Department of Chemical & Biomolecular Engineering, University of South Alabama, Mobile, Alabama 36688, USA.
Chem Commun (Camb). 2018 May 15;54(40):5019-5031. doi: 10.1039/c8cc01716f.
Thermally robust materials have been of interest since the middle of the past century for use as high temperature structural materials, lubricants, heat transfer fluids and other uses where thermal stability is necessary or desirable. More recently, ionic liquids have been described as 'thermally robust,' with this moniker often originating from their low volatility rather than their innate stability. As many ionic liquids have vanishingly low vapor pressures, the upper limit of their liquid state is commonly considered to be their degradation temperature, frequently reported from TGA measurements. The short duration ramps often used in TGA experiments can significantly overestimate the temperature at which significant degradation begins to occur when the compounds are held isothermal for even a few hours. Here, we review our recent work, and that of colleagues, in developing thermally robust ionic compounds, primarily perarylphosphonium and perarylsulfonium bistriflimide salts, in some of which cation stability exceeds that of the anion. We have used a combination of molecular design, synthesis, and computational modeling to understand the complex tradeoffs involving thermal stability, low melting point and other desirable physicochemical properties.
自上个世纪中叶以来，人们一直对耐热材料感兴趣，将其用作高温结构材料、润滑剂、热传递流体和其他需要或期望热稳定性的用途。最近，离子液体被描述为“耐热”，这个名称通常源自它们的低挥发性，而不是它们固有的稳定性。由于许多离子液体的蒸气压极低，它们液相的上限通常被认为是它们的降解温度，这通常是从 TGA 测量中报告的。在 TGA 实验中常用的短时间升温斜坡在化合物等温保持几个小时时，可能会显著高估化合物开始发生显著降解的温度。在这里，我们回顾了我们最近的工作，以及同事们在开发耐热离子化合物方面的工作，主要是全芳基膦鎓和全芳基砜双三氟甲磺酰亚胺盐，其中一些阳离子的稳定性超过了阴离子。我们结合了分子设计、合成和计算建模来理解涉及热稳定性、低熔点和其他理想物理化学性质的复杂权衡。
