Photoinduced double hydrogen-atom transfer for polymerization and 3D printing of conductive polymer

The photoinduced polymerization of electron-rich heteroaromatic pentacycles (ERHPs), such as thiophene derivatives and pyrrole derivatives, is challenging owing to the inherent stability of their aromatic structure. The resultant polymers are organic semiconductor materials that are widely used in both organic electronic and bioelectronic devices. Here we report an efficient hydrogen-atom transfer (HAT) photocatalyst, which is the dimerization product (1,2-bis(4-(2-hydroxyethoxy)phenyl)ethane-1,2-dione) of an acyl radical generated by the photolysis of Irgacure 2959, and its use for the dehydrogenation of coupled ERHPs formed in an acidic environment. The dehydrogenation occurs via a double HAT process, enabling the photopolymerization of ERHPs. This reaction also allows us to fabricate three-dimensional (3D) conductive pathways in hydrogels. The hydrogel can be printed to form free-standing 3D conductive structures of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate with a precision of 220 nm, markedly surpassing structures built using previous methods (>10 µm). The approach introduces opportunities for precision engineering of 3D electrodes with the possibility of expanding applications in organic electronics and bioelectronics. (Figure presented.)