A family of linear phenolic polymers with controlled hydrophobicity, adsorption and antioxidant properties

Abstract

A series of linear polymeric antioxidants with controllable antioxidant, hydrophobicity and surface adsorption properties was synthesized using reversible addition–fragmentation chain transfer (RAFT) polymerization. The polymers had a poly(methacrylamide) backbone and contained functional catechol-like 3,4-dihydroxybenzyl-, gallol-like 3,4,5-trihydroxybenzyl- and bromo-substituted 3,4-dihydroxy-5-bromobenzyl-(2H, 3H and BrH, respectively) groups, as well as N-hexyl (Hex) moieties. The polymers were abbreviated as P2H_ZHex, P3H_ZHex or PBrH_ZHex, where Z is the molar percentage of the polyphenol units in the polymer chains. Both the chemical functionality and the relative content of the polyphenol and hexyl units governed the hydrophobicity, adsorption and antiradical activity of these polymers. An increase in the content of the hexyl units in the polymer chains resulted in higher thicknesses of the adsorbed polymer monolayers and an increase in the water contact angles of the gold surface. Importantly, polymers with gallol-like side groups exhibited antioxidant activity (as determined using the DPPH assay in methanol solutions) and affinity to metal substrates that were superior to those of their catechol-like and bromo-substituted counterparts. The tunability of interfacial binding, hydrophobicity and antioxidant properties of these polymers are properties essential for the use of these polymers in coating applications.