A novel bonding strategy of hydrogel on titanium alloy for marine antifouling engineering: Multiple antifouling mechanisms and DFT calculations

Marine biofouling is one of the biggest problems for titanium alloys and rutile TiO ₂ coatings in marine engineering applications. Hydrogel materials are a novel and environmentally benign antifouling strategy, but they cannot be stabilized on alloy surfaces to provide long-term protection. Focusing on the challenges of bonding at the hydrogel-alloy interface, a PAA/PHEMA composite hydrogel containing Cu ₂O@PEG powder was strongly bonded to the titanium alloy by forming chemical bonds with APTES. The composite hydrogel still achieves an adhesion strength of 60–70 kPa after 7 days of immersion. The samples maintained a stable copper ion leaching rate of 2.61–3.76 μg·cm ⁻²·d ⁻¹ after 21 days of immersion. The coating-modified titanium alloys showed a 100 % bactericidal rate within three hours of contact with different bacteria and exhibited a high anti-algal adhesion rate of up to 99 %. In addition, the attachment mode of APTES on rutile TiO ₂ was clarified for the first time by Density Functional Theory (DFT) calculations. According to DFT calculations, the adsorption energy of APTES on Ti-TiO ₂ is −747.025 kJ/mol, and the adsorption energy of acrylic acid on TiO ₂-APTES is −535.152 kJ/mol. The chemical bonding connection between the hydrogel-alloy interface, as a novel interface bonding strategy, would be expected to broaden the application of titanium alloy in marine engineering.