Hernandez-Perni Graci, Leuenberger Hans
Institute of Pharmaceutical Technology, Pharmacenter University of Basel, Basel, Switzerland.
Eur J Pharm Biopharm. 2005 Oct;61(3):201-13. doi: 10.1016/j.ejpb.2005.05.008. Epub 2005 Aug 2.
In the previous papers of our research group it was shown, that the Clausius-Mossotti-Debye equation for the quasi-static dielectric constant (epsilonr) can be extended to liquids if the parameter Ei/E is introduced. Thus, it is possible to characterize polar liquids with the easily accessible parameter Ei/E. This property is also reflected by the fact that the parameter Ei/E can be directly related to the empirical ET(30) and the normalized ETN parameter to describe the polarity of liquids proposed by Reichardt (Chem. Rev. 94, 2319-2358) Ei corresponds to the local mean field due to close molecule-molecule interactions after the application of an external electric field E. In a recent work of our research group it was also demonstrated that the modified Clausius-Mossotti-Debye equation and the study of the relaxation time can be related to percolation phenomena in binary solvent mixtures leading to a valuable insight of the structure of polar liquids and to a better understanding of binary systems. In the present paper it is demonstrated that percolation phenomena for binary DMSO/water mixtures, become visible due to changes of parameters describing the dielectric spectrums. The interpretation of the percolation effects leads to the following conclusion: DMSO/water mixtures seem to have in the whole range of miscibility the same microscopic structure like water with a coordination number z approximately between 4 and 6 which could be the reason for the high permeability of DMSO through biological membranes.
在我们研究小组之前的论文中表明，如果引入参数Ei/E，准静态介电常数（εr）的克劳修斯 - 莫索蒂 - 德拜方程可以扩展到液体。因此，有可能用易于获取的参数Ei/E来表征极性液体。这一特性还体现在参数Ei/E可以直接与经验性的ET(30)以及赖夏德特提出的用于描述液体极性的归一化ETN参数相关这一事实上（《化学评论》94, 2319 - 2358）。Ei对应于施加外部电场E后由于紧密的分子 - 分子相互作用而产生的局部平均场。在我们研究小组最近的一项工作中还表明，修正的克劳修斯 - 莫索蒂 - 德拜方程以及弛豫时间的研究可以与二元溶剂混合物中的渗流现象相关，从而对极性液体的结构有宝贵的见解，并更好地理解二元体系。在本文中表明，由于描述介电谱的参数变化，二元二甲基亚砜/水混合物的渗流现象变得明显。对渗流效应的解释得出以下结论：二甲基亚砜/水混合物在整个互溶范围内似乎具有与水相同的微观结构，配位数z大约在4到6之间，这可能是二甲基亚砜透过生物膜具有高渗透性的原因。
