Dual-Strategy Design of Molecular-Weight-Engineered PEDOT:PSS Complex Films for Enhanced Mechanical Ductility and Environmental Robustness

Developing ductile and environmentally robust conductive materials is essential for next-generation wearable electronics, particularly those operating under harsh conditions. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a hygroscopic intrinsically conducting polymer, offers high electrical conductivity (σ_e) and inherent flexibility. However, its multiscale structural defects significantly limit its mechanical deformability across diverse environments. Herein, we propose a dual-strategy design that integrates (1) molecular-weight engineering and (2) hydrogen-bond-driven polymer complexation, achieved by incorporating ultrahigh molecular weight (<i>M</i>_w) poly(ethylene oxide) (PEO; subzero <i>T</i>_g) into a high-<i>M</i>_w PEDOT:PSS matrix. It enables the construction of hydrogen-bonded PEDOT:PSS/PEO complex films with enhanced mechanical ductility and environmental tolerance. Structural characterization confirms that H-bonds between PSS and PEO improve miscibility. The involvement of ultrahigh <i>M</i>_w PEO chains softens the rigid PEDOT:PSS matrix and promotes extensive chain entanglements, yielding films with elongation at break (ε_break) around 60% while maintaining a high σ_e of 100 S·cm^-1 at 40 wt % PEO. Notably, the flexible PEO chains enable hygroscopic PEDOT:PSS/PEO films to retain the ε_break > 30% across a wide temperature range (-20 to 60 °C) or at low-humidity conditions (RH = 10%). In particular, the PEDOT:PSS/PEO films exhibit antifreezing performance, retaining ε_break ∼ 42% at -20 °C. These findings demonstrate a synergistic molecular-weight engineering strategy, combined with flexible H-bond complexation to produce ductile and environmentally tolerant conductive films for next-generation wearable electronics.