(35a) Examining the Self-Assembly of Patchy Alkane-Grafted Silica Nanoparticles Using Molecular Simulation

We employ molecular dynamics simulations to study the configurations resulting from the self-assembly of anisotropically coated “patchy” nanoparticles. The introduction of directional interactions enables nanoparticle self-assemblies to generate targeted structures based on the nanoparticle shape [5] and surface chemistry [6]. Here, we have performed molecular dynamics using a coarse-grained model of silica nanoparticles coated with alkane tethers in which the poles of the grafted nanoparticle are bare, resulting in strongly attractive patches. Through a systematic screening process, the patchy nanoparticles are found to form dispersed, string-like, and aggregated phases, dependent on the combination of tether length, coating density, and fractional coated surface area of the nanoparticles. These three variables work in tandem to control the interaction between the nanoparticles by regulating the amount of the cohesive nanoparticle core that promotes aggregation. As such, it is difficult to predict which combinations of these characteristic variables will result in a particular phase. However, we have found the solvent accessible surface area (SASA), which can be obtained from shortened simulations of a single particle, to be a good predictor of the self-assembly behavior [7,8]. The results of this work enhance knowledge of the phase space of patchy nanoparticles and provide a powerful approach for screening parameter space in the design of such materials.

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