Reversible Surface Properties of Polybenzoxazine/Silica Nanocomposites Thin Films

Abstract

We report the reversible surface properties (hydrophilicity, hydrophobicity) of a polybenzoxazine (PBZ) thin film through simple application of alternating UV illumination and thermal treatment. The fraction of intermolecularly hydrogen bonded O–H⋯O=C units in the PBZ film increased after UV exposure, inducing a hydrophilic surface; the surface recovered its hydrophobicity after heating, due to greater O–H⋯N intramolecular hydrogen bonding. Taking advantage of these phenomena, we prepared a PBZ/silica nanocomposite coating through two simple steps; this material exhibited reversible transitions from superhydrophobicity to superhydrophilicity upon sequential UV irradiation and thermal treatment.