PSS are well preserved during the mechanical deformation.

Understanding the mechanism of the strain-dependent conductivity change in polymers in stretched conditions is important. We observed a strain-induced growth of the conductive regions of PEDOT:PSS films, induced by a coalescence of conductive PEDOT-rich cores. This growth due to coalescence leads to a gradual decrease in the electrical resistivity up to 95%, independent of the thickness of the PEDOT:PSS films. The primary mechanism for the evolution of the PEDOT-rich cores proceeds by the cores growing larger as they consuming relatively smaller cores. This process is caused by a strain-induced local rearrangement of PEDOT segments in the vicinity of PSS shells around the cores and also changes the chemical environment in PEDOT, induced by the electron-withdrawing effects around the PEDOT chains. The strain-induced growth mechanism is beneficial to understanding the phenomenon of polymeric chain rearrangement in mechanical deformation and to modulating the electrical conductivity for practical applications.

According to the recent growth in interest of human-friendly devices, soft conductors, which are conductive materials with an inherent compliance, must have a low electrical strain sensitivity under large deformation conditions, environmental stability in water, and reliability even for complex and repeated deformation, as well as nontoxic characteristics. In this study, we fabricated a poly­(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/polyacrylamide nanoweb that satisfies all of the above requirements through a web microstructure with entangled conductive nanofibers. Since the web structure can be deformed through structural alignment, the conductive path is stably maintained during deformation, which makes it highly conductive, electrically stable, and electrically strain insensitive. The tangled nanofibers are composed of PEDOT:PSS as a conductive component and polyacrylamide as a binding material, so it is nontoxic and has the soft properties of the material itself, which can withstand large deformations. Additionally, the material has a good electrical stability against repeated deformation so that the resistance increased by only 13% after a 50% strain was repeated 1000 times. Notably, electrical instabilities such as noise and hysteresis were not evident during the repeated deformations. Finally, the nanoweb has excellent swelling resistance and maintains its mechanical and electrical characteristics in water.

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