Poly(bisthiophene-carbazole-fullerene) Double-Cable Polymer As New Donor-acceptor Material: Preparation and Electrochemical and Spectroscopic Characterization

A new donor-acceptor dyad, namely, a 3,6-bis(thiophen-2-yl)carbazole derivative bearing a C-60 fullerene as a side group (BTC-F), was prepared and characterized. Electropolymerization of BTC-F leads to the formation of a donor-acceptor double-cable polymer (PBTC-F) with high fullerene content (63 wt %) corresponding to one C-60 per polymer repeat unit. The electronic properties of BTC-F and PBTC-F were studied by electrochemical and spectroscopic techniques. Photoluminescence quenching is observed in diluted solutions of BTC-F compared to the nongrafted monomer BTC indicating that an intramolecular charge transfer takes place between the two components of the dyad. The positions of the HOMO and LUMO levels of the monomer and the polymer were accurately determined by differential pulse voltammetry (DPV). The LUMO energy level of the fullerene moiety in BTC-F lies at 3.7 eV below the vacuum level, i.e., slightly higher than corresponding levels of C-60 and PCBM. DPV characterization of PBTC-F indicates little ground state interaction between the pi-conjugated main chain and the C-60 side groups and a high donor HOMO-acceptor LUMO gap of 1.47 eV.