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Unraveling the Complex Hydration Behavior of Ionomers Under Thin Film Confinement



Shudipto K. Dishari, Christopher A. Rumble, Mark Maroncelli, Joseph Dura, Michael A. Hickner


Ionomers in thin films behave differently from bulk membranes and their behavior is not well understood. Here, thin films (25-250 nm) of sulfonated Radel (S-Radel) were investigated to understand thickness and hydration effects on the density and mechanical properties of these sulfonated thin polymer films. The density values obtained from quartz crystal microbalance and spectroscopic ellipsometry showed a thickness trend similar to density values obtained from neutron reflectometry with thin films of 25 nm thickness having lower densities than thicker, 250 nm films. Thicker films were always more dense and less water-rich at the interface compared to thinner samples. A fluorescent rotor probe was incorporated into the polymer samples to infer material stiffness from fluorescence lifetime measurements. The lower density from ellipsometry and neutron reflectometry rationalized greater mobility from fluorescence measurements in the thinner films when dry. When the thin sample was hydrated, the film density and interfacial water volume fraction significantly increased. Also the samples with lower thickness antiplasticized indicating poor water-polymer mobility inside the film. The plasticization properties appeared to be controlled by both film density and water-polymer mobility. The complex hydration behavior of thin ionomer films in the confined state is described in this work.
Journal of Physical Chemistry C


polymer electrolyte, neutron reflectometry, mobility, interface, anitplasticization


Dishari, S. , Rumble, C. , Maroncelli, M. , Dura, J. and Hickner, M. (2018), Unraveling the Complex Hydration Behavior of Ionomers Under Thin Film Confinement, Journal of Physical Chemistry C, [online], (Accessed April 22, 2024)
Created January 15, 2018, Updated October 12, 2021