This work establishes correlations between the chemical structure of polyphenol rings and the physical and antioxidant properties of their hydrogen-bonded assemblies. Linear synthetic polyphenols, poly(N-(3,4-dihydroxybenzyl) methacrylamide) (P2HMA) and poly(N-(3,4,5-trihydroxybenzyl) methacrylamide) (P3HMA), were used with poly(ethylene oxide) (PEO) for assembly of layer-by-layer films. Film thickness, composition, and internal structure were explored using spectroscopic ellipsometry, Fourier transform infrared spectroscopy and neutron reflectometry. Gallol-containing polymers were prone to strong intramolecular hydrogen bonding, as shown by the rate of deuterium exchange using ATR FTIR that weakened intermolecular P3HMA interactions, resulting in the exponential growth of P3HMA/PEO films. In contrast, P2HMA/PEO films demonstrated linear growth. Neuron reflectometry studies employing deuterated PEO showed strong intermixing in P3HMA-containing films and fuzzy layering in the P2HMA/PEO system. The internal structure of the films correlated with differences in film swelling and the reduction of Young’s moduli upon exposure of the films to a solvent. Moreover, the gallol-containing films exhibited self-healing behavior that was quantified by AFM experiments. The assembled synthetic polyphenols preserved their radical scavenging capability, but the time scale for the radical reaction within the films was significantly longer than that in solution. Radical scavenging activity of the assembled units was also strongly dependent on the film structure, with strongly associated P2HMA/PEO films engaging only the surface region and weakly associated P3HMA/PEO assemblies being fully available to the radical species throughout the entire film thickness. The films have potential use in food packaging and biomedical applications.

Layer-by-layer hydrogen-bonded films of linear synthetic polyphenol polymers with antioxidant activity

ACS Spring Meeting 2021

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