Mechanistic insights into PEDOT:PSS/MWCNT hybrid networks on cotton: Coupled morphological, thermal, and electrical transport behavior

Cellulose-based textiles, such as cotton, represent a sustainable and versatile platform for developing functional materials for smart textiles and flexible textile-based electronics. However, achieving a balanced combination of electrical conductivity, thermal stability, and solution-processable fabrication within such natural fiber substrates remains a fundamental challenge. In this study, we combine comprehensive experimental characterization with quantitative electrical transport modeling to compare poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), multi-walled carbon nanotubes (MWCNTs) -, and PEDOT:PSS/MWCNT-coated cotton fabrics and to establish the relationship between coating structure, morphology, and conductivity. Conductive layers were fabricated by controlled drop-casting and analyzed via scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to correlate microstructural evolution with thermal integrity. PEDOT:PSS formed continuous coatings only above ∼25 wt.%, while MWCNTs exhibited a percolation threshold at ≈2.45 wt.%. The PEDOT:PSS/MWCNT composites showed the most homogeneous and compact architectures with a higher percolation threshold (≈4.5 wt.%) but a more stable conduction regime (t ≈ 1.3). The lowest sheet resistance (∼3 Ω/□) was achieved at ∼50 wt.% in the composite system. Temperature-dependent resistance analysis identified three regimes: PEDOT:PSS films displayed thermally unstable, positive- temperature coefficient of resistance (TCR) behavior (+2.45%/K at low loading), consistent with incomplete film formation and limited conductive continuity at low concentrations. MWCNT networks exhibited stable, negative TCR (–0.19 to –0.62%/K) with low activation energies (0.017–0.056 eV), reflecting the formation of conductive nanotube pathways once sufficient inter-tube connectivity was established. In the hybrid coatings, PEDOT:PSS is interpreted as improving coating continuity and interfacial coverage on the cotton fibers, while MWCNTs provide efficient long-range conductive pathways. Accordingly, the composites demonstrated near-zero activation energies (∼0.03–0.07 eV), excellent FIT model conformity (R 2 ≈ 0.90–0.99), and stable negative TCR (–0.35 to –0.73%/K), consistent with reduced transport barriers within the hybrid network. Thermogravimetric analysis showed enhanced thermal stability: decomposition onset increased from ∼320°C (pristine cotton) to ∼360°C (PEDOT:PSS) and up to ∼430°C (composites), with char yields rising to 30–35%. XRD confirmed preserved cellulose crystallinity and increasing graphitic order with MWCNT content. Together, these findings establish a structure-property framework for conductive cotton textiles and demonstrate that PEDOT:PSS/MWCNT hybrid coatings provide improved thermal and electrical performance as promising candidates for smart textile applications, with potential for future adaptation to scalable textile-coating methods.