Wavelength-resolved near infra-red light induced free-radical polymerization

Abstract

Initiating polymerization processes at long wavelengths, ideally in the near-infrared (NIR) range, is critical to enable applications where shorter wavelengths may be harmful and where high penetration depths may be required. While we have recently demonstrated that gold nanorods (AuNR) function as effective photothermal converters at 800 nm to initiate free radical polymerizations, a careful wavelength-by-wavelength assessment (photochemical action plot analysis) of their effectiveness is outstanding. Herein, we provide a full NIR action plot from 620 to 950 nm, probing the wavelength-by-wavelength monomer to polymer conversion with an identical number of photons at each wavelength. While the vast majority of action plots show a red-shift relative to the absorption spectrum, we herein observe a pronounced blue-shift for the most effective conversion.