Synthesis And Characterization Of Polythiophene Derivatives With Different Substitution Groups

Polythiophene as an important intinsic conducting polymers, it is currently used as an organic polymer solar cell materials to the research focus areas. And alkyl-substituted polythiophene derivatives have good solubility, good film-forming properties, excellent electrochemical activity and good environmental stability and ease of processing, etc. so it is widely used in the field of photovoltaic materials and color materials.Different electronic structure of alkyl-substituted monomers and oligomers polythiophene derivatives are studid using density functional theory (DFT) B3LYP optimized. With the aim to increase the number of substituents, the total energy of every molecule decreases, and WBIs remains at around1.170, it indicates that number of substituents is benefit for increasing the stability of molecules and each monomer molecules in the π electron transfer is not occured with increasing the number of substituents. When the substituent constant, as the degree of polymerization of the oligomer increases, WBIs performances are increased and the electron rich region is always in the thiophene ring. In the one hand the characteristics of these centers n bond key gradually increase, on the other hand it is beneficial for π electron mobility in the main chain. The results show that3BT,3HT tetramer have a relatively low bandgap that is1.899eV and2.196eV. Whether the degree of polymerization improves or the number of the alkyl group increases, the energy gap of polymers is gradually narrowed.Three kinds of poly (3-alkylthiophene), such as poly (3-butylthiophene)(P3BT), poly (3-hexylthiophene)(P3HT) and poly (3-dodecylthiophene)(P3DDT) are prepared by the Grignard Metathesis Method (GRIM). Their chemical structures are characterized by fourier transform infrared spectroscopy (FT-IR) and hydrogen spectrum of nuclear magnetic resonance (’H-NMR), and1-NMR result shows that regular structure of the polymers is relatively high. The GPC result shows that the molecular weight of three polymers is8.42×104g/mol,1.06×105g/mol and1.21×104g/mol with a molecular weight distribution of1.41,2.18and1.18, respectively. The DSC curves result shows that the glass transition temperature of three polymers is120.8℃,146℃,118℃, respectively. UV absorption spectrum and fluorescence spectroscopy of three polymers solution show that the maximum absorption wavelength is448nm,470nm,390nm with the band gap of2.06eV,1.86eV,2.21eV, respectively. The emission maximum of three polymers in THF solution is531nm,535nm,527nm, respectively. But the maximum absorption wavelength of three polymers film is482nm,542nm,460nm, respectively.3-thiophenecarboxaldehyde condense sulfanilic acid is synthesized by the use of ethanol and water system in this research, and its structure is characterized by FT-IR. Then poly(3-thiophenecarbaldehyde condense sulfanilic acid) is synthesized by the method Fe(III) catalyzed oxidation. The claim structure of the polymer is characterized by Infrared spectrum. The GPC result shows the molecular weight of the polymer is6980g/mol with a molecular weight distribution of1.37. The DSC curves result indicates that a glass transition temperature Tg of the polymer is153℃. The polymer has better thermal stability, which can suit to the basic requirements of a conjugated polymer organic photovoltaic material.