bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Evaluation of 5‐Thio‐L‐Fucose‐Containing Oligosaccharide
Authors: Izumi Masayuki , Tsuruta Osamu , Kajihara Yasuhiro , Yazawa Shin , Yuasa Hideya , Hashimoto Hironobu
Published: March 2005

5‐Thio‐L‐fucose‐containing trisaccharide H‐type II was synthesized. The 3′,4′‐O‐isopropylidene‐2‐azido‐2‐deoxylactoside derivative, which was prepared from lactose by azidonitration of lactal, was used as a starting material. By regio‐ and stereoselective 5‐thio‐L‐fucosylation of the 6,6′‐dibenzoate 5 with 5‐thiofucosyl trichloroacetimidate 6 and subsequent deprotection gave the 5‐thio‐L‐fucose‐containing H‐type II 1. Conformational analysis of the 5‐thio‐L‐fucose‐containing H‐type II and the native H‐type II was carried out through NOESY experiments. The observed NOE values between N‐acetylglucosamine and galactose, and galactose and fucose were same for these two trisaccharides. However, NOE values between fucose and N‐acetylglucosamine were significantly different. Binding of the 5‐thio‐L‐fucose‐containing H‐type II to lectins and antibodies were in some case stronger and in some case weaker than those of the native trisaccharide.
Organolanthanide‐Mediated Ring‐Opening Ziegler Polymerization (ROZP) of Methylenecycloalkanes: A Theoretical Mechanistic Investigation of Alternative Mechanisms for Chain Initiation of the Samarocene‐Promoted ROZP of 2‐Phenyl‐1‐methylenecyclopropane
Authors: Tobisch Sven
Published: March 2005

A detailed theoretical investigation of alternative mechanisms for chain initiation of the organolanthanide‐promoted ring‐opening polymerization of 2‐phenyl‐1‐methylenecyclopropane (PhMCP) with an archetypical [Cp2SmH] model catalyst is presented. Several conceivable pathways for important elementary steps, which also included ring‐opening isomerization of PhMCP to phenylbutadienes, were critically scrutinized for a tentative course of the catalytic reaction. The operative mechanism starts with the first exo‐methylene CC insertion into the SmH bond in a 1,2 fashion and is followed by shift‐based β‐alkyl eliminative cyclopropyl ring opening by cleavage of a proximal bond, while the alternative mechanism that commences with 2,1‐insertion and subsequent ring opening by distal bond scission is revealed to be almost entirely precluded. The facile and irreversible insertion process is not found to occur in a regioselective fashion. The ring‐opening process is analyzed as the critical step that discriminates between the two conceivable mechanisms. Opening of the cyclopropyl ring is kinetically easy and proceeds readily for the 1,2‐insertion species, while a prohibitively large barrier must be overcome for ring opening of 2,1‐insertion species. The isomerization of PhMCP in a ring‐opened fashion, which would afford phenylbutadienes as possible products, is predicted to be a less likely process, owing to both kinetic and thermodynamic factors. The phenyl functionality has been demonstrated to distinguish between the regioisomeric ring‐opening pathways, both kinetically and thermodynamically, thereby rendering this process selective with regard to the regiochemistry. Overall, chain initiation of the samarocene‐mediated ring‐opening polymerization of PhMCP is predicted to be a smooth, kinetically facile process.
Where Does the Planar‐to‐Nonplanar Turnover Occur in Small Gold Clusters?
Authors: Olson Ryan M. , Varganov Sergey , Gordon Mark S. , Metiu Horia , Chretien Steeve , Piecuch Piotr , Kowalski Karol , Kucharski Stanislaw A. , Musial Monika
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Crystal Structures of the LnCuPbSe3 (Ln: Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) Compounds.
Authors: Gulay L. D. , Olekseyuk I. D.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Improvements of and Insights into the Isolation of Bismuth Polycations from Benzene Solution — Single‐Crystal Structure Determinations of Bi8[GaCl4]2 and Bi5[GaCl4]3.
Authors: Lindsjoe Martin , Fischer Andreas , Kloo Lars
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Rapid Synthesis of Highly Luminescent CdTe Nanocrystals in the Aqueous Phase by Microwave Irradiation with Controllable Temperature.
Authors: Li Liang , Qian Huifeng , Ren Jicun
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
The 523 K Isothermal Section of La—Ni—Ge Ternary System Phase Diagram.
Authors: Zhuang Yinghong , Hu Zhengxi , Liu Jingqi , Lue Junxia , Yan Jialin
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Ni—V2O5×nH2O Core—Shell Nanocable Arrays for Enhanced Electrochemical Intercalation.
Authors: Takahashi Katsunori , Wang Ying , Cao Guozhong
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Hydrothermal Synthesis and Characterization of Two New Three‐Dimensional Open‐Framework Gallophosphates JGP‐n (n: 8,9) Constructed from Inorganic Layers and HPO4 Tetrahedra.
Authors: Yang Yulin , Mu Zhongcheng , Xu Yan , Liu Yunlin , Chen Chao , Wang Wei , Yi Zhuo , Ye Ling , Pang Wenqin
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
XeAuF.
Authors: Cooke Stephen A. , Gerry Michael C. L.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
“syn‐Effect” in the Conversion of (E)‐α,β‐Unsaturated Esters into the Corresponding β,γ‐Unsaturated Esters and Aldehydes into Silyl Enol Ethers.
Authors: Guha Samar Kumar , Shibayama Atsushi , Abe Daisuke , Sakaguchi Maki , Ukaji Yutaka , Inomata Katsuhiko
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Asymmetric Transformation of Enones with Synechococcus sp. PCC 7942.
Authors: Shimoda Kei , Kubota Naoji , Hamada Hiroki , Yamane Shin‐ya , Hirata Toshifumi
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
High‐Load, Soluble Oligomeric Carbodiimide: Synthesis and Application in Coupling Reactions.
Authors: Zhang Mianji , Vedantham Punitha , Flynn Daniel L. , Hanson Paul R.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Ruthenium‐Catalyzed Cycloisomerization of o‐(Ethynyl)phenylalkenes to Diene Derivatives via Skeletal Rearrangement.
Authors: Madhushaw Reniguntala J. , Lo Ching‐Yu , Hwang Chun‐Wei , Su Ming‐Der , Shen Hung‐Chin , Pal Sitaram , Shaikh Isak R. , Liu Rai‐Shung
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
SnCl4‐Promoted Rearrangement of 2,3‐Epoxy Alcohol Derivatives: Stereochemical Control of the Reaction.
Authors: Kita Yasuyuki , Matsuda Satoshi , Inoguchi Ryoko , Ganesh Jnaneshwara K. , Fujioka Hiromichi
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Site‐Selective Pd‐Catalyzed Coupling of 1,4‐Diiodo‐1,3‐alkadiene with Grignard Reagent and Its Application to the Synthesis of Fulvenes.
Authors: Uemura Minoru , Takayama Yuuki , Sato Fumie
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
New Synthetic Equivalent of Nitromalonaldehyde Treatable in Organic Media.
Authors: Nishiwaki Nagatoshi , Ogihara Takuma , Takami Toshiko , Tamura Mina , Ariga Masahiro
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis of Hydroxybiphenyls.
Authors: Kuznetsova E. A. , Postnova M. V. , Koshel' S. G. , Lebedeva N. V. , Yun'kova T. A. , Koshel' G. N.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Pyrazole‐Tethered Arylphosphine Ligands for Suzuki Reactions of Aryl Chlorides: How Important is Chelation?
Authors: Mukherjee Anuradha , Sarkar Amitabha
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Direct Access to Ketones from Aldehydes via Rhodium‐Catalyzed Cross‐Coupling Reaction with Potassium Trifluoro(organo)borates.
Authors: Pucheault Mathieu , Darses Sylvain , Genet Jean‐Pierre
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Stilbene‐Based Inhibitors of Estrone Sulfatase with a Dual Mode of Action in Human Breast Cancer Cells.
Authors: Walter Georg , Liebl Renate , von Angerer Erwin
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Tandem Sonogashira Coupling: An Efficient Tool for the Synthesis of Diarylalkynes.
Authors: Novak Zoltan , Nemes Peter , Kotschy Andras
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Chiral Self‐Dimerization of Vanadium Complexes on a SiO2 Surface: The First Heterogeneous Catalyst for Asymmetric 2‐Naphthol Coupling.
Authors: Tada Mizuki , Taniike Toshiaki , Kantam Lakshmi M. , Iwasawa Yasuhiro
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Photoinduced Ene‐Reaction of 9‐Methylene‐9,10‐dihydrophenanthrene with Alkenes.
Authors: Sugimoto Akira , Hiraoka Ryoichi , Yasueda Masahiro Kanayama , Mukae Hirofumi , Mizuno Kazuhiko
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Fullerides: Heterometallic Superconductors with Composition M2M′C60 (M: K, Rb; M′: Yb, Lu, Sc)
Authors: Bulychev B. M. , Lunin R. A. , Kul'bachinskii V. A. , Shpanchenko R. V. , Privalov V. I.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Mononuclear Heterocyclic Rearrangement: Synthesis of [5:5] Bicyclic [c]‐Fused 3‐Aminopyrazoles via the N—N Bond Formation Strategy.
Authors: Berry David A. , Chien Tun‐Cheng , Townsend Leroy B.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis of 2‐N‐alkyl(aryl)amino‐7‐nitrobenzothiazoles.
Authors: Huang Shenlin , Connolly Peter J.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Construction of Building‐Blocks for Polyether Synthesis Using Sequential Catalytic Ring‐Closing Enyne and Cross Metathesis.
Authors: Clark J. Stephen , Elustondo Frederic , Kimber Marc C.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Environment‐Friendly Organic Synthesis Using Bismuth Compounds. Bismuth Triflate Catalyzed Synthesis of Substituted 3,4‐Dihydro‐2H‐1‐benzopyrans.
Authors: Nguyen Mai P. , Arnold Joshua N. , Peterson Katherine E. , Mohan Ram S.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis of Pyridone and Pyridine Rings by [4 + 2] Hetero‐Cyclocondensation.
Authors: Robin Aelig , Julienne Karine , Meslin Jean Claude , Deniaud David
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Cobalt‐Mediated Cyclotrimerization of Bis‐alkynes and Cyanamides.
Authors: Bonaga Llorente V. R. , Zhang Han‐Cheng , Maryanoff Bruce E.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Absolute Configuration of the α1B‐Adrenoceptor Antagonist (+)‐Cyclazosin.
Authors: Giardina Dario , Sagratini Gianni , Grelli Massimo , Gulini Ugo , Melchiorre Carlo , Antolini Luciano
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Facile Synthesis of 7—10 Membered Rings by Intramolecular Condensation Using Dialkylcarbonate as Solvent.
Authors: Ikemoto Tomomi , Ito Tasuya , Nishiguchi Atsuko , Tomimatsu Kiminori
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Aminooxazolinate — A Chiral Amidinate Analogue.
Authors: Munslow Ian J. , Wade Andrew R. , Deeth Robert J. , Scott Peter
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Allelopathic Studies in Cultivar Species. Part 17. Bioactive Apocarotenoids annuionones F and G: Structural Revision of Annuionones A, B and E.
Authors: Macias Francisco A. , Lopez Adriana , Varela Rosa M. , Torres Ascension , Molinillo Jose M. G.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Mikanolide from Jamaican Mikania micrantha.
Authors: Bakir Mohammed , Facey Petrea C. , Hassan Ishmael , Mulder Willem H. , Porter Roy B.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
A Facile Route for the Synthesis of Limonidilactone (I) Analogues from Andrographolide (II).
Authors: Thunuguntla Siva Sanjeeva Rao , Nyavanandi Vijay Kumar , Nanduri Srinivas
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Cholinesterase Inhibiting Withanolides from Withania somnifera.
Authors: Choudhary Muhammad Iqbal , Yousuf Sammer , Nawaz Sarfraz Ahmad , Ahmed Shakil , Atta‐ur‐Rahman Atta‐ur‐Rahman
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Regioselective Acylation of Secondary Hydroxyl Groups by Means BOP‐Cl.
Authors: Dalpozzo Renato , De Nino Antonio , Maiuolo Loredana , Procopio Antonio , Sindona Giovanni , Tagarelli Antonio
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
“Double Asymmetric Induction” as a Novel Tool for High Stereocontrol in Baylis—Hillman Reaction.
Authors: Krishna Palakodety Radha , Sachwani Rachna , Kannan V.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis and Biological Evaluation of Novel 2′,3′,4′‐Triply Branched Carbocyclic Nucleosides as Potential Antiviral Agents.
Authors: Ko Ok Hyun , Hong Joon Hee
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis and Interfacial Behavior of Sulfur‐Containing Analogues of Lung Surfactant Dipalmitoyl Phosphatidylcholine.
Authors: Chang Yusuo , Wang Zhengdong , Notter Robert H. , Wang Zhongyi , Qu Long , Schwan Adrian L.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Chemical Transformations of 9,11‐Ethano‐13,15‐isoxazolinoprostanoids.
Authors: Bondar' N. F. , Isaenya L. P. , Skupskaya R. V. , Lakhvich F. A.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
A Novel Method for Synthesizing EuS Nanocrystals from a Single‐Source Precursor under White LED Irradiation.
Authors: Hasegawa Yasuchika , Afzaal Mohammad , O'Brien Paul , Wada Yuji , Yanagida Shozo
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Phosphonomethylphosphorylmethyl(oxy)‐Analogues of Geranylgeranyl Diphosphate as Stable and Selective Geranylgeranyl Protein Transferase Inhibitors.
Authors: Macchia Marco , et al. et al.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Oxide Materials as Positive Electrodes of Lithium‐Ion Batteries
Authors: Makhonina E. V. , Pervov V. S. , Dubasova V. S.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Recent Developments in Arylgold(I) Chemistry
Authors: Fernandez Eduardo J. , Laguna Antonio , Olmos M. Elena
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
A Historical Study of Structures for Communication of Organic Chemistry Information Prior to 1950.
Authors: Cooke Helen
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
A Critical Examination of the Preparation of Polychlorinated Acetones
Authors: Foehlisch Baldur , Zinser Hartmut
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Quinoxalines
Authors: Gobec S. , Urleb U.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Self‐Assembled Porphyrinic Nanoarchitectures
Authors: Chen Xin , Drain Charles Michael
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Pushing Around Electrons: Towards 2‐D and 3‐D Molecular Switches
Authors: Benniston Andrew C.
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Chemical Shifts with Hartree—Fock and Density Functional Methods
Authors: van Wuellen Christoph
Published: March 2005

For Abstract see ChemInform Abstract in Full Text.
Analysis and simulation of interrupt overhead impact on OS throughput in high‐speed networks
Authors: Salah K. , El‐Badawi K.
Published: March 2005

The paper presents analytical and simulation models to study the impact of interrupt overhead on operating system throughput of network elements such as PC‐based routers, servers, and hosts when subjected to high‐speed network traffic. Under such high network traffic, the system throughput will be negatively affected due to interrupt overhead caused by the incoming traffic. We first present an analytical model for the ideal system when interrupt overhead is ignored. We then present two models which describe the impact of high interrupt rate on system throughput. One model is for employing PIO in which network adapters are not equipped with DMA engines, and the other model is for employing DMA in which network adapters are equipped with DMA engines. The paper also describes detailed discrete‐event simulation models for the ideal system and for systems with DMA and PIO. Simulations results as well as reported experimental measurements show that our analytical models are valid and give a good approximation. Our analysis and simulation work can be valuable in providing insight to understand and predict system behaviour, as well as improving and maintaining good host performance. The paper identifies analytically critical design operation points such as that of overload condition. The paper also proposes solutions and recommendations for improving performance. Copyright © 2005 John Wiley & Sons, Ltd.
Activated CD1d‐restricted natural killer T cells secrete IL‐2: innate help for CD4+CD25+ regulatory T cells?
Authors: Jiang Shuiping , Game David S. , Davies Derek , Lombardi Giovanna , Lechler Robert I.
Published: March 2005

CD4+CD25+ and CD1d‐restricted natural killer T (NKT) cells are thymus‐derived self‐reactive regulatory T cells that play a key role in the control of pathological immune responses. Little is known about functional cooperation between innate regulatory NKT cells and adaptive CD4+CD25+ regulatory cells. Here we show that human CD4+Vα24+Vβ11+ (CD4+ NKT) cells isolated from peripheral blood by flow cytometric cell sorting secrete substantial amounts of IL‐2 after stimulation with dendritic cells (DC) and α‐Galactosylceramide. When cocultured with CD4+CD25+ cells, CD4+ NKT cells promoted moderate proliferation of CD4+CD25+ cells. The proliferation of CD4+CD25+ T cells was due to soluble IL‐2 produced by activated CD4+ NKT cells. The expanded CD4+CD25+ cells remained anergic and retained their potent suppressive properties. These findings indicate that unlike conventional CD4+ and CD8+ T cells, which are susceptible to CD4+CD25+ regulatory cell suppression, NKT cells promote CD4+CD25+ regulatory cell proliferation. These data raise the possibility that NKT cells can function as helper cells to CD4+CD25+ regulatory T cells, thereby providing a link between the two naturally occurring populations of regulatory T cells.
Selective inhibition of NF‐κB in dendritic cells by the NEMO‐binding domain peptide blocks maturation and prevents T cell proliferation and polarization
Authors: Tas Sander W. , de Jong Esther C. , Hajji Najat , May Michael J. , Ghosh Sankar , Vervoordeldonk Margriet J. , Tak Paul P.
Published: March 2005

Dendritic cells (DC) are the only antigen‐presenting cells for naive T cells and, therefore, they are crucial players in the initiation of immune responses. Because DC maturation and cytokine production are NF‐κB dependent, we hypothesized that blocking NF‐κB activity in DC by selectively targeting the inhibitor of κB (IκB) kinase (IKK) complex using the novel NF‐κB inhibitor NEMO‐binding domain (NBD) peptide could inhibit DC maturation and other functional characteristics, resulting in modulation of the immune response. We used human monocyte‐derived DC to test the biological effects of the NBD peptide in vitro. NF‐κB inhibition by the NBD peptide resulted in blockade of IKK‐mediated IκBα phosphorylation and subsequent nuclear translocation and DNA binding of NF‐κB p65 in DC. In addition, IL‐6, IL‐12, and TNF‐α production was dose‐dependently blocked and NBD peptide treatment also led to a strong reduction of LPS‐induced maturation. Functional analysis of these DC showed marked inhibition of T cell proliferation in the allogeneic mixed lymphocyte reaction, accompanied by less Th1 and Th2 polarization. The current study reveals for the first time the unique properties of this novel, highly specific NF‐κB inhibitor in DC. Also, these data indicate that the NBD peptide could be used as an elegant tool in DC based immunotherapy for unwanted cellular immune responses.
Use of the Di‐2‐pyridyl Ketone/Acetate/Dicyanamide “Blend” in Manganese(II), Cobalt(II) and Nickel(II) Chemistry: Neutral Cubane Complexes
Authors: Papaefstathiou Giannis S. , Escuer Albert , Mautner Franz A. , Raptopoulou Catherine , Terzis Aris , Perlepes Spyros P. , Vicente Ramon
Published: March 2005

The use of di‐2‐pyridyl ketone [(2‐py)2CO]/dicyanamide “blend” in cobalt(II), manganese(II) and nickel acetatechemistry has yielded neutral cubane clusters. The preparation of [Mn4(O2CMe)2{N(CN)2}2{(2‐py)2C(OH)O}4]·2(2‐py)2‐CO·4H2O (1) and [M4(O2CMe)2{N(CN)2}2{(2‐py)2C(OH)O}4]·10H2O [M = Ni (2), Co (3)] was achieved by the reaction of [M(O2CMe)2]·4H2O with (2‐py)2CO and Na[N(CN)2] in MeOH/H2O (1:5, v/v) at room temperature. The metal(II)‐mediated hydrolysis of (2‐py)2CO to give the coordinated monoanion of the hydrate gem‐diol form involves a nucleophilic attack of H2O on the carbonyl group. In the case of the cobalt reaction system, there is a second product. Upon employing an excess of (2‐py)2CO, long reaction times, reflux conditions and high dilution, slow oxidation of CoII takes place leading to the isolation of the mononuclear cobalt(III) complex [Co{(2‐py)2C(OH)O}2][N(CN)2]·4H2O (4) in yields higher than 70 %. The structures of 1, 2 and 4 have been solved by single‐crystal X‐ray diffraction studies, while a unit‐cell determination indicated that complex 3 is isostructural with 2. The tetranuclear cluster molecules of 1 and 2 have cubane [M4(μ3‐OR)4]4+ cores with divalent metal atoms and deprotonated oxygen atoms [originating from the(2‐py)2C(OH)O– ligands] occupying alternate vertices. The centrosymmetric [Co{(2‐py)2C(OH)O}2]+ cation of complex 4 has an octahedral structure with the (2‐py)2C(OH)O– ligands adopting the tridentate N,O,N‐chelating coordination mode. The magnetic properties of 1–3 have been studied by variable‐temperature dc magnetic susceptibility techniques. The studies indicate weak antiferromagnetic coupling for 1 and ferromagnetic behaviour for 2 and 3. A three‐J model was found to be adequate for describing the thermal variation of the molar magnetic susceptibilities of 1 and 2. The magnetochemical results have been compared with literature data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
New Access to Homodinuclear Half‐Sandwich Vinylidenemanganese Complexes
Authors: Venkatesan Koushik , Fox Thomas , Schmalle Helmut W. , Berke Heinz
Published: March 2005

The d6 low‐spin MnI half‐sandwich dinuclear complexes of the type [{Mn(MeC5H4)(R2PCH2CH2PR2)=C=C(SnMe3)}2{X}] (X = {μ‐1,4‐C6H4}, R = Me, 2a; X = {μ‐1,4‐C6H4}, R = Et, 2b; X = {μ‐1,3‐C6H4}, R = Me, 3a; X = {μ‐1,3‐C6H4}, R = Et, 3b; X = {μ‐4,4‐C6H4‐C6H4}, R = Me, 4a; X = {μ‐4,4‐C6H4‐C6H4}, R = Et, 4b; X = {μ‐1,4‐C4H2S}, R = Me, 5a; X = {μ‐1,4‐C4H2S}, R = Et, 5b) were obtained by the treatment of [Mn(C5H4Me)(η6‐cycloheptatriene)] with 0.5 equiv. of the corresponding acetylene Me3Sn–C≡C–X–C≡C–SnMe3 (X = {μ‐1,4‐C6H4}, {μ‐1,3‐C6H4}, {μ‐4,4‐C6H4‐C6H4}, {μ‐1,4‐C4H2S}) and R2PCH2CH2PR2 (R = Me, Et) at 50 °C for 12 h to yield the corresponding dinuclear complexes in very good yields. These dinuclear tin‐substituted vinylidene complexes were further treated with an excess of MeOH to give the corresponding dinuclear parent vinylidene complexes of the type [{Mn(MeC5H4)(R2PCH2CH2PR2)=C=C(H)}2{X}] (X = {μ‐1,4‐C6H4}, R = Me, 6a; X = {μ‐1,4‐C6H4}, R = Et, 6b; X = {μ‐1,3‐C6H4}, R = Me, 7a; X = {μ‐1,3‐C6H4}, R = Et, 7b; X = {μ‐4,4‐C6H4‐C6H4}, R = Me, 8a; X = {μ‐4,4‐C6H4‐C6H4}, R = Et, 8b). All dinuclear compounds were characterised by NMR and IR spectroscopy and elemental analysis. X‐ray diffraction studies were performed on complexes 2b, 3a, 4a and 6a. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
First Complexes of a 4‐Alkyl‐3,5‐di(2‐pyridyl)‐4H‐1,2,4‐triazole: Synthesis,X‐ray Crystal Structures and Magnetic Properties of Dinuclear Cobalt(II), Nickel(II) and Copper(II) Complexes of 4‐Isobutyl‐3,5‐di(2‐pyridyl)‐4H‐1,2,4‐triazole
Authors: Klingele Marco H. , Boyd Peter D. W. , Moubaraki Boujemaa , Murray Keith S. , Brooker Sally
Published: March 2005

The reaction of the new, bis(bidentate), potentially dinucleating ligand 4‐isobutyl‐3,5‐di(2‐pyridyl)‐4H‐1,2,4‐triazole (ibdpt) with M(ClO4)2·6H2O (M = CoII, NiII or CuII) in a1:1 molar ratio in MeCN affords the dinuclear complexes [CoII2(ibdpt)2(MeCN)2(H2O)2](ClO4)4 (1), [NiII2‐(ibdpt)2‐(MeCN)4](ClO4)4 (2) and [CuII2(ibdpt)2(MeCN)2‐(ClO4)2]‐(ClO4)2·2MeCN (3). Complex 1 is obtained as a mixture of the red‐orange polymorph 1a and the yellow‐orange polymorph 1b, the main difference between the two forms being the hydrogen bonding patterns between the H2O co‐ligands and the ClO4– counterions. The mononuclear complex [CuII‐(ibdpt)2(ClO4)2] (4) was initially obtained as a minor by‐product in the preparation of complex 3 but can also be deliberately prepared from Cu(ClO4)2·6H2O and ibdpt in MeCN using a metal‐to‐ligand molar ratio of 1:2. All five complexes have been structurally characterised by X‐ray diffraction. In the dinuclear complexes 1–3 the (N,N1,N2,N)2double bridging coordination mode is realised while the mononuclear complex 4 features the common trans‐(N,N1)2 coordination mode. In all cases the metal centres reside in distorted octahedral N4X2 coordination spheres with axially bound co‐ligands (X = H2O, MeCN or ClO4–). The dinuclear complexes 1–3 readily lose solvent when taken out of their mother liquors giving rise to partially desolvated materials. Magnetic studies have been carried out on crystalline samples of the resulting complexes that analysed as CoII2‐(ibdpt)2(ClO4)4‐(MeCN)(H2O) (5), NiII2(ibdpt)2(ClO4)4(MeCN) (6) and CuII2‐(ibdpt)2(ClO4)4(MeCN) (7). It was found that in these complexes the two 1,2,4‐triazole bridges facilitate antiferro‐magnetic coupling between the two metal centres (J =–3.76 cm–1, –13.0 cm–1 and –105 cm–1, respectively). The coordination compounds described in this paper are the first to incorporate a 4‐alkyl‐substituted 3,5‐di(2‐pyridyl)‐4H‐1,2,4‐triazole ligand. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
η6:η6 Coordination of Tetraphenylborate to Ytterbium(II): A New Class of Lanthanoid ansa‐Metallocenes
Authors: Deacon Glen B. , Forsyth Craig M. , Junk Peter C.
Published: March 2005

The ytterbium(II) complexes [Yb(tBu2pz)(THF)BPh4] (2) (tBu2pzH = 3,5‐di‐tert‐butylpyrazole) and [Yb{N(SiMe3)2}‐BPh4] (3) were synthesised by reaction of [Yb{N(SiMe3)2}‐(THF)BPh4] (1) with tBu2pzH or by in situ desolvation of the THF complex 1. X‐ray analysis of 2 and 3 reveals η6:η6 binding of chelating BPh4– to ytterbium in both cases, generating true metallocene structures. Complex 3 is distinguished by a very short Yb–N bond and an agostic Yb–Me interaction, both indicative of a highly Lewis acidic metal centre. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
The Formation of 1‐Aryl‐Substituted Naphthalenes by an Unusual Cyclization of Arylethynes Catalyzed by Ruthenium and Rhodium Porphyrins
Authors: Elakkari Elfituri , Floris Barbara , Galloni Pierluca , Tagliatesta Pietro
Published: March 2005

The dimerization of arylethynes to give 1‐aryl‐substituted naphthalenes through catalysis by rhodium and ruthenium porphyrins has been investigated. When performed at temperatures above 130 °C, this reaction affords a mixture of triarylbenzenes and 1‐aryl‐substituted naphthalenes. The yields of naphthalene derivatives range from low to high, depending on the temperature and the phenyl substituents. The concentrations of the initial compounds affect the selectivity of the reaction: the dimerization/trimerization ratios in 1,2‐dichlorobenzene increase as concentration decreases. The reaction mechanism is determined by the peculiar structure of the catalyst ligand and involves the formation of a vinylidene intermediate of the metalloporphyrins. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Coarse sediment transport in mountain streams in Colorado and Wyoming, USA
Authors: Ryan Sandra E. , Porth Laurie S. , Troendle C. A.
Published: March 2005

Since the early 1990s, US Forest Service researchers have made thousands of bedload measurements in steep, coarse‐grained channels in Colorado and Wyoming, USA. In this paper we use data from 19 of those sites to characterize patterns and rates of coarse sediment transport for a range of channel types and sizes, including step–pool, plane‐bed, pool–riffle, and near‐braided channels. This effort builds upon previous work where we applied a piecewise regression model to (1) relate flow to rates of bedload transport and (2) define phases of transport in coarse‐grained channels. Earlier, the model was tested using bedload data from eight sites on the Fraser Experimental Forest near Fraser, Colorado. The analysis showed good application to those data and to data from four supplementary channels to which the procedure was applied. The earlier results were, however, derived from data collected at sites that, for the most part, have quite similar geology and runoff regimes. In this paper we evaluate further the application of piecewise regression to data from channels with a wider range of geomorphic conditions. The results corroborate with those from the earlier work in that there is a relatively narrow range of discharges at which a substantial change in the nature of bedload transport occurs. The transition from primarily low rates of sand transport (phase I) to higher rates of sand and coarse gravel transport (phase II) occurs, on average, at about 80 per cent of the bankfull (1·5‐year return interval) discharge. A comparison of grain sizes moved during the two phases showed that coarse gravel is rarely trapped in the samplers during phase I transport. Moreover, the movement and capture of the D16 to D25 grain size of the bed surface seems to correspond with the onset of phase II transport, particularly in systems with largely static channel surfaces. However, while there were many similarities in observed patterns of bedload transport at the 19 studied sites, each had its own ‘bedload signal’ in that the rate and size of materials transported largely reflected the nature of flow and sediment particular to that system. Published in 2005 by John Wiley & Sons, Ltd.
Rock moisture measurements: techniques, results, and implications for weathering
Authors: Sass Oliver
Published: March 2005

Rock moisture is an important factor for the intensity and distribution of frost weathering processes. However, quantitative measurements are scarce, which is partly due to the lack of reliable measurement techniques. This paper presents five different techniques for obtaining rock moisture data. While collecting rock pieces and two‐dimensional geoelectric measurements allow determination of the spatial moisture distribution, the temporal variability can be derived from conductivity and time domain reflectometry records. Computer simulations, using rock properties and climatic records as input data, render it possible to clarify the important aspects that are responsible for the moisture distribution. It proved to be advisable to use several methods to check and validate the results.

The results, obtained in study areas in the Bavarian Alps, make it clear that direct rainfall is the main source of rock moisture. The influence of snow is limited to the immediate vicinity of the snow fields and is not equally pronounced at different times and positions. Rock moisture levels are higher in summer than they are in winter, since in winter less water is supplied in liquid form. Northerly exposed rockwalls are generally more moist than those exposed in a southerly direction, which is due to the different insolation as well as to the wind direction during rainfall. In every position the rock is, on average, wetter on the inside than it is on the surface. This means that shallow frost cycles, as typical for south‐exposed sites, are not affecting weathering, since they take place at a depth level that is mostly dried out.

Numerous spatial and temporal patterns of rockfall found in the same study areas can be explained through variations in rock moisture. Thus, the moisture content of the rock is considered to be one of the major controlling factors of the frost‐shattering rate. Copyright © 2005 John Wiley & Sons, Ltd.
Modelling of wetting and drying of shallow water using artificial porosity
Authors: van't Hof B. , Vollebregt E. A. H.
Published: March 2005

A new method for wetting and drying in two‐dimensional shallow water flow models is proposed. The method is closely related to the artificial porosity method used by different authors in Boussinesq‐type models, but is further extended for use in a semi‐implicit (ADI‐type) time integration scheme. The method is implemented in the simulation model WAQUA using general boundary fitted coordinates and is applied to realistic schematization for a portion of the river Meuse in the Netherlands.

A large advantage of the artificial porosity method over traditionally used methods on the basis of ‘screens’ is a strongly reduced sensitivity of model results. Instead of blocking all water transport in grid points where the water level becomes small, as in screen‐based methods, the flow is gradually closed off. Small changes in parameters such as the initial conditions or bottom topography therefore no longer lead to large changes in the model results. Copyright © 2005 John Wiley & Sons, Ltd.
New nuclear functions of the glycolytic protein, glyceraldehyde‐3‐phosphate dehydrogenase, in mammalian cells
Authors: Sirover Michael A.
Published: March 2005

Recent studies establish that the glycolytic protein, glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), is not simply a classical metabolic protein involved in energy production. Instead, it is a multifunctional protein with defined functions in numerous subcellular processes. New investigations establish a primary role for GAPDH in a variety of critical nuclear pathways apart from its already recognized role in apoptosis. These new roles include its requirement for transcriptional control of histone gene expression, its essential function in nuclear membrane fusion, its necessity for the recognition of fraudulently incorporated nucleotides in DNA, and its mandatory participation in the maintenance of telomere structure. Each of these new functions requires GAPDH association into a series of multienzyme complexes. Although other proteins in those complexes are variable, GAPDH remains the single constant protein in each structure. To undertake these new functions, GAPDH is recruited to the nucleus in S phase or its intracellular distribution is regulated as a function of drug exposure. Other investigations relate a substantial role for nuclear GAPDH in hyperglycemic stress and the development of metabolic syndrome. Considerations of future directions as well as the role of GAPDH post‐translational modification as a basis for its multifunctional activities is suggested. © 2005 Wiley‐Liss, Inc.
Functional interactions of HPK1 with adaptor proteins
Authors: Boomer Jonathan S. , Tan Tse‐Hua
Published: March 2005

Hematopoietic progenitor kinase 1 (HPK1 or MAP4K1) is a hematopoietic‐specific mammalian STE20‐like protein serine/threonine kinase, comprised of a STE20‐like kinase domain in its N‐terminus, four proline‐rich motifs, a caspase cleavage site, and a distal C‐terminal Citron homology domain. HPK1 is involved in many cellular signaling cascades that include MAPK signaling, antigen receptor signaling, apoptosis, growth factor signaling, and cytokine signaling. HPK1 binds many adaptor proteins including members of the Grb2 family, Nck family, Crk family, SLP‐76 family, and actin‐binding adaptors like HIP‐55. HPK1 tyrosine phosphorylation and kinase activation depend on the presence of adaptor proteins. Adaptor proteins are required not only for linking HPK1 to cell surface receptors like the EGFR, but also for downstream gene transcription like NFAT, AP‐1 and IL‐2. The HPK1 association with Crk, CrkL, and HIP‐55 mediate HPK1‐dependent c‐Jun N‐terminal kinase (JNK) activation, while the association of HPK1 with SLP‐76, Gads, CrkL, Grb2, and Grap affect T‐ and B‐cell dependent gene transcription. Interestingly, HPK1 has been implicated in both increasing and decreasing NFAT, AP‐1, and IL‐2 gene transcription in T‐cells where adaptor proteins play a key role. Lastly, HPK1 will phosphorylate Crk and CrkL, in vitro, which presents a novel possibility for the regulation of adaptor proteins and downstream signaling events. © 2005 Wiley‐Liss, Inc.
Fast apoptosis and erythroid differentiation induced by imatinib mesylate in JURL‐MK1 cells
Authors: Kuželová Kateřina , Grebeňová Dana , Marinov Iuri , Hrkal Zbyněk
Published: March 2005

We compare the effects of Imatinib mesylate (Glivec®) on chronic myeloid leukemia derived cell lines K562 and JURL‐MK1. In both cell lines, the cell cycle arrests in G1/G0 phase within 24 h after the addition of 1 μM Imatinib. This is followed by a decrease of Ki‐67 expression and the induction of apoptosis. In JURL‐MK1 cells, the apoptosis is faster in comparison with K562 cells: the caspase‐3 activity reaches the peak value (20 to 30 fold of the control) after about 40 h and the apoptosis proceeds to its culmination point, the DNA fragmentation, within 48 h following 1 μM Imatinib addition. Unlike K562 cells, JURL‐MK1 cells possess a probably functional p53 protein inducible by TPA (tetradecanoyl phorbol acetate) or UV‐B irradiation. However, no increase in p53 expression was observed in Imatinib‐treated JURL‐MK1 cells indicating that the difference in the apoptosis rate between the two cell lines is not due to the lack of p53 in K562 cells. Imatinib also triggers erythroid differentiation both in JURL‐MK1 and K562 cells. Glycophorin A expression occurred simultaneously with the apoptosis, even at the single cell level. In K562 cells, but not in JURL‐MK1 cells, the differentiation process involved increased hemoglobin synthesis. However, during spontaneous evolution of JURL‐MK1 cells in culture, the effects produced by Imatinib progressively changed from the fast apoptosis to the more complete erythroid differentiation. We suggest that the apoptosis and the erythroid differentiation are parallel effects of Imatinib and their relative contributions, kinetics and completeness are related to the differentiation stage of the treated cells. © 2005 Wiley‐Liss, Inc.
Protein interactions with model chromatographic stationary phases constructed using self‐assembled monolayers
Authors: Barrett David A. , Power Gillian M. , Hussain Maruf A. , Pitfield Ian D. , Shaw P. Nicholas , Davies Martyn C.
Published: March 2005

Model surfaces representative of chromatographic stationary phases were developed by immobilising an homologous series (C2–C18) of n‐alkylthiols, mixed monolayers of C4/C18 and thioalkanes with alcohol, carboxylic acid, amino and sulphonic acid terminal groups onto a flat, silver‐coated glass surface using self‐assembled monolayer (SAM) chemistry. The processes of adsorption and desorption of serum albumins onto the monolayer surfaces was monitored in real‐time using surface plasmon resonance (SPR). Alkyl‐terminated SAMs all showed a strong adsorption of bovine serum albumin which was largely independent of alkyl chain length, the ratio of mixed C4/C18 SAMs or the solution pH/ionic strength. The adsorption of human serum albumin to carboxylic and amine terminated SAMs was shown to be predominantly via non‐electrostatic interactions (hydrophobic or hydrogen bonding). However, sulphonic acid terminated SAMs showed almost exclusively electrostatic interactions with human serum albumin. This preliminary work using self‐assembled monolayer chemistry confirms the usefulness of well characterised SAMs surfaces for investigating protein adsorption and desorption onto/from model chromatography surfaces and gives some guidance for selecting appropriate functionalities to develop better surfaces for chromatography and electrophoresis.
Characterisation of poly(N‐isopropylacrylamide) by asymmetrical flow field‐flow fractionation, dynamic light scattering, and size exclusion chromatography
Authors: Yohannes Gebrenegus , Shan Jun , Jussila Matti , Nuopponen Markus , Tenhu Heikki , Riekkola Marja‐Liisa
Published: March 2005

Asymmetrical flow field‐flow fractionation (AsFlFFF) was used to determine the hydrodynamic particle sizes, molar masses, and phase transition behaviour of various poly(N‐isopropylacrylamide) (PNIPAM) samples synthesised by reversible addition–fragmentation chain transfer (RAFT) and conventional free radical polymerisation processes. The results were compared with corresponding data obtained by dynamic light scattering (DLS) and size exclusion chromatography (SEC). Agreement between the three methods was good except at higher molar masses, where the molar mass averages obtained by SEC were much lower than those obtained by AsFlFFF and light scattering. The aggregation of the polymers, which are thermally sensitive, was studied by DLS and AsFlFFF at various temperatures. In deionised water there was an abrupt change in the particle size due to phase separation at ≈32–35°C. The critical temperatures determined by AsFlFFF were 3–5°C higher than those obtained by DLS.
Preparation and evaluation of a doubly tethered chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid
Authors: Hyun Myung Ho , Kim Do Hun , Cho Yoon Jae , Jin Jong Sung
Published: March 2005

A new doubly tethered chiral stationary phase (CSP) was prepared to enhance CSP stability as well as to take advantage of the tertiary amide linkage by bonding (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid to bis(3‐aminopropyl)silica gel. The new CSP was quite effective in the resolution of α‐amino acids, β‐amino acids, amino alcohols, and amines and the chromatographic resolution behaviors of the new CSP were exactly consistent with those of the corresponding singly tethered CSP containing N—CH3 tertiary amide linkage. Direct comparison between the stabilities of the new CSP and the corresponding singly tethered CSP containing N—CH3 tertiary amide linkage under harsh chromatographic conditions reveals that the new CSP is more stable than the latter.
Polyacrylonitrile Enzyme Ultrafiltration and Polyamide Enzyme Microfiltration Membranes Prepared by Diffusion and Convection
Authors: Dayal Rajeshwar , Godjevargova Tzonka
Published: March 2005

Summary: Glucose oxidase (GOD) and catalase (CAT) were covalently immobilized onto three types of polyacrylonitrile (PAN 1, PAN 2, and PAN 3) ultrafiltration (UF) membranes with different pore sizes and one type of polyamide (PA) microfiltration (MF) membrane by the bifunctional reagent, glutaraldehyde. The initial membranes were pre‐modified to generate active amide groups in the PAN membranes and active amino groups in the PA membranes. The PAN 3 membrane contained the highest amount of active groups, and the membrane PA the lowest. The modified membranes were enzyme‐loaded by diffusion and convection (UF). The effect of membrane pore size and immobilization methods on enzymatic activity and bound protein were studied. The most effective immobilized system was prepared by diffusion using a PAN 3 membrane as a carrier (bound protein: 0.055 mg/cm2, relative activity: 87.6%). This membrane had the highest pore size of all the PAN membranes. Despite the highest pore size of PA membrane, the enzyme PA membranes prepared by diffusion showed the lowest amount of bound protein (0.03 mg/cm2) and the lowest relative activity (35.38%). This correlates with the lowest amount of active groups found in these membranes. The relative activity was higher for all the enzyme systems loaded by diffusion. The systems prepared by convection of the enzyme solution contained higher amounts of enzymes (0.035–0.13 mg/cm2 protein), which led to internal substrate diffusion resistance and a decrease in the GOD relative activity (21.55–68.5%) in these systems. The kinetic parameters (Vmax and Km) and the glucose conversion of the immobilized systems prepared by diffusion were also studied.

Relative activity of GOD in immobilized GOD plus CAT membranes prepared by different methods of enzyme loading: diffusion and convection (UF). The bars represent the difference between relative activities of immobilized GOD prepared by two methods for all the membranes. The enzyme activity was determined under static (a) and dynamic (b) conditions; 1 M glucose, pH 5.8, and 28 °C.

magnified image

Relative activity of GOD in immobilized GOD plus CAT membranes prepared by different methods of enzyme loading: diffusion and convection (UF). The bars represent the difference between relative activities of immobilized GOD prepared by two methods for all the membranes. The enzyme activity was determined under static (a) and dynamic (b) conditions; 1 M glucose, pH 5.8, and 28 °C.
Adsorption Kinetics and Thermodynamics of Acid Dyes on a Carboxymethylated Chitosan‐Conjugated Magnetic Nano‐Adsorbent
Authors: Chang Yang‐Chuang , Chen Dong‐Hwang
Published: March 2005

Summary: The monodisperse chitosan‐conjugated Fe3O4 nanoparticles with a mean diameter of 13.5 nm were fabricated by the carboxymethylation of chitosan and its covalent binding onto Fe3O4 nanoparticles via carbodiimide activation. The carboxymethylated chitosan (CMCH)‐conjugated Fe3O4 nanoparticles with about 4.92 wt.‐% of CMCH had an isoelectric point of 5.95 and were shown to be quite efficient as anionic magnetic nano‐adsorbent for the removal of acid dyes. Both the adsorption capacities of crocein orange G (AO12) and acid green 25 (AG25), as the model compounds, decreased with increasing pH, and the decreasing effect was more significant for AO12. On the contrary, the increase in the ionic strength decreased the adsorption capacity of AG25 but did not affect, obviously, the adsorption capacity of AO12. By the addition of NaCl and NaOH, both AO12 and AG25 could desorb and their different desorption behavior could be attributed to the combined effect of pH and ionic strength. From the adsorption kinetics and thermodynamics studies, it was found that both the adsorption processes of AO12 and AG25 obeyed the pseudo‐second‐order kinetic model, Langmuir isotherm, and might be surface reaction‐controlled. Furthermore, the time required to reach the equilibrium for each one was significantly shorter than those using the micro‐sized adsorbents due to the large available surface area. Also, based on the weight of chitosan, the maximum adsorption capacities were 1 883 and 1 471 mg · g−1 for AO12 and AG25, respectively, much higher than the reported data. Thus, the anionic magnetic nano‐adsorbent could not only be magnetically manipulated but also possessed the advantages of fast adsorption rate and high adsorption capacity. This could be useful in the fields of separation and magnetic carriers.

Acid dyes adsorption onto the CMCH‐conjugated Fe3O4 nanoparticles.

magnified image

Acid dyes adsorption onto the CMCH‐conjugated Fe3O4 nanoparticles.
Polymer Thermoplastic Proton Conductors Based on PPO and PS Ionomer Blends
Authors: Cánovas María José , Acosta José Luis , Linares Amelia
Published: March 2005

Summary: Two new proton‐conducting ionomers types were obtained based on poly(2,6‐dimethyl‐1,4‐phenylene) oxide (PPO) and polystyrene (PS) with different ionic group contents. They were characterized by means of infrared spectroscopy (FT‐IR), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA) and X‐ray photoelectron spectroscopy (XPS). From PPO and PS ionomers, binary blends of different compositions were prepared, the blend compatibility of the samples being assessed by means of DSC and DMA. Conducting properties of these materials were studied by means of complex impedance spectroscopy. In addition, water and methanol crossover through the different samples was measured, the results being compared with Nafion. The high conductivity and the low methanol permeability of some systems make them a valid alternative for application in fuel cells.

Variation of the interaction parameter, χ12, for PPO‐SH III/PS‐SH III blends.

magnified image

Variation of the interaction parameter, χ12, for PPO‐SH III/PS‐SH III blends.