Transport properties of water and pentane in Langmuir–Blodgett films

Abstract

The transport of water and pentane vapor in Langmuir-Blodgett (LB)

The Directional Dependence of Water Penetration into Langmuir–Blodgett Multilayers

“…Marshbanks et al (9) used infrared spectroscopy (FTIR) to study diffusion of water into films immersed in a water bath. All of these studies confirm that transport of water through these well-ordered, densely packed films is slow, with apparent diffusion coefficients ranging from 10 Ϫ9 cm 2 /s (7) to as low as 5 ϫ 10 Ϫ13 cm 2 /s, (9) with typical values hovering about 10 Ϫ12 cm 2 /s (6,8).…”

“…Fortunately, the integral nature of LB films can be exploited to identify these individual contributions (8). In particular, data is collected from a series of films differing only by their number of constituent layers.…”

“…In this way, Ariga et al (6) and later Lovell et al (7) measured the evaporation rate of water entrained during deposition. Hanley et al (8) used this technique to study water vapor sorption as a function of vapor pressure. Spectroscopic measurements offer another route to study water uptake.…”

“…Upon drying these films, the residual water content drops to about 1.2 wt%. Using the QCM, Hanley et al (8) showed that behenic acid/salt films pick up about 1.5 wt% water as the vapor pressure is increased from zero to near saturation.…”

The effect of chain density on the frictional behavior of surfaces modified with alkylsiloxanes and immersed in n-alcohols

“…The value for n-nonanol is in good agreement with the value of 1ϫ10 Ϫ12 cm 2 /s that Vanderlick and co-workers reported for diffusion of pentane normal to the alkyl chains in Langmuir-Blodgett films of arachidic acid based on uptake measurements with a QCM. 52 For a well-ordered film, the coefficient for lateral diffusion of the solvent is likely significantly smaller than the coefficient for diffusion normal to the alkyl chains. Consequently, we expect that for SAMs of OTS either the solvent is not excluded significantly from the compressed region under the tip or that solvent may ''channel'' through the SAM via a network of defects.…”