Motility-induced collapse of an active Brownian particle polymer chain.

The ability of particles to transform absorbed energy into translational movements brings peculiar order into nonequilibrium matter. Connected together into a chain, these particles collectively behave completely differently from well-known equilibrium polymers. Examples of such systems vary from nanoscale to macroscopic objects. Herein, we demonstrate the ability of self-propelled monomer units to cause chain collapse under conditions where there is no explicit attraction between particles. The resulting conformation is heterogeneous, characterized by a dense condensed core surrounded by elongated loops and stabilized by an effective temperature gradient. Polymer segments in the condensed phase display crumpled packing. Using molecular dynamics analysis, we show that this effect is similar to motility-induced phase separation in active media.