Synthesis and characterization of fluorene based π-conjugated ter-copolymers

Three conjugated ter-copolymers P1, P2 and P3 were prepared in which fluorene was a common unit and varying subunits were thiophene–pyridine, thiophene–anthracene and pyridine–anthracene, respectively. The number-average molecular weights (Mn) of the copolymers named as P1, P2 and P3 were found to be 13,400, 14,200 and 15,800 g/mol, respectively. These copolymers were soluble in common organic solvents such as chloroform, chlorobenzene, toluene, etc. and their tendency to form aggregates has been observed by the atomic force microscopy (AFM). The copolymers were investigated for their thermal, optical, electrochemical and impedance properties. They showed high glass transition temperatures and improved thermal and spectral properties. The copolymer P2 (thiophene/fluorene/anthracene) showed lower LUMO energy level and significant redox stability in respect to pyridine containing copolymers P1 (thiophene/fluorene/pyridine) and P3 (pyridine/fluorene/anthracene). The remarkable n-dope ability and stability of these polymers were discussed in the light of cyclic voltammetric and electrochemical impedance spectroscopic studies.