Motamedian S, Pusch W, Tanioka A, Becker F
Max-Planck-Institute für Biophysik, Kennedy Allee 72, Frankfurt am Main 72, D-60596, Germany
J Colloid Interface Sci. 1998 Aug 1;204(1):135-42. doi: 10.1006/jcis.1998.5554.
Sorption isotherms of glassy polymers are concave to the pressure axis, and the absolute sorption levels are almost an order of magnitude higher than that of rubbery polymers on the relatively low-pressure side. There are several models to interpret this behavior, and the dual sorption model is the most widely accepted one among them. In the present work, sorption isotherms were first derived from permeation data with several gases for four polymer membranes which might be representative of the dual sorption model: two of them were in a glassy state (cellulose acetate and polyamide), the third one was a block copolymer which was composed of a glassy polymer and a rubbery polymer at the measuring temperature, and the fourth one was a Nafion membrane which was taken as a model membrane because of its channel structure with adsorption sites of charged groups supported by a rubbery polymer. These results did not necessarily support the dual sorption model. Subsequently, the validity of the underlying assumptions of two other sorption models for glassy polymers, that is, the matrix model and the deformation model, were examined and a new equation for the sorption isotherm with an ordering parameter was derived, which implied that the glassy polymer was in a nonequilibrium state and changed from the glassy to the rubbery state by absorbing the gas. Copyright 1998 Academic Press.
玻璃态聚合物的吸附等温线向压力轴凹陷，并且在相对低压侧，其绝对吸附水平比橡胶态聚合物的绝对吸附水平高近一个数量级。有几种模型可用于解释这种行为，其中双吸附模型是最被广泛接受的一种。在本工作中，首先从四种聚合物膜对几种气体的渗透数据推导出吸附等温线，这四种聚合物膜可能代表双吸附模型：其中两种处于玻璃态（醋酸纤维素和聚酰胺），第三种是嵌段共聚物，在测量温度下由玻璃态聚合物和橡胶态聚合物组成，第四种是纳滤膜，因其具有由橡胶态聚合物支撑的带电荷基团吸附位点的通道结构而被用作模型膜。这些结果并不一定支持双吸附模型。随后，研究了玻璃态聚合物的另外两种吸附模型（即基体模型和变形模型）的基本假设的有效性，并推导了一个带有有序参数的吸附等温线新方程，这意味着玻璃态聚合物处于非平衡态，并且通过吸收气体从玻璃态转变为橡胶态。版权所有1998年学术出版社。
