ASSEMBLY AND DISASSEMBLY OF LANGMUIR-BLODGETT-FILMS ON POLY[1-(TRIMETHYLSILYL)-1-PROPYNE] - THE UNIQUENESS OF CALIX[6]ARENE MULTILAYERS AS PERMEATION-SELECTIVE MEMBRANES

series of calix[6]arene-based surfactants have been synthesized, which contain amide oxime head groups on their upper rim and 5,5-dimethylhe xyl (I), n-octyl (II), n-dodecyl (III), and n-hexadecyl (IV) groups on their lower rim. Composite membranes that were fabricated from Langmu ir-Blodgett (LB) multilayers derived from each surfactant plus poly[1- (trimethylsilyl)-1-propyne] (PTMSP) cast film showed a significant inc rease in their selectivity toward helium and nitrogen, relative to bar e PTMSP. In sharp contrast, analogous composites that were prepared wi th LB multilayers of conventional single chain surfactants [arachidic acid (AA), cadmium arachidate (AA/Cd2+), and stearoamideoxime (SA)] ex hibited permeation properties that were identical with those of bare P TMSP. When a polymeric surfactant [poly(1-octadecene-co-maleic anhydri de), POM] was used fdr LB film construction, a modest increase in sele ctivity was observed. These findings, together with an analysis of rep resentative composites by X-ray photoelectron spectroscopy, provide co mpelling evidence for the presence of intact, calix[6]arene-based LB a ssemblies on the surface of PTMSP; with the conventional single chain surfactants, however, disassembly and absorption into the bulk phase o f the support is favored. The results of this study highlight the need for having individual surfactant molecules span individual pores on t he surface of the support and strong intermolecular forces between nei ghboring surfactants to produce relatively defect-free LB films.