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

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.