Aqueous two-phase systems provide oil-free alternatives in the formulation of emulsions in food and other applications. Theoretical interpretation of measurements on such systems, however, is complicated by the high polydispersity of the polymers. Here, phase diagrams of demixing and interfacial tensions are determined for aqueous solutions of two large polymers present in a mass ratio of 1:1, dextran (70 kDa) and nongelling gelatin (100 kDa), with or without further addition of smaller dextran molecules (20 kDa). Both in experiments and in calculations from Scheutjens-Fleer self-consistent field lattice theory, we find that small polymers decrease the interfacial tension at equal tie-line length in the phase diagram. After identifying the partial contributions of all chemical components to the interfacial tension, we conclude that excess water at the interface is partially displaced by small polymer molecules. An interpretation in terms of the Gibbs adsorption equation provides an instructive way to describe effects of polydispersity on the interfacial tension of demixed polymer solutions.

中文翻译：

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相分离的多分散混合聚合物溶液的界面张力。

两相水系统为食品和其他应用中的乳液配方提供了无油替代品。但是，由于聚合物的高多分散性，使得在这种系统上进行测量的理论解释变得复杂。在这里，确定了两种大分子聚合物的水溶液的分离和界面张力的相图，两种聚合物的质量比为1：1，右旋糖酐（70 kDa）和非凝胶明胶（100 kDa），有或没有进一步加入较小的右旋糖酐分子（20 kDa）。在实验和根据Scheutjens-Fleer自洽场晶格理论进行的计算中，我们都发现，小聚合物在相图中相等的连接线长度处降低了界面张力。在确定所有化学成分对界面张力的部分贡献后，我们得出的结论是，界面上的多余水被小的聚合物分子部分取代。关于吉布斯吸附方程的解释提供了一种指导性的方法，可以描述多分散性对混合聚合物溶液界面张力的影响。