JOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2006
NIDHI YADAV
ABSTRACT An integrated approach consisting of compression and stress relaxation is performed with a simulated model system of poly dimethyl siloxane (PDMS), a viscoelastic polymer material when the compressive strain, height of sample and crosshead speed were varied. The parameters derived are the forces at the end of compression and relaxation, energy for compression and the extent of elasticity of the sample based on the ratios of forces as well as the proposed energy values. The results were verified with food doughs undergoing large deformations that show a nonlinear behavior. The proposed extent of elasticity based on the ratios of energy stored and compression can be used as an index for the characterization of viscoelasticity. A nonlinear three-parameter model had also been proposed to predict the stress decay characteristics as a function of time, which was found suitable for the PDMS system, and was better than the two-parameter Peleg model as judged by lower variance values (0.0006,0.018 and 0.002,0.048, respectively). Further, an actual system of food doughs in the form of chickpea (Cicer arietinum L.) flour dough was used to verify the proposed model and viscoelastic index at different moisture contents (27,39%) subjected to compressive strains of 25,75%. The nonlinear relaxation characteristics of the food dough are sensitive to moisture content as well as to strain level. [source]

Effect of side-chain end groups on the optical, electrochemical, and photovoltaic properties of side-chain conjugated polythiophenes

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2006
Erjun Zhou
Abstract Three new side-chain conjugated polythiophene derivatives, poly{3-[2-(3-methoxy-4-octyloxy-phenyl)-vinyl]-thiophene} (P3MOPVT), poly{3-[2-(3,5-dimethoxy-4-octyloxy-phenyl)-vinyl]-thiophene} (P3DMOPVT), and poly{3-[2-(3,4-dioctyloxy-phenyl)-vinyl]-thiophene} (P3DOPVT), were synthesized by Wittig-Hornor reaction and GRIM method and compared with poly{3-[2-(4-octyloxy-phenyl)-vinyl]-thiophene} (P3OPVT) for investigating the effect of the end groups of the conjugated side-chain on the properties of the polymers. Owing to the electron-donating ability of methoxy groups, the visible absorption peaks of P3MOPVT and P3DMOPVT solutions and films become stronger and red-shifted compared with P3OPVT. The electrochemical bandgaps of the four polymers are 2.15 eV for P3OPVT, 1.99 eV for P3MOPVT, 1.85 eV for P3DMOPVT, and 2.36 eV for P3DOPVT, respectively, which indicate that the electron-donating ability of the methoxy end group on the conjugated side chain of P3MOPVT and P3DMOPVT and the large steric hindrance of the two octyloxy end groups on the conjugated side chain of P3DOPVT have obvious influence on the electrochemical properties of the side-chain conjugated polythiophenes. Polymer solar cells were fabricated with a structure of ITO/PEDOT:PSS/Polymer:PCBM/LiF/Al. The best device, based on P3DMOPVT, shows a power conversion efficiency of 1.63% under the illumination of AM1.5, 80 mW/cm2. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4916,4922, 2006 [source]

Combined effects of conjugation pattern and alkoxy side chains on the photovoltaic properties of thiophene-containing PPE-PPVs

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2007
Daniel Ayuk Mbi Egbe
Abstract This contribution presents the synthesis and properties of four thiophene-containing poly(- p -arylene-ethynylene)/poly(- p -arylene-vinylene)s, PIa-b and PIIa-b, whose repeating units (RU) consist either of 1:2 or 2:2 triple bond/double bond ratio, and which bear linear alkoxy side chains not longer than octyloxy and branched 2-ethylhexyloxy. PIa-b and PIIa-b exhibit similar absorption and emission behaviour in dilute solution (,a = 483,486 nm, ,e = 540 nm) as well as in solid state (,a = 500, 530 nm, ,e = 560 nm), whereby slightly higher fluorescence quantum yields (,f) were obtained for PI than for PII systems, as a result of higher number of thiophene units within the RU of PII. An enhancement of the ,f -value from 0% to 3% is obtained after replacing linear octadecyloxy in PIIc-e by bulky branched 2-ethylhexyloxy in PIIa-b. Nonoptimized solar cells of configuration ITO/PEDOT:PSS/polymer: PCBM (1:3 weight ratio)/LiF/Al show open circuit voltages as high as 900 mV for PIa-b and 800 mV for PIIa-b. Reducing the size of the side chain from R = 2- ethylhexyl in PIa to R = methyl in PIb leads to a significant increase of the short circuit current, ISC, from ca. 2.5 mA to ca. 3.7 mA and consequently to an enhancement of the energy conversion efficiency, ,AM1.5, from ca. 1.2% to ca. 1.7%. This is due to an extended donor-acceptor interfacial area, as evidenced by AFM topology pictures showing smaller nanoscale clusters size in PIb than in PIa active layer. The same change led to minimal effect in PII systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1619,1631, 2007 [source]

Late-Appearing Abscesses after Injections of Nonabsorbable Hydrogel Polymer for HIV-Associated Facial Lipoatrophy

DERMATOLOGIC SURGERY, Issue 2007
DEREK H. JONES MD
First page of article [source]

A Biomimetic Potentiometric Sensor Using Molecularly Imprinted Polymer for the Cetirizine Assay in Tablets and Biological Fluids

ELECTROANALYSIS, Issue 18 2008
Mehran Javanbakht
Abstract Despite the increasing number of applications of molecularly imprinted polymers (MIPs) in analytical chemistry, the construction of a biomimetic potentiometric sensor remains still challenging. In this work, a biomimetic potentiometric sensor, based on a non-covalent imprinted polymer was fabricated for the recognition and determination of cetirizine. The MIP was synthesized by precipitation polymerization, using cetirizine dihydrochloride as a template molecule, methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross linking agent. The sensor showed high selectivity and a sensitive response to the template in aqueous system. The MIP-modified electrode exhibited Nernstian response (28.0±0.9 mV/decade) in a wide concentration range of 1.0×10,6 to 1.0×10,2 M with a lower detection limit of 7.0×10,7 M. The electrode has response time of ca. 20,s, high performance, high sensitivity, and good long term stability (more than 5,months). The method was satisfactory and used to the cetirizine assay in tablets and biological fluids. [source]

Amperometric Biosensors for Detection of Sugars Based on the Electrical Wiring of Different Pyranose Oxidases and Pyranose Dehydrogenases with Osmium Redox Polymer on Graphite Electrodes

ELECTROANALYSIS, Issue 2-3 2007
Federico Tasca
Abstract Electrical wiring of different types of pyranose oxidase (P2O) (fungal wild type, recombinant wild type with a hexa-histidine tag, mutant form E542K with a hexa-histidine tag) from Trametes multicolor, and recombinant P2O from Coriolus sp. overexpressed in Escherichia coli as well as of pyranose dehydrogenase (PDH) from Agaricus meleagris and Agaricus xanthoderma with an osmium redox polymer (poly(1-vinylimidazole)12 -[Os(4,4,-dimethyl-2,2,-dipyridyl)2Cl2]2+/+) on graphite electrodes was carried out. After optimization studies using glucose as substrate, the biosensors, which showed the best characteristics in terms of linear range, detection limit and sensitivity were selected, viz. wild type P2O from T. multicolor and PDH from A. meleagris. These two enzymes were used and investigated for their selectivity for a number of different sugars. [source]

Preparation, Characterization and Analytical Applications of a New and Novel Electrically Conducting Polymer

ELECTROANALYSIS, Issue 15 2006
F. D'Eramo
Abstract In this study, a glassy carbon electrode (GC) was modified with an electropolymerized film of 1-naphthylamine (1-NAP) with a subsequent overoxidation treatment in 0.2,M sodium hydroxide solution. This polymer p-1-NAPox film coated GC electrode was used for the selective determination of dopamine (DA) in the presence of a triple concentration of ascorbic acid (AA). These studies were performed using cyclic voltammetry and square-wave voltammetry at physiological pH. p-1-NAPox shows an attractive permselectivity, a marked enhancement of the current response and antifouling properties when compared to a bare GC electrode activated in basic media. With a preconcentration time of 3,minutes at open circuit, linear calibration plots were obtained for DA in buffer solution (pH,7.4) over the concentration range from 1×10,6,1×10,4 M with a detection limit of 1.59×10,7 M. [source]

Conducting Polymer-Based Solid-State Ion-Selective Electrodes

ELECTROANALYSIS, Issue 1 2006
Johan Bobacka
Abstract Conducting polymers, i.e., electroactive conjugated polymers, are useful both as ion-to-electron transducers and as sensing membranes in solid-state ion-selective electrodes. Recent achievements over the last few years have resulted in significant improvements of the analytical performance of solid-contact ion-selective electrodes (solid-contact ISEs) based on conducting polymers as ion-to-electron transducer combined with polymeric ion-selective membranes. A significant amount of research has also been devoted to solid-state ISEs based on conducting polymers as the sensing membrane. This review gives a brief summary of the progress in the area in recent years. [source]

Selective Electrochemical Analysis of Various Metal Ions at an EDTA Bonded Conducting Polymer Modified Electrode

ELECTROANALYSIS, Issue 16 2004
Aminur Rahman
Abstract An EDTA-bonded conducting polymer modified electrode was prepared and characterized by FT-IR. The modified electrode was used for the selective electrochemical analysis of various trace metal ions such as, Cu(II), Hg(II), Pb(II), Co(II), Ni(II), Fe(II), Cd(II), and Zn(II) at the different pHs by linear sweep and square wave voltammetry. Dynamic ranges were obtained using square wave voltammetry from 0.1,,M to 10.0,,M for Co(II), Ni(II), Cd(II), Fe(II), and Zn(II) and 0.5,nM to 20,nM for Cu(II), Hg(II), and Pb(II) after 10,min of preconcentration. The detection limits were determined to be 0.1,nM, 0.3,nM, 0.4,nM, 50.0,nM, 60.0,nM, 65.0,nM, 80.0,nM, and 90.0,nM for Cu(II), Hg(II), Pb(II), Co(II), Ni(II), Cd(II), Fe(II), and Zn(II), respectively. The technique offers an excellent way for the selective trace determination of various heavy metal ions in a solution. [source]

A Dynamically Entangled Coordination Polymer: Synthesis, Structure, Luminescence, Single-Crystal-to-Single-Crystal Reversible Guest Inclusion and Structural Transformation

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2010
Arshad Aijaz
Abstract A ZnII coordination polymer {[Zn2(cpa)2(bpy)]·3H2O}n (1) (cpa2, = 4-(methoxycarbonyl)benzoate and bpy = 4,4,-bipyridine) has been synthesized under solvothermal condition and structurally characterized. This coordination polymer has nanotubular threefold entangled (2D,3D) structure with embedded water molecules; the water molecules can be partially exchanged in reversible single-crystal-to-single-crystal (SC-SC) fashion by different solvent molecules like methanol, ethanol and acetone giving rise to {[Zn2(cpa)2(bpy)]·(0.5MeOH)·(2.5H2O)}n (2), {[Zn2(cpa)2(bpy)]·(0.5EtOH)·(0.5H2O)}n (3) and {[Zn2(cpa)2(bpy)]·(0.5Me2CO)·(H2O)}n (4). Inclusion of EtOH or MeOH leaves the size of the voids in the framework unaltered. Inclusion of acetone, however, is accompanied by shrinking of the voids in the framework. Heating of 1 at 100 °C under vacuum for 4 h affords the de-solvated compound, {Zn2(cpa)2(bpy)}n (1,). Single-crystal X-ray structure of 1, shows sliding of the individual nanotubular components expanding the overall framework. Thus, the coordination polymer exhibits dynamic motion of the molecular components in SC-SC fashion. All compounds were further characterized via IR spectroscopy, PXRD, elemental and TGA analysis. When 1 is placed in benzene at 100 °C for 2 days, compound {[Zn2(cpa)2(bpy)]·(2.5H2O)}n (5) is formed in a SC-SC fashion where coordination number of ZnII ion increases from four to five. Compound 1 also exhibits reversible guest-dependent photoluminescence properties. [source]

Self-Assembled Two-Dimensional Water-Soluble Dipicolinate Cu/Na Coordination Polymer: Structural Features and Catalytic Activity for the Mild Peroxidative Oxidation of Cycloalkanes in Acid-Free Medium

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2008
Marina V. Kirillova
Abstract The new water-soluble 2D Cu/Na coordination polymer [Cu(,-dipic)2{Na2(,-H2O)4}]n·2nH2O (1) has been synthesized by self-assembly in aqueous medium from copper(II) nitrate, dipicolinic acid (H2dipic) and sodium hydroxide in the presence of triethanolamine. It has been characterized by IR spectroscopy, FAB+ -MS, elemental and single-crystal X-ray diffraction analyses, the latter featuring a layered 2D metal,organic structure that is extended to a 3D supramolecular assembly by extensive hydrogen bonding between adjacent layers and involving crystallization water molecules. Compound 1 has been shown to act as a catalyst precursor for the peroxidative oxidation of cyclohexane and cyclopentane to the corresponding cyclic ketones and alcohols by aqueous H2O2 in MeCN solution and in the absence of acid additives.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Self-Assembly of p -Sulfonatocalix[4]arene and a Ag,hmt Coordination Polymer into a Porous Structure

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2008
Guo-li Zheng
Abstract A novel porous material constructed from p -sulfonatocalix[4]arene molecules and a AgI coordination polymer has been structurally characterized. The porous supramolecular complex features a bilayer arrangement of p -sulfonatocalix[4]arene molecules linked by a AgI,hmt (hmt: hexamethylenetetramine) coordination polymer through metal,ligand bonding, hydrogen bonding and host,guest interactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Unusual T4(1) Water Chain Stabilized in the One-Dimensional Chains of a Copper(II) Coordination Polymer

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2007
Yi Jin
Abstract A novel T4(1) water chain in a new CuII coordination polymer, {[Cu(C4H6N2)2(C4H2O4)] (H2O)3}n (1, where C4H6N2 = 2-methylimidazole, C4H2O4 = maleate), has been synthesized and structurally characterized by single-crystal X-ray diffraction. Thermogravimetry, infrared spectroscopy, elemental analysis, and magnetic analysis have also been used to characterize 1. Complex 1 crystallizes in the trigonal space group P3221, and the 1-D chains composed of cyclic water tetramers play an important role in stabilizing the overall polymeric structure. Furthermore, this 1-D water chain presents an unusual association mode of water molecules.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

A Two-Dimensional, Hydrogen-Bond-Cross-Linked Molybdenum(VI) Network Polymer with Catalytic Activity

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2007
Yi Luan
Abstract The new hybrid inorganic,organic polymer [MoO2Cl2(H2O)2]·(H2dipy-pra)Cl2 (1), where dipy-pra = 1,3-bis(4-pyridyl)propane, has been synthesized and crystallographically characterized. MoO2Cl2(H2O)2 and the [H2dipy-pra]2+ cation are cross-linked by Mo,H2O···Cl and H2dipy-pra···Cl hydrogen bonds to form a two-dimensional layer structure. Complex 1 is an efficient catalyst, with H2O2 as the oxygen-source oxidant and NaHCO3 as the cocatalyst, in the epoxidation of olefinic compounds under ambient conditions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

A 2D Thiocyanato-Bridged Copper(II)-Manganese(II) Bimetallic Coordination Polymer with Ferromagnetic Interactions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2005
Jing-Min Shi
Abstract The first ferromagnetic coupled, thiocyanato-bridged copper(II)-manganese(II) bimetallic 2D polymer {[Cu(ipa)2]2Mn(NCS)6·2H2O}n (ipa = 1,2-propanediamine) has been synthesised and characterised by a single-crystal X-ray structure determination and variable temperature magnetic susceptibility studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

[CuI(im)],: Is this Air-Stable Copper(I) Imidazolate (8210)-Net Polymer the Species Responsible for the Corrosion-Inhibiting Properties of Imidazole with Copper Metal?

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2004
Yun-Qi Tian
Abstract An air-stable two-dimensional (2D) copper(I) imidazolate polymer, [CuI(im)], (1), with a d10 -d10 interaction, was synthesized solvothermally and structurally characterized by X-ray crystallography: a = 8.069(2), b = 8.068(2), c = 13.425(3) Å, , = 99.414(3)°, monoclinic, C2/c. This is the first example of an air-stable copper(I) imidazolate polymer that may play a significant role in the corrosion-inhibition mechanism of imidazole (or its derivatives) with copper metal. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Self-Assembly of Organodiphosphonate, Polyoxomolybdate and Diphenanthrolinecobalt(II) into Two Clusters and One Linear Polymer

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2003
Rui-Biao Fu
Abstract [{Co(1,10-phen)2}2{(Mo4O12)(O3PCH2CH2PO3)}·(H2O)] (1), [{Co(1,10-phen)2}2{(Mo4O12)(O3PCH2CH2CH2PO3)}·(1.5H2O)] (2) and [{Co(1,10-phen)2(H2O)2}{Co(1,10-phen)2(H2O)}{(Mo5O15)(O3PCH2CH2CH2CH2PO3)}·(6H2O)] (3) were synthesized by self-assembly of H2O3P(CH2)nPO3H2 (n = 2,4), polyoxomolybdate and [Co(1,10-phen)2]2+ (1,10-phen = 1,10-phenanthroline) under hydrothermal conditions. Compounds 1 and 2 are novel heterometallic hexanuclear clusters, while compound 3 is a new linear polymer. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Annealing of Biodegradable Polymer Induced by Femtosecond Laser Micromachining,

ADVANCED ENGINEERING MATERIALS, Issue 4 2010
Wai Yee Yeong
Abstract Femtosecond laser is a potential tool for net shape processing of biodegradable polymers. However, laser processing of polymeric material is still a challenge and the effects induced by laser ablation needs to be investigated. Poly(, -caprolactone) was micromachined at high fluence and the heat affected zone was characterized. Two different phases of microstructure, namely the annealed spherulite zone and the amorphous zone, are found. [source]

Development of Biomimetic Chitosan-Based Hydrogels Using an Elastin-Like Polymer,

ADVANCED ENGINEERING MATERIALS, Issue 1-2 2010
Joaquim S. Barbosa
Chitosan and an elastin-like polymer, containing a specific osteoconductive sequence in the primary structure, have been combined to obtain bioactive injectable systems with enhanced mechanical properties and hydrogels. Obtained results indicate that the combination of such polymers may be very promising in the development of biomaterials for minimal invasive orthopaedic reconstructive applications or in bone tissue engineering. The figure shows a thermo-sensitive hydrogel, with a gelation point under physiological temperature. [source]

Effect of Hypervelocity Impact on Microcellular Ceramic Foams from a Preceramic Polymer

ADVANCED ENGINEERING MATERIALS, Issue 11 2003
P. Colombo
A promising material for hypervelocity impact shields in spacecraft and satellites has been found in lightweight microcellular SiOC foams. The foam stops the projectile and the debris from the impacted bumper facesheet within a few millimeters (see Figure for a cross-section of the crater) at speeds up to 5.1 km,s,1. The impacted SiOC ceramic did not react with incoming debris, and no phase transformation or compositional change was observed. [source]

Volume Organization of Polymer and Hybrid Solar Cells as Revealed by Electron Tomography

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010
Svetlana S. van Bavel
Abstract Polymer and hybrid solar cells have the potential to become the leading technology of the 21st century in conversion of sun light to electrical energy because their ease processing from solution producing printable devices in a roll-to-roll fashion with high speed and low cost. The performance of such devices critically depends on the nanoscale organization of the photoactive layer, which is composed of at least two functional materials: the electron donor and the electron acceptor forming a so-called bulk heterojunction; however, control of its volume morphology still is a challenge. In this context, advanced analytical tools are required that are able to provide information on the local volume morphology of the photoactive layer with nanometer resolution. In this report electron tomography is introduced as the technique able to explore the 3D morphology of polymer and hybrid solar cells and the first results achieved are critically discussed. [source]

Ionic Liquids: Electropolymerization of a Bifunctional Ionic Liquid Monomer Yields an Electroactive Liquid-Crystalline Polymer (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Mater.
M. A. Firestone et al. present a polymer that incorporates an electronic component with an ionic liquid and produces a mixed ionic and electronic conductor on page 2063. Electropolymerization of a bifunctional imidazolium-based ionic liquid monomer incorporating both vinyl and thiophene groups yields a liquid-crystalline polymer that adopts an interconnected network structure formed by two orthogonally oriented lamellar sheets. The structural ordering leads to enhanced electrical conductivity. [source]

Electropolymerization of a Bifunctional Ionic Liquid Monomer Yields an Electroactive Liquid-Crystalline Polymer

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Sungwon Lee
Abstract The preparation and polymerization of a bifunctional imidazolium-based ionic liquid (IL) monomer that incorporates both a vinyl group and a thiophene moiety is reported. Potentiodynamic electropolymerization of the monomer produces an optically birefringent polymer film that strongly adheres to the electrode surface. Fourier transform IR spectroscopy shows that polymerization occurs through both the vinyl and thienyl groups. Cylic voltammetry (CV) is used to determine the polymer oxidation potential (1.66,V) and electrochemical bandgap, Eg, of 2.45,eV. The polymer exhibits electrochromism, converting from yellow in the neutral form (,max,=,380,nm) to blue in the polaronic state at 0.6,V (,max,=,672,nm) and to blue-grey in the bipolaronic state at 1.2,V (,max,>,800,nm). Topographic atomic force microscopy (AFM) images reveal isolated (separated) fibrils. Grazing-incidence small-angle X-ray scattering (GISAXS) studies indicate a lamellar structure with a lattice spacing of 3.2,nm. Wide-angle X-ray diffraction (WAXD) studies further suggest that the polymerized thiophene sheets are oriented perpendicular to the polymerized vinylimidazolium. The electrical conductivity, as determined by four-probe dc conductivity measurements was found to be 0.53,S cm,1 in the neutral form and 2.36,S cm,1 in the iodine-doped state, values higher than typically observed for polyalkylthiophenes. The structural ordering is believed to contribute to the observed enhancement of the electrical conductivity. [source]

Conjugated Polymer Based on Polycyclic Aromatics for Bulk Heterojunction Organic Solar Cells: A Case Study of Quadrathienonaphthalene Polymers with 2% Efficiency

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
Shengqiang Xiao
Abstract Polycyclic aromatics offer great flexibility in tuning the energy levels and bandgaps of resulting conjugated polymers. These features have been exploited in the recent examples of benzo[2,1- b:3,4- b']dithiophene (BDT)-based polymers for bulk heterojunction (BHJ) photovoltaics (ACS Appl. Mater. Interfaces2009, 1, 1613). Taking one step further, a simple oxidative photocyclization is used here to convert the BDT with two pendent thiophene units into an enlarged planar polycyclic aromatic ring,quadrathienonaphthalene (QTN). The reduced steric hindrance and more planar structure promotes the intermolecular interaction of QTN- based polymers, leading to increased hole mobility in related polymers. As-synthesized homopolymer (HMPQTN) and donor,acceptor polymer (PQTN - BT) maintain a low highest occupied molecular orbital (HOMO) energy level, ascribable to the polycyclic aromatic (QTN) moiety, which leads to a good open-circuit voltage in BHJ devices of these polymers blended with PCBM ([6,6]-phenyl-C61 -butyric acid methyl ester; HMPQTN: 0.76,V, PQTN - BT: 0.72,V). The donor,acceptor polymer (PQTN - BT) has a smaller optical bandgap (1.6,eV) than that of HMPQTN (2.0,eV), which explains its current (5.69,mA,cm,2) being slightly higher than that of HMPQTN (5.02,mA,cm,2). Overall efficiencies over 2% are achieved for BHJ devices fabricated from either polymer with PCBM as the acceptor. [source]

Liquid-Crystal Polymers: Liquid-Crystalline Polymer with a Block Mesogenic Side Group: Photoinduced Manipulation of Nanophase-Separated Structures (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 23 2009
Mater.
The inside cover image represents a novel azobenzene liquid-crystalline (LC) polymer with a block mesogenic side group, which exhibits a lamellar structure after annealing in an LC phase. Whereas irradiation with linearly polarized light aligns the lamellae parallel to the polarization, irradiation with unpolarized light erases the surface morphology accompanied by photochemical phase transition, as reported by K. Okano et al. on page 3804. [source]

Liquid-Crystalline Polymer with a Block Mesogenic Side Group: Photoinduced Manipulation of Nanophase-Separated Structures

ADVANCED FUNCTIONAL MATERIALS, Issue 23 2009
Kunihiko Okano
Abstract In this report, a novel type of photoresponsive liquid crystalline polymer with a block mesogenic side-group is demonstrated. The block mesogene is an amphipathic molecule containing a hydrophobic mesogene (azotolane moiety) and hydrophilic oligooxyethylene moieties in the same unit. The block mesogene in the polymer plays a role in liquid crystalline, amphiphilic and photoresponsive properties. As expected, a film prepared from the polymer exhibits phase separation of a lamellar structure due to cooperative motion between liquid crystal assembly and nanophase separation. The morphology of the lamellae can be aligned upon irradiation of linearly polarized light. Moreover, a photochemical phase transition induced by unpolarized UV irradiation erases the surface morphology. The erased nanostructure can be recovered by annealing or irradiation of linearly polarized light, meaning that the surface morphology is rewritable via a photochemical process. [source]

High-Performance Air-Processed Polymer,Fullerene Bulk Heterojunction Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 22 2009
Chang-Yong Nam
Abstract High photovoltaic device performance is demonstrated in ambient-air-processed bulk heterojunction solar cells having an active blend layer of organic poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), with power conversion efficiencies as high as 4.1%, which is comparable to state-of-the-art bulk heterojunction devices fabricated in air-free environments. High-resolution transmission electron microscopy is combined with detailed analysis of electronic carrier transport in order to quantitatively understand the effects of oxygen exposure and different thermal treatments on electronic conduction through the highly nanostructured active blend network. Improvement in photovoltaic device performance by suitable post-fabrication thermal processing results from the reduced oxygen charge trap density in the active blend layer and is consistent with a corresponding slight increase in thickness of an ,4,nm aluminum oxide hole-blocking layer present at the electron-collecting contact interface. [source]

Low-Distortion Holographic Data Storage Media Using Free-Radical Ring-Opening Polymerization

ADVANCED FUNCTIONAL MATERIALS, Issue 22 2009
Kyongsik Choi
Abstract Holographic data storage, due to its potential to increase capacity beyond one terabyte per disk, is tipped to be one of the next generation optical data storage technologies. Polymer-based systems are leading candidates due to their high dynamic range, high sensitivities, and flexible and easy production, and yet polymerization-shrinkage-induced distortion is a major hurdle for its reliable use. In this paper, a new free radical polymerization holographic recording medium, based on low shrink cyclic allylic sulfides (LS-CASs) ring-opening monomers, is proposed and demonstrated. The percentage of volume shrinkage is measured to be 0.02%, with refractive index (RI) contrast of (1.01,±,0.5),×,10,3. The measured volume shrinkage is, to the authors' best knowledge, the best reported so far in the literature. Other parameters such as sensitivity, dynamic range, and dark reaction properties are also measured, where the values can be optimized with high RI functional groups without sacrificing the low shrinkage. [source]

The Design and Realization of Flexible, Long-Lived Light-Emitting Electrochemical Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2009
Junfeng Fang
Abstract Polymer light-emitting electrochemical cells (LECs) offer an attractive opportunity for low-cost production of functional devices in flexible and large-area configurations, but the critical drawback in comparison to competing light-emission technologies is a limited operational lifetime. Here, it is demonstrated that it is possible to improve the lifetime by straightforward and motivated means from a typical value of a few hours to more than one month of uninterrupted operation at significant brightness (>100,cd m,2) and relatively high power conversion efficiency (2 lm W,1 for orange-red emission). Specifically, by optimizing the composition of the active material and by employing an appropriate operational protocol, a desired doping structure is designed and detrimental chemical and electrochemical side reactions are identified and minimized. Moreover, the first functional flexible LEC with a similar promising device performance is demonstrated. [source]

A New Carbazole-Constructed Hyperbranched Polymer: Convenient One-Pot Synthesis, Hole-Transporting Ability, and Field-Effect Transistor Properties

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2009
Zhong'an Li
Abstract A new hyperbranched polymer (HB-car), constructed fully by carbazole moieties, is successfully synthesized through a one-pot Suzuki coupling reaction. The resultant polymer is well-characterized, and its hole-transporting ability is studied carefully. The device, in which HB-car is utilized as a hole-transporting layer and tris-(8-hydroxyquinoline) aluminum as an electron-emitting layer as well as electron-transporting layer, gives a much higher efficiency (3.05,cd A,1), than that of a poly(N -vinylcarbazole) based device (2.19,cd A,1) under similar experimental conditions. The remarkable performance is attributed to its low energy barrier and enhanced hole-drifting ability in the HB-car based device. In addition, for the first time, a field-effect transistor (FET) based on the hyperbranched polymer is fabricated, and the organic FET device shows that HB-car is a typical p -type FET material with a saturation mobility of 1,×,10,5,cm2 V,1 s,1, a threshold voltage of ,47.1,V, and an on-to-off current ratio of 103. [source]