Rams-Baron Marzena, Musiał Małgorzata, Kramarczyk Daniel, Paluch Marian
August Chełkowski Institute of Physics, University of Silesia, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.
J Chem Phys. 2022 Apr 21;156(15):154501. doi: 10.1063/5.0080726.
We present here the results of high-pressure broadband dielectric spectroscopy (BDS) measurements for a mixture of liquid-crystalline drug itraconazole (ITZ) and glycerol (GLY) at a critical concentration of 5% w/w in which the nematic order is eliminated. In the investigated system, smectic-A to isotropic phase transition leaves a clear fingerprint on the dielectric response, allowing for a phase diagram creation using BDS data. By following the α-relaxation dynamics under different thermodynamic conditions, we provide insights into the effect of pressure on temperature and the phenomenology of smectic-A to the isotropic phase transition. Additional measurements of specific volume as a function of pressure and temperature provide us with a deeper insight into material properties that could be analyzed comprehensively via the equation of state. We proved the validity of the density scaling concept, showing that the mixture's complexity does not exclude thermodynamic scaling of dynamic properties related to the α-process in the smectic-A phase. The low value of scaling exponent γ = 2.00 ± 0.02 and a high ratio of the activation energy at constant volume, E, to the activation enthalpy at constant pressure, H, indicate that temperature is a dominant variable controlling α-relaxation dynamics in the ordered smectic-A phase of the ITZ-GLY mixture.
我们在此展示了高压宽带介电谱（BDS）对液晶药物伊曲康唑（ITZ）和甘油（GLY）的混合物在5% w/w的临界浓度下进行测量的结果，在该浓度下向列相序被消除。在所研究的体系中，近晶A相到各向同性相的转变在介电响应上留下了清晰的印记，从而可以利用BDS数据创建相图。通过跟踪不同热力学条件下的α弛豫动力学，我们深入了解了压力对温度的影响以及近晶A相到各向同性相转变的现象学。作为压力和温度函数的比容的额外测量为我们提供了对材料性质的更深入理解，这些性质可以通过状态方程进行全面分析。我们证明了密度标度概念的有效性，表明混合物的复杂性并不排除与近晶A相中α过程相关的动态性质的热力学标度。标度指数γ = 2.00 ± 0.02的低值以及恒容下的活化能E与恒压下的活化焓H的高比值表明，温度是控制ITZ - GLY混合物有序近晶A相中α弛豫动力学的主导变量。
