Humidity-Induced Phase Transitions in Ion-Containing Block Copolymer Membranes

The phase behavior of ion-containing block copolymer membranes in equilibrium with humidified air is studied as a function of the relative humidity (RH) of the surrounding air, ion content of the copolymer, and temperature. Increasing RH at constant temperature results in both disorder-to-order and...

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Bibliographic Details
Published in:Macromolecules 2008-03, Vol.41 (6), p.2271-2277
Main Authors: Park, Moon Jeong, Nedoma, Alisyn J, Geissler, Phillip L, Balsara, Nitash P, Jackson, Andrew, Cookson, David
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Exchange resins and membranes
Forms of application and semi-finished materials
Polymer industry, paints, wood
Technology of polymers
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Summary:The phase behavior of ion-containing block copolymer membranes in equilibrium with humidified air is studied as a function of the relative humidity (RH) of the surrounding air, ion content of the copolymer, and temperature. Increasing RH at constant temperature results in both disorder-to-order and order-to-order transitions. In-situ small-angle neutron scattering experiments on the open block copolymer system, when combined with water uptake measurement, indicate that the disorder-to-order transition is driven by an increase in the partial molar entropy of the water molecules in the ordered phase relative to that in the disordered phase. This is in contrast to most systems wherein increasing entropy results in stabilization of the disordered phase.
ISSN:0024-9297
1520-5835
DOI:10.1021/ma702320t