Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, PL-60-179 Poznań, Poland.
J Phys Chem B. 2010 Jan 21;114(2):737-41. doi: 10.1021/jp909094x.
On the basis of the static dielectric permittivity temperature behavior of the supramolecular polymer formed by N,N'-di(2-methyl-2-pentylheptyl)urea (MPHU) in carbon tetrachloride diluted solution (10% in mole fraction) and that of neat acetonitrile, it was found that two liquids of the same macroscopic polarity (expressed by the same value of the dielectric permittivity approximately 35) exhibit an essential difference in the field-induced orientational entropy change. A much higher entropy effect is observed for the liquid composed of not too numerous but highly polar molecular entities (MPHU + CCl(4)) than for the liquid composed of numerous but less polar entities (neat acetonitrile). The analysis of the dielectric relaxation spectra of MPHU + CCl(4) solutions was performed with the Davidson-Cole (DC) model. It was found that the DC exponent beta changes its value in a quite important range of 0.4-0.8, depending on MPHU concentration and temperature. This reflects an important deviation of the relaxation mechanism occurring in the supramolecular system investigated from that corresponding to the normal Brownian rotational diffusion (beta = 1).
基于 N,N'-二（2-甲基-2-戊基庚基）脲（MPHU）在四氯化碳稀释溶液（摩尔分数为 10%）中形成的超分子聚合物的静态介电常数温度行为和纯乙腈的介电常数温度行为，发现两种宏观极性相同的液体（用大约 35 的介电常数值表示）在电场诱导的取向熵变化方面表现出本质的差异。由数量不多但极性很强的分子实体（MPHU+CCl4）组成的液体比由数量众多但极性较弱的实体（纯乙腈）组成的液体观察到更高的熵效应。用戴维森-科尔（DC）模型对 MPHU+CCl4 溶液的介电弛豫光谱进行了分析。结果发现，DC 指数β在相当大的范围内（0.4-0.8）变化，这取决于 MPHU 浓度和温度。这反映了所研究的超分子体系中发生的弛豫机制与正常的布朗旋转扩散（β=1）对应的机制有很大的偏差。
