Swelling of ultrathin crosslinked polyamide water desalination membranes

Abstract

ABSTRACT:We study the water swelling behavior of semiaromatic crosslinked polyamide (PA) ultrathin films to characterize the network properties of the polymer. Specifically, we use Xray reflectivity to measure film thickness increase and polymer density decrease of the PA films due to swelling. With the aid of a modified Flory-Rehner theory used to describe the constrained swelling behavior of polymer networks, we are able to extract the Flory interaction parameter and the monomer units between crosslinks by performing the swelling experiments at different levels of hydration.

Swelling of Ultrathin Molecular Layer‐by‐Layer Polyamide Water Desalination Membranes

“…Specular XR, a nondestructive technique that can resolve subnanometer thickness and electron density distribution, was used to measure the thickness and density changes of the swollen PA films. It is especially useful for water vapor swelling studies of PA thin films because it allows for repetitive measurements on the same sample …”

“…Recently, we applied X‐ray Reflectivity (XR) to measure the 1‐dimensional swelling of ultrathin semiaromatic PA films when exposed to water vapor . We were able to quantify both network parameters by using FR to predict the change in PA film thickness or density as a function of water activity.…”

Utilizing vapor swelling of surface-initiated polymer brushes to develop quantitative measurements of brush thermodynamics and grafting density

“…This assessment has been previously demonstrated in the vapor swelling of crosslinked polyamide films using XRR [48] and ellipsometry measurements [49]. The comparison between thickness and volumetric swelling allows for a preliminary qualitative determination of the grafting density regime of the brush.…”

Neutron Reflectivity and Performance of Polyamide Nanofilms for Water Desalination

“…Formally, the organic-soluble component (acid chloride) is insoluble into the polymer, whereas the water-soluble component (diamine) diffuses through the film to react with the acid chloride at the film/organic phase interface, where the film grows. [25,30,31] Toward this goal, considerable effort has been dedicated to the structural characterization of the skin layer of commercially available RO membranes, [26,[28][29][30][31][32][33][34][35][36][37] generally carried out under vacuum (away from operating conditions), molecular modeling, [38][39][40][41][42][43] or by developing more controlled synthetic pathways. [27] Despite being widely used on an industrial scale, membranes obtained via IP are generally inhomogeneous in terms of spatial variation, chemistry, and porosity at the micrometer to nanoscales.…”

“…[35][36][37]44,45] Combined with neutron reflectivity (NR) and isotopic contrast variation, we are able to resolve the membrane structure and selectively elucidate its various components, under dry and hydrated states, for various reactant stoichiometries and reaction times. X-ray reflectivity allows a robust quantification of the film thickness and roughness, as well as the scattering length density (SLD) profile with Å resolution.…”