253e Langmuir-Blodgett Films with Fluorinated Surfactants Bilayers on Polymer Supports as Membrane for Gas Separations

Donald H. McCullough III1, Ruslan Grygorash2, Bingwen Jing2, James T. Hsu1, and Steven L. Regen2. (1) Chemical Engineering, Lehigh University, 6 East Packer Ave, Bethlehem, PA 18015, (2) Chemistry, Lehigh University, 6 East Packer Ave, Bethlehem, PA 18015

We have recently introduced the concept of “glued” Langmuir-Blodgett (LB) films, in which polyelectrolytes are used to ionically cross-link multiply charged surfactants. For this study, a series of multiply-charged surfactants with perfluorinated alkyl chains have been synthesized. The surface pressure-area isotherms and their relative surface viscosities were measured over a pure water subphase and over aqueous subphases containing either poly(styrene sulfonate) (5.0 mM of repeat unit; Mw = 70 000) or poly(acrylic acid) (5mM repeat units, Mw 240 000, pH = 4.2, 7.0, or 10.2). Transfer of these glued bilayers was carried out onto silylated silicone substrates (silylation was performed using n-octadecyltrichlorosilane). The transfer ratios of the various bilayers were compared. The bilayers were then characterized using ellipsometry and contact angle surface methods. The resulting bilayers were then exposed to a 2.5:1 chloroform trifluoroethanol (TFE) mixture to test their stability. Transfer of glued bilayers onto poly[1-(trimethylsilyl)-1-propyne] (PTMSP) was also carried out to measure the gas permeation properties with respect to He, N2, and CO2 and trichloroethylene (TCE). The properties of these fluorinated surfactants/bilayers were then compared to an analogous nonfluorinated surfactant. For comparison, singly-charged surfactants, a fluorinated and a non-fluorinated, were synthesized and tested.