# Very long-range attractive and repulsive forces in Model Colloidal Dispersions

## TL;DR

This paper uses integral equations theory to model colloidal dispersions, revealing very long-range attractive and repulsive forces among macroions, aligning qualitatively with experimental observations and explained via energy-entropy considerations.

## Contribution

It introduces a theoretical approach to explain long-range forces in colloidal dispersions, which are not accounted for by conventional short-range potentials.

## Key findings

- Identification of very long-range forces among macroions
- Qualitative agreement of distribution functions with experiments
- Discussion of forces based on energy-entropy balance

## 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 can not 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.