Morphological Investigations of Anion-Conducting Polymer-Catalyst Interface*

The heterogeneous microstructure of the electrode in polymer electrolyte-based electrochemical devices is not well understood. This is due in part to complex interactions between the ion-conducting polymer (ionomer), catalyst particles, and carbon. It is known that interactions at the polymer-catalyst interface induce restructuring that propagates through the bulk morphology of the material [1]. This is potentially to the detriment of species transport in the electrode, ultimately affecting device performance.
To simplify the system, model interfaces of polymer thin films on silver surfaces are studied. A set of tunable block copolymers, post-quaternized to produce anion-conducting polymers, are used to investigate how different parameters influence interfacial morphology. Their synthesis has been optimized to achieve a variety of block lengths and ratios, each with a unique set of characteristics (ionic conductivity, water uptake) and morphologies. Films have been investigated using GISAXS and AFM. An understanding of the ionomer morphology at the ionomer-catalyst interface will provide key insight toward rationally designing block copolymers for the electrode.
[1] D.K. Paul et al, Macromolecules, 2013, 46 (9), 3461-3475.