Donor-π-acceptor double-cable polythiophenes bearing fullerene pendant with tunable donor/acceptor ratio: A facile postpolymerization

Abstract

A novel type of donor-π-acceptor double cable poly(3-hexylthiophene) (P3HT) derivative bearing a fullerene pendant and a phenyl group as the linking bridge between the P3HT donor and C₆₀ acceptor (C₆₀-Ph-P3HT-1,2,3,4) with tunable donor/acceptor ratio was synthesized via a facile postpolymerization functionalization. The molecular structure, electronic property and molecular arrangement, as well as the surface morphology of the synthesized C₆₀-Ph-P3HT-1,2,3,4 were characterized by FTIR, ¹H NMR, UV-Vis and fluorescence emission spectroscopies, XRD and AFM. FTIR and ¹H NMR spectroscopic studies confirm the polymeric structures of C₆₀-Ph-P3HT-1,2,3,4 with the successful grafting of the C₆₀ moiety with tunable donor/acceptor ratio (wt.% ∼1 : 1; 1 : 0.9; 1 : 0.8; 1 : 0.6). UV-Vis absorption spectroscopic study confirms the nature of C₆₀-Ph-P3HT as the mono-adduct of C₆₀, and indicates a very weak perturbation of the molecular arrangement of the P3HT backbone upon the grafting of the C₆₀ pendant. The fluorescence intensity of C₆₀-Ph-P3HT-1,2,3,4 is found to be dramatically quenched compared to that of the P3HT and P3HT/C₆₀ (1 : 1) blend, and notably, C₆₀-Ph-P3HT-1 approaches 98% quenching. The molecular arrangement of C₆₀-Ph-P3HT is investigated by XRD analysis, suggesting that the grafted C₆₀ moieties in the side chain slightly interferes with the lamellar stacking of the polythiophene main chain of P3HT. The AFM measurements on the surface film morphology of C₆₀-Ph-P3HT-1,2,3,4 reveal that the rms roughness of C₆₀-Ph-P3HT-1,2,3,4 is larger than that of P3HT.