SWELLING BEHAVIOR OF THE FILLING-TYPE MEMBRANE

A model that can express the swelling of the filling-type membrane was developed by modifying a model that was developed for a crystalline p olymer. The filling-type membrane is composed of two different polymer s. One is porous substrate and another is a polymer that filled pores of the substrate. The filling technique can effectively suppress polym er swelling due to the substrate matrix. The model needs two parameter s: one is a unit ratio of tie segments in the substrate to the filling polymer, f, which can express a mechanical strength of the substrate, and another is the Flory interaction parameter, chi, between the fill ing polymer and a solvent that expresses a mixing energy. A porous hig h-density polyethylene him was used as a porous substrate, and plasma- graft filling polymerization technique could make the filling-type mem brane. Methylacrylate was used as a grafting monomer that filled the p ores of substrate. A swelling behavior of the filling-type membrane an d pure poly(methylacrylate) were measured by the vapor sorption method at different solvent activities. The model was in good agreement with experimental results for the filling-type membrane. Using the model, swelling of the filling-type polymer was compared with a crosslinked p olymer, which can be expressed by Flory and Rehner model. The comparis on showed that the filling technique is a good way to suppress polymer swelling, and a high crosslinking density is needed to obtain the sam e level of swelling suppression effect the filling type membrane showe d. (C) 1997 John Wiley & Sons, Inc.