Long aging time thermal degradation of the ac conductivity and complex permittivity of conducting polypyrrole

TL;DR

This study investigates the long-term thermal aging effects on the ac conductivity and permittivity of conducting polypyrrole over two years at 343K, revealing degradation patterns and relaxation behaviors.

Contribution

It provides the first detailed analysis of how prolonged thermal aging influences the dielectric and conductive properties of polypyrrole, highlighting invariant relaxation regions and relaxation splitting.

Findings

Reduction of crossover frequency correlates with dc-conductivity degradation.

Universal dielectric relaxation remains stable during the first year of aging.

Dielectric loss peak splits into two relaxations during intermediate aging stages.

Abstract

The modification of the ac conductivity and the complex permittivity of conducting polypyrrole was monitored throughout a two years thermal aging at 343K. Reduction of the cross-over frequency is correlated with the degradation of dc-conductivity, while the ac conductivity region corresponding to the so-called 'universal' dielectric relaxation remains practically invariant during the first year of ageing, which implies a collective co-operativity among multiple degradation processes that yield a practically time-independent effective disordered environment. A broad dielectric loss peak recorded in fresh specimens splits into two distinct relaxations for intermediate stages of the annealing process. The ageing-time evolution of the dc component and the relaxations are qualitatively analysed and time constants are determined.