Learning from the trees: biomimetic crosslinking of silicones by phenolic coupling

Abstract

Phenolic compounds undergo radical coupling under oxidizing conditions. Silicone oils were modified with eugenol using hydrosilylation to create oils and elastomers that exhibited antioxidant activity due to the presence of phenols, as shown by DPPH and other oxidative assays. At room temperature, phenolic coupling was not observed, as judged by lack of changes in viscosity or formation of gels. By contrast, peroxide oxidants at temperatures above 90 °C led to crosslinked materials whose physical properties (related to crosslink density) correlated with eugenol content, equivalents of peroxide added and reaction time. The product elastomers were also efficient antioxidants, although there was some attenuation of activity in higher crosslinked materials, consistent with diverse radical recombination processes.