The synthesis of a series of antioxidant polymers with varied capability to scavenge radicals and alter the wettability of surfaces is reported.

While antioxidants are widely known as natural components of healthy food and drinks or as additives to commercial polymer materials to prevent their degradation, recent years have seen increasing interest in enhancing the antioxidant functionality of newly developed polymer materials and coatings. This paper provides a critical overview and comparative analysis of multiple ways of integrating antioxidants within diverse polymer materials, including bulk films, electrospun fibers, and self-assembled coatings. Polyphenolic antioxidant moieties with varied molecular architecture are in the focus of this Review, because of their abundance, nontoxic nature, and potent antioxidant activity. Polymer materials with integrated polyphenolic functionality offer opportunities and challenges that span from the fundamentals to their applications. In addition to the traditional blending of antioxidants with polymer materials, developments in surface grafting and assembly via noncovalent interaction for controlling localization versus migration of antioxidant molecules are discussed. The versatile chemistry of polyphenolic antioxidants offers numerous possibilities for programmed inclusion of these molecules in polymer materials using not only van der Waals interactions or covalent tethering to polymers, but also via their hydrogen-bonding assembly with neutral molecules. An understanding and rational use of interactions of polyphenol moieties with surrounding molecules can enable precise control of concentration and retention versus delivery rate of antioxidants in polymer materials that are critical in food packaging, biomedical, and environmental applications.

We report on the role of the chemical structure of polyphenol pendant groups in linear antioxidant polymers in their assembly and chain intermixing within layer-by-layer (LbL) films, as well as in the antioxidant performance of interfacial assemblies. When assembled with poly(ethylene oxide) (PEO) within hydrogen-bonded films, the antioxidant polymerspoly(3,4dihydroxybenzyl methacrylamide) (P2HMA) and poly(3,4,5-trihydroxybenzyl methacrylamide) (P3HMA)which contain catechol-and gallol-like moieties, respectively, generated films with drastically different structure and functionality. Specifically, while catechol-based P2HMA deposited within LbL films linearly with a low increment of mass increase per step, the growth of P3HMA/PEO films was strongly exponential. Dramatic differences in chain intermixing and layering in these films are revealed by the application of neutron reflectometry using deuterated PEO, dPEO, to create marker layers. Differences in film structure strongly affected film antioxidant performance, as demonstrated by the radical scavenging assay. While assembled P3HMA was fully available for scavenging 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS •+ ) radical cations, in assembled P2HMA, radical scavenging was restricted to the top ∼35 nm of the LbL film, highlighting the effect of LbL film structure on antioxidant performance.

We report synthesis of temperature-responsive linear and star poly(2-ureido aminoethyl methacrylates) (PUEMs) of matched molecular weights, their phase transitions in aqueous solutions and interactions with hydrogen bonding and hydrophobic small...

Rapid, accurate, and real-time measurements of ocean salinity are of great importance for a host of scientific, commercial, and defense applications. We demonstrate a highly sensitive, fast-responding fiber-optic salinity sensor that integrates long-period fiber gratings (LPFGs) with ionic strength-responsive hydrogel. The submicron-thick hydrogel was synthesized via layer-by-layer electrostatic assembly of partially quaternized poly(4-vinylpyridine) (qP4VP) and poly(acrylic acid), followed by chemical cross-linking. Spectroscopic ellipsometry measurement of a hydrogel made of 37% quaternized qP4VP showed robust and reversible swelling/deswelling in solutions with salt concentrations ranging from 0.4 to 0.8 M (22.8–44.7 g/kg) around pH 8.1. The swelling/deswelling process induced large changes in the refractive index of the hydrogel, leading to resultant shift in the resonance wavelength (RW) of LPFGs. The salinity-dependent optical response of the hydrogel-coated LPFGs is in good agreement with ellipsometry measurement. LPFGs coated with the hydrogel exhibited a sensitivity of 7 nm RW shift/M (125.5 pm/‰) with a measurement time less than 5 s. The shift in the resonance wavelength correlated linearly with salt concentration, making quantification of measured salinity straightforward.