Polarity-Switchable Maleic Anhydride Copolymer for an Eco-Friendly Waterborne Multifunctional Anti-Icing Coating

Global environmental concerns drive efforts to reduce the use of toxic and volatile organic solvents in polymer coatings. Because conventional anti-icing polymers are typically hydrophobic, they require such solvents for processing, which conflicts with sustainability goals. Although water and ethanol are eco-friendly alternatives, they are generally limited to hydrophilic polymers, which lack durability in humid environments. To overcome this limitation, we develop a polarity-switchable styrene–maleic anhydride (SMA) copolymer. Base-induced ring opening of MA renders the polymer hydrophilic and water-soluble for water-based coating formulations, while subsequent heat treatment triggers ring closing, restoring hydrophobicity and ensuring robust performance. With MA’s near-zero reactivity ratio, equimolar SMA forms an alternating architecture with a high T g of 213 °C, while styrene-rich feeds give gradient-like structures with reduced but still elevated T g values (205–189 °C) after purification. To realize a passive, eco-friendly, multifunctional anti-icing material, graphene oxide is incorporated into the SMA film, leveraging its excellent water dispersibility. After aqueous casting and heat treatment, the resulting hydrophobic composite film exhibits outstanding thermal and mechanical properties, low ice adhesion, and photothermal deicing capability. Moreover, both the matrix polymer and filler are recoverable, offering a recyclable and sustainable anti-icing platform.