The phase behavior of nanocolloids in solution is determined by an interplay of their van der Waals and electrostatic interactions on one side and mean solvation forces on the other side. Colloids charges are screened by a solvent dielectric constant and Debye screening by counterions in solution. This picture is captured in the Deryagin-Landau-Verwey-Overbeek (DLVO) effective potential empirically constructed as a van der Waals attractive well and a Yukawa screened repulsive potential of the electric double layer. DLVO has been widely used to explain dispersion and flocculation of colloids in aqueous solution. However, the picture gets complicated for non-aqueous solvents and solvent mixtures with such additives as polymers to control flocculation. Understanding and design of these systems requires solvation theory beyond DLVO empirical level. A molecular description is provided by the three-dimensional reference interaction site model with the Kovalenko-Hirata closure relation (3D-RISM-KH molecular theory of solvation)1-3 which properly accounts in a single formalism for both electrostatic and non-polar effects and readily reproduces structural and phase transitions in molecular liquids and solutions. The method produces 3D maps of solvation structure and free energy, and potentials of mean force (PMFs) in solution orders of magnitude faster than molecular simulations.3 In particular, 3D-RISM-KH describes effective forces between cellulose nanocrystals (CNC) forming suspensions in aqueous NaCl at concentration 0.0–0.25 mol/kg.4,5 The CNC electric interfacial layer thickness dependence on electrolyte concentration plays an important role in the mechanisms of phase transitions and chiral ordering in CNC suspensions.4,5 As another example, 3D-RISM-KH yields potentials of mean force of kaolinite nanoplatelets in non-aqueous solvents,6,7 as well as in aqueous electrolyte solution with polymer flocculants. This opens up a possibility of high throughput screening of polymer additives as flocculants and dispersants. Furthermore, it provides means to derive coarse-grained force fields for suspensions of mineral and organic nanoparticles.8 (1) Molecular Theory of Solvation. Hirata, F. (ed.) Kluwer, Dordrecht, 2003. (2) J. Chem. Phys. 1999, 110, 10095. (3) Pure Appl. Chem. 2013, 85, 159. (4) Nordic Pulp Paper Res. J. 2014, 29, 144. (5) Langmuir 2015, 31, 7106. (6) J. Phys. Chem. C 2014, 118, 23821. (7) J. Phys. Chem. C 2013, 117, 18556. (8) Phys. Chem. B 2014, 118, 12034.

Beyond DLVO: Solvation structure and effective interactions of nanocolloids in solutions from 3D-RISM-KH molecular theory of solvation

251st National Meeting (2016)

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