Equilibrium swelling, conductivity and electroactive characteristics of polyacrylamide hydrogels

Polyelectrolyte hydrogels are currently being studied extensively towards the realization of soft actuators. The conductivity, swelling behaviour and electroactive characteristics of partially hydrolysed polyacrylamide hydrogels, crosslinked to various extents are investigated. Conductivity studies have been made by means of dielectric relaxation spectroscopy both for hydrogels and dry gel powders over a wide range of frequency. The water dependent a.c. conductivity has been found to attain a plateau at higher frequencies whereas the a.c. conductivity of gel powders continued to increase as the frequency increases. The magnitude of the conductivity values is dependent on the extent of swelling for the hydrogels whereas it is dependent on the network structure for the gel powders. The electrical responses of hydrolysed polyacrylamide gels are also investigated and its correlation with hydration properties is also made. The on-off stimulation has been monitored by measuring the angular displacement of the hydrogels. A systematic analysis of the obtained results indicates that the electrical response and the water dependent conductivities of the gels have a direct correlation with the hydration properties.