A series of bithiophene-based compounds, 2-(5′-alkyl-2,2′-bithiophene-5-yl)-benzoxazole derivatives (nTBx), bearing different substituents (H, CH3, Cl, NO2) at the 5-position, were prepared and characterized. They exhibit enantiotropic mesophases with temperature ranges of 3°C–61°C and 4°C–71°C during heating and cooling, and nTBx with electron-withdrawing substituents (NO2, Cl) display higher clearing temperatures and wider mesophase ranges than those of corresponding homologues with electron donating substituents. Compared to biphenyl-based analogs (nB-x), nTBx show much larger red-shifted absorption bands (374–388 nm) and photoluminescence emission peaks (453–458 nm), thereby illustrating the impact of the bithiophene core on electronic properties originating from the π-molecular orbitals.
Yan Zhang,Lingqian Kong,Xuezhong Liu,Chunlei Wang,Jinsheng Zhao
Two monomers including 4,4′,4″-tris(3-methoxythiophene-2-yl)triphenylamine ( M1 ) and 4,4′,4″-tris(3,4-dimethoxythiophene-2-yl)triphenylamine ( M2 ) with triphenylamine as their core were synthesized and the corresponding polymers were obtained by electrochemical polymerization. Their electrochemical properties were investigated using scanning electron microscopy, UV–Vis, and cyclic voltammetry. It was found that the two polymers had reversible redox behavior with the different color change under the applied potentials. Both the polymers displayed high switching efficiency and optical contrast. Moreover, the corresponding electrochromic devices (ECDs) employing the synthesized polymers and poly(3,4-ethylenedioxythiophene) were constructed. The spectroelectrochemical experiments illustrated that the ECDs exhibited fast response time, reasonable optical contrast, favorable optical memories, and redox stability.
Ionic liquids 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM]BF 4 ), 1-butyl-3-methylimidazoliumhexafluorophosphate ([BMIM]PF 6 ) and conventional medium tetrabutylammonium perchlorate (TBAP) were utilized as electrolyte for the preparation of poly(4,4′,4′'-tris[4-(2-bithienyl)phenyl]amine) (PTBTPA) films and assembling of EC devices. FTIR spectra and EDX pattern demonstrate an effective doping of the anion into the PTBTPA film at the oxidation state. SEM images investigate the thickness of the polymer films and the morphologies of crimped structure at the oxidation state. The ion diffusion distance (the thickness of polymer film) plays a more critical role for the EC switching speed. According to the electrochemical impedance spectra, the improved ionic conductivity with ionic liquid [BMIM]BF 4 as the electrolyte promote ions more easily dope into the polymer film which leads to the higher optical contrast. In addition, the size of doping anion during the redox process has essential influence on the electrochemical stability.
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