Self-Organization of Colloidal Particles Driven by Surface Force: Brownian Dynamics Study

Abstract

Soft colloidal crystals are ordered arrays composed of colloidal particles suspended in a solvent at a certain interparticle distance. Practical applications of soft colloidal crystals require the controlled formation with desired periodicity. However, the physical factors determining the order–disorder transitions of colloidal dispersions have not yet been clarified, and accordingly the prediction of the resultant periodicity has been a challenge. In this article, we introduce the findings through our Brownian dynamics simulations of the order formation of electrostatically stabilized colloidal particles. The important conclusions we drew are as follows: (1) A colloidal crystal is found to form only if a controlling factor, the “average force” acting between particles, exceeds a limiting value that is common to various ionic strengths; (2) A general concept extended from the Alder transition is proposed to give a comprehensive understanding of the characteristics of the “average force”, with which the controlling factor and resultant ordered structure can be predicted a priori for any combination of temperature, ionic strength and particle size, as long as the interaction potential between particles is known; (3) The concept is applicable to both 2D and 3D soft colloidal crystals, which indicates the universality of the order formation.

Graphical Abstract