Active Polymers

Active Brownian Ring Polymers

We consider the conformational and dynamical properties of semiflexible ring polymers consisting of chains of active Brownian particles (ABPs). The motion of the individual ABP monomers is characterized by a body-fixed propulsion direction plus orientational diffusion. An experimental realization can be chains of diffusiophoretic Janus colloids.

The fluctuation spectrum of normal-mode amplitudes is analyzed. At elevated activities, flexible (tension) modes dominate over bending modes even for semiflexible rings, corresponding to enhanced conformational fluctuations. The pertinent result is that the amplitudes of the long-wavelength modes are strongly enhanced by activity. The fluctuation spectrum exhibits a crossover from a quadratic to a quartic dependence with increasing mode number. Conformationally, the mean square ring diameter exhibits swelling qualitatively comparable to linear polymers. The ring’s diffusive dynamics is enhanced, and the mean square displacement shows distinct activity-determined regimes, consecutively, a ballistic, a subdiffusive, and a diffusive regime.

Reference: S.M.Mousavi, G.Gompper, amd R.G. Winkler, Active Brownian ring polymers. The Journal of Chemical Physics 150, 064913 (2019)