Effect of Background Ions on the Morphological and Electrochemical Properties of Polyampholyte Hydrogels

Polyampholyte (PAm) hydrogels are a class of electroneutral physical gels, formed by inter and intra chain ionic cross-linking between counter charged functional groups, present on the polymer chains. Recently, PAm hydrogels have gained intensive attention because of their typical properties including high toughness, self healing and self adjustable adhesion. We have previously shown that PAm hydrogels show potential as gel electrolyte in electrochemical energy storage devices; in addition to its stretchable and self-healing properties, they displayed high ionic conductivity at low temperatures due to inhibited ice formation. When dialyzed in different electrolyte solutions, PAm hydrogels undergo structural changes due to the charge screening effect of foreign ionic species. Electrochemical properties were consequently affected. In this work, we have carried out a systematic study to understand the effect background ionic species- of varying charge, valency and size, on the chain conformation of PAm hydrogels. A combination of mechanical, morphological and electrochemical studies has revealed structure-property relations in the context of energy storage devices that can operate over a wide range of temperatures.