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Phenylene
Terms modified by Phenylene Selected AbstractsOligomers and Cyclooligomers of Rigid Phenylene,Ethynylene,Butadiynylenes: Synthesis and Self-Assembled Monolayers,ANGEWANDTE CHEMIE, Issue 35 2010Stefan-S. Ausgehend vom gleichen Bisacetylen entstanden abhängig von den Reaktionsbedingungen (Palladium- oder Kupferkatalyse) selektiv cyclische oder acyclische Oligomere mit n=2,6 (siehe Bild für den Fall n=3), die durch frei rotierende Eckstücke verknüpft sind. Aus STM-Bildern der selbstorganisierten Monoschichten folgt der Unterschied im Adsorptionsverhalten der acyclischen und cyclischen Oligomere. [source] ChemInform Abstract: Synthesis of Bent [4]Phenylene (Cyclobuta[1,2-a:3,4-b,]bisbiphenylene) and Structure of a Bis(trimethylsilyl) Derivative: The Last [4]Phenylene Isomer.CHEMINFORM, Issue 23 2002Dennis T.-Y. Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Towards a Better Understanding of Magnetic Interactions within m -Phenylene ,-Nitronyl Nitroxide and Imino Nitroxide Based Radicals, Part III: Magnetic Exchange in a Series of Triradicals and Tetraradicals Based on the Phenyl Acetylene and Biphenyl Coupling UnitsCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2005Laure Catala Dr. Abstract The present work completes and extends our previous reports1,,2 on the determination of the magnetic ground state and on the strength of the through bond exchange coupling within series of biradicals. This knowledge was subsequently exploited for the analysis of the magnetic interactions in their crystals. We report here the studies of series of triradicals incorporating ,-nitronyl nitroxides (NN) or ,-imino nitroxides (IN) as terminal radical fragments connected through a m -phenylene coupling unit in one case and a phenyl acetylene unit in other case. Tetraradical derivatives have also been studied. The studies of isolated molecules (EPR in solution and DFT calculations) allow the assessment of the magnetic interactions through the magnetic coupling unit. All triradical derivatives are found to exhibit a quartet ground state, whereas a singlet ground state is determined for the tetraradical. This last result reinforces previous findings that the singlet ground state is favoured in related biradicals involving similar m -phenylene couplers. Moreover, the through bond magnetic exchange coupling for the ortho,meta connectivity could be demonstrated as being ferromagnetic, thus ascertaining our previous hypotheses.1 The magnetic properties of the triradicals and tetraradicals in their solid state have been rationalized by using a previously proposed methodology,2 allowing to identify the most relevant magnetic pathways. Le présent travail complète et étend nos travaux précédents portant sur la détermination des couplages d'échange magnétique intramoléculaires de séries de biradicaux,1,,2 et partant de cette connaissance, de l'analyse des corrélations magnétostructurales dans l'état cristallin. Nous présentons ici l'étude de séries de triradicaux comprenant des radicaux , -nitronyl nitroxydes (NN) ou , -imino nitroxydes (IN) substitués en méta d'un groupement phénylène d'une part, et en para d'un groupement phénylène éthynylène d'autre part. Des dérivés tétraradicalaires ont aussi été synthétisés et étudiés. Les interactions d'échange magnétique à travers les liaisons sont estimées d'après l'étude de ces molécules isolées par RPE en solution ainsi que par des calculs effectués dans l'approximation de la fonctionnelle densité (DFT). Alors que l'ensemble des dérivés triradicalaires présente un état fondamental magnétique quartet de spin, un état singulet est proposé pour les tétraradicaux. Ce dernier résultat confirme nos travaux précédents1 ayant conclu à un état fondamental singulet pour des biradicaux basés sur le même coupleur. De plus, le couplage d'échange magnétique au travers du coupleur phénylène éthynylène pour des biradicaux substitués dans une topologie ortho,méta est ferromagnétique, confirmant ainsi les hypothèses antérieures.1 Suivant une méthodologie précédemment décrite,2 les propriétés magnétiques des triradicaux à l'état cristallin ont pu être analysées dans le détail et permettent de proposer des chemins d'interaction magnétique et des géométries de contacts intermoléculaires précises pour l'établissement d'interactions magnétiques bien identifiées. El presente trabajo completa y extiende nuestras anteriores estudios1,,2 sobre la determinacion del estado fundamental magnético y la fuerza del intercambio magnetico a través del enlace en una serie de biradicales. Esta información es luego usada en el análisis de las interacciones magneticas dentro de sus cristales. En este trabajo presentamos los estudios sobre una serie de triradicales que contienen , -nitroxidos nitronílicos (NN) o , -imino nitróxidos (IN) como fragmentos radicalarios terminales conectados a través de unidades acopladoras del tipo m -phenilénicas, en un caso, y fenil acetilénicas, en el otro. Se han estudiado también tetraradicales. Los estudios con moleculas aisladas (EPR en disolución y DFT) permiten evaluar las interacciones magneticas a través de las unidades acopladoras. Todos los triradicales se ve que presentan un estado fundamental del tipo cuadruplete, mientras que el cuadruplete se cree que tienen un estado fundamental singlete. Este último resultado refuerza las conclusiones de un estudio previo en el que se vió que el singlete es el estado fundamental en biradicales similares conectados por una unidad m -fenilénica. Además, el intercambio magnético a través del enlace para la conectividad orto y meta se demuestra que es ferromagnetica, confirmando hipótesis anteriores.1 Las propiedades magnéticas de los triradicales y tetraradicales en su estado sólido se han racionalizado empleando una matodología propuesta anteriormente,2 identificando los caminos magnéticos relevantes. [source] Improved and Controlled Complexation of Paraquat Derivatives by the Formation of a Bis(m -phenylene)-26-Crown-8-Based Lariat EtherEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2010Mingming Zhang Abstract A novel bis(m -phenylene)-26-crown-8-based lariat ether (i.e., 3b) was synthesized and characterized. It can bind paraquat derivatives more strongly than bis(m -phenylene)-26-crown-8 in solution. It forms pseudorotaxanes with two paraquat derivatives in the solid state. N -Methyl substitution was found to play an important role on the binding strength of lariat ether 3b. Furthermore, due to the introduction of two benzyloxy groups, its binding to paraquat derivatives can be switched off (and back on) by adding K+ (and then dibenzo-18-crown-6), and the disassociation percentage depends on the concentration of the added K+ ions. [source] Preparation of Bis(m -phenylene)-32-crown-10-Based Cryptand/Bisparaquat [3]Rotaxanes with High EfficiencyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 36 2008Shijun Li Abstract Two [3]rotaxanes were synthesized from two bis(m -phenylene)-32-crown-10-based cryptands and a bisparaquat derivative by using a threading-followed-by-stoppering method. As a result of strong association and positive cooperative complexation between the cryptands and the bisparaquat derivative, high yields and high selectivities were achieved. No [2]rotaxanes were found during the preparation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Helically ,-Stacked Conjugated Polymers Bearing Photoresponsive and Chiral Moieties in Side Chains: Reversible Photoisomerization-Enforced Switching Between Emission and Quenching of Circularly Polarized FluorescenceADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Hiroyuki Hayasaka Abstract Novel multifunctional conjugated polymers, [poly(p -phenylene)s and poly(bithienylene-phenylene)s with (R)- and (S)-configurations], which have fluorescence, chirality, and photoresponsive properties, have been designed and synthesized. The polymers are composed of ,-conjugated main chains, where poly(p -phenylene) and poly(bithienylene-phenylene) are fluorescence moieties, and the side chains of the photochromic dithienylethene moiety are linked with chiral alkyl groups. The polymer films exhibit right- or left-handed circularly polarized fluorescence (CPF) and also show reversible quenching and emitting behaviors as a result of photochemical isomerization of the dithienylethene moiety upon irradiation with ultraviolet and visible light. This is the first report realizing the reversible switching of CPF using chirality and photoresponsive properties. [source] Heat resistance and flammability of high performance fibres: A reviewFIRE AND MATERIALS, Issue 4-5 2002Serge Bourbigot The heat and flame resistance of high performance fibres are reviewed according to the literature data. The performance is discussed considering the physical and chemical structure of the fibres. Some selected high performance fibres are then evaluated using the cone calorimeter as a fire model to provide realistic data on the fire behaviour of the fibres. They are also examined in terms of heat resistance using combined TGA/DSC. The results are discussed and compared with literature data. Heterocyclic rigid-rod polymers (poly (p-phenylene-2,6-benzobisoxazole or PBO (Zylon®) and poly(2,6-diimidazo (4,5-b:4,,5,-e) pyridinylene-1,4 (2,5-dihydroxy) phenylene or PIPD (M5)) exhibit the best performance (little or contribution to fire, low smoke and good heat resistance) and offer a good combination between heat and flame resistance and mechanical properties. Copyright © 2002 John Wiley & Sons, Ltd. [source] PIPD, a new high-modulus and high-strength polymer fibre with exceptional fire protection propertiesFIRE AND MATERIALS, Issue 4-5 2002M.G. Northolt The development of the new high-modulus and high-strength fibre M5, made of poly{2,6-diimidazo[4,5-b:4,,5, -e]-pyridinylene-1,4(2,5-dihydroxy)phenylene} or PIPD, has resulted in an organic polymer fibre with exceptional fire protection properties when compared with PBO, Twaron, Kevlar and Nomex fibres. The PIPD as-spun fibre with a modulus of 150 GPa and a tensile strength of 2.5 GPa is a crystal hydrate containing 21 wt% water. Cone calorimeter measurements yielded a fire performance index (FPI) 20 times higher than Nomex, with extremely low value for the specific extinction area (SEA) characterizing the smoke formation. The PIPD-HT fibre (recrystallized in an after treatment into the anhydrous crystalline structure) with a modulus >300 GPa and a strength >5 GPa has a FPI value similar to PBO but shows much less smoke formation than this fibre. Copyright © 2002 John Wiley & Sons, Ltd. [source] Intercalating Dye Harnessed Cationic Conjugated Polymer for Real-Time Naked-Eye Recognition of Double-Stranded DNA in SerumADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Kan-Yi Pu Abstract Thiazole orange (TO), an intercalating dye, is integrated into cationic poly(fluorene- alt -phenylene) (PFP) to develop a macromolecular multicolor probe (PFPTO) for double-stranded DNA (dsDNA) detection. This polymer design not only takes advantage of the high affinity between TO and dsDNA to realize dsDNA recognition in biological media, but also brings into play the light-harvesting feature of conjugated polymers to amplify the signal output of TO in situ. PFPTO differentiates dsDNA from single-stranded DNA (ssDNA) more effectively upon excitation of the conjugated backbone relative to that upon direct excitation of TO as a result of efficient fluorescence resonance energy transfer from the polymer backbone to the intercalated TO. In the presence of dsDNA, energy transfer within PFPTO is more efficient as compared to that for free TO/PFP system, which leads to better dsDNA discriminability for PFPTO in contrast to that for TO/PFP. The distinguishable fluorescent color for PFPTO solutions in the presence of dsDNA allows naked-eye detection of dsDNA with the assistance of a hand-held UV lamp. The significant advantage of this macromolecular fluorescent probe is that naked-eye detection of label-free dsDNA can be performed in biological media in real-time. [source] Amplified Spontaneous Emission of Poly(ladder-type phenylene)s , The Influence of Photophysical Properties on ASE Thresholds,ADVANCED FUNCTIONAL MATERIALS, Issue 20 2008Frédéric Laquai Abstract Amplified spontaneous emission (ASE) of a series of blue-emitting poly(ladder-type phenylene)s (LPPP)s has been studied in thin film polymer waveguide structures. The chemically well-defined step-ladder polymers consist of an increasing number of bridged phenylene rings per monomer unit starting from fully arylated poly(ladder-type indenofluorene) up to poly(ladder-type pentaphenylene). The ASE characteristics of the polymers including the onset threshold values for ASE, the gain and loss coefficients as well as the photoluminescence (PL) properties, i.e., the solid state fluorescence lifetimes, decay kinetics and solid state quantum efficiencies have been studied by time-resolved PL spectroscopy. A fully arylated polyfluorene has been synthesized and its photophysical properties were compared to the step-ladder polymers. Steady-state photoinduced absorption and ultrafast transient absorption spectroscopy have been used to study excited state absorption of singlet and triplet states and polarons present in the solid state. The results demonstrate a minimum regarding the onset threshold value of ASE for a fully arylated poly(ladder-type indenofluorene) and a successive increase of the ASE threshold for the step-ladder polymers with more bridged phenylene rings. In particular, carbazole-containing step-ladder LPPPs exhibit significantly increased ASE threshold values as compared to their carbazole-free analogues due to a pronounced overlap of stimulated emission (SE) and photoinduced absorption (PA). [source] Phase Segregation in Thin Films of Conjugated Polyrotaxane, Poly(ethylene oxide) Blends: A Scanning Force Microscopy Study,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007L. Sardone Abstract Scanning force microscopy (SFM) is used to study the surface morphology of spin-coated thin films of the ion-transport polymer poly(ethylene oxide) (PEO) blended with either cyclodextrin (CD)-threaded conjugated polyrotaxanes based on poly(4,4,-diphenylene-vinylene) (PDV), ,-CD,PDV, or their uninsulated PDV analogues. Both the polyrotaxanes and their blends with PEO are of interest as active materials in light-emitting devices. The SFM analysis of the blended films supported on mica and on indium tin oxide (ITO) reveals in both cases a morphology that reflects the substrate topography on the (sub-)micrometer scale and is characterized by an absence of the surface structure that is usually associated with phase segregation. This observation confirms a good miscibility of the two hydrophilic components, when deposited by using spin-coating, as suggested by the luminescence data on devices and thin films. Clear evidence of phase segregation is instead found when blending PEO with a new organic-soluble conjugated polymer such as a silylated poly(fluorene)- alt -poly(para -phenylene) based polyrotaxane (THS,,-CD,PF,PPP). The results obtained are relevant to the understanding of the factors influencing the interfacial and the intermolecular interactions with a view to optimizing the performance of light-emitting diodes, and light-emitting electrochemical cells based on supramolecularly engineered organic polymers. [source] Tetrathiafulvalene-, 1,5-Dioxynaphthalene-, and Cyclobis(paraquat- p -phenylene)-based [2]Rotaxanes with Cyclohexyl and Alkyl Chains as Spacers: Synthesis, Langmuir,Blodgett Films, and Electrical Bistability,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2007X. Guo Abstract The synthesis and characterization of two new (TTF-DNP-CBPQT4+) [2]rotaxanes 1 and 2 is reported, based on tetrathiafulvalene (TTF), 1,5-dioxynaphthalene (DNP), and cyclobis(paraquat- p -phenylene) (CBPQT4+) with cyclohexyl and alkyl chains as the spacers. Multilayer Langmuir,Blodgett (LB) films of [2]rotaxanes 1 and 2 are prepared. Conducting atomic force microscopy, scanning tunneling microscopy, and two-terminal junction device studies indicate that the LB films of [2]rotaxanes 1 and 2 show electrical bistability behavior. By comparing with the TTF-DNP-CBPQT4+ [2]rotaxanes reported by Stoddart et,al. previously, the present results imply that proper modification of the chemical structures of the TTF unit and the spacer have negligible effect on the electrical bistability behavior of these TTF-DNP-CBPQT4+ [2]rotaxanes. These findings will allow for the design and preparation of new multifunctional TTF-DNP-CBPQT4+ [2]rotaxanes in the future. [source] Observation of Structural and Conductance Transition of Rotaxane Molecules at a Submolecular Scale,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2007M. Feng Abstract Rotaxane molecules have attracted considerable interest because of their good performance in both molecular electronic devices and nanoscale data-storage media. Low-temperature scanning tunneling microscopy is used to investigate the structure and conductance of single H2 rotaxane molecules on a buffer-layered Au(111) substrate at 77,K. It is demonstrated that the conductance switching in rotaxane-based, solid-state devices is an inherent property of the rotaxane molecules. These results provide evidence that the conductance switching might arise from the movement of the cyclobis(paraquat- p -phenylene) ring along the rod section of the dumbbell-shaped backbone of the rotaxane molecule. [source] Cationic Conjugated Polyelectrolytes with Molecular Spacers for Efficient Fluorescence Energy Transfer to Dye-Labeled DNA,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2007Y. Woo Abstract Two water-soluble conjugated polyelectrolytes, poly(9,9,-bis(6- N,N,N -trimethylammoniumhexyl)fluorene- alt -1,4-(2,5-bis(6- N,N,N -trimethylammoniumhexyloxy))phenylene) tetrabromide (P1i) and poly((10,10,-bis(6- N,N,N -trimethylammoniumhexyl)-10H-spiro(anthracene-9,9,-fluorene))- alt -1,4-(2,5-bis(6- N,N,N -trimethylammoniumhexyloxy))phenylene) tetrabromide (P2i) are synthesized, characterized, and used in fluorescence resonance energy transfer (FRET) experiments with fluorescein-labeled single-stranded DNA (ssDNA-Fl). P1i and P2i have nearly identical ,-conjugated backbones, as determined by cyclic voltammetry and UV-vis spectroscopy. The main structural difference is the presence of an anthracenyl substituent, orthogonal to the main chain in each of the P2i repeat units, which increases the average interchain separation in aggregated phases. It is possible to observe emission from ssDNA-Fl via FRET upon excitation of P2i. Fluorescein is not emissive within the ssDNA-Fl/P1i electrostatic complex, suggesting Fl emission quenching through photoinduced charge transfer (PCT). We propose that the presence of the anthracenyl "molecular bumper" in P2i increases the distance between optical partners, which decreases PCT more acutely relative to FRET. [source] 2,7-Carbazolenevinylene-Based Oligomer Thin-Film Transistors: High Mobility Through Structural Ordering,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2005N. Drolet Abstract We have fabricated organic field-effect transistors based on thin films of 2,7-carbazole oligomeric semiconductors 1,4-bis(vinylene-(N -hexyl-2-carbazole))phenylene (CPC), 1,4-bis(vinylene-(N,-methyl-7,-hexyl-2,-carbazole))benzene (RCPCR), N -hexyl-2,7-bis(vinylene-(N -hexyl-2-carbazole))carbazole (CCC), and N -methyl-2,7-bis(vinylene-(7-hexyl- N -methyl-2-carbazole))carbazole (RCCCR). The organic semiconductors are deposited by thermal evaporation on bare and chemically modified silicon dioxide surfaces (SiO2/Si) held at different temperatures varying from 25 to 200,°C during deposition. The resulting thin films have been characterized using UV-vis and Fourier-transform infrared spectroscopies, scanning electron microscopy, and X-ray diffraction, and the observed top-contact transistor performances have been correlated with thin-film properties. We found that these new ,-conjugated oligomers can form highly ordered structures and reach high hole mobilities. Devices using CPC as the active semiconductor have exhibited mobilities as high as 0.3,cm2,V,1,s,1 with on/off current ratios of up to 107. These features make CPC and 2,7-carbazolenevinylene-based oligomers attractive candidates for device applications. [source] Donor,Acceptor-Substituted Oligo(1,4-phenylene)sHELVETICA CHIMICA ACTA, Issue 6 2009Soungkyoo Kim Abstract Oligo(para -phenylene)s (DAOPPs) 2a,2d (n=1,4) with terminal donor,acceptor substitution (D=C6H13O, A=NO2) were prepared by applying Suzuki cross-couplings for chain extension and end capping. The push,pull effect induces short-reaching polarizations of the chain consisting of conjugated but twisted benzene rings, which was studied by NMR measurements. Electron excitation from the ground-state S0 to the more planar first-excited singlet state S1 is combined with a strong intramolecular charge transfer (ICT), which is documented by the red shift of the long-wavelength absorption (charge-transfer band) for short chains (one or two repeat units, n,=,1 or 2). The opposite influence of decreasing ICT and increasing conjugation length leads to a bathochromic series (,max(n+1),,max(n)) with a fast saturation of ,max (n). The effective conjugation length nECL=4 corresponds to ,, 349,nm. These results are discussed in the context of other oligo(para -phenylene)s (OPPs). [source] Polymer Photovoltaics with Alternating Copolymer/Fullerene Blends and Novel Device ArchitecturesADVANCED MATERIALS, Issue 20 2010Olle Inganäs Abstract The synthesis of novel conjugated polymers, designed for the purpose of photovoltaic energy conversion, and their properties in polymer/fullerene materials and photovoltaic devices are reviewed. Two families of main-chain polymer donors, based on fluorene or phenylene and donor,acceptor,donor comonomers in alternating copolymers, are used to absorb the high-energy parts of the solar spectrum and to give high photovoltages in combinations with fullerene acceptors in devices. These materials are used in alternative photovoltaic device geometries with enhanced light incoupling to collect larger photocurrents or to enable tandem devices and enhance photovoltage. [source] Pirouetting in chiral [2]catenanes,ISRAEL JOURNAL OF CHEMISTRY, Issue 2 2007Seogshin Kang One of the best known classes of mechanically interlocked molecules is the category of [2]catenanes, which exhibit donor-acceptor interactions between the 1,5-dioxynaphthalene (DNP) units in a crown ether and the bipyridinium units in the tetracationic cyclophane, cyclobis(paraquat- p -phenylene) (CBPQT4+). In order to gain an in-depth understanding and appreciation of the stereochemistry and dynamic behavior of these [2]catenanes, chiral analogues,having both the DNP ring, which is capable of displaying planar chirality, and the axially chiral binaphthol (BINAP) moiety (as both enantiomers and as the racemic modification), in a crown ether, in addition to the CBPQT4+ cyclophane,have been synthesized using a template-directed protocol. Dynamic 1H NMR spectroscopy shows that (i) the presence of immutable axial chirality, arising from the BINAP moiety in the crown ether component, leads to no induction of diastereoselectivity,the chiral catenanes exist as a mixture of diastereoisomers in solution at low temperatures in the approximate ratio of 1:1, (ii) the barrier (,GcD,) to the interconversion between these two diastereoisomers is 7.9 ± 0.1 kcal mol,1 at 171 K, and (iii) no induction of diastereoselectivity is observed upon the addition of a chiral solvating agent to the chrial catenanes. The pattern of behavior in the variable temperature 1H NMR spectra and the low ,TGcD, value indicates that the dynamic process involving the interconversion between these two diastereoisomers is one of a pirouetting nature. Of the four possible diastereoisomers, only two, (R)-(pR/pS) or (S)-(pR/pS), are shown to exist in solution. [source] Application of standard DFT theory for nonbonded interactions in soft matter: Prototype study of poly- para -phenyleneJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2006Marcelo Alves-Santos Abstract We present a detailed analysis of the application of density functional theory (DFT) methods to the study of structural properties of molecular and supramolecular systems, using as a paradigmatic example three para -phenylene-based systems: isolated biphenyl, single chain poly- para -phenylene, and crystalline biphenyl. We use different functionals for the exchange correlation potential, the local density (LDA), and generalized gradient approximations (GGA), and also different basis sets expansions, localized, plane waves (PW), and mixed (localized plus PW), within the reciprocal space formulation for the hamiltonian. We find that regardless of the choice of basis functions, the GGA calculations yield larger interring distances and torsion angles than LDA. For the same XC approximation, the agreement between calculations with different basis functions lies within 1% (LDA) or 0.5% (GGA) for distances, and while PW and mixed basis calculations agree within 1° for torsion angles, the localized basis results show larger angles by , 8° and a nonmonotonic dependence on basis size, with differences within 6°. The most prominent features, namely the torsion between rings for isolated molecule and infinite chain, and planarity for the molecule in crystalline environment, are well reproduced by all DFT calculations. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 217,227, 2006 [source] Synthesis of novel amide-crownophanes and Schiff base-crownophanes based on p -phenylene, 2,6-naphthalene, and 9,10-anthraceneJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2009Hussni A. Muathen The novel macrocyclic diamides 11,13, 16,18 are obtained in 45,66% yields by the reaction of dipotassium salts 10a,c and 15 with each of 1,4-di(bromomethyl)benzene 4, 2,6-di(bromomethyl)naphthalene 6 and 9,10-di(bromomethyl)anthracene 8, repectively, in boiling DMF. On the other hand, the new macrocyclic Schiff bases 28 and 29 are obtained in 44% and 42% yields by heating the appropriate bis-amines 25b, 26b with the corresponding bis-aldehydes 21, 22, respectively, in refluxing acetic acid under high-dilution conditions. J. Heterocyclic Chem. (2009). [source] Synthesis of thiophene/phenylene co-oligomers.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2003We report the synthesis of various thiophene/phenylene co-oligomers with a total number of thiophene and benzene (phenylene) rings of 6 to 8. These compounds include a phenyl-capped sexithiophene, a thienyl-capped quaterphenylene, as well as block and alternating co-oligomers. The synthesis is based on either the Suzuki coupling reaction or the direct dimerization coupling. The latter method produces symmetric molecules with an even total ring number. These reaction schemes enabled us to obtain the target compounds in high quality. Although the resulting materials are difficult to dissolve in organic solvents and therefore difficult to identify by usual 1H nmr spectroscopy, they have successfully been identified through Fourier-transform ir spectroscopy. The specific group frequencies of ring-stretching and out-of-plane deformation modes are characteristic of the substitution pattern of the individual thiophene and benzene rings. [source] Thiophene,phenylene/naphthalene-based step-ladder copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2008Torsten W. Bünnagel Abstract A series of step-ladder copolymers based on thiophene,phenylene,thiophene SL1 - SL3 and thiophene,naphthylene,thiophene SL4 repeat units with varying lengths of the oligothiophene segment has been designed and synthesized via a microwave-assisted Stille-type cross-coupling reaction followed by a polymer-analogous cyclization reaction. The optical properties of the step-ladder copolymers have been investigated in detail, in particular at low temperature and in the solid-state. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7342,7353, 2008 [source] Synthesis of soluble poly(para -phenylene) with a long polymer chain: Characteristics of regioregular poly(1,4-phenylene)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2008Itaru Natori Abstract Soluble poly(para -phenylene) having a long polymer chain (more than six repeat units) was synthesized with a tert -butyl end-group (t -PPP) and was found to have improved solubility and excellent optical properties. Poly(1,3-cyclohexadiene) (PCHD) consisting of only 1,4-cyclohexadiene (1,4-CHD) units was synthesized with a tert -butyl end-group (t -PCHD), and completely dehydrogenated to obtain t -PPP. This end-group effectively prevented the crystallization of t -PPP, and polymers containing up to 16 repeat units were soluble in tetrahydrofuran. Soluble t -PPP obtained had an ability to form a tough thin film prepared by spin-coating method. Optical analyses of t -PPP provided strong evidence for a linear polymer chain structure. A block copolymer of t -PPP and a soluble polyphenylene (PPH) was then synthesized, and the excellent optical properties were retained by this block copolymer along with its solubility. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5223,5231, 2008 [source] Synthesis and Study of CdS Nanoparticle-Doped Poly(1,4-dihexyloxybenzene)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 4 2008Gouri Sankar Paul Abstract A simple, economical and high yielding method to prepare poly(1,4-dihexyloxybenzene), an alkylated derivative of poly(para -phenylene) (PPP), is reported. We further prepared a composite of poly(1,4-dihexyloxybenzene) and CdS nanoparticles and studied their structural, optical, stability and transport properties. It was observed that the conductivity of poly(1,4-dihexyloxybenzene) increased by several orders of magnitude when doped with CdS nanoparticles. Similarly, CdS nanoparticle-doped PPP showed higher thermal stability, when compared to the neat polymer. As these composites could be processed in the same way as organic polymers, they would find applications in many low-cost optoelectronic devices. [source] Synthesis and Properties of Novel Fluorinated Poly(phenylene- co -imide)sMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2007Wenmu Li Abstract A new class of high-performance materials, fluorinated poly(phenylene- co -imide)s, were prepared by Ni(0)-catalytic coupling of 2,5-dichlorobenzophenone with fluorinated dichlorophthalimide. The synthesized copolymers have high molecular weights (,=,5.74,×,104,17.3,×,104 g,·,mol,1), and a combination of desirable properties such as high solubility in common organic solvent, film-forming ability, and excellent mechanical properties. The glass transition temperature (Tgs) of the copolymers was readily tuned to be between 219 and 354,°C via systematic variation of the ratio of the two comonomers. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 66.7,266 MPa, 2.7,13.5%, and 3.13,4.09 GPa, respectively. The oxygen permeability coefficients () and permeability selectivity of oxygen to nitrogen () of these copolymer membranes were in the range of 0.78,3.01 barrer [1 barrer,=,10,10 cm3 (STP) cm/(cm2,·,s,·,cmHg)] and 5.09,6.25, respectively. Consequently, these materials have shown promise as engineering plastics and gas-separation membrane materials. [source] Blue Emission of a Soluble Poly(p -phenylene) with a Cross-Conjugated Bisimidazole-Based ChromophoreMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2007Frank Dierschke Abstract A novel poly(p -phenylene) (6) has been synthesized by a cruciform combination of a polyphenylene backbone with 2,2,-(p -phenylene)-bis(4,5-diphenylimidazole) (5) as an additional, orthogonal chromophore. Polymer 6 showed in solution and in the solid state, a blue-green emission, which is obviously arising from the second bisimidazole-based chromophore. UV-Vis spectroscopy, and cyclic voltammetry revealed that the optical and electronic properties of 6 were fully determined by the incorporated 2,2,-(1,4-phenylene)bisimidazole structure. The bisimidazole unit led to high solubility and, despite the steric demand of the substituents, at the same time to the blue-green emission of the poly(p -phenylene) (6). In addition, the oxidation of 6 with potassium ferricyanide yielded a low bandgap polymer with a quinoid-type structure and a bandgap of 1.6 eV. [source] Copolymers of Poly(2,5-benzimidazole) and Poly[2,2,-(p -phenylene)-5,5,-bibenzimidazole] for High-Temperature Fuel Cell ApplicationsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 11 2008Sung-Kon Kim Abstract Copolymers of poly(2,5-benzimidazole) (ABPBI) and poly[2,2,-(p -phenylene)-5,5,-bibenzimidazole] (pPBI) were synthesized for use as fuel cell membranes to take advantage of the properties of both constituents. The composition of the copolymers were controlled by changing the feed ratio of 3,4-diaminobenzoic acid and terephthalic acid with 3,3,-diaminobenzidine in the polycondensation reaction. The copolymer membranes showed higher conductivities, better mechanical properties, and larger acid absorbing abilities than commercial poly[2,2,-(m -phenylene)-5,5,-bibenzimidazole] membranes. [source] Thienopyrazine-Based Low-Bandgap Poly(heteroaryleneethynylene)s for Photovoltaic DevicesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 17 2006Raja Shahid Ashraf Abstract Summary: Low-bandgap ,-conjugated polymers that consist of alkyl thiophene/alkoxy phenylene and 2,3-diphenylthieno[3,4- b]pyrazine units have been prepared in high yields by a Sonogashira polycondensation. The copolymers are characterized by NMR, IR, UV, GPC, and elemental analysis. Thin films of the polymers P1, P2, and P3 exhibit an optical bandgap of ,1.57,1.60 eV. Under simulated AM 1.5 conditions P2/PCBM devices on polyester foil provide a short circuit current of ISC,=,10.72 mA,·,cm,2, an open circuit voltage of Voc,=,0.67 V, and a power conversion efficiency of 2.37%. Schematic of the photovoltaic device made from the polymers synthesized here. [source] Polymer-Based Rectifying Diodes on a Glass Substrate Fabricated by Ink-Jet PrintingMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2005Yi Liu Abstract Summary: The fabrication of polymer diodes on a glass substrate by an ink-jet printing technique is reported. Both an n-type semiconductive polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovinylene)phenylene] (CN-PPV), and a p-type semiconductive polymer, polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene) (PEDOT), were printed through a piezoelectric ink-jet printer. The printed CN-PPV/PPy and CN-PPV/PEDOT diodes showed good rectifying characteristics. These results indicate the potential of the low-cost ink-jet printing technique to produce polymer microelectronic devices and circuits. Schematic diagram of the printed polymer diode [source] Polybenzimidazoles for High Temperature Fuel Cell ApplicationsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2004Hyoung-Juhn Kim Abstract Summary: Fuel cells were designed for high temperature operations. Poly[2,2,-(m -phenylene)-5,5,-bibenzimidazole] (PBI) was synthesized in a solution of P2O5, CH3SO3H, and CF3SO3H. The PBI was dissolved in a mixture of CF3CO2H and H3PO4 and the solution was used for the preparation of Pt catalyst slurry for membrane electrode assembly. The single cell showed a current density of 280 mA,·,cm,2 at a cell voltage of 0.5 V with feeds of H2 and O2 at 160,°C and without external humidification. [source] | ||||||||||||||||||||||||||||