Alternating copolymers of thiadiazole and quaterthiophenes – Synthesis, electrochemical and spectroelectrochemical characterization

摘要: Abstract A series of copolymers consisting alternating thiadiazole and unsubstituted or alkyl disubstituted quaterthiophene units, were synthesized by electropolymerization 2,5-bis(2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P1 ), 2,5-bis(4′-octyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole P2 2,5-bis(3′-octyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole P3 2,5-bis(3-decyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole P4 ). For comparative reasons was also obtained via Suzuki coupling 2,5-bis(5-bromo-2-thienyl)-1,3,4-thiadiazole neopentyl ester 4,4′-dioctyl-2,2′-dithienyl-5,5′-diboronic acid. As evidenced cyclic voltammetry studies the presence electron accepting unit in main polymer chain results an increase reductive doping potential studied compounds as compared to polythiophene poly(alkylthiophene). Electrochemically determined affinities values found range from −3.10 eV −3.14 eV, showing a negligible effect substituent on this parameter. To contrary, oxidation strongly depended position group. donating properties substituents particularly pronounced leading decrease its oxidative 210 mV, case ( corresponding drop ionization potentials +5.75 eV +5.54 eV. The characteristic capacitive plateau's following dopings suggests that both redox reactions are true polymers can be transformed either n-type p-type conductors. these findings additionally corroborated UV–vis-NIR spectroelectrochemical data which unequivocally show formation polaronic/bipolaronic bands upon dopings. analysis Raman for , supported theoretical calculations vibrational model, leads conclusion mechanism electrochemical is same poly(alkylthiophene) homopolymers involves transformation benzoid-like structure into quinoid one. judged copolymers, seems most promising candidate application such organic electronic devices p-channel field transistors (FETs), photodiodes (PD) photovoltaic cells (PC), however use air operating n-channel ambipolar FETs excluded due relatively high absolute value affinity.