Molecular Insights into the Self-Assembly of Janus Nanoparticles Obtained from Coarse-Grained Molecular Dynamics Simulations

Grafting polymeric chains onto surfaces of nanoparticles generates amphiphilic Janus nanoparticles (JNPs) that can self-assemble into a variety of well-ordered and/or functional nanostructures. The self-assembly structures of JNPs can be designed by the manipulation of grafting schemes, but only if the self-assembly rule can be well understood. By using coarse-grained molecular dynamics (CGMD) simulations, we investigated the self-assembly process and morphology of triblock JNPs with varying chain lengths, chain ratios, and grafting topology. The HTH type of JNPs which possesses a middle hydrophobic block and two terminal hydrophilic blocks tends to aggregate into film structures via a shoulder-by-shoulder packing mode. The THT (Hydrophobic-Hydrophilic-Hydrophobic) type of JNPs is likely to form string structures via a head-to-head packing mode. The self-assembled film structures and string structures can be further regulated by the hydrophilic-hydrophobic chain ratio and length, forming rigid flakes, vesicles, porous structures, and so forth. Based on the molecular insights revealed by the example models, some plausible rules and strategies for tuning the self-assembly of nanoparticles are discussed in this paper. They are expected to facilitate future studies on the application of chemical self-assembly in materials science.