Halloysite Nanotubes as Active Modulators for Tunable Charge Transport in PEDOT:PSS

Halloysite nanotubes (HNTs) are investigated as functionally active nanofillers for tuning PEDOT:PSS thin films. HNTs from Dragon Mine (DG, USA) and Matauri Bay (NZ, New Zealand), characterized by different aspect ratios and surface chemical characteristics, are incorporated at 1.0–7.5 wt.% without secondary dopants to highlight specific HNT-related interfacial effects. A non-monotonic dependence of local conductance on DG content is observed, with a maximum at low loading (2.5 wt.%). This trend reflects the balance between enhanced connectivity of PEDOT-rich domains at low concentrations and disruption of conductive pathways due to nanotube aggregation at higher loadings. It is suggested that DG acts as an active modulator, promoting polymer chain reorganization and enabling a denser hopping network, thereby enhancing local electrical response and mechanical stiffness. In contrast, NZ behaves as a passive filler, preserving the intrinsic ion-storage capability of PEDOT:PSS without improving charge transport, highlighting the dominant role of interfacial electrostatic interactions. Electrochemical analysis shows that DG favors electronic transport at the expense of ionic accumulation, whereas NZ maintains capacitive behavior. The nanocomposites exhibit good biocompatibility, with improved SH-SY5Y cell viability at low DG loading. These results provide design guidelines for independently tuning electrical, electrochemical, and mechanical properties in conductive polymer nanocomposites.