(409e) Self-Assembly of Magnetic Janus Colloids Via Brownian Dynamics Simulation

Authors: 
Córdova-Figueroa, U. M., University of Puerto Rico at Mayagüez
Kretzschmar, I., City College of New York
DeLaCruz-Araujo, R. A., University of Puerto Rico - Mayagüez
Vega-Bellido, G., University of Puerto Rico - Mayagüez
Magnetic colloids are of great interest for materials design due to the ease of controlling their structure after tuning their magnetic interactions. Previous studies of anisotropic magnetic particles have focused on discovering their ground state configurations for a few magnetic interaction strengths, however, they have not delved into the dynamics behind their aggregation. Understanding the evolution of these systems is useful for predicting their behavior when employed in realistic conditions. In this contribution, the self-assembly of colloidal magnetic Janus particles with a laterally displaced (or shifted), permanent dipole in a quasi-two-dimensional system is studied using Brownian dynamics simulations. Herein, the rate of formation of clusters and their structures are quantified for all values of dipolar shift from the particle center, which is made non-dimensionalized using the particle’s radius so that it takes values ranging from 0 to 1, and examined under different magnetic interaction strengths relative to Brownian motion. For dipolar shifts of less than 0.1 (shifts close to particle center), chain-like structures are formed which grow at long times following a power law, while particles of shift higher than 0.2 generally aggregate in ring-like clusters and as such clusters experience limited growth. In the case of shifts between 0.4 and 0.5, the particles tend to aggregate in clusters of 3 to 6, while for all shifts higher than 0.6 clusters scarcely contain more than 3 particles due to the antiparallel dipole orientations which are most stable at those shifts. The strength of the magnetic interactions hastens the rate at which clusters are formed, however the effect it has on cluster size is lessened by increases in the shift of the dipoles. These results contribute to better understand the dynamics of magnetic Janus particles and can help the synthesis of functionalized materials for specific applications like drug delivery.