Polyalkylthiophene-containing electron donor and acceptor heteroaromatic bicycles: synthesis, photo-physical, and electroluminescent properties

The synthesis and characterization of a series of polyalkylthiophenes-containing electron-rich thienothiophene (donor heteroaromatic bicycle) and electron-deficient benzothiadiazole (acceptor heteroaromatic bicycle) block have been reported. The polymers are synthesized by Stille cross-coupling reaction and are found to be having high molecular weight with number-average molecular weight in the range of 7.1 x 10(4)-5.7 x 10(4). The photo-physical, electro-chemical, and electroluminescent (EL) properties of the polymers are investigated in detail. The optical band gap of the polymers is found to be in the range of 1.53-1.54 eV. These new polymers are luminescent in nature and showed red photoluminescence in chloroform solution (722-740 nm) as well as in thin film (781-786 nm). Ionization potential for these polymers is calculated and falling in the range of 5.23-5.33 eV. Polymer light emitting diodes with configuration ITO/PDOT:PSS/polymer/BCP/Alq(3)/LiF/Al have been fabricated, and a deep red emission is observed. The EL maxima of polymers are found to be in the range of 750-760 nm with threshold voltages around 4.0-5.5 V. The fabricated devices show luminescence around 40 cd/m(2) at current density of 100 mA/cm(2) with maximum value of 580-810 cd/m(2) at 11 V

Fluorene-based conjugated poly(arylene ethynylene)s containing heteroaromatic bicycles: preparation and electro-optical properties

A series of high molecular weight fluorene-based soluble poly(arylene ethynylene)s (PAEs) have been prepared and characterized. The polymers consist of 2,5-bis(3-tetradecylthiophen-2-yl)-3a,6a-dihydrothieno[3,2-b]thiophene, 2,5-bis(3-tetradecylthiophen-2-yl)-3a,6a-dihydrothiazolo[5,4-d]thiazole, or 4,7-bis(3-tetradecylthiophen-2-yl)benzo[c] [1, 2, 5] thiadiazole unit with an electron donor 9,9-bis(2-ethylhexyl)-9H-fluorene unit connected via electron accepting ethynylene linkage. The molecular weights (M (w)) of the polymers were found to be in the range of 103600-179000 g/mol with polydispersity index (PDI) of 3.9-5.0. Optical and redox properties have been investigated by UV-visible, fluorescence spectroscopy, and cyclic voltammetry (CV) measurements. Combination of experimental and density functional theory (DFT) calculations indicated that the benzothiadiazole unit incorporated polymer has lowest band gap with most stable lowest unoccupied molecular orbital (LUMO) energy level. Polymer light emitting diode properties have been investigated for the polymer having highest molecular weight with device configuration ITO/PEDOT:PSS/Polymer/LiF/Al. Well-behaved diode characteristics with EL maxima at 600 nm were observed

Dithieno[3,2-b:2′,3′-d]pyrrole–alkylthiophene–benzo[c][1,2,5]thiadiazole-based highly stable and low band gap polymers for polymer light-emitting diodes

A series of new low band gap π-conjugated polymers containing N-alkyldithieno[3,2-b:2′,3′-d]pyrrole, benzo[c][1,2,5]thiadiazole, and alkylthiophenes are reported. The polymerization condition was standardized and the use of CuO to obtain high-molecular-weight polymer was also realized. The molecular weight of the polymers was found to be in the range of 45,000–53,000. All the polymers were found to be soluble in most of the common organic solvents, such as chloroform, dichloromethane, THF, and chlorobenzene with excellent film forming properties. The λmax of the polymers was found to be in the range of 687–663 nm with band gap in the range of 1.35–1.43 eV. The oxidation potential of the polymers from cyclic voltammetry was determined to be 0.5–0.75 V. The HOMO levels of the above synthesized polymers were found to be between 5.24 and 5.54 eV. All the polymers exhibited a PL emission in between 755 and 773 nm. The polymers were found to be thermally stable above 277 °C with only a 5% weight loss. From the thermal stability values, it is expected that the current set of polymers are stable enough for the application in electronic devices. To realize the potential use of the polymers, EL devices were fabricated and found to show red emission with comparatively low threshold voltage. A brightness of 54 cd m−2 for the device with polymer PC could be reached

Dendronized electrochromic polymer based on poly(3,4-ethylenedioxythiophene)

In order to improve electrochromic contrast, 3,4-ethylenedioxythiophene (EDOT) substituted with the first generation dendritic wedge based on gallic acid (M2) was synthesized by connecting 3,4,5-tribenzyloxy benzyl chloride to hydroxymethyl EDOT (M1). Electropolymerization of M1 and M2 resulted in the formation of an electroactive and well adhered film on the electrode surface. In the case of PEDOT substituted with the dendritic wedge (P2), it was observed that the resistance of the film increases with thickness. Spectroelectrochemical studies indicated that the polymers switch from a highly opaque dark-blue reduced state to highly transmissive oxidized state with a contrast of 67% in P2 and 46% in P1. In situ conductivity studies showed a sharp transition from a dedoped insulating state to doped conducting state at around −0.4 V with maximum in situ conductance of 0.06 S for P1 and 0.04 S for P2.© Elsevie

Hyperbranched Poly(arylene ethynylene)s with Triphenylamine Core for Polymer Light-Emitting Diodes

A series of light-emitting hyperbranched poly(arylene ethynylene)s (HB-PAEs) were prepared by the Sonogashira coupling from bisethynyl of carbazole, fluorene, or dialkoxybenzenes (A2 type) and tris(4-iodophenyl)amine (B3 type). For comparison, two linear polymers (L-PAEs) of the HB analogs were also synthesized. The polymers were characterized by Fourier transform infrared, NMR, and GPC. The HB polymers showed excellent solubility in chloroform, THF, and chlorobenzene when compared with their linear analogs. The number-average molecular weight (Mn) of the polymers determined from GPC was found to be in the range of 18,600–34,200. The polymers were thermally stable up to 298–330 °C with only 5% weight loss. The absorption maxima of the polymers were between 354 and 411 nm with optical band gap in the range of 2.5–2.9 eV. The HB polymers were found to be highly fluorescent with photoluminescence quantum yields around 33–42%. The highest occupied molecular orbital energy levels of the polymers calculated from onset oxidation potentials were found to be in the range from −5.83 to −6.20 eV. Electroluminescence (EL) properties of three HB-PAEs and one L-PAE were investigated with device configuration ITO/PEDOT:PSS/Polymer/LiF/Al. The EL maxima of HB-PAEs were found to be in the range of 507–558 nm with turn-on voltages around 7.5–10 V and maximum brightness values of 316–490 cd/m2. At the same time, linear analog of one HB-PAE was found to show a maximum brightness of 300 cd/m2 at a turn-on voltage of 8.2 V

Synthesis and characterization of alternative donor–acceptor arranged poly(arylene ethynylene)s derived from 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP)

A series of donor–acceptor type poly(arylene ethynylene)s (PAEs) have been synthesized through Sonogashira polycondensation. The polymers consist of an electron donating 9,9-bis(2-ethylhexyl)-9H-fluorene, triphenylamine, 1,4-dialkoxybenzene or 9-(2-ethylhexyl)-9H-carbazole unit and an electron accepting 2,5-bis(2-ethylhexyl)-3,6-diphenylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (EH-DPP) unit, alternately connected through ethynyl bridge. The polymers exhibit weight-average molecular weights (Mw) up to 68, 500 and are soluble in chlorobenzene, dichlorobenzene, THF, chloroform and toluene. A brilliant red solution with absorption maxima between 491 and 500 nm was observed for all the polymers. An intense red fluorescent with photoemission maxima between 551 and 571 nm was observed from polymer solutions. The polymers showed good thermal stability with decomposition temperature more than 260 °C at 5% weight loss. Onset oxidation potentials of the polymers were observed between 1.30 and 1.58 V with HOMO energy levels in the range of −6.10 to −6.38 eV. The OLED devices were fabricated with configuration of ITO/PEDOT:PSS/polymer/LiF/Al for all the polymers and EL maxima between 666 and 684 nm were observed

Novel high contrast electrochromic polymer materials based on 3,4-propylenedioxythiophene

Mono and di allyl and napthyl substituted 3,4-propylenedioxythiophenes were synthesized and polymerized electrochemically. All the monomers were characterized for their molecular structures, and the polymers were characterized for their electrochemical properties. The disubstituted derivatives showed higher contrast than the corresponding mono substituted derivatives. The allyl substituted polymers showed higher contrast and faster switching time than corresponding napthyl substituted derivatives. The presence of the allyl group as the pendant can be used for further functionalization of the polymer

High contrast solid-state electrochromic devices from substituted 3,4-propylenedioxythiophenes using the dual conjugated polymer approach

Solid-state electrochromic windows from 3,4-propylenedioxythiophene (ProDOT) derivatives using dual polymer electrochromic architecture were fabricated and their electro-optical characteristics were recorded. DibenzylProDOT (DiBz-ProDOT) and biphenylmethyloxymethyl ProDOT (BPMOM-ProDOT) were used as cathodically coloring polymers, whereas bis(2-(3,4-ethylenedioxy)thienyl)-N-methyl carbazole (BEDOT-NMCz) was used as their complementary anodically coloring polymer. Straightforward assembly of the devices was designed by means of using a UV photo-curable gel. These devices exhibited response speeds of approximately 1 s with photopic contrasts as high as 52% for the complete device, and were found to exhibit good stability under open circuit conditions. Convenience of reporting photopic values to characterize electrochromic devices compared to reporting contrasts at a single wavelength is remarked.© Elsevie