| dc.description.abstract | This dissertation is focused on synthesis of a new class of polyphenol polymers with antioxidant properties which are potentially useful in adhesives, anticorrosion coatings, food packaging, and biomedical applications. It also explores the effect of chemical structure of the polyphenol pendant groups and polymer backbone on the layer-by-layer (LbL) assembly of these polymers, and the performance of the resultant films in radical scavenging and self-healing applications.
Linear polymeric polyphenol antioxidants with designed molecular weights and narrow molecular weight distributions were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were based on the polymethacrylamide or the polyacrylamide backbone and contained functional catechol-, gallol-, or bromocathechol- polyphenol moieties. The developed synthetic routes enabled controlling antioxidant activity and hydrophobicity of these polymers simultaneously. That was achieved via variation of the chemical structure of the polyphenol groups and the introduction of non-oxidant hydrophobic units via copolymerization.
Linear homopolymers of gallol-based and catechol-based polyphenols were assembled with a neutral polymer within hydrogen-bonded LbL films, revealing drastic differences in film growth modes and the internal film structure for the films built with different polyphenols. Spectroscopic ellipsometry was used to determine growth regimes and swelling characteristics of these films, while neutron reflectometry involving deuterated marker layers enabled studies of internal film structure. Differences in the film structure strongly affected antioxidant performance and dynamics of hydrogen-bonded films in aqueous environment. In particular, gallol-based polymethacrylamide demonstrated the highest antioxidant activity because of self-association of
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gallol units and weaker intermolecular binding within LbL films, which allowed deeper penetration of radicals and their more efficient interactions with polyphenol moieties. In contrast, catechol-containing LbL films demonstrated lowest activity due to densely assembled layered structure, which limit interactions between assembled polyphenols and free radicals in solution. Additionally, differences in strength of intermolecular binding resulted in diverse self-healing behavior. As demonstrated by in situ atomic force microscopy (AFM), while robust self-healing of gallol-containing films occurred at the time scale of minutes, no healing was observed in the case of catechol-containing films. These results are rationalized through differences in the polymer chain mobility in these two cases, which are further quantified by in situ ellipsometry and neutron reflectometry studies. | en |
