Challenges in forming successful mixed matrix membranes with rigid polymeric materials

Mixed matrix materials comprised of molecular sieve domains embedded in processable polymer matrices have the potential to provide membranes with higher permselectivity and equivalent productivity compared to existing membrane materials. It has been shown that successful mixed matrix materials can be formed using relatively low glass transition (T-g) polymers that have a favorable interaction with the sieves. This article extends this earlier work to include the use of more practical rigid matrix polymers with high T(g)s that can ultimately be used in forming high-performance mixed matrix layers for composite membranes. Initial attempts to form mixed matrix materials based on high T-g polymers with a type 4A zeolite resulted in poor adhesion between the polymer and sieve. Correcting composite material close to the T-g of the polymer by addition of a plasticizer to match the matrix T-g with the solvent volatility. Forming the films at elevated temperatures presented substantial challenges, and this work discusses overcoming these challenges in detail. With some modifications in the film casting procedure, successful materials were achieved. Promising oxygen/nitrogen transport results are presented for these zeolite 4A-Matrimid(R)/plasticizer membranes, and this data compares favorably with predictions of the well-known Maxwell model for composite systems. (C) 2002 Wiley Periodicals, Inc.