Reversible formation and control of linear conjugation in polymers

The emergence of organic semiconductors has laid the foundation for the field of plastic electronics. Controlling π-conjugation by designing proper conjugated moieties is one of the commonest strategies for achieving desired semiconducting properties in conjugated materials. Despite significant advancements in the field, the reversible formation of extended conjugation to in situ switch the nature of macromolecules between semiconductors and insulators remains elusive. Here we disclose a generic strategy for developing polymeric structures that incorporate molecular switch units. These units enable the controlled activation and deactivation of linear conjugation in response to acid-base or electronic stimuli. This is achieved by copolymerizing non-π-conjugated lactone-functionalized xanthene moieties with traditional π-conjugated building blocks. With 2,6-dihydroxynaphthalene as an 'electro-acid', the electrochromic-like properties of these polymers were explored, demonstrating an effective in situ conversion of the non-conjugated, colourless polymers into conjugated, coloured polymers.