Self-assembled surfactant-polymer composite membrane for gas separation

The goal of this research has been to examine the feasibility of using self-assembly techniques to fabricate surfactant/polymer composite membranes for gas separation composed of a self-assembled monolayer of Ia as a primary barrier for transport and poly[1-(trimethylsilyl)-propyne] (PTMSP) as support material.*; Preliminary studies of Ia adsorbed on a hydrophobic surface of octadecyltrichlorosilane (OTS)-coated silicon wafer, which was used as a model surface, showed close to monolayer coverage using a saturated solution of Ia in 35/65, 50/50, and 65/35 (v/v) methanol/water. In addition, methanol/water solutions were found to influence swelling and the gas transport properties of the PTMSP membrane (the support), when the percentage of methanol was greater than 50% by volume. Various degrees of swelling could be induced into the PTMSP membrane, based on the ratio of methanol and water that was used. Thus, a careful choice of solvent was needed to reduce this swelling effect, which could significantly impact the gas permeability of the PTMSP support used in our studies. The surface of PTMSP cast films, before and after deposition of Ia, has been characterized by contact angle measurements, and by atomic force microscopy (AFM). Quantitative thin layer chromatography (TLC) was also used to determine the amount of Ia adsorbed on the surface of PTMSP membranes. Finally, the gas transport properties of these self-assembled composite membranes have been determined by measuring the gas permeability of He, N₂, and SF₆ relative to bare PTMSP supports. The fact that these membranes showed gas selectivity that was close to that of bare PTMSP supports, indicates that the membranes contain some defects in the surfactant layer. Post-treatment strategies that were examined for plugging these defects included the use of naphthalene vapors, the use of the alternate layers of poly(styrenesulfonic acid) (PS) and poly(allylamine) (PA), and the use of polyethyleneglycol (PEG)-cholesterol conjugates.*; *Please refer to dissertation for diagram.