Highly Transparent and Water-Enabled Healable Antifogging and Frost-Resisting Films Based on Poly(vinyl alcohol)-Nafion Complexes

Highly transparent polymeric antifogging and frost-resisting films capable of conveniently healing scratches and cuts are fabricated by the dip-coating technique from a solution of hydrogen-bonded poly(vinyl alcohol) (PVA) and Nafion complexes (denoted as PVA-Nafion), and then the as-prepared PVA-Nafion films are soaked in an aqueous NaOH solution to induce the formation of PVA crystallites. The dip-coated PVA-Nafion films can be deposited on plastic substrates such as poly(ethylene terephthalate) and polycarbonate eyeglasses and are sufficiently flexible to endure repeated bending-unbending treatments. The PVA crystallites act as physical cross-linkers and significantly improve the stability of the PVA-Nafion antifogging films in water. Nafion has a hydrogen-bonding interaction with PVA that further improves the stability of the PVA-Nafion films. The excellent antifogging and frost-resisting capabilities of the PVA-Nafion films even under aggressive fogging and frosting conditions originate from the remarkable water-absorbing capacity of PVA in the films. The reversible hydrogen-bonding interactions between PVA and Nafion and the high mobility of the polymer chains triggered by water endow the PVA-Nafion films with the ability to rapidly and repeatedly heal scratches and cuts several hundreds of micrometers wide to restore their high transparency as well as antifogging and frost-resisting functions.