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43g

Swelling and Transport Properties of Epoxy-Amine Gels with Nanoscopic Morphologies

Vijay I. Raman, ISIS - groupe BASF, 8, allée Gaspard Monge, Strasbourg, F-67083, France and Giuseppe R. Palmese, Department of Chemical and Biological Engineering, Drexel University, 3141 Chestnut St., CAT 283, Philadelphia, PA 19104.

In this work epoxy-amine gels were synthesized using reactive encapsulation of a solvent (RES) technique by carrying out step-growth epoxy-amine cross-linking polymerization in a miscible solvent. It was found that gelation could be carried out without macroscopic phase separation using step-growth reactions of epoxy-amine (diglycidyl ether of bisphenol A - EPON 828 and 4,4'-methylenebiscyclohexanamine) in the presence of tetrahyrdofuran (THF) as the solvent. As a result gels with nanoscopically distributed solvent phase were obtained. This was confirmed by the nanoporous structures observed in the SEM analysis after supercritically drying the gels. In this study we experimentally determine the equilibrium swelling behavior and the transport properties (permeability, diffusivity and partition coefficient) of these gels. The objective was to analyze how the solvent content during the synthesis of these gels influenced the swelling and transport properties by influencing the polymer network structure and their morphology. It was found that conventional swelling analysis based on Bray and Merrill's theory could not explain the observed swelling behavior. It was found that a correction factor accounting for polymer network connectivity had to be incorporated. Accordingly, the predictions of Mc after incorporating the correction factor described the experimentally determined glass transition behavior of these networks much more closely. Transport properties of the gels showed that the solvent content directly influenced permeability of the membrane and that this method could be used to improve diffusivity without affecting partition behavior of the gels.