Self-assembly in patchy colloidal rods

Abstract

Nanoparticle self-assembly is largely guided by two essential particle features - shape and chemistry. We have studied equilibrium chemically anisotropic colloidal rods with attractive and repulsive patches. Self-assembly in these rod suspensions depends on temperature, density, and aspect ratio. We have predicted fluid, macrophase separated, and microphase separated regions in the temperature-density phase diagrams of these suspensions. For a given rod architecture and chemistry we have predicted attraction-driven and repulsion-driven microphase separated structures by changing the temperature-density conditions. Further, different selfassembled morphologies are predicted for different rod architectures. We have studied the coherence lengths, and number of nearest neighbors. The coherence lengths demonstrate that these morphologies are spatially persistent. Variation of the number of nearest neighbors with temperature suggests a strong correlation between this local structural quantity with the peak value of the structure factor, a global measure of order. In this way, chemically patchy colloidal rods present rich and varied phase diagrams, whose distinct regions represent spatially persistent self-assembled morphologies.