How Spatially Modulated Activity Reshapes Active Polymer Conformations

TL;DR

This paper investigates how spatially patterned activity influences the conformations of semiflexible active polymers, revealing a transition from compact to swollen states depending on activity patterns and polymer modes.

Contribution

It introduces a systematic analytical framework for understanding how sinusoidal activity modulates polymer conformations, extending passive polymer models to active, non-equilibrium systems.

Findings

Structured activity induces mode-dependent conformational transitions.

Higher modes lead to alternating stretched and compressed segments.

Simulations confirm analytical predictions across different polymer sizes.

Abstract

Active polymers are driven out of equilibrium by internal forces and exhibit conformational properties that differ fundamentally from those of passive chains. Here we study how spatially modulated tangential activity reshapes the conformations of semiflexible polymers. Using a continuum Rouse model with bending rigidity, we develop a systematic expansion in the limit of weak activity and derive analytical expressions for mode correlations, gyration radius, and end-to-end distance under sinusoidally varying propulsion. We show that spatially structured activity breaks self-similar scaling and induces a mode-dependent transition between polymer shrinking and swelling. Uniform or low-mode forcing produces compact, globule-like conformations, whereas higher modes generate alternating stretched and compressed segments, leading to globally swollen chains. Different polymer sizes respond differently to activity, allowing for conformations that are compact in gyration radius yet extended in end-to-end distance. Langevin dynamics simulations quantitatively confirm the theoretical predictions. Our results demonstrate that even weak, patterned activity provides a powerful mechanism to control polymer conformations far from equilibrium.