Conjugated Polymers with Switchable Carrier Polarity

Abstract

Stimuli responsive polymers can change their properties as a result of their environment. Factors such as temperature, light, pH, or solvent can all trigger a polymer response. We present conjugated polymers with switchable carrier polarity, accomplished using a functional group that can be converted from electron donating to electron withdrawing. The polymers presented herein are polyselenophenes containing α-ketal side-chains. The α-ketal side-chains can be converted to electron withdrawing α-ketone side-chains postpolymerization. Since the starting monomer is relatively electron-rich, it can be polymerized using chain growth methods. Switching the electron donating ability of the side chain postpolymerization is an effective way to synthesize electron-deficient conjugated polymers from electron-rich monomers. Whereas the α-ketal polymer has optoelectronic properties that are consistent with other electron-rich (p-type) polymers, the α-keto polymer features a broad red optical-absorption, narrow HOMO–LUMO gap (∼1.5 eV), low-lying HOMO and LUMO levels, and ambipolar charge transport properties. We support these observations using density functional theory calculations.