作者:Ruijian Xu、Jacques Léonard、V. Tam Bui
DOI:10.1039/ft9959102797
日期:——
Volume investigations have been carried out on the solutions of two pairs of linear and cyclic (ring) oligomers in chloroform and in p-dioxane. For both pairs, the linear and cyclic oligomers had similar molar masses (244 and 384 g mol–1). The densities of pure liquid components and solutions were determined using a vibrating tube densitometer (Sodev) at 25, 30, 35 and 40 °C; the concentrations of the solutions varied by up to 20% in mass/volume of solvent. The densities of three solid oligomers were measured with a pycnometer using water as the reference liquid over the same temperature range. Partial molar volumes of the components, excess molar volumes of the solutions and thermal expansion coefficients of components were all deduced from the density data. The negative departure from the ideal mixing law of most linear and cyclic oligomer solutions is attributed to specific intermolecular interactions between the solvent and the oligomer as well as to the free-volume effect related to the molecular configuration of each compound. There is a clear difference in volume properties between linear and cyclic oligomers of the same molar mass.
我们对两对线性和环状(环状)低聚物在氯仿和对二氧六环中的溶液进行了体积研究。对于这两对低聚物,线性低聚物和环状低聚物具有相似的摩尔质量(244 和 384 g mol-1)。纯液体成分和溶液的密度是在 25、30、35 和 40 °C 温度下使用振动管密度计(Sodev)测定的;溶液的浓度在质量/溶剂体积上的变化不超过 20%。在相同的温度范围内,以水为参比液体,用比重计测量了三种固体低聚物的密度。各组分的部分摩尔体积、溶液的过量摩尔体积和各组分的热膨胀系数都是从密度数据中推导出来的。大多数线性和环状低聚物溶液与理想混合定律的负偏离归因于溶剂和低聚物之间特定的分子间相互作用,以及与每种化合物分子构型相关的自由体积效应。摩尔质量相同的线性低聚物和环状低聚物在体积特性上存在明显差异。