Advances in interfacially engineered surface‐functionalized fillers for multifunctional polymer composite coatings

Abstract The demand for multifunctional, high‐performance materials has driven advancements in surface‐functionalized fillers for polymer composite coatings. Despite progress, integrating multiple protective properties within a single hybrid formulation remains a challenge. This review explores recent developments in surface and interfacial engineering of biosourced fillers, including nanocellulose, and 2D materials like graphene oxide, MXenes, and layered double hydroxides, all of which have the potential to enhance the chemical resistance, mechanical strength, and thermal stability of polymer coatings. Key strategies include physical/chemical surface treatments, nanostructuring, and multiscale engineering to optimize cohesion, adhesion, and multivalent interactions among fillers, matrices, and substrates. The role of computational modeling in performance prediction and optimization is also discussed. The review concludes with current challenges and future directions, highlighting the importance of surface functionalization and interfacial engineering in developing next‐generation, multifunctional, and protective polymer coatings. Highlights Functionalized fillers boost polymer coatings' performance. 2D nanomaterials enhance coatings' resistance to corrosion, wear, and fire. Bio‐based fillers offer sustainable solutions for lightweight, robust coatings. Advanced interfacial engineering improves adhesion and coating durability. Modeling accelerates coating design by predicting interfacial interactions.