Radically Different Antioxidants:  Thermally Generated Carbon-Centered Radicals as Chain-Breaking Antioxidants

Abstract

A new class of thermally activated chain-breaking antioxidants is presented. Dimers of persistent carbon-centered radicals are able to inhibit the autoxidation of cumene and styrene with better rate constants than the commercial antioxidant Irganox HP-136 and 3,5-di-tert-butyl-4-hydroxyanisole. A dramatic increase in antioxidant activity is observed with increasing temperature as more dimers dissociate to their corresponding persistent radicals.

Mechanophores with a Reversible Radical System and Freezing‐Induced Mechanochemistry in Polymer Solutions and Gels

“…Thework of Cheng and co-workers supported this observation because the molar mass of polystyrene calculated from SEC decreased by freezing the solution but recovered by heating to 100 8 8C. [37][38][39] Because of these distinctive properties,t his radical system enables in situ quantitative evaluation of polymer chain scission through electron paramagnetic spectroscopic (EPR) studies,u nlike previously reported mechanophores. [31,32] These studies suggest that freezing polymer solutions does not generate polymer chain scission but conformational changes.T herefore,w hether freezing polymer solutions actually induces mechanical force along the polymer chains and if so,t he magnitude of the force generated, remains unclear.…”

Carbon Radicals of Low Reactivity against Oxygen: Radically Different Antioxidants

“…[12] Recently, Scaiano and co-workers introduced a new class of "radically different antioxidants". [13] These compounds, instead of being H-atom donors as the common antioxidants, thermally dissociate into carbon-centered radicals, thus taking advantage of the high rates of radical-radical reactions for the antioxidative activity.…”

Dynamic covalent bond from first principles: Diarylbibenzofuranone structural, electronic, and oxidation studies

“…That could be an explanation why only the meso dimer is experimentally obtained and why dynamical equilibrium promotes carbon‐centered radicals to combine, leading to higher reaction rates than other reactions . This result is particularly interesting since DABBF, a well‐known molecule, has been studied as an antioxidant . In consequence, the persistent radical effect reinforces broad applicability in the self‐healing materials area, where resistance to oxygen reaction (autoxidation) is essential.…”