Pyromellitic diimide-based donor-acceptor poly(phenylene ethynylene)s

A series of donor-acceptor poly(phenylene ethynylene)s (PPEs) with N,N′-dialkylpyromellitic diimide (PMDI) as electron acceptor and various donor units are reported. Optoelectronic properties were investigated by UV/vis absorption and electrochemical measurements, revealing constant LUMO energies (∼-3.6 eV) across the series with HOMO energy levels governed by the donor monomers and optical band gaps from 2.30 to 1.50 eV. With a high volume fraction of solubilizing side chains, the polymers are soluble in common organic solvents, but solution NMR measurements and thermochromism in solution indicate aggregation due to additive intermolecular interactions between donor and acceptor units.