# Designing n‑Type Thermogalvanic TEMPO-Substituted Polyacrylamide via Conformational Entropic Modulation

## TL;DR

This paper introduces a new n-type thermoelectric polymer that uses redox reactions to improve performance for waste heat recovery.

## Contribution

The study introduces entropy modulation via redox-induced conformational changes in TEMPO-substituted polyacrylamide for n-type thermoelectric materials.

## Key findings

- Electrochemical oxidation of PTAm produces a water-soluble polyelectrolyte with TEMPO and oxoammonium species.
- Redox transitions lead to an n-type thermopower of −0.76 mV K–1 and a power output of 1.18 mW m–2 K–2.
- Entropy modulation in redox-active polymers is shown to enhance thermoelectric performance.

## Abstract

This work pioneers
the use of TEMPO-substituted polyacrylamide
(PTAm) for n-type thermogalvanic (TG) systems, uniquely harnessing
redox-induced conformational entropy changes to enhance the thermoelectric
performance. Through the electrochemical oxidation of low-molecular-weight
PTAm, which is initially water-insoluble, a water-soluble polyelectrolyte
(ox-PTAm) is formed, containing both TEMPO and oxoammonium species,
as indicated by cyclic voltammetry. The redox transitions induce conformational
entropy changes, which are corroborated by electrochemical and thermoelectric
measurements, leading to an observed n-type thermopower (α)
of −0.76 mV K–1. A maximum power output of
1.18 mW m–2 K–2 is achieved under
a thermal gradient of 3.8 K. This work highlights the potential of
entropy modulation in redox-active polymers as a strategy for advancing
organic thermoelectric materials targeting low-grade waste heat recovery.