bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclodextrin derivatives in enantiomer GC separation of volatiles. Part XXI: Complexation of some terpenoids with 2‐O‐acetyl‐3‐O‐methyl‐ and 2‐O‐methyl‐3‐O‐acetyl‐6‐O‐t‐hexyldimethylsilyl‐γ‐cyclodextrins: Molecular Mechanics and Molecular Dynamics
Authors: Bicchi Carlo , Brunelli Claudio , Cravotto Giancarlo , Rubiolo Patrizia , Galli Mario , Mendicuti Francisco
Published: November 2003

Molecular Mechanics and Molecular Dynamics calculations were performed to simulate the 1 : 1 complex formation of 2‐O‐acetyl‐3‐O‐methyl‐ and 2‐O‐methyl‐3‐O‐acetyl‐6‐O‐t‐hexyldimethylsilyl‐γ‐cyclodextrins with a group of monoterpenoids having the p‐menthane skeleton (menthol, i‐menthol, neo‐menthol, neo‐i‐menthol, menthone, i‐menthone, and 3‐oxo‐1,8‐cineole) using nitrogen as simulated gas carrier. 1 : 1 complexes of the terpenoids studied are stable and non‐bonded van der Waals interactions are mainly responsible for complexation. The results suggest that the nature of the substituent (hydroxyl or oxo groups) at C3 on the cyclohexane ring, and its configuration for hydroxylated racemates, are responsible for the differences in complexation energies between the two investigated CD derivatives. This is in agreement with considerations of the difference in the experimental values of thermodynamic parameters, reported elsewhere, and may explain the difference in the enantioselectivity of the two CD derivatives for the terpenoids investigated. The substituents in position 1 are less involved in the chiral recognition process.
Structure‐enantioselectivity relationships for the study of chiral recognition in peptide enantiomer separation on cinchona alkaloid‐based chiral stationary phases by HPLC: Influence of the N‐terminal protecting group
Authors: Czerwenka Christoph , Lämmerhofer Michael , Lindner Wolfgang
Published: November 2003

Eleven different N‐terminal protecting groups (acetyl, benzoyl, FMOC, etc.) were employed for the HPLC separation of oligoalanine peptide enantiomers containing up to six amino acids. Isocratic HPLC separations were performed using a hydro‐organic buffered mobile phase and 4 mm ID columns containing three different chiral anion exchange stationary phases based on cinchona alkaloid‐derived chiral selectors. For most peptides successful separations could be obtained with all protecting groups, although those comprising aromatic moieties were found to yield higher enantioselectivities than those with aliphatic residues, since they are capable of undergoing favourable π‐π interactions with the selector. Systematic investigations concerning the presence or absence of structural features of related protecting groups showed that the use of protecting groups that are optimally adjusted to the binding pocket of the chiral selector effects a significant gain in enantioselectivity. At the same time these studies provided new insights into the chiral recognition mechanism.
Fast GC for the analysis of fats and oils
Authors: Mondello Luigi , Tranchida Peter Quinto , Costa Rosaria , Casilli Alessandro , Dugo Paola , Cotroneo Antonella , Dugo Giovanni
Published: November 2003

Fast and conventional GC techniques were both applied to ten different lipidic matrices and the results then compared. The fats and oils were of fish, animal, and vegetable origin and were all simultaneously transesterified with acidic methanol before performing batch analysis of the fatty acid methyl esters (FAMEs) obtained. All FAMEs samples were consecutively analyzed three times by each method. The fast method significantly reduced the time required for analysis by a factor of 5 while maintaining a similar resolution. Furthermore, the reproducibility of relative quantitative data was measured on going from one method to the other. Peak identification was achieved through conventional GC‐MS in combination with linear retention index values contained in a home library and information derived from comprehensive 2D GC group patterns.
Comparison of two sample clean‐up methodologies for the determination of polycyclic aromatic hydrocarbons in edible oils
Authors: Barranco Alejandro , Alonso‐Salces Rosa M. , Berrueta Luis A. , Gallo Blanca , Vicente Francisca , Sarobe Martin
Published: November 2003

An off‐line high‐performance normal‐phase liquid chromatography procedure with a silica column followed by reversed‐phase high‐performance liquid chromatography (HPLC) with fluorescence detection for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils is reported. The method was validated using certified reference materials and compared with a standardized method widely used in the food industry, consisting in low pressure column chromatography with alumina as stationary phase followed by reversed phase HPLC determination. The limits of detection were lower than 1 ng/g and good selectivity was achieved for both methods. There were no significant differences in accuracies and precisions obtained for each approach. The advantages and disadvantages of the two methods are discussed.
Parameters Affecting the Lower Critical Solution Temperature of Linear and Crosslinked Poly(N‐ethylacrylamide) in Aqueous Media
Authors: Xue Wei , Huglin Malcolm B. , Jones Timothy G. J.
Published: November 2003

A series of linear poly(N‐ethylacrylamide) (PEA) samples varying in molar mass has been prepared by free radical polymerization in the absence and presence of a chain transfer agent and a hydrogel of PEA has been prepared using N,N‐methylenebisacrylamide (BIS) as crosslinker. The lower critical solution temperatures (LCST) of the linear polymers in water and aqueous media were determined turbidimetrically as a function of molecular weight, concentration, heating/cooling rate, and concentrations of KCl and anionic surfactant sodium dodecyl sulfate (SDS) in the aqueous solution. The corresponding LCST for the hydrogel was determined from the gravimetric swelling ratios (r). In pure water the values of LCST for linear polymer and hydrogel are 73 °C and 62 °C, respectively. The LCST of linear PEA increases with decreasing molecular weight. The swelling ratio for gels and the LCST for solutions and gels increased with the inclusion of SDS into water. The opposite effects prevailed on inclusion of KCl into water or incorporation of crosslinker. Additionally, the rates of heating/cooling play a significant role in the measured value of LCST. Hence the swelling ratio of hydrogel or the LCST can be adjusted via 1) addition of either SDS or KCl into water; 2) use of different molecular weight samples; 3) incorporation of crosslinker into polymer chain.

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The Fabrication of Very Small Miniemulsion Latexes from N‐Stearoylglutamate and Lauryl Methacrylate: Evidence for Droplet Budding
Authors: Yildiz Ufuk , Landfester Katharina , Antonietti Markus
Published: November 2003

A new, biodegradable surfactant with high efficiency, N‐stearoyl‐di(sodium)glutamate (SDG), was used for miniemulsion polymerization of styrene and lauryl methacrylate (LMA). In the case of styrene, SDG produces latexes at least as small as those produced by sodium dodecyl sulfate (SDS), over a range of concentrations. In the case of LMA, a combination of SDG with an appropriate costabilizer allows one to obtain very small particles. With potassium persulfate (KPS) as initiator, the SDG/LMA system deviates significantly from the ideal miniemulsion, forming extremely small particles, which was speculatively attributed to a budding phenomenon.

The new, biodegradable surfactant, N‐stearoyl‐di(sodium)glutamate.

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The new, biodegradable surfactant, N‐stearoyl‐di(sodium)glutamate.
Synthesis and Characterization of Block Copolymers of ε‐Caprolactone and DL‐Lactide Initiated by Ethylene Glycol or Poly(ethylene glycol)
Authors: Huang Ming‐Hsi , Li Suming , Coudane Jean , Vert Michel
Published: November 2003

Biodegradable copolymers were prepared by ring‐opening polymerization of sequentially added ε‐caprolactone and DL‐lactide in the presence of ethylene glycol or poly(ethylene glycol), using zinc metal as catalyst. Polymerization was performed in bulk and yielded block copolymers with predetermined PEG/PCL/PLA segments. The obtained polymers were characterized by 1H NMR, SEC, IR, DSC, TGA, and X‐ray diffraction. Data showed that the copolymers preserved the excellent thermal behavior inherent to PCL. The crystallinity of PLA‐containing copolymers was reduced with respect to PCL homopolymer. The presence of both hydrophilic PEG and fast degrading PLA blocks should improve the biocompatibility and biodegradability of the materials, which are of interest for applications as substrate in drug delivery or as scaffolding in tissue engineering.

Block copolymerization of ε‐caprolactone and DL‐lactide initiated by dihydroxyl PEG.

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Block copolymerization of ε‐caprolactone and DL‐lactide initiated by dihydroxyl PEG.
Investigation of Templated Mesoporous Silicate Thin Films Using High Speed, Solid‐State 1H MAS and Double Quantum NMR Spectroscopy
Authors: Alam Todd M. , Fan Hongyou
Published: November 2003

Two‐dimensional DQ 1H MAS NMR has been used the investigate the local structure of a surfactant‐templated silicate thin film prepared from adding 4% polyoxyethylene(10) cetyl ether to an acidic TEOS silica sol. A close spatial contact between the surfactant and the silicate present in these materials could be demonstrated, while the high sensitivity of the NMR experiments allowed systems with limited amounts of material to be investigated. The detected inorganic‐organic interactions in these materials provide additional information into the chemical processes occurring during the self‐assembly process and the formation of meso‐structured materials.

Graphical representation of the spatial interactions observed between the silanols, oxomethylene protons of the surfactant and water within the template silicate material.

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Graphical representation of the spatial interactions observed between the silanols, oxomethylene protons of the surfactant and water within the template silicate material.
Versatile Synthesis of Soluble Multifunctional Thiophene Copolymers with NLO Activity
Authors: Costa‐Bizzarri Paolo , Lanzi Massimiliano , Paganin Luisa , Della‐Casa Carlo , Bertinelli Franco , Casalboni Mauro , Sarcinelli Felice , Quatela Alessia
Published: November 2003

Functionalized second‐order nonlinear optical (NLO) thiophene copolymers were synthesized. Two elegant syntheses based on the post‐functionalization of polymeric precursors obtained by oxidative polymerization were developed, leading to copolymers that proved to be fully soluble in common organic solvents. The new materials were characterized by NMR, FT‐IR, and UV‐vis spectroscopies, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). Moreover, the NLO activity of the new materials, as determined by corona poling alignment and second harmonic generation (SHG) measurements, showed a good agreement between the second‐order NLO coefficient and the chromophore concentration.

Three‐dimensional optimization of the chromophore thiophene‐functionalized comonomer.

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Three‐dimensional optimization of the chromophore thiophene‐functionalized comonomer.
Effect of a Water‐Soluble Polymer on Polymer Interdiffusion in P(MMA‐co‐BA) Latex Films
Authors: Wu Jun , Winnik Mitchell A. , Farwaha Rajeev , Rademacher Jude
Published: November 2003

We describe non‐radiative energy‐transfer experiments to measure the rates of polymer interdiffusion in P(MMA‐co‐BA) latex films formed in the presence of poly(vinyl alcohol) (PVOH). PVOH had relatively little effect on the initial efficiency of energy transfer, even when the amount of PVOH was large enough to form the continuous phase. Since ΦET(0) is a measure of the interfacial area between D‐ and A‐labeled cells in the film, we conclude that under these circumstances the dispersed P(MMA‐co‐BA) copolymer is in the form of clusters with many contacts between particles containing D and A labels. These large amounts of PVOH also reduce the amount of polymer diffusion that takes place when the films are annealed. When smaller amounts of PVOH are present, the effects are measurable but much smaller. In the presence of 2 to 17 wt.‐% PVOH, the polymer diffusion rate is retarded. The magnitude of the effect increases with the amount of PVOH present, and the effect is larger at 45 °C than at 63 °C. We show that the PVOH has its largest influence at the very early stages of polymer diffusion.

Schematic representation of an energy transfer experiment, which monitors polymer interdiffusion in a latex film.

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Schematic representation of an energy transfer experiment, which monitors polymer interdiffusion in a latex film.
Propene Polymerisation with rac‐[Me2Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)2]ZrCl2 as a Highly Active Catalyst: Influence of Monomer Concentration, Polymerisation Temperature and a Heterogenising Support
Authors: Frediani Marco , Kaminsky Walter
Published: November 2003

Propene was polymerised at high temperatures (up to 90 °C) using rac‐[Me2Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)2]ZrCl2/MAO as the catalytic system. The increasing deactivation reaction rate of the catalyst for polymerisations above 60 °C was less for a silica supported catalyst compared with the homogeneous one. The isotacticity of polypropene decreases from 99 to 96%. Also the morphology changes with different temperatures.

Increasing of the thermal stability for the rac‐[Me2Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)2]ZrCl2/MAO/SiO2 with respect of the rac‐[Me2Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)2]ZrCl2/MAO system.

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Increasing of the thermal stability for the rac‐[Me2Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)2]ZrCl2/MAO/SiO2 with respect of the rac‐[Me2Si(2‐Me‐4‐(α‐naphthyl)‐1‐Ind)2]ZrCl2/MAO system.
Synthesis, Characterization and Properties of 2‐(Perfluorooctyl)ethylacrylate Grafted Segmented Polyurethaneureas
Authors: Tomita Takehiro , Li Yu‐Jun , Nakaya Tadao
Published: November 2003

We report herein that 2‐(perfluorooctyl)ethylacrylate (PFEA) was successfully grafted onto a segmented polyurethaneurea (SPUU). We found that certain PFEA orientated onto the grafted SPUU film surface could significantly improve hemocompatibility. 1,2‐Propanediamine (PD) as a chain extender was used to synthesize the SPUU, which was based on diphenylmethane diisocyanate (MDI), vinyl group‐containing poly(butadiene) diol (PBD), and hydrogenated poly(isoprene) diol (HPIP). PFEA was copolymerized with the SPUU using α,α′‐azobis(isobutyronitrile) (AIBN) as a radical initiator. Various feed ratios of PFEA grafted polymers were synthesized (SPUU‐F‐0.5, SPUU‐F‐0.75, and SPUU‐F‐1.0) while non‐grafted SPUU was abbreviated as NG‐SPUU. The bulk characteristics of the resulting polymers were investigated by infrared spectroscopy (IR) measurement. Mechanical properties of the typical PFEA grafted SPUU were measured by dynamic viscoelasticity and tensile measurements. We found that PFEA orientated on the surface, as revealed by attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), electron spectroscopy for chemical analysis (ESCA), and water contact angle measurements. The hemocompatibility in vitro was evaluated with rabbit platelet‐rich plasma (PRP) contact tests and viewed by electron probe microanalyzer (EPM) using NG‐SPUU as a reference. We found that fewer platelets adhered to the PFEA grafted surfaces. New polymer SPUU‐F‐0.5 showed the best hemocompatibility in the tested samples. Platelet adhesion to PFEA grafted polymers SPUU‐F‐0.5, SPUU‐F‐0.75, and SPUU‐F‐1.0 was inhibited 91%, 58%, and 50% compared with NG‐SPUU. The relative clotting time of the cast films in contact with cow platelet‐poor plasma (PPP) was 3.26, 2.94, 1.95, 2.39 and 1.00 for SPUU‐F‐0.5, SPUU‐F‐0.75, SPUU‐F‐1.0, NG‐SPUU, and glass, respectively. The new polymers also showed the common characters of fluorinated polymers as revealed by water vapor transmission, dielectric constant, and index of refraction measurements.

Structure of the synthesized PFEA Grafted SPUU.

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Structure of the synthesized PFEA Grafted SPUU.
Direct Synthesis of Controlled Poly(styrene‐co‐acrylic acid)s of Various Compositions by Nitroxide‐Mediated Random Copolymerization
Authors: Couvreur Laurence , Charleux Bernadette , Guerret Olivier , Magnet Stéphanie
Published: November 2003

Styrene and acrylic acid were copolymerized under controlled conditions, in 1,4‐dioxane solution at 120 °C and 2 bar, using an alkoxyamine initiator based on the N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) nitroxide, SG1. A broad composition range from 90/10 to 10/90 was investigated. With slightly different initiator concentrations and a similar initial proportion of free SG1 (4.5 mol‐% with respect to the initiator) the polymerizations exhibited very similar rates, irrespective of the proportion of acrylic acid in the comonomer mixture (80% conversion within 8 h). In all cases, the copolymers presented number average molar masses, $\overline M _{\rm n}$, that increased linearly with overall monomer conversion, and polydispersity indexes that ranged between 1.2 and 1.4. Moreover, $\overline M _{\rm n}$ followed the calculated values, based on the initial concentrations of monomers and initiator. The variation in the initiator concentration allowed to target various molar masses, but some limitation appeared at low initiator concentration owing to chain transfer to 1,4‐dioxane. From the kinetic data, the reactivity ratios were determined: rA = 0.27 ± 0.07 for acrylic acid and rS = 0.72 ± 0.04 for styrene. Depending on the initial comonomer composition, chains exhibited no or small composition drift, and hence a slightly pronounced gradient structure.

Reactivity ratios for acrylic acid and styrene.

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Reactivity ratios for acrylic acid and styrene.
Radical Cation, Dimer Radical Cation and Neutral Radical of 2,3‐Dihydropyran – Possible Initiators of its Polymerisation?
Authors: Naumov Sergej , Janovský Igor , Knolle Wolfgang , Mehnert Reiner
Published: November 2003

The radical cation, distonic dimer radical cation, and radical of 2,3‐dihydropyran (DHP), which may play an important role in mechanism of radical polymerisations of DHP, were radiolytically generated at low temperatures in freon matrices and investigated by electron paramagnetic resonance (EPR) spectroscopy, as well as by quantum chemical methods. DHP radical cation with a half‐chair conformation and six coupling protons (0.88, 0.18, 4.60, 1.88, 1.27, 0.56 mT) was found to be stable in CF3CCl3 between 77 and 145 K. The same radical cation was observed at 77 K also in CF2ClCFCl2, but on increasing temperature, transformation into the neutral 4‐dihydropyryl radical occurred; the latter also shows the half‐chair conformation at 140 K and is characterised by six coupling protons (0.14, 2.31, 0.92, 1.42, 0.28, 1.35 mT). At a high DHP concentration in CF2ClCFCl2 a distonic DHP dimer radical cation, with strongly separated spin and charge and only two coupling protons (1.8 and 3.2 mT) was identified at 100 K, also yielding, at higher temperatures, the 4‐dihydropyryl radical.

The radiolytically generated species from DHP and their observed EPR spectra.

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The radiolytically generated species from DHP and their observed EPR spectra.
Block Copolymers of Methyl Vinyl Ether and Isobutyl Vinyl Ether With Thermo‐Adjustable Amphiphilic Properties
Authors: Verdonck Beatrice , Goethals Eric J. , Du Prez Filip E.
Published: November 2003

The thermo‐adjustable hydrophilic/hydrophobic properties of AB, ABA and BAB block copolymers in which A is poly(methyl vinyl ether) (PMVE) and B is poly(isobutyl vinyl ether) (PIBVE) have been investigated. The block copolymers were prepared by “living” cationic polymerization using sequential addition of monomers. The polymerizations were carried out with the system acetal/trimethylsilyl iodide as initiator and ZnI2 as activator. The initiating system based on diethoxyethane leads to AB block copolymers whereas the initiating system based on tetramethoxypropane leads to ABA or BAB triblock copolymers. Well‐defined block copolymers of different composition with controlled molecular weights up to approx. 10 000 have been prepared. When IBVE is added to living PMVE, PIBVE‐blocks form only in the presence of an additional amount of ZnI2, which is attributed to the fact that part of the ZnI2 is inactive because of complex formation with PMVE. At room temperature, the combination of hydrophilic (PMVE) and hydrophobic (PIBVE) segments provides the copolymers with surfactant properties. Above the lower critical solution temperature (LCST) of PMVE, situated around 36 °C, the PMVE‐blocks become hydrophobic and the amphiphilic nature of the block copolymers is lost. The corresponding changes in hydrophilic/hydrophobic balance have been evaluated by investigation of the emulsifying properties of the block copolymers for water/decane mixtures as a function of the temperature. Below the LCST, the block copolymers have emulsifying properties similar to or better than those of the commercial PEO‐PPO block copolymers (Pluronic®). Either oil‐in‐water or water‐in‐oil emulsions can be obtained, depending on the polymer architecture and the water/decane volume ratio. The emulsifying properties are strongly reduced or completely lost above 40 °C. Emulsions obtained with a PMVE36‐b‐PIBVE54 block copolymer for a water/decane (v/v) ratio of 85/15 remained stable for more than six months.

50/50 and a 85/15 water/decane w/o emulsion (15 g/l) with the PMVE36‐b‐PIBVE54 block copolymer at 20 °C.

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50/50 and a 85/15 water/decane w/o emulsion (15 g/l) with the PMVE36‐b‐PIBVE54 block copolymer at 20 °C.
Synchrotron X‐ray and DSC Studies of the Phase Behaviour of Poly(diethylene glycol p,p′‐bibenzoate)
Authors: Pérez Ernesto , Benavente Rosario , Cerrada María L. , Bello Antonio , Pereña José M.
Published: November 2003

Time‐resolved synchrotron X‐ray and DSC experiments were applied to investigate the phase behaviour of poly(diethylene glycol p,p′‐bibenzoate), PDEB. The DSC results are indicative of the formation of a smectic mesophase, previously identified as a SmCA type, which can be easily quenched down to room temperature. However, the synchrotron results show that the SmCA phase undergoes some kind of ordering or transformation at temperatures below 110 °C. Moreover, the annealing of PDEB at temperatures above Tg for sufficiently long times leads to the formation of a highly ordered structure, although very thin crystals and low crystallinities are obtained.

Scattering profiles corresponding to sample PDEB85 in a melting experiment.

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Scattering profiles corresponding to sample PDEB85 in a melting experiment.
Side‐chain Cholesteric Liquid Crystalline Elastomers Derived from Nematic Bis‐olefinic Crosslinking Units
Authors: Zhang Bao‐Yan , Hu Jian‐She , Jia Ying‐Gang , Du Bing‐Guang
Published: November 2003

The synthesis of the nematic crosslinking agent (4′‐allyloxy‐benzoyl)‐(4″‐undec‐10‐en‐1‐oyl‐benzoyl)‐p‐benzenediolate (M‐1), the cholesteric monomer cholesteryl undec‐10‐en‐1‐oate (M‐2) and side‐chain cholesteric liquid crystalline elastomers is described. The chemical structures of the obtained monomers and elastomers were confirmed by FTIR and 1H NMR spectroscopy. Their mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction measurements. The influence of the crosslinking M‐1 units on phase behavior of different elastomers prepared by a one‐step hydrosilation reaction was discussed. The elastomers containing less than 20 mol‐% of the crosslinking M‐1 units showed elasticity, reversible phase transition and cholesteric texture. The experimental results demonstrated that the glass transition temperatures and isotropization temperatures of P‐2 ∼ P‐6 increased with increasing the concentration of crosslinking M‐1 units.

Synthesis and schematic representation of elastomers.

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Synthesis and schematic representation of elastomers.
Phase Behavior of Poly(methyl methacrylate)/Poly(vinylidene fluoride) Blends in the Presence of High‐Pressure Carbon Dioxide
Authors: Walker Teri A. , Melnichenko Yuri B. , Wignall George D. , Lin J. S. , Spontak Richard J.
Published: November 2003

Previous efforts have demonstrated that high‐pressure CO2 can markedly influence the phase behavior of amorphous polymer blends. In this work, we examine the effect of high‐pressure CO2 on the miscibility of blends composed of glassy poly(methyl methacrylate) (PMMA) and semicrystalline poly(vinylidene fluoride) (PVDF). Blends of this type are known to exhibit lower critical solution temperature (LCST) behavior with partial miscibility up to ≈50–60 wt.‐% PVDF at ambient conditions. Two miscible PMMA/PVDF blends have been systematically exposed to high‐pressure CO2 at 35 °C and pressures below and above the critical pressure. Small‐angle X‐ray scattering reveals that the scattering intensity at high scattering angles shows little dependence on pressure at low CO2 pressures, but increases substantially at relatively high CO2 pressures. Transmission electron microscopy and differential scanning calorimetry analyses confirm that the blends are initially quasi‐homogeneous with diffuse PVDF‐rich dispersions and a single glass transition temperature. After exposure to relatively high CO2 pressures, however, the PVDF is found to crystallize within the PMMA‐rich matrix. Thermal recycling of these blends promotes homogenization, indicating that such CO2‐altered phase behavior is reversible.

SAXS patterns acquired from the 69/31 w/w PMMA/PVDF blend.

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SAXS patterns acquired from the 69/31 w/w PMMA/PVDF blend.
Morphology Evolution during the Phase Separation of Polyetherimide/Epoxy Blends
Authors: Gan Wenjun , Yu Yingfeng , Wang Minghai , Tao Qingsheng , Li Shanjun
Published: November 2003

The results of time‐resolved light scattering for the phase separation of epoxy/polyetherimide/anhydride blends show that the evolution of scattering vector qm follows a Maxwell‐type relaxation equation. The relaxation time may be suggested as the time taken for the diffusion of the epoxy‐anhydride n‐mers from the PEI‐rich phase by their relaxation movement, and the apparent activation energy of the relaxation movement is obtained.

Values of qm versus time at different temperatures.

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Values of qm versus time at different temperatures.
Polymerization of Vinyl Ethers by (α‐diimine)NiII/Methylaluminoxane Catalysts
Authors: Kim Il , Ha Yun Sun , Ha Chang‐Sik
Published: November 2003

Polymerizations of vinyl ethers are carried out with (α‐diimine)nickel(II) catalysts in the presence of methylaluminoxane. Effects of structural variations of the ligand on the activities of catalysts and polymer microstructure are described. The catalysts prepared by changing the bulkiness of ligand substituents in the ortho aryl position result in no specific trends terms of the yield and molecular weight of polymer. Poly(vinyl ether)s are atactic regardless of the structure of the catalyst used.

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Tartaric Acid Starch Ether: A Novel Biopolymer‐Based Polyelectrolyte
Authors: Grote Carsten , Lazik Waldemar , Heinze Thomas
Published: November 2003

New tartaric acid starch ethers have been synthesized applying starch sources of different amylose content. The reactions were carried out heterogeneously in ethanol/water mixtures with cis‐disodiumepoxysuccinate as etherifying reagent leading to products of a degree of substitution (DS) up to 0.3. The molecular structure of the new starch ethers was evaluated by elemental analysis, FTIR and 13C NMR spectroscopy. Preliminary studies using a convenient titration method indicate a high binding capacity for Ca2+ ions which is dependent on the starch source and DS.

Tartaric acid starch ethers.

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Tartaric acid starch ethers.
2020 foresight: What the HR world may look like then
Authors: Beaumont Richard A.
Published: November 2003

Looking back, one can laboriously trace how a current event or situation happened. Looking forward, however,
it is never so easy to discern trends out of current events, and correctly guess where they may lead. This
article is a well‐informed leap ahead to the year 2020 by an HR leader and innovator who looks backward
from there to imagine the direction that many current trends in the human resource management of major companies
may have taken, as a result of their own and societal actions. © 2003 Wiley Periodicals,
Inc.
Goalsharing plan helps Stillwater Mining Company through tough times
Authors: Stark John , Dalton Glenn L. , Carroll Donncha
Published: November 2003

When the market price of its palladium skyrocketed to an unsustainable high, Stillwater Mining Company
(SMC) faced a small window of opportunity to put the brakes on escalating operating costs. To do that,
it turned to a goalsharing incentive plan to unify the workforce in focused, committed action. By educating SMC
executives, involving employees—including the union—in plan design, and linking the plan to computer
modeling technology, SMC overcame employee skepticism and avoided the goal‐setting problems that had doomed
its previous attempts at goalsharing arrangements. © 2003 Wiley Periodicals, Inc.
Hillenbrand industries builds leadership capabilities to drive its new business strategy
Authors: McMillen Steve , Luebbe Deborah , Lauber Mindy
Published: November 2003

When successful Hillenbrand Industries adopted an aggressive new business strategy, it realized it might not
have the leadership capabilities to execute it. It rethought its approach to leadership talent management,
partnered with topnotch vendors, and employed leading‐edge technologies to create integrated systems and
processes for acquiring, developing, and deploying the best talent in its industries. Now, four years later, the
cadre of leaders that has emerged has taken the company to even higher levels of performance © 2003
Wiley Periodicals, Inc.
GMFAC: How a simply successful approach to organizational improvement worked at a large city hospital
Authors: Kopelman Richard E.
Published: November 2003

Rather than making major training investments in sophisticated methodologies, some organizations may find that
the five basic concepts embodied in the GMFAC framework are all they need to lay the foundation for continuous,
sustainable improvement. For members of a New York City hospital, learning the GMFAC principles in the context of
solving an actual operational problem led to visible, measurable improvements in quality and the confidence to
tackle even bigger problems. © 2003 Wiley Periodicals, Inc.
Valuing the worker
Authors: Batstone David
Published: November 2003

In the wake of corporate scandals that have revealed seemingly unbridled greed and unprincipled management
practices, journalist David Batstone has identified eight principles for deciding whether an organization is as
credible, trustworthy, and soluble as it seems. One of those principles, valuing the worker, is explored here
in detail, along with six compelling stories of companies that have—or have not—made this principle
part of their corporate fabric. © 2003 David Batstone
Stromfluss durch ein Molekül: Molekulare Elektronik
Authors: Weber Heiko B. , Mayor Marcel
Published: November 2003

Heute gelingt es, einzelne organische Moleküle mit zwei Goldelektroden zu kontaktieren. Dass es sich wirklich um einzelne Moleküle handelt, zeigt das elektrische Leitverhalten eines solchen Kontakts: Verschiedene Moleküle erzeugen unterschiedliche, aber charakteristische Kennlinien. In Zukunft könnten durch Einsatz geeigneter Moleküle die elektronischen Eigenschaften des Einzelmolekül‐Kontakts maßgeschneidert werden. Amerikanischen Wissenschaftlern gelang bereits die Herstellung von Einzelmolekül‐Feldeffekttransistoren und der Bau eines molekularen Speicherbausteins mit 64 Bit. Bis zur technischen Anwendung ist der Weg allerdings noch weit.
Selbstorganisation in der Nanowelt: Nanostrukturierung
Authors: Teichert Christian
Published: November 2003

Die Mikroelekronik steuert auf kleinste Nanostrukturen zu, die heutige lithographische Verfahren nicht mehr erzeugen können. Einen Ausweg bieten Selbstorganisationsprozesse. Mit ihnen sind im Prinzip großflächige Anordnungen von Nanostrukturen auf Silizium‐Wafern erreichbar. Ein Weg ist das heteroepitaktische Aufwachsen von Filmen, deren Kristallgitter vom Silizium abweicht. Ein anderer Weg nutzt aus, dass Ionenstrahlen die Oberflächen ausgeprägt strukturieren können. Beide Wege erlauben es, nur mit einer Materialklasse einen Fülle von Nanostrukturen zu erzeugen. Diese eignen sich für viele Anwendungen: Sie reichen von der Optoelektronik über magnetische Datenspeicher bis zu flächig angeordneten organischen Nanostrukturen.
ANTARES: Neutrino‐Daten aus der Tiefe: Neutrino‐Teleskop im Mittelmeer
Authors: Brunner Jürgen
Published: November 2003

ANTARES ist ein Teleskop, das Neutrinos von entfernten kosmischen Quellen nachweisen soll. Da Neutrinos kaum mit Materie reagieren, nutzt ANTARES ein großes Wasservolumen im Mittelmeer. Um das Teleskop von störenden Sekundärteilchen zu schützen, die beim Auftreffen der kosmischen Strahlung auf die Atmosphäre entstehen, wird es in 2400 Metern Tiefe installiert. Anfang 2003 passierte ANTARES zwei wichtige Bauetappen, darunter die erfolgreiche Installation eines Prototyp‐Strings mit Photosensoren. 2006 sollte der Ausbau des Detektors abgeschlossen sein.
Klimawandel auf dem Mars: Planetenforschung
Authors: Hauber Ernst
Published: November 2003

Es gibt mittlerweile eine bemerkenswerte Übereinstimmung zwischen geomorphologischen Beobachtungen und Vorhersagen über die Stabilität von Bodeneis sowie Klimamodellen des Mars. Letztere weisen darauf hin, dass es auf dem Mars in den letzten Millionen Jahren klimatische Umschwünge gegeben haben könnte. Dabei lagerten sich in höheren und mittleren Breiten mehrere Meter mächtige Schichten aus Eis und Staub ab, die sich später zwischen etwa 30° und 60° nördlicher und südlicher Breite teilweise wieder auflösten. Sollte diese Theorie zutreffen, könnten auch heute noch eishaltige Materialien unter einer isolierenden Schicht aus Staub bis in die Äquatorregionen zu finden sein.
Die derzeitige Marsflotte
Authors: Hauber Ernst
Published: November 2003

http://mars.jpl.nasa.gov/missions

http://sci.es.int/marsexpress

http://www.dlr.de/dlr/Raumfahrt/Missionen/marsexpress
USA weisen zunehmend ausländische Physikstudenten ab
Authors: Bührke Thomas
Published: November 2003

In keinem anderen Land der Erde ist der Anteil ausländischer Studenten im Fach Physik größer als in den USA. Nach den Terroranschlägen vom 11. September werden jedoch zunehmend ausländische Studenten, insbesondere aus China und dem mittleren Osten, abgewiesen — zum Leidwesen der Studenten und der Universitäten.

http://www.aip.org/statistics
Der Spion, der die Wärme untersuchte
Authors: Heering Peter
Published: November 2003

Der in Massachusetts geborene Benjamin Thompson, der ab 1792 auch den Titel eines Grafen von Rumford führte, ist eine der schillerndsten Figuren der Physikgeschichte. Berühmt wurde er insbesondere wegen seiner Experimente zur Wärmetheorie.

http://www.famousamericans.net/benjaminthompsonrumford
Die Welt in DIN A4
Authors: Bührke Thomas
Published: November 2003

Der Mensch ist in seinem Vorstellungsvermögen weitgehend auf die sichtbare und erlebbare Umwelt beschränkt. Die Skalen der atomaren Welt sind uns ebenso verschlossen wie die Weiten des Universums. Ein einfaches (Gedanken‐)Experiment erschließt den gesamten Größenbereich jedoch auf erstaunliche Weise.
Preparation and characterization of polypropylene/mesoporous silica nanocomposites with confined polypropylene
Authors: Nakajima Hiroyoshi , Yamada Katsuhiro , Iseki Yuki , Hosoda Satoru , Hanai Ayako , Oumi Yasunori , Teranishi Toshiharu , Sano Tsuneji
Published: November 2003

Polypropylene (PP)/Ti‐MCM‐41 nanocomposites were prepared by isospecific propylene polymerization with Ti‐MCM‐41/Al(i‐C4H9)3 catalyst. The cross polarization/magic angle spinning (CP/MAS) 13C NMR spectrum of the composite was similar to that of the conventional isotactic PP, and the decrease in the pore volume of Ti‐MCM‐41 in the nanocomposites, as measured by N2 adsorption, was consistent with the value calculated from the weight loss in the thermogravimetric analysis (TGA) curve; both these facts attest to propylene polymerization within the mesopores of Ti‐MCM‐41. Alkali treatment followed by extraction with o‐dichlorobenzene allows us to extract the confined PP out of the Ti‐MCM‐41 mesopores. Although the PP/Ti‐MCM‐41 nanocomposites do not exhibit a crystalline melting point, the same PP when extracted from the mesopores showed a clear melting point at 154.7 °C; this indicates that the crystallization of PP confined in mesopores is strongly hindered. For the PP polymerized within the confinement, the molecular weight (Mw) and molecular weight distribution (Mw/Mn) were 84,000 and 4.3, respectively; these values were considerably smaller than those of the PP polymerized concurrently outside the Ti‐MCM‐41 mesopores (Mw = 200,000–450,000, Mw/Mn = 40–75). Therefore, the confinement also has a marked effect on the molecular weight of the PP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3324–3332, 2003
Coagulation method for preparing single‐walled carbon nanotube/poly(methyl methacrylate) composites and their modulus, electrical conductivity, and thermal stability
Authors: Du Fangming , Fischer John E. , Winey Karen I.
Published: November 2003

A coagulation method providing a better dispersion of single‐walled carbon nanotubes (SWNTs) in a polymer matrix was used to produce SWNT/poly(methyl methacrylate) (PMMA) composites. Optical microscopy and scanning electron microscopy showed an improved dispersion of SWNTs in the PMMA matrix, a key factor in composite performance. Aligned and unaligned composites were made with purified SWNTs with different SWNT loadings (0.1–7 wt %). Comprehensive testing showed improved elastic modulus, electrical conductivity, and thermal stability with the addition of SWNTs. The electrical conductivity of a 2 wt % SWNT composite decreased significantly (>105) when the SWNTs were aligned, and this result was examined in terms of percolation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3333–3338, 2003
Synthesis and characterization of block copolymer/ceramic precursor nanocomposites based on a polysilazane
Authors: Garcia Carlos B. W. , Lovell Conrad , Curry Chris , Faught Marybeth , Zhang Yuanming , Wiesner Ulrich
Published: November 2003

The amphiphilic block copolymer poly(isoprene‐block‐ethylene oxide) was used as a structure‐directing agent for a polysilazane preceramic polymer commercially known as Ceraset. Two block copolymers of different molecular weights and poly(ethylene oxide) weight fractions with body‐centered cubic sphere and hexagonal cylinder morphologies were used. To both polymers, 50 wt % of the silazane oligomer (Ceraset) was added. The resulting composites were cast into films and characterized by small‐angle X‐ray scattering and transmission electron microscopy. The silazane was chemically compatible with the poly(ethylene oxide) microdomains of the block copolymer, and this resulted in a swelling of those domains. After the cooperative self‐assembly of the block copolymer and Ceraset, for both systems the structure was permanently set in the lamellar morphology by the crosslinking of the silazane oligomer with a radical initiator at 120 °C. These results suggest that the use of block copolymer mesophases may provide a simple and easily controlled pathway for the preparation of various high‐temperature SiCN‐type ceramic mesostructures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3346–3350, 2003
Simulation insights on the structure of nanoscopically confined poly(ethylene oxide)
Authors: Kuppa V. , Menakanit S. , Krishnamoorti R. , Manias E.
Published: November 2003

We employ atomistic computer modeling to investigate the structure and morphology of poly(ethylene oxide) (PEO) chains confined in 1‐nm slit pores defined by montmorillonite silicate layers. Molecular dynamics computer simulations reveal the Li+ cations to be located in the immediate vicinity of the silicate surfaces and PEO to adopt highly amorphous conformations in a liquidlike bilayer across the slit pores. Despite the orienting influence of the parallel stacked silicate walls, PEO shows no indication of crystallinity or periodic ordering; in fact, for all temperatures simulated, it is less ordered than the most disordered bulk PEO system. These amorphous PEO film configurations are attributed to the combination of severe spatial confinement and the strong coordination of ether oxygens with the alkali cations present in the interlayer gallery. These conclusions challenge the picture traditionally proposed for intercalated PEO, but they agree with a plethora of experimental observations. Indicatively, the simulation predictions are confirmed by wide‐angle neutron scattering and differential scanning calorimetry experiments on PEO/montmorillonite intercalates. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3285–3298, 2003
Deintercalation of a chemically switchable polymer from a layered silicate nanocomposite
Authors: Vohra Vaishali R. , Schmidt Daniel F. , Ober Christopher K. , Giannelis Emmanuel P.
Published: November 2003

The phenomenon of intercalation is widely known as a key process in the area of polymer/layered silicate nanocomposites. In the formation of such nanocomposites, a polymer chain is intercalated between the layers of a layered (silicate) host, typically giving a well‐ordered multilayered stack with a repeat distance of only a few nanometers. Intercalated systems are excellent models for studies of confined geometries, and they often display enhanced material properties as well. In this study, we examined a series of polymers in which it was possible to reverse the intercalation process (i.e., to achieve deintercalation). Homopolymers and copolymers of poly(methyl methacrylate) and poly(tetrahydropyranyl methacrylate) (PTHPMA) were intercalated into an organically modified synthetic fluoromica. Thermally induced deprotection of the tetrahydropyranyl group resulted in the transformation of PTHPMA into poly(methacrylic acid), which was then observed to deintercalate from the silicate host. X‐ray diffraction and thermogravimetric analysis were used to study the deintercalation process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3151–3159, 2003
11th International Conference on II–VI Compounds (II–VI 2003), Niagara Falls, USA, 22–26 September 2003
Authors: Gutowski J.
Published: November 2003

Conference Reports are meant to offer an authoritative view on a recently held scientific meeting rather than a comprehensive list of the conference presentations. Authors are invited to describe what they feel were the most interesting contributions.

The full Proceedings of the 11th International Conference on II–VI Compounds (II–VI 2003) will be published in phys. stat. sol. (c) in early Spring 2004. Conference papers will also be published in phys. stat. sol. (b). (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton–exciton correlation effects on FWM in GaN
Authors: Adachi Satoru , Sasakura Hirotaka , Muto Shunichi , Hazu Kouji , Sota Takayuki , Chichibu Shigefusa F. , Mukai Takashi
Published: November 2003

Bound and unbound biexcitons in a free‐standing bulk GaN are investigated by time‐integrated and spectrally‐resolved four‐wave mixing measurements, where the formation of hetero‐biexcitons that consist of A and B excitons (XXAB) as well as A biexcitons and their unbound biexciton are clearly observed. Through the FWM spectra and delay‐time dependence, it is found that the interaction between A and B excitons gives rise to the phase shifts of the quantum beating and the energy shifts of the spectra, which is considered as the effect of the unbound state of XXAB (i.e. XX*AB). This interaction is found to play an important role in the FWM signals for all polarizations. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarity dependent properties of GaN layers grown by hydride vapor phase epitaxy on GaN bulk crystals
Authors: Tuomisto F. , Suski T. , Teisseyre H. , Krysko M. , Leszczynski M. , Lucznik B. , Grzegory I. , Porowski S. , Wasik D. , Witowski A. , Gebicki W. , Hageman P. , Saarinen K.
Published: November 2003

Hydride vapor phase epitaxy (HVPE) was used to grow nominally undoped 30–160 μm thick GaN layers on both the Ga and N polar sides of high pressure grown single crystal GaN substrates. Measurements of photoluminescence, infrared reflectivity, μ‐Raman scattering and positron annihilation were performed on the samples. The obtained characteristics are strongly dependent on the growth polarity. The material grown on the N polar side has identical properties with the substrate bulk GaN crystals, i.e. high free electron, impurity and point defect concentrations. In the layers grown on the Ga polar side, these concentrations are very low. The results show that the structural and optical properties of homoepitaxial GaN layers grown by HVPE are homogeneous across the layer thickness, which is in contrast to the heteroepitaxial HVPE GaN layers. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of InGaN/GaN single quantum wells by X‐ray scattering and transmission electron microscopy
Authors: Smeeton T. M. , Kappers M. J. , Barnard J. S. , Vickers M. E. , Humphreys C. J.
Published: November 2003

A set of InxGa1−xN/GaN single quantum wells (SQWs) were analysed using X‐ray reflectivity (XRR), high resolution X‐ray diffraction (HRXRD) and high resolution transmission electron microscopy (HRTEM). A method for determining the thickness and composition of the single quantum well layers using only X‐ray scattering measurements is described – the results agree very closely with those determined from HRTEM analysis of the same samples. HRTEM lattice fringe images obtained from InGaN subjected to minimal exposure to the electron beam were used to determine local lattice parameter maps. These show the indium to be distributed uniformly within the alloy. The electron beam very rapidly caused damage to the InGaN which could be falsely interpreted as an inhomogeneous indium distribution. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characteristics of AlN growth on vicinal SiC(0001) substrates by molecular beam epitaxy
Authors: Brault J. , Bellet‐Amalric E. , Tanaka S. , Enjalbert F. , Le Si Dang D. , Sarigiannidou E. , Rouviere J.‐L. , Feuillet G. , Daudin B.
Published: November 2003

We present the growth of AlN films on vicinal substrates of SiC(0001). The layers were grown by plasma‐assisted molecular beam epitaxy (PAMBE) and examined in‐situ using reflection high‐energy electron diffraction (RHEED). Morphological and structural properties were characterized by atomic force microscopy (AFM) and High Resolution X‐Ray Diffraction (HRXRD), respectively. The obtained results by AFM show two main differences with AlN films grown on nominally flat SiC substrates: a) the absence of spiral growth hillocks, and b) the formation of predominantly straight steps. HRXRD measurements on misoriented substrate rocking curves have revealed good structural quality of AlN films (tilt and twist), as well as a disorientation of the c‐planes of the AlN with respect to the substrate. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of oxygen on luminescence and vibrational spectra of Mg‐doped GaN
Authors: Koide Yasuo , Walker D. E. , White B. D. , Brillson L. J. , Itoh T. , McCreery R. L. , Murakami Masanori , Kamiyama S. , Amano H. , Akasaki I.
Published: November 2003

Mg‐doped GaN epilayers are analyzed by Raman and low‐energy electron‐excited nanoluminescence (LEEN) spectroscopies before and after oxygen ambient annealing at temperatures from 450 to 550 °C. Annealing as low as 450 °C shows the appearance of a local vibrational mode of the MgGa acceptor. Correspondingly, LEEN emission at 2.8 eV increases and that at 3.27 eV decreases after annealing in oxygen ambient. On the other hand, electron beam treatment decreases 2.8 eV emission and increases 3.27 eV emission. These luminescence properties are explained by a donor‐acceptor pairs transition model due to hydrogen‐related deep and shallow donors and MgGa acceptor. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)