Self-assembly of colloidal polymers via depletion-mediated lock and key binding

TL;DR

This study investigates how indented colloids self-assemble into polymers through depletion forces, revealing shape-dependent chain structures and improving theoretical models to match simulation results.

Contribution

It introduces a simulation approach for depletion-driven colloidal assembly and develops a modified theory that better captures shape effects and packing.

Findings

Colloids assemble via a lock-and-key mechanism leading to polymerization.

Chain morphology depends on indentation size, with smaller indentations allowing branching.

Modified theory improves agreement with simulation over Wertheim's original approach.

Abstract

We study the depletion-induced self-assembly of indented colloids. Using state-of-the-art Monte Carlo simulation techniques that treat the depletant particles explicitly, we demonstrate that colloids assemble by a lock-and-key mechanism, leading to colloidal polymerization. The morphology of the chains that are formed depends sensitively on the size of the colloidal indentation, with smaller values additionally permitting chain branching. In contrast to the case of spheres with attractive patches, Wertheim's thermodynamic perturbation theory fails to provide a fully quantitative description of the polymerization transition. We trace this failure to a neglect of packing effects and we introduce a modified theory that accounts better for the shape of the colloids, yielding improved agreement with simulation.