Sunscreens protect human skin by absorbing harmful ultraviolet light and converting it into heat or red shifted wavelengths. Commercial sunscreens have the limitations of short lifetimes and photochemical degradation. In the course of our investigations, we discovered a new class of polymeric sunscreens that absorb UV light and possess built in antioxidant characteristics to delay photochemical degradation.<br/>s-Tetrazines, well known click reagents, undergo Inverse Electron Demand Diels Alder (IEDDA) reactions with polybutadienes converting the liquid oligomers into a solid polymer. The IEDDA reaction leads to the conversion of alkene groups in polybutadiene to dihydropyridazine groups that can bear a variety of substituents and generates nitrogen gas as a byproduct. Polymeric dihydropyridazines containing specific substituents show excellent UV absorbance and free radical inhibition activity making them photooxidation resistant sunscreen materials. In vitro SPF and UV stability measurements of polymeric sunscreens were carried out according to Cosmetics Europe protocols. The antioxidant activity of the sunscreens was evaluated using cyclic voltammetry. The photooxidation of the dihydropyridazine groups in the polymeric sunscreens to pyridazine groups can be monitored visually through attenuation of fluorescent activity.<br/>The inherent antioxidant activity, strong UV absorbance and photostability of these polymeric dihydropyridazines have the potential for applications as sunscreens, UV screening agents in coatings or additives.<br/>

Antioxidant sunscreen polymers through click modification of polybutadienes with s-tetrazines

2019 Fall National Meeting

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