Alladi Ramakrishnan Hall

Theory of soft matter systems: Surprises in electrostatic interaction

Arghya Majee

Max Planck Institute for Intelligent Systems, Stuttgart, Germany

In this talk, we will discuss novel aspects of the electrostatic interactions between charged colloidal particles in bulk or at fluid interfaces. In the first part, interaction between chemically identical charge-regulated surfaces in bulk electrolyte solution will be considered. It is shown that, contrary to common assumptions, such surfaces are not necessarily equally charged and the resulting interaction can be attractive instead of repulsive [1, 2]. As a second example, interaction between particles trapped at fluid interfaces will be discussed. Both chemically identical and non-identical particles are considered but unlike the previous part, their surfaces carry fixed charges or potentials [3 – 7]. Effects of several factors like particle size, wetting properties, inter-particle separation, solvation properties of the fluids are also considered. Of particular interest is the observation of attractive pairinteraction under certain circumstances within the framework of nonlinear PoissonBoltzmann (PB) theory [4], which cannot be captured by using the linearized PB theory [3]. The addressed problems illustrate the power of classical density functional theory in the investigation of soft matter systems. And finally, possible future directions will also be discussed.
[1] A. Majee, M. Bier, and R. Podgornik, Soft Matter 14, 985 (2018).
[2] A. Majee, M. Bier, R. Blossey, and R. Podgornik, Phys. Rev. E 100, 050601(R) (2019).
[3] A. Majee, M. Bier, and S. Dietrich, J. Chem. Phys. 140, 164906 (2014).
[4] A. Majee, M. Bier, and S. Dietrich, J. Chem. Phys. 145, 064707 (2016).
[5] A. Majee, T. Schmetzer, and M. Bier, Phys. Rev. E 97, 042611 (2018).
[6] A. Majee, M. Bier, and S. Dietrich, Soft Matter 14, 9436 (2018).
[7] R. Bebon and A. Majee (submitted).