Functionalized Tetrasiloxane Enables Superhydrophilicity and Water Drainage in Waterborne Acrylic Coatings

Water condensation can reduce optical clarity on transparent surfaces, while causing persistent water retention on heat-transfer surfaces. Although superhydrophilic coatings promote droplet spreading, enhanced hydrophilicity alone does not necessarily ensure efficient water drainage. In this work, a waterborne acrylic coating combining superhydrophilic wetting with gravity-driven water removal was developed using a polyether- and epoxy-functionalized tetrasiloxane (PESiE). PESiE was synthesized by sequential hydrosilylation and incorporated into a glycidyl-functional acrylic latex (PBMG). Meanwhile, γ-aminopropyltriethoxysilane (KH550) was introduced as an amino-functional silane to promote network formation through possible amino–epoxy reactions and silanol condensation. The surface composition and morphology were characterized by XPS depth profiling and SEM, while water-management performance was evaluated through contact angle, droplet-sliding, spray-drainage, and antifogging tests. The results showed that PESiE was preferentially enriched near the coating surface, where the enriched polyether- and siloxane-containing species may increase surface water affinity and facilitate water spreading. At an optimized PESiE content of 7.5 wt %, the water contact angle decreased from 72.5° to 8.1°, while the apparent water-removal efficiency at 300 s increased from 5.0% to 75.0%. The optimized coating also maintained approximately 86–90% visible-light transmittance after vapor exposure and about 88% transmittance over 20 fogging/drying cycles. Taken together, these results show that the coating combines strong water affinity with effective water removal, while maintaining high optical transparency and repeatable antifogging performance. This formulation-based strategy provides a simple route for condensate-management coatings, with potential applications on heat-exchanger fins, antifogging glass, observation windows, and optical protective covers.