The Ultrasensitivity of Living Polymers

TL;DR

This paper demonstrates that living polymers exhibit ultrasensitive responses to small perturbations, causing significant changes in their chain length distributions due to rapid relaxation of mass variables, with experimental validation on synthetic systems.

Contribution

It reveals the ultrasensitive dynamics of living polymers and explains the underlying mechanism involving fast mass variable relaxation affecting chain length distributions.

Findings

Viscosity relaxation matches experimental data on alpha-methylstyrene.

Small perturbations cause large, nonlinear changes in chain length distributions.

Fast relaxation of mass variables drives the ultrasensitive response.

Abstract

Synthetic and biological living polymers are self-assembling chains whose chain length distributions (CLDs) are dynamic. We show these dynamics are ultrasensitive: even a small perturbation (e.g. temperature jump) non-linearly distorts the CLD, eliminating or massively augmenting short chains. The origin is fast relaxation of mass variables (mean chain length, monomer concentration) which perturbs CLD shape variables before these can relax via slow chain growth rate fluctuations. Viscosity relaxation predictions agree with experiments on the best-studied synthetic system, alpha-methylstyrene.