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Underscreening Stable colloidal systems at very high electrolyte concentrations
In colloidal systems the range and strength of electrostatic interactions has a profound effect on a range of properties including the stability of colloidal dispersions and the phase behaviour of surfactant and polymer systems. The Debye length has proven to be a very effective measure of the range of electrostatic interactions as confirmed by direct force measurements at low to moderate salt concentrations over many years . However, recent force measurements on ionic liquid systems has revealed that at high electrolyte concentration the electrostatic interactions are much longer ranged than the Debye length[1-5]. This has implications for all colloidal systems at high electrolyte concentrations.
In this talk I will describe a series of experiments probing the impact of underscreening on colloidal systems and discuss the current state of understanding of the origin of underscreening.
References
[1] M.A. Gebbie, M. Valtiner, X. Banquy, E.T. Fox, W.A. Henderson, J.N. Israelachvili, Ionic liquids behave as dilute electrolyte solutions, Proc. Nat. Acad. Sci. 110(24) (2013) 9674-9679.
[2] A.M. Smith, A.A. Lee, S. Perkin, The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration, J. Phys. Chem. Lett. 7(12) (2016) 2157-2163.
[3] M.A. Gebbie, A.M. Smith, H.A. Dobbs, A.A. Lee, G.G. Warr, X. Banquy, M. Valtiner, M.W. Rutland, J.N. Israelachvili, S. Perkin, R. Atkin, Long range electrostatic forces in ionic liquids, Chem. Commun. 53(7) (2017) 1214-1224.
[4] A.A. Lee, C.S. Perez-Martinez, A.M. Smith, S. Perkin, Scaling Analysis of the Screening Length in Concentrated Electrolytes, Phys. Rev. Lett. 119 (2017) 026002.
[5] A.A. Lee, C.S. Perez-Martinez, A.M. Smith, S. Perkin, Underscreening in concentrated electrolytes, Faraday Discuss. 199 (2017) 239-259.