The transport of water and pentane vapor in Langmuir-Blodgett (LB) fil
ms of arachidic acid is investigated A quartz cr),stal microbalance is
used to monitor the mass increases of the films upon exposure to the
vapor as a function of the pressure. By examining films of different t
hicknesses, it is shown that it is possible to measure both surface ad
sorption and solubility. Diffusivity is calculated from the rate of up
take. Water and pentane have Fickian diffusion coefficients of 4 x 10(
-12) cm(2) . s(-1) and 1 x 10(-12)cm(2) . s(-1), respectively. The eff
ect of both aging and annealing of the LB films on the vapor uptake is
studied and it is shown that the uptake is sensitive to the state of
the film.