bluuebunny/crossref_metadata_2025 huggingface dataset:
Exogenous succinate increases resistance of maize plants to copper stress
Authors: Doncheva Snejana , Stoyanova Zlatimira , Georgieva Katya , Nedeva Dimitrina , Dikova Rumyana , Zehirov Grigor , Nikolova Ana
Published: March 2006

The effect of copper (Cu) excess (1.5, 4.7, 31, 78, 156 μM) and exogenously supplied succinate on plant growth, chlorophyll content, chlorophyll fluorescence, and isoenzym profiles of some antioxidant enzymes in maize plants was studied. Excessive Cu supply led to a reduction in the relative growth rate (RGR), tolerance index (TI), chlorophyll a and chlorophyll b contents, and the quantum yield of PSII electron transport in the light‐adapted state (ΦPSII). Copper treatment induced several changes in the anionic and cationic peroxidases (PODs), as well as superoxide dismutase (SOD) isoenzyme profiles. After 8 d of 78 μM–Cu treatment, two new anionic and two new cationic peroxidase isoenzymes in the roots were registered. Copper applied at concentrations above 31 μM resulted in higher levels of manganese superoxide dismutase (Mn‐SOD) in the roots and Cu,Zn‐superoxide dismutase (Cu,Zn‐SOD) in the leaves. However, the addition of Na‐succinate (200 μM) to the root medium prior to Cu treatment increased the capacity of the plants to partially overcome Cu toxicity.
Physiological changes and defense mechanisms induced by cadmium stress in maize
Authors: Pál Magda , Horváth Eszter , Janda Tibor , Páldi Emil , Szalai Gabriella
Published: March 2006

Heavy metals such as cadmium (Cd) enter the ecosystem chiefly as the result of human activities. Nowadays the heavy‐metal pollution of the soil is causing ever greater problems, exacerbated by the fact that the heavy metals accumulated in plants may, either directly or indirectly, find their way into animals and human beings. Maize is one of the world's most important crops, ranking third after wheat and rice, so the changes induced by one of the most toxic heavy metals, Cd, in maize plants is a cause of some concern. This review discusses not only the toxic symptoms caused by Cd stress, but also the tolerance mechanisms activated in the plants. Cadmium induces a number of physiological changes, such as growth inhibition, changes in the water and ion metabolism, the inhibition of photosynthesis, changes in enzyme activities, and the formation of free radicals. The synthesis and compartmentalization of phytochelatins is induced shortly after the initiation of Cd stress, while other defense mechanisms also play an important role.
Near‐infrared spectroscopy can predict the composition of organic matter in soil and litter
Authors: Terhoeven‐Urselmans Thomas , Michel Kerstin , Helfrich Mirjam , Flessa Heiner , Ludwig Bernard
Published: March 2006

The usefulness and limitations of near‐infrared reflectance spectroscopy (NIRS) for the assessment of several soil characteristics are still not sufficiently explored. The objective of this study was to evaluate the ability of visible and near‐infrared reflectance (VIS‐NIR) spectroscopy to predict the composition of organic matter in soils and litter. Reflectance spectra of the VIS‐NIR region (400–2500 nm) were recorded for 56 soil and litter samples from agricultural and forest sites. Spectra were used to predict general and biological characteristics of the samples as well as the C composition which was measured by 13C‐CPMAS‐NMR spectroscopy. A modified partial least‐square method and cross‐validation were used to develop equations for the different constituents over the whole spectrum (1st to 3rd derivation). Near‐infrared spectroscopy predicted well the C : N ratios, the percentages of O‐alkyl C and alkyl C, the ratio of alkyl C to O‐alkyl C, and the sum of phenolic oxidation products: the ratios of standard deviation of the laboratory results to standard error of cross‐validation (RSC) were greater than 2, the regression coefficients (a) of a linear regression (measured against predicted values) ranged from 0.9 to 1.1, and the correlation coefficients (r) were greater than 0.9. Satisfactorily (0.8 ≤ a ≤ 1.2, r ≥ 0.8, and 1.4 ≤ RSC ≤ 2.0) assessed were the contents of C, N, and production of DOC, the percentages of carbonyl C and aromatic C and the ratio of alkyl C to aromatic C. However, the N‐mineralization rate and the microbial biomass were predicted unsatisfactorily (RSC < 1.4). The good and satisfactory predictions reported above indicate a marked usefulness of NIRS in the assessment of biological and chemical characteristics of soils and litter.
Kinetics of nonexchangeable‐potassium release and plant response in some calcareous soils
Authors: Jalali M. , Zarabi M.
Published: March 2006

Nonexchangeable K+ constitutes a slowly available reserve that may significantly influence K+ fertility of soils. Laboratory and greenhouse experiments were conducted to characterize the K+ supply and nonexchangeable K+–release kinetics in 10 calcareous soils using 0.01 M CaCl2 and 0.01 M oxalic acid extractions. Total K+ uptake by wheat (Triticum aestivum L.) grown in the greenhouse was used to measure plant‐available K+. The release of K+ was characterized by an initial fast rate followed by a slower rate. The nonlinear relationship in the early stages of the K+ release may be attributed to the edge sites, and release of K+ from interlayer exchange sites may be responsible for the second part of the K+ release. Kinetics of K+ release was described best with power function, which showed the best fit of the four models tested. Parameters of kinetics models in 0.01 M CaCl2 were significantly related to K+ uptake by wheat. Potassium release was also correlated to initial NH4OAc‐extratable K+ and to HNO3‐extractable K+.
Soil organic matter beyond molecular structure Part I: Macromolecular and supramolecular characteristics
Authors: Schaumann Gabriele E.
Published: March 2006

This contribution reviews and discusses structural aspects of soil organic matter (SOM) and humic substances (HS) with special respect to the macromolecular and the supramolecular view. It can be concluded that (1) dissolved humic acids behave as supramolecular associations of relatively small molecules with an enormous flexibility of reaction of environmental conditions, (2) multivalent cations may increase the apparent molecular weight by the formation of coordinative crosslinks in dissolved and undissolved natural organic matter (NOM), (3) sorption nonlinearity in solid humic acids and SOM may be due to polymer properties of NOM, (4) sorbates affect sorbent characteristics of SOM, and (5) hysteresis and conditioning effects in SOM can up to now best be explained with the polymer analogy. A distinct polydispersivity of SOM over a wide range of molecular masses is to be assumed.

The supramolecular and the macromolecular models were derived from humic acids with different composition and on the basis of different sample states. Although the supramolecular model has not explicitely been shown for unfractionated DOM, the combination of all discussed studies suggests supramolecular as well as macromolecular characteristics of NOM. Neither macromolecules nor small molecules can be fully excluded in solid and dissolved SOM. Microregions with different properties provide different types of sorption sites. SOM is suggested to be regarded as amorphous material. This point of view is not restricted to high molecular masses and may supplement our understanding of SOM by the model of physical aging.
Soil organic matter beyond molecular structure Part II: Amorphous nature and physical aging
Authors: Schaumann Gabriele E.
Published: March 2006

Glassy, rubbery, and crystalline phases are representatives of supramolecular structures which strongly differ in order, density, and other characteristics. In this contribution, the amorphous nature of soil organic matter (SOM) is reviewed with respect to the glassy/rubbery model, glass transition mechanisms, interactions of SOM with water, and physical aging. Glass‐transition behavior and physical aging are inherent properties of amorphous solids, and numerous spectroscopic investigations give insights into different domain mobilities of humic substances (HS). The correlation between sorption nonlinearity and glassiness of polymers and HS supports a relation between sorption and amorphicity in Aldrich humic acid. Further evidence is still required for the transfer to soil HS and SOM. Sorption and differential scanning calorimetry (DSC) data suggest a correlation between aromaticity and glassiness in HS, and the available data do currently not allow to decide unambiguously between specific sorption and hole filling as explanation. This needs to be verified in future research. Although parts of the investigations have up to now only been conducted with humic substances, the collectivity of available data give strong support for the glassy/rubbery conception of SOM. They clearly indicate that amorphous characteristics cannot be excluded in SOM.

This is further supported by the observation of different types of glass‐transition behavior in samples of whole humous soil. In addition to classical glass transitions in water‐free soil samples, water surprisingly acts in an antagonistic way as short‐term plasticizer and long‐term antiplasticizer in a second, nonclassical transition type. Latter is closely connected with physico‐chemical interactions with water and suggests water bridges between structural elements of SOM (HBCL‐model). The gradual increase of Tg* in SOM indicates physico‐chemical aging processes, which are not restricted to polymers. They may be responsible for contaminant aging, changes in surface properties and increased soil compaction in agricultural soils.
Estimating soil stress distribution by using depth‐dependent soil bulk‐density data
Authors: Bachmann Jörg , Hartge Karl Heinrich
Published: March 2006

Depth‐dependent soil bulk density (BDS) is usually affected by soil‐specific factors like texture, structure, clay mineralogy, soil organic‐matter content, soil moisture content, and composition of soil solution and is also affected by external factors like overburden‐stress history or hydrological fluxes. Generally, the depth‐dependent BDS cannot be predicted or extrapolated precisely from a limited number of sampling depths. In the present paper, an easy method is proposed to estimate the state of soil mechanical stress by analyzing the packing characteristics of the profile using soil bulk‐density data. Results for homogeneous loess profiles exposed to the site‐specific climatic conditions show that the depth‐dependent relation of void ratio vs. weight of overburden soil can be described systematically so that deviations from the noncompacted reference state can be detected. We observed that precompaction increased from forest soils (reference) to agricultural soils with decreasing depth.
Structure properties and pore dynamics in aggregate beds due to wetting–drying cycles
Authors: Seguel Oscar , Horn Rainer
Published: March 2006

Aggregate hierarchy and porosity changes in aggregate beds as a consequence of wetting–drying cycles were studied in two Andisols and one Mollisol from Chile, collected at two depths. Bulk density and indirect tensile strength were measured in aggregates of different sizes. Aggregate beds were prepared in cylinders with two size classes. Six wetting–drying cycles between 0 and –60 hPa were applied. Bulk density (Db) of soil matrix was controlled after each cycle, and the macroporosity was calculated. A repellency index was measured in one of the Andisols. In addition, also the air permeability was measured after the sixth cycle.

It could be proofed, that the aggregate strength is an appropriate parameter to evaluate the aggregate hierarchy, and this parameter is also more sensitive than aggregate Db to discriminate between the effects of land‐use intensity. Aggregate strength is furthermore well correlated with changes in pore water pressure and can be applied to relate strength values with aggregate development level. Only if the predrying exceeds pF > 3.0, aggregate strength correlates with Db. The more pronounced is the land‐use, the higher is the increase of Db values for aggregate beds. The decrease of coarse porosity during wetting–drying cycles can be explained by mass differences between saturated and equilibrated water conditions that considers the water around aggregates and within the contact area. Nevertheless, the relation of relative macroporosity change, calculated by Pexped where Dagg is the Db measured by clod method, and the relative Db change, is useful to explain possible presence of coarse pores inside the aggregates. The newly formed porosity prevents the water repellency, but after six cycles of drying, the repellency index increased in the topsoil while we could detect a decrease in the subsoil samples (under defined conditions in the laboratory) which we assume to be caused by microbial activity. The approaching of aggregates by drying cycles generates in Andisols a reduced area to air fluxes, with low values of air permeability.
Elastomeric Poly(propylene) from “Dual‐side” Metallocenes: Reversible Chain Transfer and its Influence on Polymer Microstructure
Authors: Hild Sabine , Cobzaru Cecilia , Troll Carsten , Rieger Bernhard
Published: March 2006

Summary: The influence of the cocatalyst nature on the distribution of the stereoerrors along the polymer chain has been studied using either MAO or [(C6H5)3C+] [(C6F5)4B−] to activate a C1‐symmetric (Flu‐Ind) complex in propene polymerization experiments. The in situ activation with borate indicated the chain back‐skip as the decisive mechanism responsible for stereoerror formation. When MAO is used for activation, additionally the reversible chain transfer to aluminum occurs, which can be called into account as a second mechanism for stereoerror formation. By the combination of 13C NMR, DSC, WAXS and SFM, it was shown that the differences in polymerization mechanisms result in variations of stereoerror formation. Due to this, the isotactic block length niso as well as their distribution along the chain changes. Using MAO activation, polypropenes with crystallizable blocks consisting of 23–32 monomers in isotactic sequences were generated, which co‐crystallized in α‐ and γ‐phase lamellae. When the reversible chain transfer was occluded (in situ borate activation) the bimodal distribution of crystalline lamellae strongly referred to a homogeneous random distribution of stereoerrors. In this case, two crystalline populations were present. The prevailing one, which crystallized in the orthorhombic γ‐modification, contained 23 consecutive isotactic blocks. Additionally, small amounts of α‐phase lamellae were present consisting of longer isotactic blocks (niso > 35). The different crystalline modifications resulted in different polymer morphologies. These changes caused in turn variations in the mechanical properties, such as elasticity and mechanical strength. This clearly shows that, by using different cocatalysts for activating C1‐symmetric complexes, the properties of poly(propylenes) with statistically distributed stereoerrors can be tailored.

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Macromolecule‐Metal Nanoparticle Complexes for Novel Development of Information Technology and Energy Conversion
Authors: Toshima Naoki
Published: March 2006

Summary: Macromolecule‐metal nanoparticle complexes have achieved a great deal of attention from the researchers since the nanotechnology boom, because nanoparticles can be easily prepared by chemical reactions, often stabilized by complex formation with macromolecules, and can play important roles in the construction of nanostructured materials for novel technologies. Here I would like to introduce three typical examples which are going to be developed in our group and will be potentially applied to novel information and energy‐conversion technology, i.e., super‐high‐density magnetic recording media, fast‐responsive liquid‐crystal display, and processable thermoelectric materials.
Metal Complexes of Phthalocyanines in Polymers as Suitable Materials for Optical Limiting
Authors: Slodek A. , Wöhrle D. , Doyle J. J. , Blau W.
Published: March 2006

Summary: Germanium and tin phthalocyanines containing peripheral and axial different substituents were synthesized. Thin multi‐layer films of PMMA and PVC containing monomolecular phthalocyanines were obtained by spin‐coating on glass substrates. The phthalocyanines were characterized by their absorption spectra. Optical limiting properties of the phthalocyanines in solution and in polymer films were investigated.
Membrane Preparation of Polysulfonic Acid Complexes by Layer‐by‐Layer Adsorption
Authors: Tago Takahiro , Shibata Hirokazu , Nishide Hiroyuki
Published: March 2006

Summary: The water‐insoluble, thermostable and homogeneous polymer complex membrane formation of polysulfonic acids was examined by modifying the preparation conditions of the layer‐by‐layer adsorption method of the acid and base polymers. The complexation of poly(4‐styrenesulfonic acid) in the 0.15 unit mM solution with poly(allylamine) gave a polymer complex membrane on a gold substrate in which one polymer layer was formed with a thickness of 1 nm. Properties including the proton conductivity of the membrane suggested possible applications of the polymer complex membrane.
Synthesis of A New Terpyridine Ligand Combined with Ruthenium(II) Complex and its Usage in the Stepwise Fabrication of Complex Polymer Wires on Gold
Authors: Ohba Yoshiki , Kanaizuka Katsuhiko , Murata Masaki , Nishihara Hiroshi
Published: March 2006

Summary: A ruthenium complex‐combined terpyridine ligand, tpyRu(dpp)‐(epe)‐ tpyPF6, was synthesized. Stepwise coordination reactions at the gold surface using this ligand gave Co‐Ru hetero‐metal complex wires, [1Co1Ru], which underwent reversible redox reactions of both redox complex units.
Preparation of Metal Oxide Nanotubes Using Gelators as Structure‐Directing Agents
Authors: Hanabusa Kenji , Numazawa Tomohiko , Kobayashi Satoshi , Suzuki Masahiro , Shirai Hirofusa
Published: March 2006

Summary: Cationic gelators, capable of gelling alcohols, were developed as structure‐directing agents for preparing metal oxides. The sol‐gel polymerization of metal alkoxides using the gelators as templates afforded metal oxide nanotubes. The unique structure of metal oxides was created by transferring the shape of fibrous aggregates of gelator. The electrostatic interaction between cationic gelator and anionic metal oxide precursor plays an important role for acting as templates.
Zero‐Birefringence Optical Polymer by Birefringent Crystal and Analysis of the Compensation Mechanism
Authors: Koike Yasuhiro , Yamazaki Keita , Ohkita Hisanori , Tagaya Akihiro
Published: March 2006

Summary: We reported a method for compensating the birefringence of optical polymers by doping them with inorganic birefringent crystals. In this method, an inorganic birefringent material is chosen that has the opposite birefringence to the polymer and needle‐like shape crystals which are oriented when the polymer chains are oriented. The birefringence of the polymer is thus compensated by the opposing birefringence of the crystal. Orientation behavior of the needle‐like crystals and polymers was investigated. The orientation function of the needle‐like crystal was increased with an increase in the aspect ratio of the needle‐like crystal.
Behavior of Linear and Cross‐Linked Polyelectrolytes in Metal Salt Solutions
Authors: Bekturov Esen , Suleimenov Ibragim
Published: March 2006

Summary: Comparison of swelling properties of linear and cross‐linked polyelectrolytes on the basis of diffusion theory is carried out. It is shown that viscosity of both positively and negatively charged macromolecules in solutions containing low‐molecualr ions may be predicted with the help of generalized Fuoss's law.
Design of Enzyme‐like Complexing Polymer Sorbents and Metal‐Polymer Complex Catalysts with Memory to Substrates
Authors: Efendiev Ayaz
Published: March 2006

Summary: A new principle of design of enzyme‐like complexing polymer sorbents and metal polymer complex catalysts has been developed. The principle is based on the use of memory of polymer composition and consists in conformational prearrangement of macromolecules of noncrosslinked complexing polymer favorable for sorbing metal ions and/or catalyzing substrate position followed by intermolecular crosslinking. It has been shown that prearranged polymer sorbents and catalysts demonstrate significantly improved sorption and catalytic properties.
Metal‐Containing Poly(Organophosphazenes)
Authors: Pertici Paolo , Vitulli Giovanni , Gleria Mario , Facchin Giacomo , Milani Roberto , Bertani Roberta
Published: March 2006

Summary: In this paper we highlighted the general situation of metal containing poly(organophosphazenes) and we presented the status of the art in this area in terms of interactions between phosphazene materials and different types of metals. Possible practical utilization of the polymers obtained is also envisaged.
Studies of the Interaction of Platinum Drugs with DNA Using Oligonucleotide Microarrays
Authors: Guiseppi‐Elie Anthony , Taylor Scott , Lingerfelt Louise , Nixon Chris , Georgiana Ryan , Kim Joy , Smith Stephanie , Mangrum Brad , Farell Nicholas
Published: March 2006

Summary: A novel method for the study of the interaction of the platinum drug cis‐diamminedichloroplatinum(II) (cis‐DDP or cisplatin) with 50‐mer oligonucleotides that were printed in high throughput microarray format is introduced. Our aim has been to identify sequence level differences in the interaction of various drug candidates that may serve to enable rational targeting of drugs to specific genes. A microarray of 26 control genes commonly used in oligonucleotide, Affymetrix and c‐DNA microarray platforms were microcontact spotted as amine‐terminated 50‐mer oligonucleotides onto glycidoxypropyltimethoxy silane (GPMS)‐modified glass slides. The generalized study format involved hybridization of probes with 10 fluorescently labeled complements as target followed by confocal imaging to reveal original spot intensities. Microarrays were then incubated at 37 °C with hydrolysed cisplatin while in hybridization cassettes, washed in buffer and then scanned again to reveal secondary intensities. We have investigated the influence of cisplatin to stabilize the relative fluorescence intensity via intrastrand crosslinking by studying the impact of varying drug:probe‐DNA mole ratio (0:1 (blank), 1:1, 25:1 and 50:1) and annealing temperatures (36, 46, or 56 °C) on retained intensity. ANOVA revealed that 4 of the 10 genes demonstrated (p < 0.0001) the expected result of increased signal retention with decreased temperature and increased drug concentration.
Modification and Electrochemical Properties of Poly(phenylazomethine) Derivatives
Authors: Higuchi Masayoshi , Hayashi Akari , Yamamoto Kimihisa
Published: March 2006

Summary: Oligo(phenylazomethine)s (OPAs) and aniline‐capped OPAs (OPA's) are used as model compounds of polyphenylazomethine (PPA), and their fundamental properties and their modification methods are investigated. Cyclic voltammograms of bis(diphenylmethyleneamino)benzene (OPA2′) showed irreversible redox response in the presence of trifluoroacetic acid. A selective synthesis of oligophenanthridine was achieved through the photocyclization of OPA2′ in concentrated sulfuric acid. Stepwise complexation behavior in dendritic poly(phenylazomethine)s (DPAs) was supported by the shell‐selective reduction of the imines. Using the shell‐selective reduction method and the terminal‐modification method of the DPAs, the core and terminals of DPAs were functionalized by ferrocene units, respectively.
Catalytic Activity of Copper(II) Enzyme‐like Catalysts, Prepared by Molecular Imprinting Technique in Oxidation of Phenols
Authors: Jakubiak Anna , Kolarz Bożena N. , Jezierska Julia
Published: March 2006

Summary: Molecularly imprinted polymer copper(II) catalysts were prepared by suspension polymerization of 4‐vinylpyridine, trimethylolpropane trimethacrylate (series A) and additional monomer – acrylonitrile (series B) in the presence of Cu(II) ions and template: 4‐metoxybenzyl alcohol; two samples were also prepared by surface molecular imprinting technique utilizing W/O emulsion. The catalytic activity was tested in model oxidation reactions of hydroquinone and 2,5‐di‐tert‐butylhydroquinone using hydrogen peroxide. The imprinted catalysts were more effective in both reactions than non‐imprinted but their activity strongly depended on Cu(II) loading. Surface imprinted samples showed the highest activity (LH up to 100%).
Organic Ion Exchangers. Synthesis and Their Behaviour in the Retention of Some Metal Ions
Authors: Neagu Violeta , Bunia I. , Luca Cornelia
Published: March 2006

Summary: Three pyridine strong base anion exchangers as beads were obtained by quaternization reactions of a 4‐vinylpyridine : 8% divinylbenzene copolymer of gel type. These resins possess methyl / ethyl / butyl radicals as substituents on N+ atoms and have exchange capacities of 4.80 mEq/g and 2.10 mEq/mL. For pyridine strong base anion exchangers, the behaviours in the retention processes of Cr(VI) as oxyanions and Ga(III) as [GaCl4]− complex anion were evaluated with the bath method. All the resins exhibited retention properties, but the retained amounts of the metal cations are different as a function of the alkyl length as substituent on N+ atoms and the complex anion nature. Thus, Cr(VI) oxyanions are best retained by the resin with CH3 as substituent on N+ atoms while [GaCl4]− complex anion by the resin with C4H9 as substituent on N+ atoms. By aminolysis reaction of an ethylacrylate : acrylonitrile : divinylbenzene copolymer as beads of macroporous type with NH2OH · HCl in the presence of C2H5OH a new chelating ion exchanger was performed which contains both amidoxime and hydroxamic acid functional groups.

This ion exchanger has the retention property for different metal cations but its retention capacities values are strongly dependent of the nature of metal cation and the counterion as well as pH of the solution. Thus, in the static conditions Zn(II) cation with NO anion as counterion is retained with the best result at pH = 5. As an example, for the aqueous metal cation solution of 10−2 M concentration for Zn(NO3)2 the resin possess at equilibrium a retention capacity of 6.70 mmol Zn/g dry resin and for Cu(II) from Cu(NO3)2 solution of same concentration, the retention capacity is 0.22 mmol Cu/g dry resin and Fe(III) from Fe(NO3)3 solution is not retained.
Metal Ion Removal from Aqueous Solution by Liquid Phase Polymer‐Based Retention Technique
Authors: Rivas Bernabé L. , Pereira Eduardo D. , Robles Pamela , Cid Rocío
Published: March 2006

Summary: Water‐soluble poly[3‐(dimethylamino)propylacrylate] is synthesized by radical polymerization with a yield of 87%. The polymer structure is confirmed by FT‐IR and 1H‐NMR spectroscopies. The polymer lost only 3% of weight up to 100 °C. The narrowest molecular weight distribution is observed with the fraction between 3,000 and 10,000 Da. P(DAPA) presents a high affinity for the metal ions Pb2+ and Cu2+, while the other metal ions are not significantly retained. By increasing the filtration factor, Z, metal ion affinity decreases, indicating a very weak ligand‐metal interaction and the possibility of its destruction when washed with water at the filtration cell's pH. For Z = 10, the retention values of Pb2+ and Cu2+ at pH 5 are 76.5% and 48.5%, respectively, while the values for Cu2+ and Cd2+ at pH 7 are 89.5% and 40.4%, respectively.
Spectrocyclic Voltammetry of Ruthenium Purple Electrodeposited on a WO3/Tris(2,2′‐bipyridine)‐ruthenium(II)/Polymer Hybrid Film
Authors: Sone Koji , Yagi Masayuki
Published: March 2006

Summary: Electrochemical reactions of Ruthenium purple, Fe[RuII(CN)6]3 (RP; FeIII‐RuII) were studied using a spectrocyclic voltammetry (SCV) technique. The SCV measurement for an RP film coated on an ITO electrode showed a reversible redox between RP and Ruthenium white (RW; FeII‐RuII) at 0.14 V vs saturated calomel reference electrode (SCE). An RP film was electrodeposited on a hybrid film of tungsten trioxide (WO3)/tris(2,2′‐bipyridine)ruthenium(II) ([Ru(bpy)3]2+; bpy = 2,2′‐bipyridine)/poly(sodium 4‐styrenesulfonate) (PSS) (denoted as WRP film) from a colloidal solution containing 0.5 mM FeCl3, 0.5 mM K4[Ru(CN)6] and 40 mM KCl using a potentiodynamic multi‐sweep technique. In a cyclic voltammogram (CV) of a WRP/RP film, a redox response was observed at 0.61 V in addition to essential redox responses of WRP hybrid film (a [Ru(bpy)3]2+/[Ru(bpy)3]3+ redox at 1.03 V and a HxWO3/WO3 redox below 0.09 V), but a redox response of RW/RP was not observed at 0.14 V. The SCV measurement for the WRP/RP film suggested that the redox response at 0.61 V is attributed to a redox of [Ru(bpy)3]2+/[Ru(bpy)3]3+ interacted electrostatically with RP. It also showed that RW is oxidized to RP via [Ru(bpy)3]2+/[Ru(bpy)3]3+ redox and RP is reversibly reduced to RW via HxWO3/WO3 redox. This unique geared electrochemical reaction for the WRP/RP film leads to a hysteresis property of an RW/RP redox.
Synthesis of Citric Acrylate Oligomer and Its In‐Situ Reaction with Chrome Tanned Collagen (Hide Powder)
Authors: Haroun A. A. , Masoud R. A. , Bronco S.
Published: March 2006

Summary: The purpose of this study was to formulate the new combined system of acrylic and citric acids, which was prepared by free radical polymerization and esterification reaction at the same time to form citric‐acrylate CAC oligomer. The presumable chemical structure of this oligomer and the reaction mechanism were investigated by different spectroscopic tools (1H,13C‐NMR and ATR‐IR), GPC and TGA/DTA. The effect as masking agent of the eco‐friendly oligomer (CAC) in the chrome tanning of the collagen and the pickling of the hide was approached by the study of the hydrothermal and mechanical properties of in‐situ treated/grafted chrome tanned collagen (hide powder) and pickled hide, respectively. The use of citric acrylate CAC oligomer instead of the traditional strong acids resulted in significant improvement in chrome exhaustion and physical properties of the leather.
Water Soluble Dextran‐Polyacrylamide Graft Copolymers for Capturing Metal Ions
Authors: Kutsevol N. , Guenet J.‐M. , Melnyk N. , Sarazin D.
Published: March 2006

Summary: The graft copolymers of Polyacrylamide (PAA) to Dextran (Mw = 20000 and Mw = 70000) have been synthesised by ceric‐ion‐reduced redox initiation method. Molecular characteristic of graft copolymers were determined from light scattering, SEC, and viscometry data. It was established that the increase of molecular weight of Dextran component up to 3.5 times do not influence essentially organization at molecular level of these copolymers in aqueous solution. Thet D‐g‐PAA copolymers capable of binding the heavy metal ions.
Dissociation Energy Computations for Saline Bonds Implied in Interactions Mediated by Peptidoglicans
Authors: Muntean Simona , Kurunczi Ludovic , Bologa Cristian , Ilia Gheorghe , Simon Zeno
Published: March 2006

Summary: Dissociation energy and hydration energy calculations, in water solution, are presented for saline bonds mediated by Ca2+ and Mg2+ ions with Brőnstedt type bases (COO, OSO3, OH). A computationally intensive method, Polarisable Continuum Model (PCM) using 6‐31G* basis set, was applied. Hydration energies were computed by various methods, as well as dissociation energies of some L2M complexes. L2Ca complexes result as more stable against dissociation than L2Mg complexes. Hydration energy calculation results, for some of the methods, here used, seem rather reliable as compared to experimental results.
Colouring Agents for SBR Vulcanizates and Their Effects on Ageing and UV Radiation Resistance
Authors: Botros Samir H. , Eid Mahmoud A. M. , Abd‐El‐Ghaffar Mahmoud A.
Published: March 2006

Summary: Metal free and some metal‐perylene polymers as well as some metal phthalocyanine polymers were incorporated into styrene butadiene rubber (SBR) compounds as colouring agents. The ageing and UV resistance of the vulcanizates obtained were studied in terms of their mechanical properties. The results obtained revealed that cobalt perylene and cobalt phthalocyanine polymers showed superior performance in SBR vulcanizates against thermal ageing and UV radiation. The optimum concentration of cobalt phthalocyanine polymer was found to be 1 phr (parts per hundred parts of rubber).
Cover Picture: Macromol. Symp. 236/2006
Authors: Rulhoff S. , Kaminsky W.
Published: March 2006

Cover: The Hamburg Macromolecular Symposia have been organized by the Institute of Technical and Macromolecular Chemistry of the University of Hamburg on annual basis since 1976. The meetings are dedicated to different specific fields of polymer science and are the place for discussions of leading research groups from academies and industry. The Hamburg Macromolecular Symposium 2005 had the topic “Polyolefin polymerization”. This research field is predestined for a cooperation between different faculties such as physics, chemistry, materials science, and engineering under the slogan “From molecule to material”. As an example, the picture shows 13C NMR spectra of long‐chain branched syndiotactic poly(propylene) with ethene‐based side chains (please see contribution by S. Rulhoff and W. Kaminsky).
Ansa‐Metallocenes by Intramolecular Ring Closure Reactions – Syntheses and Applications
Authors: Erker Gerhard
Published: March 2006

Examples of a functional group chemistry at the Group 4 bent metallocene frameworks are presented and discussed that allow for the preparation of ansa‐metallocenes at the stage of the intact organometallic complexes. These examples include ansa‐metallocene formation by means of intramolecular olefin metathesis reactions, by photochemical [2+2] cycloadditions of pendant olefinic moieties and even of a Mannich‐type carbon carbon coupling reaction of enamino substituents attached at the Cp‐rings. Many of the resulting ansa‐metallocene systems were employed as components of reactive homogeneous Ziegler‐Natta olefin polymerization and copolymerization catalysts. The Mannich coupling reaction was also used in 3ferrocenophane chemistry, eventually leading to novel chelate ligand systems that were employed in catalytic asymmetric polyketone formation.
Living Olefin Polymerisation and Block Copolymer Synthesis in the Presence of a Single‐site Catalyst Containing a Phenoxyimine Ligand
Authors: Weiser Marc‐Stephan , Mülhaupt Rolf
Published: March 2006

A new phenoxyimine catalyst (Bis‐(N‐(3′,5′‐diiodo‐salicylidene)‐2,6‐difluoroaniline)‐titanium(IV)‐dichloride) has been synthesised and characterised. After activation with MAO, it was used as highly active catalyst in living olefin polymerisation of ethylene and propylene. Ultra‐high molecular weight polyethylene and atactic polypropylene of low polydispersity were obtained. The living character of the polymerisation was shown by on‐line polymerisation kinetics and linear growth of number‐average molar mass with polymerisation time. A block copolymer of the type PE‐block‐P(E‐co‐P) was prepared and characterised by CRYSTAF analysis and AFM micrographs.
Synthesis of Very Small Polymer Particles by Catalytic Polymerization in Aqueous Systems
Authors: Mecking Stefan , Monteil Vincent , Huber Johannes , Kolb Ludmila , Wehrmann Peter
Published: March 2006

The preparation of aqueous dispersions of very small particles (size < 30 nm) of various polymers (polyethylenes, stereoregular 1,2‐polybutadiene, and polyalkenamers) by catalytic polymerization with a water‐soluble catalyst, or with microemulsions of lipophilic catalysts is reviewed.
Tandem Copolymerization: An Effective Control of the Level of Branching and Molecular Weight Distribution
Authors: Frediani Marco , Piel Christian , Kaminsky Walter , Bianchini Claudio , Rosi Luca
Published: March 2006

The term “tandem catalysis” addresses the action of two or more different catalysts in a single reactor to yield a product that is otherwise inaccessible to the individual catalysts. Its application to the production of branched polyethylene from ethylene feedstock as well as of homopolymers or copolymers with controlled molecular weight distribution is a relatively recent and successful technique. A great variety of combinations of late and early metal precursors, in different experimental conditions, have been successfully employed in tandem processes to prepare polyolefins with improved properties and performance parameters. In this article, we report on two examples of tandem catalysis, where either cooperative or independent actions take place.
Using the Transfer Function of an Isoperibolic Reaction Calorimeter for Thermo‐kinetic Analysis
Authors: Gaulke Arnd‐Lüder , Pauer Werner , Moritz Hans‐Ulrich
Published: March 2006

It is an aim of the present work to determine the chemical heat flow rate of a reaction without explicitly solving the heat balance equations. Therefore, it is necessary to calculate the heat flow rate directly from the temperature course of an experimentally determined reaction. For this transformation the transfer function of the calorimeter is needed1. An isoperibol reaction calorimeter was used for the experiments. With different calibrations and gained transfer functions, it is shown that the chemical heat flow rate can be determined from the temperature course of a reaction. The evaluation is fast and easy to use, which improves automation and prevents possible input errors.
Metallocene Catalysts for Olefin Oligomerization
Authors: Janiak Christoph , Blank Frederik
Published: March 2006

Metallocene complexes with a cocatalyst such as methylalumoxane, MAO can be used as catalysts in the dimerization or oligomerization of olefins (alkenes) including the (co‐/hydro‐)oligomerization of ethene, of the α‐olefins propene, 1‐butene, 1‐pentene, 1‐hexene, and higher α‐olefins, branched α‐olefins, cyclic olefins and α,ω‐dienes. Possible applications of α‐olefin oligomers are summarized. Oligo‐olefins can be analyzed by gel permeation chromatography (GPC) or 1H NMR spectroscopy for molecular weight determinations and by 1H and 13C NMR spectroscopy or MALDI‐TOF mass spectrometry for their end group structure.
New Polyolefin Nanocomposites and Catalyst Supports Based on Organophilic Boehmites
Authors: Xalter Rainer , Halbach Tobias S. , Mülhaupt Rolf
Published: March 2006

PE‐boehmite nanocomposites were prepared by means of metallocene‐catalyzed in situ polymerization of ethylene in presence of dispersed boehmites which were rendered organophilic by modification with organic acids. Polymerization activity, filler dispersion and mechanical properties of the nanocomposites were investigated as a function of type and concentration of the organophilic boehmites. Sulfonate modified boehmites were used as supports for MAO‐activated single site metallocene catalysts and nanocomposite formation via fragmentation of the self‐assembled nanoparticles and redispersion during polymerization.
Control of Ultrahigh Molecular Weight Polypropene Microstructures via Asymmetric “Dual‐Side” Catalysts
Authors: Cobzaru C. , Rieger B.
Published: March 2006

Asymmetric ansa‐metallocene catalysts based on fluorenyl and specifically substituted indenyl ligands allow a continuous change of the properties of isotactic polypropene and thus generate a new portfolio of polypropene materials, ranging from excellent thermoplastic elastic to stiff plastomers. Controlling the length of the crystallizable, isotactic segments by means of isolated stereoerrors introduced into the isotactic enchainment made this possible. The combination of synthetic, structural and polymerization studies of a series of ansa‐asymmetric catalysts has provided much insight into the effectiveness of the substitution patterns on tailoring the polymer microstructures. Ligand substitution, temperature and concentration of the propene monomer in the reaction medium can influence stereoerrors distribution, and therefore the crystallinity of the materials. Ultrahigh molecular weight polypropenes with tacticities varying in a broad range (20% < [mmmm] < 80%) are available via (Ind‐Flu)‐based asymmetric hafnocenes.
Ethylene/1,3‐Cyclohexadiene Copolymerization by Means of Methylaluminoxane Activated Half‐Sandwich Complexes
Authors: Heiser Dirk E. , Pelascini Frederic , Kramer Dominic , Scott Jennifer , Gambarotta Sandro , McCahill Jennifer , Stephan Douglas W. , Okuda Jun , Mülhaupt Rolf
Published: March 2006

Ethylene copolymerization with 1,3‐cyclohexadiene (CHD) was investigated by using methylaluminoxane (MAO) activated single‐site catalysts including bridged and non‐bridged titanium half‐sandwich and bimetallic cobalt(I) complexes. MAO activated CpTiCl2[NP(tBu)3] (Cp = cyclopentadienyl, tBu = tert‐butyl) gave high molecular weight CHD copolymers without encountering catalyst activity losses. According to the NMR microstructure investigation the resulting copolymers are highly regioregular.
Direct Copolymerization of Propene and Ethene‐based Macromers to Produce Long Chain Branched Syndiotactic Polypropene
Authors: Rulhoff S. , Kaminsky W.
Published: March 2006

Copolymers of propene and ethene‐based macromers have been prepared in a direct copolymerization. First macromers in a range of 3000–11600 g/mol were synthesized by varying the polymerization temperature and ethene concentration with the metallocene catalyst [(CH3)2CCp2]ZrCl2/MAO. These vinyl terminated ethene oligomers were copolymerized with propene by Cs symmetric catalyst [Ph2C(Cp)(Flu)]ZrCl2 to a long‐chain branched syndiotactic polypropylene. The LCB‐sPP was separated from the bimodal product by a fractional crystallization with p‐xylene and 2 ‐ ethoxy ethanol at 130 °C. A detailed analysis of the purified copolymer was given by GPC, DSC and 13C NMR spectroscopy.
New Materials Designed by Coordination Polymerization of ω‐undecenyl Macromonomers
Authors: Peruch Frédéric , Catari Edgar , Zahraoui Said , Isel François , Lutz Pierre Joseph
Published: March 2006

The major part of the present paper discusses the ability of well‐defined ω‐undecenyl polystyrene, polyisoprene or poly(styrene‐block‐isoprene) macromonomers to undergo coordination homopolymerization in the presence of selected titanium catalysts. Special emphasis is given to the influence of the nature of the catalyst, the polymerization temperature and the macromonomer molar mass and concentration on homopolymerization yield and average degree of homopolymerization (DPn). Titanium‐based catalytic systems such as CpTiCl3/MAO and Cp*TiCl3/MAO only yielded dimers. The use of the homogeneous metallocene catalyst with constrained ligand geometry (CGC‐Ti/MAO) having an open active site, significantly improved the degree of polymerization. Increasing macromonomer molar mass, causes only a slight decrease of DPn whereas conversion increased moderately. The final section briefly discusses the copolymerization of ω‐undecenyl polystyrene macromonomers with ethylene in the presence of Versipol™ catalysts.
Synthesis of Copolymers with Sterically Hindered and Polar Monomers
Authors: Donner Matthias , Fernandes Mercia , Kaminsky Walter
Published: March 2006

Different highly substituted C1 symmetric metallocenes have been investigated for the copolymerization of ethene and norbornene. The influence of the feed ratio and the polymerization temperature were varied to characterize the polymer by means of microstructure, thermal properties and catalysts activity. The bulky structured ligands of the catalysts lead to highly stereoregular copolymers with semi‐crystalline phases even at low norbornene incorporation. Two different allyl ethers (allyl ethyl and allyl propyl ether) have been used to copolymerize with ethene using metallocene catalyst system (rac‐[Me2Si(2‐Me‐4‐(1‐Ph)Ind)2]ZrCl2/MAO). In order to investigate the influence to ether incorporation to polymer properties, we have performed experiments varying comonomers concentration in feed, polymerization temperature and ratio Al(MAO)/Zr. The higher comonomer incorporation was followed by loss of cristallinity of the produced polymer. Additionally, the catalytic activity and melting point of the polymers also decrease with increase in comonomer concentration in feed.
Rheological Characterization of Long‐chain Branched Polyethylenes and Comparison with Classical Analytical Methods
Authors: Stadler Florian J. , Piel Christian , Kaminsky Walter , Münstedt Helmut
Published: March 2006

Long‐chain branched polyethylenes are still of great interest today. In some cases their characterization is not an easy task with classical analytic methods (GPC‐MALLS and NMR) because of the limited sensitivity at low concentrations of long‐chain branches. Rheological methods make a valuable contribution to the characterization due to their high sensitivity with respect to long‐chain branches. Using rheology it was possible to get an insight into the influence of different comonomers and comonomer concentrations on the long‐chain branch incorporation in LLDPE. A variation of polymerization parameters such as polymerization pressure was found to influence the rheological behavior. From these findings some conclusions with respect to the molecular structure could be drawn.
The Rheology of Linear and Long‐chain Branched Polymer Melts
Authors: Wagner Manfred H.
Published: March 2006

By generalising the Doi‐Edwards tube model to the Molecular Stress Function theory, the non‐linear rheology of polymer melts can be described quantitatively. The strain‐hardening of linear polymer melts in extensional flows can be accounted for by a strain energy function, which reflects the increase of strain energy due to tube squeeze. In comparison to linear polymer melts, long‐chain branched polymer melts show enhanced strain‐hardening. This is due to the fact that while the backbone of the branched macromolecule is stretched by deformation, side chains are compressed. It is demonstrated that the experimentally observed slope of the elongational viscosity after inception of strain‐hardening depends on the ratio β of total molar mass to backbone molar mass as predicted by the model. The steady‐state (plateau) value of the elongational viscosity depends on the maximum relative stretch, $f_{MAX}^2$, which can be supported by chain segments and which represents the maximum elastic energy storable in the polymeric system.
Syndiospecific Polymerization Catalysts for Styrene Based on Rare Earth Metal Half‐Sandwich Complexes
Authors: Hitzbleck Julia , Beckerle Klaus , Okuda Jun , Halbach Tobias , Mülhaupt Rolf
Published: March 2006

In the presence of an trialkyl aluminum cocatalyst the activation of scandium, yttrium and lutetium mono(cyclopentadienyl) complexes with various substituted cyclopentadienyl ligands by [Ph3C][B(C6F5)4] results in highly efficient catalysts for the syndiospecific polymerization of styrene. As active species half‐sandwich alkyl cations is assumed that is isostructural with the mono(cyclopentadienyl) titanium alkyl cation originally proposed by Zambelli.
Sorption Studies of Propylene in Polypropylene Polymerized with Novel Ziegler‐Natta‐Catalysts in Liquid and Gas Phase
Authors: Patzlaff M. , Wittebrock A. , Reichert K.‐H.
Published: March 2006

Polypropylene was produced in gas phase and liquid phase using different supported Ziegler‐Natta‐catalysts. Sorption behaviour of propylene in polymer particles was studied gravimetrically. The analyzed polymer fractions have average diameters between 250 and 875 µm. Generally it was found that the effective diffusion coefficient is increasing with increasing size of polymer particles. With electron microscopy a change of polymer particle morphology with particle size and type of catalysts was observed.