"Push-kill-repel" synergistic antifouling: Coral-inspired polypyrrole/quaternary ammonium molecular brushes via electrochemical layer-by-layer assembly for dynamic biofouling control.

Marine biofouling has long posed a major challenge for marine applications. In this work, inspired by the tentacle-like structures of corals and their remarkable dynamic antifouling capability, a novel "push-kill-repel" polypyrrole/quaternary ammonium molecular brush (PPy/QAS) antifouling system was constructed by electrochemical layer-by-layer assembly. PPy-DBSA was first prepared, followed by voltage-driven grafting of CTAB onto PPy-DBSA, yielding a PPy/CTAB-E system with dynamic coral-like tentacles under cathodic polarization, actively pushing away fouling organisms. Moreover, the inherent bactericidal properties of the quaternary ammonium groups of CTAB significantly enhanced the system's antifouling capability. In addition, the cathodic polarization generates an electrostatic repulsion effect that further deters biofouling. This integrated system establishes a multifunctional dynamic antifouling interface that combines "push-kill-repel" mechanisms, showing potential for marine applications. The successful formation and dynamic antifouling behavior of PPy/CTAB-E was confirmed by electrochemical quartz crystal microbalance (EQCM), in-situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). In CTAB solution (2.5 mM), the adsorption amount of CTAB at -1 V was approximately 12 times more than that under natural adsorption. Under cathodic polarization (-1 V), the obtained PPy/CTAB-E brush system achieved the antibacterial rates of 99.4%, 99.3%, and 98.3% for Escherichia coli, Staphylococcus aureus, and Alteromonas, respectively.