Kinetically controlled hetero-fusion is a systems-level behaviour of polymer nanoparticle populations

Particle fusion is key for establishing communication between biological components. For this reason, whole cell fusion plays a crucial role in many processes, including infection, muscle formation and tissue repair. Analogous co-assembly between synthetic nanoparticles represents a similar type of communication mechanism in artificial systems. Other approaches to control such co-assembly rely on incorporating anisotropic recognition units onto particle surfaces to provide a thermodynamic driving force. Here we present a fundamentally different approach, where hetero-fusion between two populations of undecorated polymer nanoparticles is regulated using kinetic control. Fusion extent is tuned simply by adjusting polymer chain length. Fusion is probed using an elemental tagging strategy for cryogenic scanning transmission electron microscopy combined with electron energy loss spectroscopy (cryo-STEM-EELS). Our results demonstrate the emergence of a complex process between populations of synthetic nanoparticles akin to communication. We anticipate such systems-level behaviour that results from hetero-fusion can enable future technologies.