The effect of para- and meta-substituted fluorine on optical behavior of benzimidazole derivatives

Design, synthesis, and electrochemical properties of two novel donor-acceptor-donor type benzimidazole and thiophene based monomers; 2-(4-fluorophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole (BIPF) and 2-(3-fluorophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole (BIMF) were highlighted. The position of fluorine as a substituent was varied from para- to meta- in order to investigate position effects on the electrochemical and optical properties of electrochemically synthesized polymers. Both polymers were p type dopable and they can be switched between orange and blue color during p-doping/dedoping. Significant improvements in the percent transmittance for PBIMF were observed compared to similar molecules in literature

Novel poly(2,5-dithienylpyrrole) (PSNS) derivatives functionalized with azobenzene, coumarin and fluorescein chromophore units: spectroelectrochemical properties and electrochromic device applications

Three novel 2,5-dithienylpyrrole (SNS) derivatives containing strong chromophore units such as azobenzene, coumarin and fluorescein were synthesized to investigate the effects of chromophore substituents on the electrochemical and spectroelectrochemical properties of resulting polymers. Electrochemical and optoelectronic characteristics of the homopolymers, poly(1-(2-(4-(phenyldiazenyl)phenoxy)ethyl)-2,5di(thiophen-2-yl)-1H-pyrrole) (PTPTAz), poly(4-(2-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)ethoxy)-2H-chromen-2-one) (PTPTCo) and poly(methyl 2-(6-(2-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl) ethoxy)-3-oxo-3H-xanthen-9-yl) benzoate) (PTPTFlo), were investigated in detail. The combination of a strong chromophore pendant group with a poly(2,5-dithienylpyrrole) (PSNS) backbone significantly influences the electronic and optoelectronic behaviors of conducting polymers. PTPTAz and PTPTCo exhibited different colors in their neutral and oxidized states while PTPTFlo showed a yellow color in all states. The optical band gap (E-g) values of PTPTAz, PTPTCo and PTPTFlo films were calculated as 2.81 eV, 2.44 eV and 2.31 eV respectively. Moreover, a PTPTFlo/PEDOT based dual type solid state electrochromic device (ECD) was constructed. The ECD exhibited quite good long-term stability with reasonable optical memory performance under ambient conditions

Investigation of Optical and Electrochemical Properties of Benzene Based Solution Processable 2,1,3-Benzooxadiazole Comprising Polymers

Four novel solution processable benzooxadiazole containing alternating copolymers namely poly (5,6-bis(octyloxy)-4-(5-phenylthiophen-2-yl)-7-(thiophen-2-yl)benzo[c][1,2,5]oxadiazole)PBOTPh, poly (5,6-bis(octyloxy)-4-(5-phenylselenophen-2-yl)-7-(selenophen-2-yl)benzo[c][1,2,5]oxadiazole)PBOSPh, poly (4-(furan-2-yl)-5,6-bis(octyloxy)-7-(5-phenylfuran-2-yl)benzo[c][1,2,5]oxadiazole)PBOFPh and poly (5,6-bis(octyloxy)-4-(5-phenylthieno[3,2-b]thiophen-2-yl)-7-(thieno[3,2-b]thiophen-2-yl)benzo[c][1,2,5]oxadiazole) PBOTTPh incorporating 5,6-bis(octyloxy)benzo[c][1,2,5]oxadiazole as the acceptor moiety and benzene as the donor moiety were synthesized via Suzuki polycondensation reaction. Various electron donor moieties were used as pi bridges in the polymer backbone to tailor the optoelectronic properties of the polymers. To explore the electrochemical and electrochromic properties and the photovoltaic properties of the copolymers, cyclic voltammetry, spectroelectrochemistry and kinetic studies were conducted. Thiophene, selenophene, furan and thienothiophene pi bridges were incorporated into the polymer backbones. Thiophene and selenophene based alternating copolymers showed purple color in its neutral state whereas furan and thienothiophene bearing copolymers have pinkish purple and dark purple in their neutral states respectively. The optical band gaps of the polymers were calculated as 1.85, 1.76, 1.58, 1.79 eV for thiophene, selenophene, thienothiophene and furan based copolymers, respectively. Among all the alternating copolymers, the lowest optical band gap corresponds to thienothiophene comprising alternating copolymer which is 1.58 eV and red shifted in absorption due to the stronger donor character compared to other analogs. HOMO and LUMO levels were calculated from cyclic voltammetry studies using onsets of oxidation and reduction, respectively. HOMO levels were calculated as -5.96 eV for PBOTPh, -5.85 eV for PBOSPh, -5.63 eV for PBOTTPh and -5.74 eV for PBOFPh. LUMO levels were determined as -4.02 eV for PBOSPh, -4.03 eV for PBOTTPh and -3.87 eV for PBOFPh. Bulk heterojunction (BHJ) polymer solar cells based on selenophene containing polymer were fabricated. The device architecture was: ITO/PEDOT:PSS/PBOSPh:PC71BM/Ca/Al. After optimization studies, best results for 130 nm thickness, Polymer:PC71BM with 1:2 ratio, V-oc, J(sc), FF, PCE (%) were found as 0.62 V, 4.53 mA cm(-2), 0.58, 1.63% under illumination of AM 1.5 G 100 mW cm(-2)

Synthesis and spectroelectrochemical characterization of multi-colored novel poly(3,6-dithienylcarbazole) derivatives containing azobenzene and coumarin chromophore units

Azobenzene and coumarin units bearing four novel 3,6-linked thiophene-carbazole-thiophene type electroactive monomers were synthesized in order to observe the effects of strong chromophore units on the electrochemical and spectroelectrochemical behaviors of resulting pi-conjugated conducting polymers (PTCbzAz, PECbzAz, PTCbzCo and PECbzCo). Electronic and optoelectronic properties of all polymers were investigated by cyclic voltammetry and in situ spectroelectrochemical studies, and their oxidation potentials, HOMO/LUMO energy levels, band gaps (E-g(op)), optical contrasts (Delta T%) and switching times were reported in detail. It was observed that incorporation of strong chromophore units in polymer backbones resulted in poly(3,6-dithienylcarbazole) derivatives with different optical band gap values and different number of colored states. The optical band gap values for PECbzAz, PECbzCo, PTCbzAz, PTCbzCo and were calculated as 1.71 eV, 1.75 eV, 1.93 eV and 2.07 eV, respectively, from the onset of pi-pi* transition in polymer films' neutral state absorptions. All polymers exhibited multicolored electrochromic behavior upon extarnally applied potential. Reported electrochemical and optical features of PECbzAz, PECbzCo, PTCbzAz, PTCbzCo suggest that these poly(3,6-dithienylcarbazole) derivatives are promising candidates for multicolored electrochromic device applications

Long wavelength photosensitizers in photoinitiated cationic polymerization: The effect of quinoxaline derivatives on photopolymerization

This article describes the use of functionalized quinoxaline derivatives as photosensitizers for diaryliodonium salt photoinitiators. Highly conjugated compounds with good absorption bands in long wavelength UV and visible region are presented. These versatile intermediates facilitate photoinitiated cationic polymerization of commercially important monomers such as cyclic ethers and vinyl epoxides. Polymerizations were carried out using long wavelength UV light in the presence of diphenyliodonium hexafluorophosphate (Ph2I+PF6-). The polymerizations were monitored by optical pyrometry (OP). In addition, we also demonstrate that it was also possible to initiate photopolymerizations under solar irradiation in the presence of these photosensitizers

Long wavelength photosensitizers in photoinitiated cationic polymerization: The effect of quinoxaline derivatives on photopolymerization

This article describes the use of functionalized quinoxaline derivatives as photosensitizers for diaryliodonium salt photoinitiators. Highly conjugated compounds with good absorption bands in long wavelength UV and visible region are presented. These versatile intermediates facilitate photoinitiated cationic polymerization of commercially important monomers such as cyclic ethers and vinyl epoxides. Polymerizations were carried out using long wavelength UV light in the presence of diphenyliodonium hexafluorophosphate (Ph2I+PF6-). The polymerizations were monitored by optical pyrometry (OP). In addition, we also demonstrate that it was also possible to initiate photopolymerizations under solar irradiation in the presence of these photosensitizers

Synthesis and Electrochromic Properties of Triphenylamine Containing Copolymers: Effect of pi-Bridge on Electrochemical Properties

In this study, a series of benzotriazole (BTz) and triphenylamine (TPA)-based random copolymers; poly4-(5-(2-dodecyl-7-methyl-2H-benzo[d][1,2,3]triazol-4-yl)thiophen-2-yl)-N-(4-(5-methylthiophen-2-yl)phenyl)-N-phenylaniline (P1), poly4-(2-dodecyl-7-methyl-2H-benzo[d][1,2,3]triazol-4-yl)-N-(4-methyl-[1,1-biphenyl]-4-yl)-N-phenyl-[1,1-biphenyl]-4-amine (P2), and poly4-(5-(2-dodecyl-7-(5-methylthiophen-2-yl)-2H-benzo[d][1,2,3]triazol-4-yl)-[2,2-bithiophen]-5-yl)-N-(4-(5-methylthiophen-2-yl)phenyl)-N-phenylaniline (P3) were synthesized to investigate the effect of TPA unit and -bridges on electrochemical and spectroelectrochemical properties of corresponding polymers. The synthesis was carried out via Stille coupling for P1, P3, and Suzuki coupling for P2. Electrochemical and spectral results showed that P1 has an ambipolar character, in other words it is both p-type and n-type dopable, whereas P2 and P3 have only p-doping property. Effect of different -bridges and TPA unit on the HOMO and LUMO energy levels, switching time, and optical contrast were discussed. All polymers are promising materials for electrochromic devices. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 537-54

Syntheses, electrochemical and spectroelectrochemical characterization of benzothiadiazole and benzoselenadiazole based random copolymers

Three novel donor-acceptor-donor type random copolymers based on benzothiadiazole (BTh) and benzoselenadiazole (BSe) were synthesized via Pd (0) catalyzed Suzuki polycondensation reaction. The two acceptor units were coupled with electron rich moieties which are carbazole (CZ), fluorene (FL) and silafluorene (SiFL). Monomers were characterized using H-1 and C-13-NMR spectroscopy. The number and weight average molecular weights of the polymers were calculated using gel permeation chromatography (GPC). All three polymers were electrochemically and spectroelectrochemically characterized. PBThBSeCZ, PBThBSeFL and PBThBSeSiFL showed only p-dopable character and their doping/dedoping potentials were determined as 1.4V/1.2V, 1.53V/1.27V and 1.8V/1.3V, respectively. Corresponding HOMO energy levels were calculated as -5.85eV, -6.05eV and -6.15eV whereas LUMO energy levels were found to be -3.67eV, -3.84eV and -3.77eV, respectively. PBThBSeCZ had lower HOMO level and band gap than PBThBSeFL and PBThBSeSiFL due to its increased electron donating capability of nitrogen atom in carbazole unit

Syntheses and Optical Properties of Perfluorophenyl Containing Benzimidazole Derivatives: The Effect of Donor Units

Synthesis of two novel donor - acceptor - donor type monomers containing benzimidazole as the acceptor unit and thiophene and 3,4-ethylenedioxythiophene (EDOT) as the donor units were performed. 2-(Perfluorophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole and 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-(perfluorophenyl)-1H-benzo[d]imidazole were synthesized successfully and polymerized electrochemically. The electrochemical and spectroelectrochemical studies of the polymers were studied. The effect of electron donating moieties on the optical properties of electrochemically polymerized polymers was investigated. Both polymers were p type dopable and possessed multi-chromic property. Optical studies demonstrated that the polymer based on EDOT unit (P2) resulted in lower band gap since EDOT is higher electron donating group than thiophene

A Low Band Gap Benzimidazole Derivative and Its Copolymer with 3,4-Ethylenedioxythiophene for Electrochemical Studies

A novel monomer; 2-(3-nitrophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole) (BIMN) was used for electrochemical copolymerization with 3,4-ethylenedioxythiophene (EDOT). Polymerization was achieved in acetonitrile (ACN)/dichloromethane (DCM) (1:1, 1:3 and 1:5, molar ratios) solution containing sodium perchlorate (NaClO4) and lithium perchlorate (LiClO4) mixture as the supporting electrolyte on an ITO electrode. The chemical structures of monomer and copolymers were characterized by nuclear magnetic resonance (H-1 NMR) and scanning electron microscopy (SEM). The optical and electrochromic properties were investigated by UV-vis spectrophotometer and cyclic voltammetry, respectively. Combination of BIMN and EDOT provides lower oxidation potential, lower bandgap and higher optical contrast. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved