Hydrogen Bonding in Carboxyl/Amido-Functionalized PEDOT:PSS Copolymers: Breaking the Conductivity–Interfacial Property Trade-Off for Low-Impedance, High-Fidelity Epidermal Bioelectrical Monitoring

High-fidelity bioelectric signal acquisition is crucial for wearable precision medicine, but traditional poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) electrodes struggle to balance conductivity, stretchability, and skin compatibility, particularly under perspiration or physical activity. To address this challenge, we developed a PEDOT-based functional system doped with PSS-co-poly(acrylic acid)/poly(acrylamide) binary copolymers (PSA/PSM). Through multiscale characterization, molecular simulations, and in vitro testing, we systematically investigated the unique roles of carboxyl (−COOH) and amide (−CONH2) groups in regulating microstructure, electrical and interfacial properties, and hydrogen bond network dynamics. Key findings reveal that −COOH groups enhance π-π stacking interactions and charge doping effects in PEDOT. The PSA 3:1 sample exhibits the highest conductivity, surpassing pure PEDOT:PSS, but displays severe swelling and poor adhesion owing to strong electrostatic interactions. In contrast, −CONH2 groups in PSM form a hydrogen bond network with distinct static structural features characterized by uniform bond length and angle distributions and a homogeneous network structure. This optimizes interfacial performance with only a minor conductivity loss (≤10%). The PSM 3:1 electrode demonstrates strong adhesion, low contact impedance (62.8 kΩ at 10 Hz), swelling resistance, and high electromechanical stability. Molecular dynamics simulations confirm that the static structural advantages of the PSM hydrogen bond network, including stable distribution of bonding sites and moderate fluctuations in bond length and angle, are critical to enhancing electromechanical stability and wet performance. In practical electrocardiogram (ECG)/electromyogram (EMG) monitoring, the PSM 3:1 electrode achieves low noise (ECG RMS: 10.3 μV) and high signal fidelity during both resting and exercise states. Under a 25 kg grip force, it reaches an EMG peak-to-peak voltage of 0.32 mV, outperforming commercial Ag/AgCl electrodes. This study provides a molecular-level synergistic multiperformance optimization strategy for conductive polymers, advancing the development of high-fidelity wearable bioelectronics.