In this study, we report the thermodynamics and kinetic parameters for the water absorption by thermo-elastic and self-healing polyacrylamide-commercial graphene (PAM-CG) composite hydrogels. The fundamental studies for such self-healing hydrogels would give us useful insights towards the material design for a specific application. The PAM-CG composite hydrogels were prepared by a two-step method consisting of the synthesis of PAM-CG polymer via inverse emulsion polymerization followed by the preparation of PAM-CG hydrogel by in-situ mixing. The thermal and rheological properties of the composite hydrogels were examined by using thermogravimetric analyzer (TGA), and differential scanning calorimetry (DSC). In addition, the swelling kinetics of the prepared hydrogels were studied as a function of temperature. From the obtained kinetic curves, the hydrogel can absorb water upto 16,000% at 25°C and reaches the saturation in 30 h. Meanwhile, the increase in temperature of the system would result in an overall decrease in the water uptake for the hydrogel. The experimental kinetic data were found to fit in pseudo second-order kinetic model. The calculated free energy (∆G) values are negative and hence the water absorption by the composite hydrogels is spontaneous. The positive enthalpy (∆H) values are indicative of exothermic behavior. The negative entropy (∆S) (i.e. decrease in degree of freedom), values are in line with absorption phenomenon of water molecules by the composite hydrogels. In addition, the PAM-CG hydrogels exhibit excellent recyclability upto eight consecutive cycles.

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