Investigating the Crosslinking Mechanism of Cinnamate-Modified Silicones

Abstract

Given the negative impacts of synthetic polymer plastics on the environment, it is of interest to develop syntheses for polymers and polymeric materials that either utilize naturally occurring resources or are biodegradable in an effort to promote sustainability. Cinnamate silicone polymers can be synthesized chemoenzymatically using cinnamic acid, a naturally occurring compound from the oil of cinnamon. Cinnamate side groups are well known photoreactive molecules that undergo [2+2] cycloaddition reactions but whose thermal reactivity was presumed to be forbidden by the Woodward-Hoffmann rules. We have synthesized cinnamate silicones that cure at 110 °C in less than 24 hours to form solid materials via a short-lived free radical reaction that was confirmed using electron paramagnetic resonance (EPR) spectroscopy. The cinnamate silicones were used to produce a series of materials. The properties of the silicone materials and a proposed mechanism for their formation will be discussed.