Scanning Force Microscopy and Wetting Study of the Surface Modification of a Polypropylene Membrane by Means of Langmuir-Blodgett Film Deposition

Studies on the Diffusion of Molecules through Pores in Monolayer and Multilayer Films

“…[4] or [5]. Gas fluxes of N 2 , O 2 , and CO 2 through various numbers of cadmium-modified polyelectrolyte-arachidic acid complex LB monolayers have been reported (8). These data do not behave according to Eq.…”

“…It is expected that the diffusion of the gases with different number of monolayers, n, is yet to be tested. can be collapsed into one common graph provided that k for Experimental results for transport in films with a number of each gas is normalized by its molecular weight; k O 2 /k N 2 Å monolayers show that the flux decreases with n (8,14).…”

“…In this case, following Chen and Yang's (13) analysis, a molecular flux through the pores is There is increasing interest in transport of molecules derived as follows: a molecule may reside on an adsorption through ultrathin multilayer films because of potential applisite at the external surface of the upstream monolayer, actications in molecular electronics devices (1)(2)(3)(4), electrovated and deactivated, then may jump into a vacant adsorpchemical devices (5,6), separation of gas molecules (7,8), tion site, return back to the original site due to blockage by and in delivering drugs to a patient over a controlled period another adsorbate, move on to the next vacant site or jump of time (9). Some of the applications are based on use of downstream through the pore to the next monolayer.…”

“…The structured multilayer films, such as those produced by the net rate of change of activated molecules coverage, du*/ Langmuir-Blodgett (LB) technique (10,11). Langmuirdt, comprising the above processes, is derived, to include Blodgett films can have pore sizes that are of the order of porosity effects on the diffusion through ultrathin films: the molecular size (6,8). LB films exhibit short diffusion times due to the fact that the film thickness is of the molecudu*/dt Å ku 0 2k m u*u v 0 k m u*u p 0 k b u*u, [1] lar scale.…”

“…[4] prevents a negative contribution to the net rate is obtained from Eqs. [7] and [8]. of migration away from the outlet site when a high blockage (l ¢ 1) exists by the occupied site.…”