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Behavior of passive polymeric tracers of different topologies in a dilute bath of active Brownian particles

Ramanand Singh Yadav1, Ralf Metzler2,3,†, and Rajarshi Chakrabarti1,*

  • *Contact author: rajarshi@chem.iitb.ac.in
  • †Contact author: rmetzler@uni-potsdam.de
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Phys. Rev. Research 8, 013053 – Published 20 January, 2026

DOI: https://doi.org/10.1103/qrjy-9yt6

Abstract

Using computer simulations in two dimensions, we investigate the dynamics and structure of a passive polymeric tracer with different topologies immersed in a low-density active particle bath. One of the key observations is that polymers exhibit faster dynamics compared to passive colloidal particles at high activity, for the same particle density, in both linear and star polymer topologies. This enhanced motion is attributed to the accumulation of active particles, which induces prolonged and persistent movement of the polymer. Further analysis reveals that star polymers exhibit more complex and intriguing behavior than their linear counterparts. Notably, the accumulation of active particles promotes the pairing of arms in star polymers. For instance, a three-armed star polymer adopts a conformation similar to a linear polymer with two arms due to this pairing; as a result, at high activity, the dynamics of both the polymers converge. Finally, we explore the dynamics of a linear polymer with the same total number of beads as the star polymer. Interestingly, at high activity—where arm pairing in the star polymer is significant—the star polymer demonstrates faster dynamics than the linear polymer, despite having the identical number of beads. These findings contribute to a broader understanding of the interactions between active and passive components of varying topologies in dilute systems and highlight their potential for innovative applications ranging from materials science to biomedicine.

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Phys. Rev. Research 8, 013053– Published 20 January, 2026
  • Received 26 August 2025
  • Accepted 6 December 2025
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