Radical crossover reactions of a dynamic covalent polymer brush for reversible hydrophilicity control

Abstract

Reversible hydrophilicity control of a radically exchangeable polymer brush with dynamic covalent linkages was successfully demonstrated. A polymer brush with alkoxyamine units was prepared via surface-initiated atom transfer radical polymerization, and reversible surface hydrophilicity control was achieved via dynamic covalent exchange reactions of alkoxyamines. Exchange reactions between alkoxyamine units in the side chains of the polymer brush and the terminal of poly(4-vinylpyridine) (P4VP) were carried out in order to prepare a side-chain functionalized polymer brush. Subsequent quaternization of P4VP chains with iodomethane was carried out to prepare a more hydrophilic surface. In addition, a de-grafting reaction of the quaternized P4VP side chains was performed to confirm reversibility of the alkoxyamine via radical exchange reactions on the surface. All the composition and wettability changes were investigated via X-ray photoelectron spectroscopy and contact angle measurements.