Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland.
J Phys Chem B. 2012 Mar 29;116(12):3789-94. doi: 10.1021/jp3007798. Epub 2012 Mar 16.
The dielectric studies performed for cyclooctanone in its static dielectric regime have shown that at the phase transition from liquid to disordered (plastic) solid phase of the compound, the following singular phenomena occur: (a) the static permittivity (ε(s)) exhibits a small increase at the transition, instead of that usually observed for polar liquids, a strong decrease of the permittivity at the transition to the crystalline solid phase; (b) temperature dependence of the permittivity, ε(s)(T), is practically the same in both phases, reflecting the same dipolar orientational entropy increment induced by the probing electric field; (c) a distinct jump occurs in the slope of the frequency dependence (in log-log scale) of the dielectric losses due to an ionic current, from the "ohmic" value -1 in the liquid phase to about -0.9 just after the transition to the plastic phase; (d) a similar jump is observed in the shape of the electric modulus spectra of cyclooctanone. The results clearly show the liquid-like freedom in the molecular dynamics in the plastic phase as well as similar intermolecular interactions in both phases of cyclooctanone. The differences in the dielectric losses frequency behavior may reflect the change in the ions dynamics: from the normal translational Brownian diffusion in the liquid phase to the subdiffusional dynamics in the plastic phase.
在静态介电领域对环辛酮进行的介电研究表明，在化合物从液相向无序（塑性）固相转变时，会出现以下奇异现象：(a) 静态介电常数（ε(s)）在相变时略有增加，而不是通常观察到的极性液体在向结晶固体相转变时介电常数的强烈下降；(b) 在两相中，介电常数ε(s)(T)的温度依赖性几乎相同，反映了探测电场引起的相同偶极取向熵增量；(c) 由于离子电流，介电损耗的频率依赖性（在对数-对数标度上）的斜率会发生明显的跳跃，从液相中的“欧姆”值-1 跃升至约-0.9，就在向塑性相转变之后；(d) 在环辛酮的电模量谱中也观察到类似的形状跳跃。结果清楚地表明，在塑性相中分子动力学具有类似液体的自由度，并且在环辛酮的两相中具有相似的分子间相互作用。介电损耗频率行为的差异可能反映了离子动力学的变化：从液相中的正常平移布朗扩散到塑性相中的亚扩散动力学。
