Self-assembly of "Mickey Mouse" shaped colloids into tube-like structures: experiments and simulations

TL;DR

This study investigates how uniquely shaped 'Mickey Mouse' colloids self-assemble into tube-like structures through experiments and simulations, revealing the influence of particle geometry and attraction strength on the resulting structures.

Contribution

It introduces a novel 'Mickey Mouse' shaped colloid design and demonstrates their ability to form one-dimensional tubes, expanding understanding of anisotropic particle self-assembly.

Findings

Tube-like structures form at strong attractions.

Internal structures can be straight or twisted.

Growth is limited to one dimension by steric constraints.

Abstract

The self-assembly of anisotropic patchy particles with triangular shape was studied by experiments and computer simulations. The colloidal particles were synthesized in a two-step seeded emulsion polymerization process, and consist of a central smooth lobe connected to two rough lobes at an angle of $\sim$90$^{\circ}$, resembling the shape of a "Mickey Mouse" head. Due to the difference in overlap volume, adding an appropriate depletant induces an attractive interaction between the smooth lobes of the colloids only, while the two rough lobes act as steric constraints. The essentially planar geometry of the "Mickey Mouse" particles is a first geometric deviation of dumbbell shaped patchy particles. This new geometry is expected to form one-dimensional tube-like structures rather than spherical, essentially zero-dimensional micelles. At sufficiently strong attractions, we indeed find tube-like structures with the sticky lobes at the core and the non-sticky lobes pointing out as steric constraints that limit the growth to one direction, providing the tubes with a well-defined diameter but variable length both in experiments and simulations. In the simulations, we found that the internal structure of the tubular fragments could either be straight or twisted into so-called Bernal spirals.