Amphiphilic block-copolymer silane coupling agents enable simultaneous enhancement of adhesion, water resistance, and corrosion protection in waterborne acrylic–polyurethane coatings

Waterborne resins are widely recognized as eco-friendly alternatives to solvent-based systems. However, in many cases, their practical applications may still be hindered by insufficient adhesion to low-surface-energy substrates, poor water resistance, and inadequate corrosion protection. Furthermore, conventional silane coupling agents are typically oil-soluble and exhibit poor compatibility with some water-based resins, restricting their utility in such systems. To address these limitations, we developed a novel amphiphilic block -copolymer silane coupling agent (MPEG n -b-PBA m -APTES) for high-performance waterborne acrylic-polyurethane (APU) coatings. A well-designed amphiphilic block structure ensures uniform dispersion and compatibility within the aqueous matrix. Meanwhile, reactive silane groups form a robust Si–O–Si crosslinked network, significantly enhancing interfacial bonding with the substrate. By systematically optimizing the ratio of hydrophilic to hydrophobic segments and the additive concentration, we achieve significant enhancements in overall coating performance. Among all modified coating formulations, the APU11/22–10 sample demonstrated the optimal barrier performance, achieving a water absorption rate of only 4.7%. This value was 43.3% lower than that of the APU22/11–10 sample (8.3%) and represented a 42.0% reduction relative to the blank APU-0 coating (8.1%). Meanwhile, the APU22/11–10 system achieved a peak pull-off adhesion strength of 5.33 MPa, outperforming the blank sample (2.64 MPa) by 86.4% and substantially surpassing the values obtained for APU11/22–10 (4.16 MPa) and APU45/22–10 (3.21 MPa) in terms of interfacial bonding capacity. Furthermore, the modified coatings display enhanced mechanical hardness and thermal stability. Consequently, this amphiphilic silane modification strategy enables simultaneous improvements in adhesion, water resistance, corrosion protection, hardness, and thermal stability, presenting a highly effective approach for developing high-performance and eco-friendly waterborne coatings.