title: Increased water retention in polymer electrolyte membranes at elevated temperatures assisted by capillary condensation.
abstract: We establish a new systematic methodology for controlling the water retention of polymer electrolyte membranes. Block copolymer membranes comprising hydrophilic phases with widths ranging from 2 to 5 nm become wetter as the temperature of the surrounding air is increased at constant relative humidity. The widths of the moist hydrophilic phases were measured by cryogenic electron microscopy experiments performed on humid membranes. Simple calculations suggest that capillary condensation is important at these length scales. The correlation between moisture content and proton conductivity of the membranes is demonstrated.
authors.affiliation: Department of Chemical Engineering, University of California, Berkeley, California 94720, USA.
authors.forename: Moon Jeong
authors.initials: MJ
authors.lastname: Park
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Downing
authors.forename: Andrew
authors.initials: A
authors.lastname: Jackson
authors.forename: Enrique D
authors.initials: ED
authors.lastname: Gomez
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Minor
authors.forename: David
authors.initials: D
authors.lastname: Cookson
authors.forename: Adam Z
authors.initials: AZ
authors.lastname: Weber
authors.forename: Nitash P
authors.initials: NP
authors.lastname: Balsara
mesh_terms: D000388:Air; D002196:Capillaries / Q000378:metabolism*; D004573:Electrolytes; D005583:Fourier Analysis; D006813:Humidity; D008854:Microscopy, Electron; D046529:Microscopy, Electron, Transmission; D015233:Models, Statistical; D008970:Molecular Weight; D036103:Nanotechnology / Q000379:methods*; D011108:Polymers / Q000737:chemistry*; D011522:Protons; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D004573:Electrolytes; D011108:Polymers; D011522:Protons; D014867:Water