Self-healing polymers from bio-based benzoxazine blended with poly (ethylene glycol) for anti-biofouling applications

Abstract Biofouling remains a significant challenge in marine industries, as conventional coatings often lose their anti-biofouling efficacy once they become damaged. Incorporating self-healing capabilities into antifouling coatings has therefore emerged as a promising strategy to extend service life and maintain long-term performance. In this study, self-healing polymers were developed based on a bio-based benzoxazine resin (E-fa), synthesized from renewable precursors including eugenol, furfurylamine and paraformaldehyde, and subsequently blended with poly(ethylene glycol) (PEG). The blends were formulated with varying weight ratios and PEG molecular weights. This work investigates the effects of PEG content and molecular weight on self-healing performance under thermal triggering, coating performance, water absorption, marine resistance, and antibacterial activity of the developed blended bio-derived E-fa/PEG polymer (P(E-fa/PEG)). The results indicated that coating performance (i.e., pencil hardness and adhesion) was found to be markedly affected by increasing PEG content, which is due to the flexible and hydrophilic nature of PEG. However, PEG incorporation significantly improved adhesion, increasing the adhesion grade from 1 A in neat bio-based polybenzoxazine (P(E-fa)) to 4 A in the blends, with no substantial differences observed across PEG molecular weights. The increase in PEG contents can enhance the self-healing efficiency of the P(E-fa/PEG) up to 86% healing, attributed to the increased chain mobility of PEG and the reversible reactions within the E-fa network. The P(E-fa/PEG) blends also exhibited excellent antibacterial performance, achieving up to 100% inhibition of E. coli and 73% inhibition of S. aureus . Hence, self-healable E-fa/PEG polymer blends have been successfully developed in this work, with potential applications in marine antifouling coatings.