Directing Assembly Through Variation of the Inter-Particle Attractive Interactions

The self-assembly of complex structures typically occurs within a narrow window of interaction strength due to large kinetic barriers that emerge as attractive interactions become too strong. At moderate interaction strengths, thermodynamic products form as the system relaxes to thermodynamic equilibrium. However, as interaction strength increases, there is a switch from thermodynamic to kinetic products, which emerge as high energetic barriers develop. By dynamically changing the free energy landscape through modification of the inter-particle interactions, certain kinetic traps may be overcome or the system may assemble into novel non-equilibrium structures. In this work, we model the assembly of rigid, 2D triangular particles into capsid-like hexamers to investigate the relationship between assembly and dynamic changes in the inter-particle potential. Specifically, we examine how oscillations of the attractive interactions in time and spatially variant attractions can allow for differences within the assembly process. Variation of the attractive interactions enables particles to diffuse out of original configurations and readily reorganize. We find that oscillation periods that are equivalent to the timescales needed for particles to diffuse from one another shifts the window of capsid formation. The distance particles diffuse from one another to shift the window of assembly is comparable to the lengthscales of the inter-particle interactions and particle size. Our results provide insights on how dynamic inter-particle interactions can alter self-assembly, and predicts how different systems can respond to attractive interaction variation.