Abstract
Polymer-based ion exchange membranes (IEMs) are utilized for many applications such as in water desalination, energy storage, fuel cells and in electrophoretic drug delivery devices, exemplified by the organic electronic ion pump (OEIP). The bulk of current research is primarily focused on finding highly conductive and stable IEM materials. Even though great progress has been made, a lack of fundamental understanding of how specific polymer properties affect ionic transport capabilities still remains. This leads to uncertainty in how to proceed with synthetic approaches for designing better IEM materials. In this study, an investigation of the structure-property relationship between polymer size and ionic conductivity was performed by comparing a series of membranes, based on ionically charged hyperbranched polyglycerol of different polymer sizes. Observing an increase in ionic conductivity associated with increasing polymer size and greater electrolyte exclusion, indicating an ionic transportation phenomenon not exclusively based on membrane electrolyte uptake. These findings further our understanding of ion transport phenomena in semi-permeable membranes and indicate a strong starting point for future design and synthesis of IEM polymers to achieve broader capabilities for a variety of ion transport-based applications.
Highlights
Ion exchange membranes (IEMs) are a key component in a wide variety of technologies due to their ability to selectively conduct ionic species of a given electrical polarity [1]
Methylene blue transportation Using an organic electronic ion pump (OEIP) filled with A (80)-hyperbranched polyglycerols (HPGs) 10 kDa, methylene blue transportation was characterized by filling the source reservoir with 10 mM methylene blue (Fig. 3) and the target reservoir with 10 mM KCl solution and applying a constant 3 V potential between the source and target
Molecular weights for variously sized HPGs were measured using 1H NMR polymer molecular weight analysis [36]
Summary
Ion exchange membranes (IEMs) are a key component in a wide variety of technologies due to their ability to selectively conduct ionic species of a given electrical polarity [1]. HPGs were multi-functionalized into hyperbranched poly electrolytes with controlled amounts of charged groups and available cross-linking groups, enabling the fabrication of free-standing AEMs and CEMs. Our essential conclusion is that larger polyelectrolytes provide an increased ionic conductivity and fixed charge concentration without compromising selectivity or increasing swelling/hydration. Our essential conclusion is that larger polyelectrolytes provide an increased ionic conductivity and fixed charge concentration without compromising selectivity or increasing swelling/hydration These find ings hope to further the understanding of ion-exchange phenomena and provide a templet for synthetic design of new generations of poly electrolytes. We demonstrate these hyperbranched polyelectrolyte-based membranes as having large molecular ionic transportation capabilities, an important aspect in the field of organic bioelectronics
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