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Fluorene Units (fluorene + unit)
Selected AbstractsA Bipolar Host Material Containing Triphenylamine and Diphenylphosphoryl-Substituted Fluorene Units for Highly Efficient Blue ElectrophosphorescenceADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Fang-Ming Hsu Abstract Highly efficient blue electrophosphorescent organic light-emitting diodes incorporating a bipolar host, 2,7-bis(diphenylphosphoryl)-9-[4-(N,N -diphenylamino)phenyl]-9-phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6-difluoro-phenyl)pyridinato- N,C2´]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron-donating (p-type) triphenylamine group and an electron-accepting (n-type) 2,7-bis(diphenyl-phosphoryl)fluorene segment linked through the sp3 -hybridized C9 position of the fluorene unit. The lack of conjugation between these p- and n-type groups endows POAPF with a triplet energy gap (ET) of 2.75,eV, which is sufficiently high to confine the triplet excitons on the blue-emitting guest. In addition, the built-in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF-based device doped with 7,wt% FIrpic exhibits a very low turn-on voltage (2.5,V) and high electroluminescence efficiencies (20.6% and 36.7,lm W,1). Even at the practical brightnesses of 100 and 1000,cd m,2, the efficiencies remain high (20.2%/33.8,lm W,1 and 18.8%/24.3,lm W,1, respectively), making POAPF a promising material for use in low-power-consumption devices for next-generation flat-panel displays and light sources. [source] A New Donor,Acceptor,Donor Polyfluorene Copolymer with Balanced Electron and Hole Mobility,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007A. Gadisa Abstract A new alternating polyfluorene copolymer poly[2,7-(9,9-dioctylfluoren)- alt -5,5-(5,,8,-di-2-thienyl-(2,,3,-bis-(3,,-octyloxyphenyl)-quinoxaline))] (APFO-15), which has electron donor,acceptor,donor units in between the fluorene units, is synthesized and characterized. This polymer has a strong absorption and emission in the visible range of the solar spectrum. Its electroluminescence and photoluminescence emissions extend from about 560 to 900 nm. Moreover, solar cells with efficiencies in excess of 3.5,% have been realized from blends of APFO-15 and an electron acceptor molecule, a methanofullerene [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM). It has also been observed that electron and hole transport is balanced both in the pure polymer phase and in polymer/PCBM bulk heterojunction films, which makes this material quite attractive for applications in opto-electronic devices. [source] Insight into the Role of Oxidation in the Thermally Induced Green Band in Fluorene-Based Systems,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2007R. Grisorio Abstract The causes of the spectral instability of poly[9,9-dioctylfluoren-2,7-diyl-co-2,,7,-spiro(cyclohexane-1,9,-fluorene)] during thermal annealing in air, which leads to a green photoluminescence (PL) emission band, are investigated. The Igreen/Iblue ratio evolution (I,=,intensity) is found to be independent of the amount of monoalkylfluorene defects, despite the fact that their presence might be regarded as a trigger for the radical process leading to polymer degradation in the presence of a trace amount of metal catalyst. Furthermore, the absence of a correlation between the degree of oxidation of the material and the Igreen/Iblue ratio indicates that the spatial disposition of fluorenones formed during the thermal degradation of the material, rather than their amount, is to be strictly related to the Igreen/Iblue ratio. The evidenced formation of fluorenone agglomerates, which could be considered the cause for the consistent increase in the Igreen/Iblue ratio during a thermal oxidation of a polyfluorene, confirms that the radical mechanism can also involve dialkylfluorene systems. Finally, the higher resistance to thermal degradation shown by spirocyclohexane fluorene units with respect to dioctylfluorene ones allows the synthesis of new, spectrally stable, fluorene-based copolymers. [source] Triphenylamine-based fluorescent conjugated copolymers with pendant terpyridyl ligands as chemosensors for metal ionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2010Yi Cui Abstract Two well-defined triphenylamine-based fluorescent conjugated copolymers with pendant terpyridyl ligands were synthesized through Suzuki coupling polymerization and were further characterized by 1H-NMR, 13C-NMR, gel permeation chromatography, Infrared, and UV-vis spectra. Polymer P-1, terpyridine-bearing poly(triphenylamine- alt -fluorene) with a high fluorescence quantum yield (62%) shows much higher sensitivities toward Fe3+, Ni2+, and Cu2+ as compared with the other metal ions investigated. Especially, Fe3+ can lead to an almost complete fluorescence quenching of polymer P-1. Whereas, the analogous polymer P-2, in which N -ethylcarbazole repeat units replace the fluorene units in P-1, shows a very poor selectivity. It demonstrates that polymers with a same receptor may show different sensitivity to analytes owing to their different type of backbones. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1310,1316, 2010 [source] New environmentally responsive fluorescent N -isopropylacrylamide copolymer and its application to DNA sensingJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2006Chang-Chung Yang Abstract We report two novel multifunctional copolymers consisting of a temperature-responsive poly(N -isopropylacrylamide) (PNIPAA) segment and a fluorescent fluorene-containing acrylic polymer segment with pH responsiveness and/or DNA-sensing ability. The functional acrylic monomer with a fluorene dimer side group substituted with amino units was synthesized first. Then, it was copolymerized with N -isopropylacrylamide to result in a new water-soluble, fluorescent PNIPAA copolymer (P1). The fluorescent properties of P1 under neutral and acidic conditions did not change with the temperature. However, significant variation was observed under basic conditions. The protonation of the amino moiety at a low pH improved the solubility and prevented aggregation for fluorescence quenching, but not under the basic conditions. Although aggregation of the fluorene units was significant at room temperature under basic conditions, the aggregation was resolved at a temperature above the lower critical solution temperature. These findings indicated the pH- and temperature-responsive characteristics of P1. Moreover, after the amino groups were quaternized, the obtained polymer could be used as a biosensor because the fluorescence intensity was quenched with the addition of DNA. This study demonstrates that multifunctional materials with pH- and temperature-sensing characteristics and biological molecules could be realized by the incorporation of a functional fluorene-containing moiety with PNIPAA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5495,5504, 2006 [source] Highly soluble diphenylfluorene-based cardo copolyimides containing perylene units,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7-8 2006Shengang Xu Abstract Two series of novel ternary copolyimides containing perylene and fluorene units in the backbone were synthesized by one-step polycondensation of diamine (4,4,-(9H-fluoren-9-ylidene)bisphenylamine, FBPA) with perylene dianhydride (3,4,9,10-perylenetetracarboxylic dianhydride, PTCDA) and a comonomer [4,4,-(hexafluoroisopropylidene) diphthalic anhydride, 6FDA or 3,3,,4,4,-benzophenonetetracarboxylic dianhydride, BDTA]. The polymers were named as PFFx (PTCDA-FBPA-6FDA) and PFBx (PTCDA-FBPA-BTDA), respectively, and their chemical structures were identified by FT-IR spectra and elemental analyses. Perylene contents in the copolyimides were determined through a quantitative UV-vis spectroscopy method, which are in agreement with the values calculated from the added raw materials both for PFFx and PFBx. Gel permeation chromatography (GPC) measurement suggested that the weight average molecular weight (Mw) is in the range 2.1,5.09,×,104 and the molecular weight distribution (MWD) is 1.86,2.72 for PFFx, and those for PFBx are 2.64,4.73,×,104 and 2.44,2.92, respectively. Thermogravimetric analysis (TGA) measurements showed that the copolyimides are very thermally stable with a temperature of 10% weight loss (T10) in the range 546,563°C for PFFx, and 538,548°C for PFBx. The copolyimides also have good solubility in common organic solvents such as chloroform and tetrahydrofuran. These unique properties can be attributed to the existence of the bulky diphenylfluorene moieties in the polymer backbone. All the copolyimides can emit strong fluorescence both in solution and in films, which make them possibly be used as thermostable light-emitting materials for organic light-emitting diodes. Copyright © 2006 John Wiley & Sons, Ltd. [source] Conjugated Polyelectrolytes for Protein Assays and for the Manipulation of the Catalytic Activity of EnzymesCHEMISTRY - AN ASIAN JOURNAL, Issue 8-9 2008Lingling An Abstract A new method has been developed to discriminate between proteins with different isoelectric points by using fluorescent conjugated polyelectrolytes. Charged water-soluble polyfluorenes that contain 2,1,3-benzothiadiazole (BT) units demonstrate intramolecular energy transfer from the fluorene units to the BT sites when oppositely charged proteins are added to the mixture. This results in a shift in emission color from blue to green and a change in the emission intensity of conjugated polyelectrolytes, which makes it possible to assay proteins. The formation of conjugated polyelectrolyte/enzyme complexes by electrostatic interactions can be utilized to manipulate the activity of enzymes by means of local alteration of enzyme charge density. The oppositely charged substrate binds to conjugated polyelectrolyte and reduces the distance between the enzyme and the substrate, leading to an increase in the cleavage reaction rate. The new method has three important features: 1),it offers a convenient "mix-and-detect" continuous approach for protein assays and rapid detection of enzyme activity; 2),the use of water-soluble conjugated polyelectrolytes imparts the sensor with a high sensitivity; 3),this method does not require fluorescent labels on the targets, which should significantly reduce the cost. [source] | ||||||||||