Rheology of Poly(N-isopropylacrylamide)-Clay Nanocomposite Hydrogels
D Xu and D Bhatnagar and D Gersappe and JC Sokolov and MH Rafailovich and J Lombardi, MACROMOLECULES, 48, 840-846 (2015).
We used molecular dynamics simulations and experiments to study the rheology of polymerclay nanocomposite hydrogels. The molecular dynamics simulations studied the formation of physical cross-linked networks as a function of the clay concentration. Simulations showed that while the local structure changed from isolated polymerclay clusters to a percolating network with increasing clay concentration the networks were only able to sustain stress at concentrations of roughly 1.5 times the percolation transition. Experiments using poly(N-isopropylacrylamide) (PNIPA)clay nanocomposites at different clay concentrations were compared with simulation results. Experiments showed a transition from viscous to gel like behavior at a clay concentration of 15.24g/L, in good agreement with simulations. The modulus, G' and G '', prior to yield was observed to increase exponentially with clay concentration and G' at yield could be fitted to the modified Mooneys equation.
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