Alhadid Ahmad, Jandl Christian, Nasrallah Sahar, Kronawitter Silva M, Mokrushina Liudmila, Kieslich Gregor, Minceva Mirjana
Biothermodynamics, TUM School of Life Sciences, Technical University of Munich, Freising, Germany.
Department of Chemistry, TUM School of Natural Sciences, Technical University of Munich, Garching, Germany.
J Chem Phys. 2023 Sep 7;159(9). doi: 10.1063/5.0158985.
Eutectic systems design requires an in-depth understanding of their solid-liquid equilibria (SLE). Modeling SLE in eutectic systems has as prerequisites, the melting properties and activity coefficients of components in the liquid phase. Thus, due to the unavailable melting properties of thermally unstable substances, it is impossible to estimate their activity coefficients from experimental SLE data and model the SLE phase diagram of their eutectic systems. Here, we evaluate the activity coefficients of thermally unstable constituents in the liquid phase, which were calculated independent of their melting properties by correlating the SLE data of their cocrystals. Differential scanning calorimetry and powder x-ray diffraction were employed to obtain the SLE phase diagram of three eutectic systems, i.e., tetramethylammonium chloride/catechol, tetraethylammonium chloride/catechol, and betaine/catechol systems, and identify the formation of nine cocrystals. The non-random, two-liquid equation was used to calculate the activity coefficients of the components in the liquid phase. The substantial negative deviation from ideality in the three studied systems indicated strong hydrogen bonding interactions in the liquid solution. Furthermore, modeling ion-ion interactions in eutectic systems containing ionic constituents is of utmost importance for understanding their nonideality.
低共熔体系设计需要深入了解其固液平衡（SLE）。对低共熔体系中的固液平衡进行建模，需要先了解液相中各组分的熔化特性和活度系数。因此，由于热不稳定物质的熔化特性无法获取，所以无法根据实验得到的固液平衡数据估算其活度系数，也无法对其低共熔体系的固液平衡相图进行建模。在此，我们评估了液相中热不稳定成分的活度系数，该系数通过关联其共晶体的固液平衡数据独立于其熔化特性进行计算。采用差示扫描量热法和粉末X射线衍射法获得了三个低共熔体系（即氯化铵/儿茶酚、四乙基氯化铵/儿茶酚和甜菜碱/儿茶酚体系）的固液平衡相图，并确定了九种共晶体的形成。使用非随机双液方程计算液相中各组分的活度系数。在研究的三个体系中，与理想情况的显著负偏差表明在液体溶液中存在强烈的氢键相互作用。此外，对含有离子成分的低共熔体系中的离子-离子相互作用进行建模，对于理解其非理想性至关重要。
