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

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.