Tailoring of Clay/Poly(ethylene oxide) Hydrogel Properties by Chitosan Incorporation

This paper aims to investigate the possibility to modify the rheological properties of hydrogels based on Laponite RD/poly(ethylene oxide) by adding small amounts of chitosan to improve their elasticity. The continuous shear measurements of the hydrogels in the presence/absence of chitosan have revealed a pseudoplastic behavior with yield stress. The elastic recovery after the application of a constant shear stress diminishes with increasing chitosan concentration. The addition of chitosan into Laponite RD/poly(ethylene oxide) hydrogel decreases the negative magnitude of the zeta potential, and the isoelectric point at 37 °C was established at 0.037% chitosan. Zeta potential increased from −24.80 mV for Laponite RD/poly(ethylene oxide) hydrogel (in the absence of chitosan) to 7.86 mV for the hydrogel with 0.050% chitosan. The structural properties, investigated by small-angle X-ray scattering measurements of neat Laponite RD hydrogel and Laponite RD/poly(ethylene oxide) hydrogels in the absence/presence of chitosan, have been discussed in correlation with their rheological properties.