Two colours of light drive PET–RAFT photoligation

Abstract

Within the field of photopolymerisation, photoinduced reversible deactivation radical polymerisation (RDRP) techniques such as photoreversible addition–fragmentation chain transfer (photoRAFT) polymerisation allow fine control over both molecular weight and macromolecular architecture. However, exploiting a second colour of light to further functionalise the generated polymers remains in its infancy. Critically, the selective activation of a photoactive group within the same structure is challenging and requires truly wavelength orthogonal systems. Herein, a custom-made RAFT agent bearing a tetrazole moiety was employed to polymerise methyl acrylate (MA) and N,N-dimethylacrylamide (DMA) via photoinduced electron/energy-transfer RAFT (PET–RAFT) at 590 nm. Subsequently, employing a shorter wavelength at 415 nm activates the tetrazole end-group, allowing the photoligation of the well-defined polymers with small molecules or polymers bearing a maleimide, fumarate or carboxylic acid moiety. By fusing the realms of photopolymerisation and photoligation, we herein exploit two orthogonal wavelengths of visible light to readily synthesise and functionalise polymers.