title: Bilayer mass transport model for determining swelling and diffusion in coated, ultrathin membranes.
abstract: Water transport and swelling properties of an ultrathin, selective polyamide layer with a hydrophilic polymer coating, i.e., a polymer bilayer, are studied using quartz crystal microbalance with dissipation (QCM-D). Specifically, QCM-D is used to measure the dynamic and equilibrium change in mass in a series of differential sorption experiments to determine the dependence of the apparent diffusion coefficient and equilibrium swelling of the bilayer as a function of the water vapor activity. To determine transport properties specific to the polyamide layer, sorption kinetics of the bilayer was modeled with a bilayer mass transport model. The swelling and water diffusion coefficients are interpreted according to the Painter-Shenoy polymer network swelling model and the solution-diffusion model, respectively.
authors.affiliation: Materials Science and Engineering Division, National Institute of Standards and Technology , 100 Bureau Drive, MS 8542, Gaithersburg, Maryland 20899, United States.
authors.forename: Nichole K
authors.initials: NK
authors.lastname: Nadermann
authors.forename: Edwin P
authors.initials: EP
authors.lastname: Chan
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Stafford
keywords: bilayer mass transport; desalination; diffusion; polyamide