Collective sedimentation of colloids in grafted polymer layers

TL;DR

This study uses Monte Carlo simulations to explore how colloids interact with grafted polymer layers under external forces, revealing size-dependent behaviors and the formation of ordered structures that can be controlled for material design.

Contribution

It introduces a detailed simulation analysis of colloid-polymer layer interactions, highlighting collective behaviors and pattern formation influenced by external fields.

Findings

Colloids can penetrate polymer layers under strong external forces.

Ordered, columnar colloidal structures can form within the polymer layer.

Pattern morphology is controllable via external field parameters.

Abstract

We present Monte Carlo simulations of colloidal particles pulled into grafted polymer layers by external fields. The insertion free energy of a single colloid into the polymer layer is qualitatively different for surfaces with an ordered and a disordered distribution of grafting points. Moreover, the tendency of colloidal particles to traverse the grafting layer is strongly size dependent. In dense colloidal suspensions, under the influence of sufficiently strong external force, a collective instability allows the colloids to penetrate and form internally ordered, columnar structures spanning the polymer layer. Depending on the conditions, these colloidal clusters may be isolated or laterally percolating. The morphology of the observed patterns can be controlled by the external fields, which opens up new routes for the design of thin structured films.