Two Colour Photoflow Chemistry for Macromolecular Design

• Matthias Van De Walle
• Kevin De Bruycker
• James P. Blinco
• Christopher Barner-Kowollik

• Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology (QUT)2 George St., Brisbane, QLD 4000 (Australia)

We report a photochemical flow setup that exploits λ‐orthogonal reactions using two different colours of light (λ1=350 nm and λ2=410 nm) in sequential on‐line irradiation steps. Critically, both photochemically reactive units (a visible‐light reactive chalcone and a UV‐activated photo‐caged diene) are present in the reaction mixture. We demonstrate the power of two colour photoflow by the wavelength‐selective end group modification of photo‐caged polymer end groups and the subsequent polymer ring closure driven by a [2+2] cycloaddition. Importantly, we evidence that the high energy gate does not induce the visible light reaction of the chalcone, which attests the true λ‐orthogonal nature of the flow reaction system. For the first time, this study opens the realm of photoflow reactions to λ‐orthogonal photochemistry.

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