Donor-acceptor-donor polymers utilizing pyrimidine-based acceptors

Pyrimidine acceptor groups were coupled with thienyl, 3,4-ethylenedioxythienyl (EDOT), and 3,4-(2,2-dibutylpropylenedioxy)thienyl (ProDOT-Bu2) donor groups in an attempt to synthesize stable n-doping polymers. Monomers were synthesized using a triorganoindium coupling reaction and characterized using nuclear magnetic resonance spectroscopy, X-ray crystallography, and electrochemical characterization techniques. The monomers undergo oxidative polymerization, with the alkylenedioxy-functionalized rings reducing oxidation and reduction potentials of monomer and polymer relative to the non-functionalized thiophene analogues, yielding electroactive polymers. The unsymmetrical nature of the monomers leads to unusual redox processes apparent during electrochemical polymerization. The polymer containing ProDOT-Bu2 groups was soluble in chloroform, while the other two polymers were insoluble. Band gaps were 1.6 eV for the ProDOT-based polymer and 1.8 eV for the EDOT-based polymer, which are comparable to other bisalkylenedioxyarylene-based polymers.