Rotational dynamics and assembly strategies of nanoscale rough colloids mediated by liquid interfaces

It has been well established that surface roughness plays an increasingly crucial role in modulating interparticle interactions and their phase behaviors. However, how liquid interfaces influence the rotational diffusion of particles with varying surface roughness remains poorly understood. This work first employs the dissipative particle dynamics (DPD) model to construct nanoscale colloids with controlled surface roughness, followed by numerical investigations into the rotational diffusion of a single particle, a pair of particles, and a multi-particle assembly. For the case of a particle pair, relative mean-square angular displacement (relative MSAD) is innovatively proposed to characterize their relative rotation. Surprisingly, a liquid–liquid interface can significantly preserve their relative rotation and suppress their interlocking, which is also reflected in the interparticle distance and the trajectory of one tracer particle moving around the other. Presumably arising from the competition between entropy-driven assembly and roughness-induced interfacial pinning, such rotational preservation can effectively facilitate the formation of compact and energetically favorable oriented domains of particles. These findings confirm the crucial role of surface roughness in regulating nanoparticles’ relative rotation and self-assembled structures at liquid interfaces, and can potentially impact the physical mechanisms underlying some biological processes (e.g., viral adsorption).