(376bc) On the Phase Behavior of Water like Fluid Models in Slit-like Pores with Walls Covered By Molecular Brushes

The phase behavior, density profiles, and adsorption isotherms of a water like fluid models in slit-like pore with walls modified by pre-adsorbed tethered chain molecules have been studied in the framework of a density functional theory. The model for water taken from the work of Clark et al.[1] reproduces successfully the bulk equation of state. The mean field theory and the first-order mean spherical approximation have been applied to account for the attractive interactions. The chemical association effects are taken into account by using the first-order thermodynamic perturbation theory of Wertheim. The influence of the slit-like pore width, the gas-solid interaction energy, and of the square well width on the phase behavior have been explored in detail. We have shown that the value of the parameters of the model has important consequences for the adsorption and phase behavior of confined water. Capillary condensation, evaporation, and in some cases layering phase transition have been obtained as well. A comparison with computer simulation data has been performed. We have found that the presence of molecular brushes on the pore walls has important consequences for the adsorption and phase behavior of confined water. If the brush segments do not attract water molecules strongly, the vapor-liquid coexistence envelope shrinks upon increasing brush density, but the critical temperature is weakly affected. Alteration from capillary condensation to evaporation is observed with changes in the brush density, number of segments of tethered chains, and/or chemical identity of segments. Finally, the theory and the results presented here can be considered as a first step toward the description of hairy colloidal particles of different shapes (e.g., sheets of small thickness, like graphene sheets, in particular) immersed in water [2-6].

References

[1] G. N. Clark, A. J. Haslam, A. Galindo, and G. Jackson, Mol. Phys. 104, 3561 (2006).

[2] V. M. Trejos, O. Pizio, S. Sokołowski, Fluid Phase Equil. 473, 145 (2018).

[3] V. M. Trejos, J. Quintana-H, J. Chem. Phys. 148, 074703 (2018).

[4] V. M. Trejos, O. Pizio, and S. Sokołowski, J. Chem. Phys. 149, 134701 (2018).

[5] V. M. Trejos, O. Pizio, and S. Sokołowski, J. Chem. Phys. 149, 234703 (2018).

[6] V.M. Trejos, O. Pizio, S. Sokolowski. Fluid Phase Equil. 483, 92 (2019).