Membrane-based separations are attractive because of their simplicity, low energy costs, and ability to operate in remote locations. Full utilization of the advantages of membrane technology, however, will require new membranes with increased permeabilities and selectivities. Unfortunately, flux through membranes is generally inversely related to selectivity. The development of ultrathin membranes will allow high flux, but synthesis of such structures with sufficient selectivity, strength, and quality is an ongoing challenge. This proposal addresses the challenge of developing and understanding selective and ultrathin (< 50 nm) gas-separation membranes through the use of hyperbranched poly acrylic acid (PAA) films grafted onto porous supports. PAA films will provide an ultrathin and selective layer while the highly permeable substrate is required for mechanical stability. Hyberbranced PAA films will be unique membrane materials because their branched structure will allow full coverage of substrate pores, their layer-by-layer synthesis will yield films whose thickness can be varied from 3-100 nm, and the high density of carboxylic acid groups in the film will permit a wide range of chemical modifications even after membrane formation
