A sheet of glassy polymers placed in solvent shows a swelling behavior quite different from that of soft polymers (rubbers and gels). In the classical work of Thomas and Windle, they reported the following characteristics in the swelling of PMMA in methanol. (1) Non-Fickian diffusion (called case II diffusion): the thickness of the sample increases in time in proportion to the time   instead of following the Fickian diffusion law. (2) Anomalous swelling: The thickness first increases, while the area remains constant. After some time, thickness starts to decrease in time, while the area starts to increase, towards the equilibrium value. Such behaviors have been observed for other polymers, e.g., PVC with acetone, PS with alkane, and samples with other geometry. Moreover, case II diffusion appears in other systems, like the permeation of ions into conjugated polymers and so on. We propose a three-dimensional theory for the swelling of glassy polymers. We show that this simple model explains all anomalies observed in the swelling of glassy polymers. The theory also predicts how the permeation speed of solvent and the characteristic times depend on material parameters and experimental conditions. It provides effective ways to control the swelling of glassy polymers.

报告人简介

David Andelman completed his PhD studies in Physics at MIT in 1984. Between 1984-1987 he was a Joliot-Curie post-doc fellow at College de France (in the group of P.G. de Gennes) and at Exxon Research and Engineering (New Jersey). Since 1987 he has been on the faculty of the School of Physics of Tel Aviv University. His interest lies in modeling soft and biological matter within the tools of statistical physics. In recent years, he worked on charged soft matter including polyelectrolytes, ionic liquids and solutions, and charged membranes, exploring their equilibrium and electrokinetic properties.

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欧阳钟灿 研究员