Translating the Precision Photochemistry Paradigm into Multi-Colour Multi-Material 3D Printing

Over the last decade our laboratory has employed monochromatic tuneable laser systems to reveal a strong mismatch between the absorptivity of a chromophore and its photochemical reactivity in the vast majority of covalent bond forming as well as bond cleavage reactions. Our data overturns the long-held paradigm that effective photochemical reactions are obtained in situations where there is strong overlap between the absorption spectrum and the emission wavelength under a given set of reaction conditions. However – as we explore herein – the absorption spectrum of a molecule provides only information about singlet excitation and remains largely silent on specific microenvironments that shape photochemical reactivity via the red-edge effect. We propose a theory on how photochemical action plots can be understood and demonstrate how they are of key importance for tailoring photochemical applications in light-driven soft matter materials design – most-notably in advanced light-driven multi-material 3D printing – with never-before-seen precision, exploiting wavelength orthogonal, synergistic, cooperative and antagonistic photochemical reaction modes.