Hierarchically featured and substrate independent bulk-deposition of ‘reactive’ polymeric nanocomplexes for controlled and strategic manipulation of durable biomimicking wettability

Abstract

The synthesis of ‘chemically-reactive’ and porous polymeric coatings with the ability to regulate the desired chemistry, covalently and three-dimensionally (including interior/interface), through facile and robust synthetic processes, is fundamentally challenging, and is important for designing various practically relevant durable and smart materials. Here, chemically reactive polymeric nanocomplexes with tailored sizes that are synthesized in alcoholic solvents through a catalyst-free, 1,4-conjugate addition reaction, are strategically exploited in developing a hierarchically featured and chemically reactive thick (254 ± 10 μm) polymeric coating for manipulating special biomimicking wettability three dimensionally. The ‘amine-reactive’ residual acrylate moieties in the porous polymeric thick coating provided a facile chemical avenue for regulating the desired chemistry covalently, and eventually yielded bulk polymeric coatings with chemically modulated Cassie–Baxter and Cassie–Wenzel transitional states through controlled optimization of the metastable trapped air level in the bulk polymeric coating. The fraction of contact area between a beaded water droplet and trapped air in the polymeric coating was tailored from 0 to above 0.9. Thus, the same ‘reactive’ polymeric interface is capable of displaying both highly non-adhesive and controlled adhesive superhydrophobicity. The biomimicking wettability remained unperturbed even after being subjected to severe physical/chemical insults, including physical removal of material, prolonged (30 days) exposure to UV-irradiation etc. This simple design is capable of coating a wide range of substrates, irrespective of their chemical compositions, geometries and dimensions. Even some practically relevant flexible and complex objects, such as printing paper (A-4 size) and shoes, are decorated with durable bio-inspired properties as an early demonstration of protecting manually written text and printed text from aqueous exposure, and self-cleaning of dust-contaminated interfaces. This bulk optimization of essential chemistry could be useful in the synthesis of various other smart materials for many relevant outdoor applications.