Eur. Phys. J. Special Topics 227, 2375–2390 (2019)
https://doi.org/10.1140/epjst/e2018-800089-0

Regular Article

Very long-range attractive and repulsive forces in model colloidal dispersions

¹ Instituto de Energías Renovables, Universidad Nacional Autónoma de México (U.N.A.M.), 62580 Temixco, Mor., Mexico
² Instituto de Física, Universidad Autónoma de San Luis Potosí, Álvaro Obregón 64, 78000 San Luis Potosí, S.L.P., Mexico

^b e-mail: marcelolcmx@ier.unam.mx

Received: 5 May 2018
Received in final form: 16 July 2018
Published online: 28 January 2019

Abstract

Experiments with polymer latex solutions show the coexistence of order-disorder structures of macroions. Because of the large macroions’ sizes, this order–disorder phase coexistence imply the existence of very long-range attractive and repulsive forces, which cannot be explained in terms of conventional direct interaction potentials, which are short-range. Here, we apply an integral equations theory to a simple model for colloidal dispersions, at finite concentrations, calculate the particles distribution functions and the involved effective forces. We find very long-range attractive and repulsive forces among the like-charged macroions. The distribution functions are in qualitative agreement with experimental results. The origin of these forces are discussed in terms of an energy–entropy balance.