Layered polymer nanocoatings synthesized by vapor phase polymerization deposition enable underwater superoleophobic surfaces with excellent oil–water separation capability and ultradurability.

Asymmetric divinyl monomers are attractive candidates for constructing functional polymer thin films owing to their ability to undergo further reactions after polymerization. Here, the first solventless synthesis of poly(allyl methacrylate) (PAMA) film with retention of abundant allyl groups using initiated chemical vapor deposition (iCVD) is reported. It is demonstrated that lower substrate and filament temperatures lead to better allyl retention, while higher temperatures lead to intramolecular cyclization. The retained allyl groups can be further crosslinked under UV light, and the crosslinking degree can be easily tuned by adjusting the exposure time. Patterning of iCVD PAMA films with 20 µm resolution using a TEM grid as photomask is also demonstrated. The reported synthesis method suggests possible solventless incorporation of AMA in thin films as a latent crosslinker or anchoring sites for further functionalization. The solventless patterning can also extend patterning technique to solvent‐sensitive and non‐planar substrates.