Characterizing Free Volumes and Layer Structures in Asymmetric Thin-Film Polymeric Membranes in the Wet Condition Using the Variable Monoenergy Slow Positron Beam

Abstract

The free volume sizes and distributions and multilayer structures in asymmetric thin layer polyamide membranes in the wet state have been first time measured using the variable monoenergy slow positron beam (VMSPB). This paper presents a newly developed method which combines the technique of plasma-enhanced chemical vapor deposition to form a barrier layer for high-vacuum condition to seal the composite polyamide and of interfacial polymerization between 2-aminoethanethiol (AETH) and trimesoyl chloride (TMC) on the surface of modified asymmetric polyacrylonitrile (mPAN) membrane (AETH-TMC/mPAN), under the wet condition encountered during the pervaporation process in which they are in direct contact with the liquid environment provided by the feed solution. During the VMSPB experiments under a high vacuum, our new method maintained the thin-film composite (TFC) membrane in the wet conditions typically experienced in VMSPB experiments wherein it directly contacts the liquid feed environment, which is essent...