# Charge Storage Mechanisms in Redox-Active Polymer Brushes

## TL;DR

This paper studies how redox-active polymer brushes store charge in supercapacitors, showing how their structure and environment affect performance.

## Contribution

The study reveals how polymer brushes combine double-layer and pseudocapacitive mechanisms for enhanced charge storage.

## Key findings

- Brush swelling and counterion uptake are controlled by solvent quality and grafting density.
- Differential capacitance peaks reach 15–30 F/m² during collapsed-to-swollen transitions.
- Redox-active brushes integrate both electric double-layer and pseudocapacitive charge storage mechanisms.

## Abstract

Electroconductive
polymer brushes grafted to conductive electrodes
are investigated as model electrodes for aqueous supercapacitors using
the Scheutjens–Fleer self-consistent field (SF-SCF) framework.
The model self-consistently resolves polymer conformations, ion partitioning,
and redox-mediated electron hopping under applied potentials (0–0.7
V). We show that solvent quality and grafting density govern brush
swelling and counterion uptake, thus shaping the charge-potential
response. In a good solvent, brushes provide volumetric charge storage
throughout a swollen layer, while in a poor solvent, charging drives
a collapsed-to-swollen transition that produces sharp capacitance
peaks. During this transition, the differential capacitance reaches
15–30 F/m2, an order of magnitude higher than the
bare-electrode baseline. These results demonstrate how redox-active
electroconductive brushes integrate electric double-layer and pseudocapacitive
mechanisms, providing design principles for polymer-brush-modified
electrodes in both supercapacitors and ion-selective membranes.