# Self-assembly in a model colloidal mixture of dimers and spherical particles

## TL;DR

This study uses Monte Carlo simulations to explore how mixtures of amphiphilic dimers and spherical particles self-assemble into various structures, revealing how cluster size and shape depend on guest concentration and temperature.

## Contribution

It provides new insights into the self-assembly behavior of dimer-sphere mixtures, highlighting the dependence of cluster morphology on concentration and temperature, and identifying conditions for lamellae formation.

## Key findings

- Clusters grow and become elongated with increasing guest concentration.
- At 50% guest concentration, the system forms metastable lamellae.
- Clusters shrink and become homogeneous upon heating.

## Abstract

We investigate the structure of a dilute mixture of amphiphilic dimers and spherical particles, a model relevant to the problem of encapsulating globular "guest" molecules in a dispersion. Dimers and spheres are taken to be hard particles, with an additional attraction between spheres and the smaller monomers in a dimer. Using Monte Carlo simulation, we document the low-temperature formation of aggregates of guests (clusters) held together by dimers, whose typical size and shape depend on the guest concentration $\chi$. For low $\chi$ (less than $10\%$), most guests are isolated and coated with a layer of dimers. As $\chi$ progressively increases, clusters grow in size becoming more and more elongated and polydisperse; after reaching a shallow maximum for $\chi\approx 50\%$, the size of clusters again reduces upon increasing $\chi$ further. In one case only ($\chi=50\%$ and moderately low temperature) the mixture relaxed to a fluid of lamellae, suggesting that in this case clusters are metastable with respect to crystal-vapor separation. On heating, clusters shrink until eventually the system becomes homogeneous on all scales. On the other hand, as the mixture is made denser and denser at low temperature, clusters get increasingly larger until a percolating network is formed.