Nanoporous gold-polypyrrole hybrid electrochemical actuators with tunable elasticity

This study explores the effective elastic response of hybrid electrochemical actuators based on nanoporous gold - decorated with a thin film of an electrosynthesized polypyrrole - during charging in an aqueous electrolyte. We found a new and yet unrevealed phenomenon in the hybrids - a reversible change of the material's elasticity with alternating stiffening and softening behavior. Remarkably, the stiffness variations are larger and of opposite sign as compared to a non-coated nanoporous gold. The amplitude of the elastic modulus variation increases with the thickness of the polypyrrole layer, pointing to a dominant role of processes in the polymer bulk upon its doping or undoping. We propose that the reversible stiffness of the hybrid material is governed by the competition between the increased intermolecular bonding as consequence of interactions between the charged chains and dopant anions in the polymer and its plasticization due to solvent intake. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study reveals a new phenomenon of reversible change in the elastic response of hybrid electrochemical actuators, attributed to the thickness of the polypyrrole layer. The interaction between polypyrrole and gold, as well as solvent intake, play crucial roles in determining the elastic properties of the material.