Aggregation kinetics of irreversible patches coupled with reversible isotropic interaction leading to chains, bundles and globules

TL;DR

This study uses simulations to explore how irreversible patchy and reversible isotropic interactions influence the self-assembly of colloidal particles into chains, bundles, and globules, revealing effects of patch size and solvent quality.

Contribution

It introduces a combined model of irreversible patchy and reversible isotropic interactions, analyzing their impact on colloidal self-assembly and bundle formation.

Findings

Smaller patches favor chain formation at low volume fractions.

Bundle formation resembles nucleation and growth phenomena.

Bond angle distributions vary with patch size and aggregation state.

Abstract

In the present study we are performing simulation of simple model of two patch colloidal particles undergoing irreversible diffusion limited cluster aggregation using patchy Brownian cluster dynamics. In addition to the irreversible aggregation of patches, the spheres are coupled with isotropic reversible aggregation through the Kern-Frenkel potential. Due to the presence of anisotropic and isotropic potential we have also defined 3 different kinds of clusters formed due to anisotropic potential and isotropic potential only as well as both the potentials together. We have investigated the effect of patch size on self-assembly under different solvent qualities for various volume fractions. We will show that at low volume fractions during aggregation process, we end up in a chain conformation for smaller patch size while in a globular conformation for bigger patch size. We also observed a chain to bundle transformation depending on the attractive interaction strength between the chains or in other words depending on the quality of the solvent. We will also show that bundling process is very similar to nucleation and growth phenomena observed in colloidal system with short range attraction. We have also studied the bond angle distribution for this system, where for small patches only 2 angles are more probable indicating chain formation, while for bundling at very low volume fraction a tail is developed in the distribution. While for the case of higher patch angle this distribution is broad compared to the case of low patch angles showing we have a more globular conformation. We are also proposing a model for the formation of bundles which are similar to amyloid fibers using two patch colloidal particles.