 63177 Aubière, France.
J Chem Phys. 2014 Jun 28;140(24):244514. doi: 10.1063/1.4885361.
The glass transition pressure at room temperature, pg, of six ionic liquids based on 1-alkyl-3-methylimidazolium cations and the anions BF4, PF6, and bis(trifluromethanesulfonyl)imide, NTf2, has been obtained from the pressure dependence of the bandwidth of the ruby fluorescence line in diamond anvil cells. Molar volume, Vm(pg), has been estimated by a group contribution model (GCM) developed for the ionic liquids. A density scaling relation, TV(γ), has been considered for the states Vm(pg, 295 K) and Vm(Tg, 0.1 MPa) using the simplifying condition that the viscosity at the glass transition is the same at pg at room temperature and at atmospheric pressure at Tg. Assuming a constant γ over this range of density, a reasonable agreement has been found for the γ determined herein and that of a previous density scaling analysis of ionic liquids viscosities under moderate conditions. Further support for the appropriateness of extrapolating the GCM equation of state to the GPa pressure range is provided by comparing the GCM and an equation of state previously derived in the power law density-scaling regime.
基于1-烷基-3-甲基咪唑鎓阳离子以及阴离子[BF4]-、[PF6]-和双（三氟甲磺酰）亚胺（[NTf2]-）的六种离子液体在室温下的玻璃化转变压力pg，已通过金刚石对顶砧池中红宝石荧光线带宽对压力的依赖性获得。摩尔体积Vm(pg)已通过为离子液体开发的基团贡献模型（GCM）估算。对于状态Vm(pg, 295 K)和Vm(Tg, 0.1 MPa)，考虑了密度标度关系TV(γ)，使用的简化条件是在玻璃化转变时的粘度在室温下的pg以及在Tg时的大气压下相同。假设在该密度范围内γ为常数，本文确定的γ与先前在中等条件下对离子液体粘度进行的密度标度分析中的γ之间已发现合理的一致性。通过比较GCM和先前在幂律密度标度 regime中推导的状态方程，进一步支持了将GCM状态方程外推到GPa压力范围的适用性。
