The modified van der Waals’model which has only one molecular size-dependent parameter is used to calculate the internal pressures of liquids.It is found that the model parameter has very good linear relation with the molar volume of liquids at normal boiling point.A group contribution method is established for the molar volume of liquids at normal boiling point.Therefore the internal pressures of various liquids can be predicted.On the basis of the generalized Gibbs free energy model for mixing of liquids,proposed by our previous work,a new solubility parameter had been defined,which is equal to the ratio of the cohesive energy density with the square root of internal pressure.This definition is more strict and its range of application is more exten sive than classical Hildebrand solubility parameter.In present work,the values of new solubility parameter for 170 solvents at 298.15 K are obtained.
如同先前报道的液态聚合物一样,298.15 K时一般小分子液体的内压平方根l与摩尔体积Vm的乘积亦正比于它们的van der Waals体积Vvdw,而且两者有相同的比例系数。这说明各种液体的lVm具有相同的基团加和性。据此,利用它们的内压和摩尔体积的实验值建立了一个lVm的基团贡献法,它能用来预测各种液态有机物,包括聚合物在298.15 K时的内压值。本法不仅适用于非极性和弱极性液体,而且也适用于强极性和缔合液体。熟知的Small溶解度参数基团贡献法只不过是本工作的一个特例。对120种有机液体和液态聚合物的l值预测结果表明,其与实验值的一致性令人满意。
