bluuebunny/crossref_metadata_2025_split huggingface dataset:
Grain boundary morphology of lamellar microdomains
Authors: Nishikawa Y. , Kawada H. , Hasegawa H. , Hashimoto T. 
Published: April 2003

AbstractThe grain boundary morphology of lamellar microdomains in block copolymers was investigated by means of transmission electron microscopy. A variety of patterns which can be successfully reproduced by the computer simulation using Scherk's first surface or deformed Scherk's first surfaces as a calculation model were observed. This implies that the microdomains with lamellar morphology which locally have only two‐dimensional continuity are topologically continuous in three dimensional space as a whole through the grain boundaries, but the lamellae are essentially flat within the grains.
A fast membrane osmometer based on a porous glass membrane: first results
Authors: Köhler W. , Kühn A. , Motsch A. 
Published: April 2003

AbstractThe prototype of a fast and versatile membrane osmometer based on a capillary shaped porous glass membrane has been developed and successfully tested with solutions of polystyrene in toluene. The coaxial design of the cell is ideally suited both for batch and continuous flow operation. Time constants on the order of several seconds are observed with membranes of 10 nm and 20 nm nominal pore size. Important design criteria are discussed and first results for the cut‐off molar mass are reported.
In‐situ absorption studies of nonlinear optically active side‐chain polymers during corona poling
Authors: Wedel A. , Strohriegl P. , Danz R. 
Published: April 2003

AbstractAbsorption measurements in the wavelength range from 300 to 700 nm are used to study the orientation of nonlinear optical side groups in an acrylic polymer oriented by corona poling inside a spectrophotometer. The poling and relaxation behavior of these films are measured. The in‐situ poling process produces efficient orientational order in acrylic side‐chain polymers, which can be described by an order parameter.
Orientational measurements on a crosslinkable thermotropic main‐chain copolyester using FTIR spectrometry
Authors: Sahre K. , Eichhorn K.‐J. , Reichelt N. , Hummel D. O. 
Published: April 2003

AbstractThe orientation capability of thin solution‐cast films of a new synthesized crosslinkable thermotropic main chain copolyesterwith itaconoyl units was demonstrated by means ofpolarized FTIR spectrometry. The isotropic films with a thickness of about 10 μm were drawn uniaxially and annealed to get a preferential alignment of the polymer backbone in the drawing direction and an increase of the state of order. The resulted state should be fixed by a following crosslinking reaction of the itaconoyl unit to obatin a thermostable polymeric material with reduced anisotropy of mechanical properties. The orientation effects of mesogenic units dominate in the drawn films of the ternary copolyester. WAXS and DSC results show that annealing of the films produce an increase in crystallinity. More ordered regions in the solid polymer are formed which cause typical changes in the IR spectra.
The kinetics of cellulose fiber degradation and correlation with some tensile properties
Authors: Testa G. , Sardella A. , Rossi E. , Bozzi C. , Seves A. 
Published: April 2003

AbstractCellulosic degradation of cotton and flax yarns caused by light, heat and heterogeneous acid‐catalyzed hydrolysis was studied. These processes were followed by measuring changes in intrinsic fluidity (1/DPw): two principal stages, characterized by different zero‐order kinetics, take place. A relation between changes in intrinsic fluidity with some mechanical properties of the same yarns during the degradation process was found.
Structural investigation of phthalocyaninatopoly(siloxane) Langmuir–Blodgett films by X‐ray diffraction
Authors: Albouy P.‐A. , Schaub M. , Wegner G. 
Published: April 2003

AbstractThe structure of Langmuir–Blodgett (LB) films of a rigid rod phthalocyanatopoly(siloxane) substituted by alkoxy side chains has been investigated by X‐ray diffraction using thin silicon wafers as a substrate for deposition. Freshly prepared samples do not possess a truely periodic multilayer structure. The polymer backbones lie flat in the substrate plane and are preferentially oriented along the dipping direction. Each macromolecule is surrounded by parallel adjacent rods and a first‐neighbor distance is found in every direction. This structure recalls the local organization of a nematic liquid crystal. Short annealing of the as‐deposited films leads to a highly oriented hexagonally dense packing as of cylinders. The alignment of the backbones along the dipping direction becomes nearly perfect and the most densely packed plane is oriented in the substrate plane. A helical order within the macromolecules of the annealed samples is suspected from extra reflections appearing in the diffraction pattern.
Polyphenothiazinobisthiazole: A novel polymer for third‐order nonlinear optics
Authors: Kistenmacher A. , Soczka Th. , Baier U. , Ueberhofen K. , Bubeck Chr. , Müllen K. 
Published: April 2003

AbstractThe synthesis and the optical properties of the novel polymer polyphenothiazinobisthiazole (PPT) are described. The design of this polymer was planned taking into consideration several aspects that were anticipated to lead to a material with an enhanced nonlinear optical susceptibility (χ(3)). Monomer 16 was prepared in a five‐step synthsis starting from N‐dodecyl‐3,7‐diaminophenothiazin (11). 16 was reacted with terephthaloyl chloride to yield the precursor polyamide 17. This precursor polyamide was subjected to a thermal cyclization at 300°C under vacuum leading to the title polymer PPT (18). PPT shows UV/vis absorption maxima at λ=282 nm, 305 nm and 463 nm. The macroscopic nonlinear optical susceptibility χ(3)(−3ω;ω,ω,ω,) of a thin film of PPT was determined with a third harmonic generation (THG) technique at a fundamental laser wavelength λL=1064 nm. The results show that PPT exhibits nonlinear optical properties comparable to those of poly‐p‐phenylenevinylene (PPV).
Dihydroanthracene dimers as novel bifunctional initiators for anionic polymerization
Authors: Bartz Th. , Klapper M. , Müllen K. 
Published: April 2003

AbstractAnionic polymerizations initiated with an alkylene bridged dihydroanthracene dimer as a bifunctional initiator are described as a synthetic route to polymers containing the dianthryl species in the center of the macromolecular chain. The approach taken herein involves the twofold deprotonation of 1,3‐di‐(9,9′,10,10′ ‐tetrahydro‐9,9′ ‐anthryl)propane and the initiation of methyl methacrylate polymerization at both anionic sites. The synthesis of ABA block copolymers by addition of tert‐butyl acrylate as a second monomer is described. Polymer analogous aromatization of the initiator generates the corresponding polymer with two anthracene units in the main chain. The synthezised homo‐ and block copolymers have been fully characterized by GPC, UV and NMR measurements.
Chain stiffness of poly‐methoxypropyl[1.1.1]propellane
Authors: Lassale I. , Schmidt M. , Schlüter A. D. 
Published: April 2003

AbstractThe chain stiffness of a methoxypropyl‐substituted poly[1.1.1]propellane in solution is investigated by static and dynamic light scattering. The Kuhn statistical segment length is determined aslk=150Å utilizing the Kratky–Porod wormlike chain model. It is, however, not yet clear whether the derived Kuhn length characterizes the chain stiffness of a perfect polypropellane chain or rather originates from “kinks” in the polymer backbone due to the presence of possible side reactions during polymerization.
Redox active LC ionomers: LC ionomers as materials for compatible blends with amorphous ionomers
Authors: Wiesemann A. , Zentel R. , Lieser G. 
Published: April 2003

AbstractRedoxactive liquid crystalline (LC) side group polymers were prepared by copolymerization of liquid crystalline acrylates and ferrocene‐containing acrylates. The corresponding liquid crystalline ionomers were synthesized by a reversible redox reaction. The incorporation of tetra‐alkylated ferrocene derivatives leads to LC polymers with reduced redox potential. These polymers can be oxidized under mild conditions to the corresponding ionomers, which are much more stable in solution than LC ionomers containing monoalkylated ferrocenium ions. Dynamic mechanical measurements and small angle X‐ray scattering (SAXS) perfomed on LC ionomers prove the existence of ionic superstructures (clusters) which are typical for ionomers and a gelation of the LC ionomers.In biphasic polymer blends consisting of liquid crystalline and amorphous ionomers (partially sulfonated polystyrene) we investigated the influence of the concentration of ionic groups in the LC component on the size of phase separated regions. It was found that blends without ionic interactions are macroscopically phase separated. In blends consisting of two ionic components, microphase separated regions of approximately 100 nm were found. The size of phase separated regions decreases continuously with increasing concentration of ionic groups in the LC component and can therefore be adjusted by a reversible redox reaction.The incorporation of ionic groups in LC polymers leads on a macroscopic scale to a combination of the liquid crystalline properties of the LC component with the elastic behavior of the amorphous ionomer. Therefore microphase separated ionomer blends show homogeneous liquid crystalline textures and behave mechanically like reversible crosslinked ionomers.
Preparation and characterization of cellulose/glycidyl methacrylate/acrylic acid cation exchange composites
Authors: Ibrahim N. A. , Abo‐Shosha M. H. 
Published: April 2003

AbstractAcrylic acid (AA)/glycidyl methacrylate (GMA) mixtures were bulk polymerized in the presence of cellulose in order to prepare cellulose/GMA/AA cation exchange composites using sodium persulfate as an oxidant, alone or in conjunction with sodium sulfite, sodium thiosulfate, sodium metabisulfite or glucose as a reductant. The presence of the reductant has the effect of shortening the polymerization time, expressed as the solidification time (ST), with little improvement in the polymerization extent, expressed as percentage total conversion (%TC), as well as the percentage yield and the carboxyl content of the crude and the purified composites. Sodium sulfite was selected as the the reductant that can achieve best polymerization. The effect of the concentrations of “sodium persulfate/sodium sulfite, redox system, acrylic acid and glycidyl methacrylate” and temperature on the formation of the composite were investigated. Four cation exchange composites were prepared and characterized by investigating their potentiometric titration, water solubility and swellability as well as durability.
Surface orientation of liquid crystalline poly(alkylsilanes)
Authors: Factor B. J. , Russell T. P. , Toney M. F. , Miller R. D. 
Published: April 2003

AbstractX‐ray diffraction measurements on thin films of poly(hexyl‐pentylsilane) cast on silicon substrates are presented. The polymer chains pack in a hexagonal lattice which is oriented such that the chains lie parallel to the surface. In addition, a remarkable degree of orientational order was found with the planes containing the neighbor molecules lying in the surface plane. Parallel to the film surface, the average crystallite size is 600 Å, while perpendicular to the surface, there is nearly perfect interchain stacking of the polymers throughout the thickness of the film.
Polymers of 1‐azabicyclooctane[4,2,0]. Part 3. Modification of polystyrene‐block‐poly‐1‐azabicyclooctane[4,2,0]
Authors: Mühlbach K. , Schulz R. C. 
Published: April 2003

AbstractPolystyrene‐block‐poly‐1‐azabicyclooctane[4,2,0] has been modified by protonation or alkylation of the polyamine moiety. Short chain alkyl iodides lead to quantitatively quarternized products while longer alkyl chains or alkyl‐bromides give incomplete conversion. The viscosimetric behavior of the charged blockcopolymers is dominated by the polyelectrolyte block although the polyelectrolyte effect is drastically reduced by the presence of the polystyrene block.The blockcopolymers are insoluble in water, but concentrated solutions of the polymers in DMF can be diluted with any amount of water without any precipitation. Although the blockcopolymers have an amphiphilic structure they do not exhibit any surface activity. In a water/DMF (9/1) solution the polymers have a core‐shell micelle‐like structure of collapsed polystyrene block which is solubilized by the surrounding polyelectrolyte block.
Aspects of thermal grafting of acrylonitrile onto ethyl cellulose in homogeneous media
Authors: Abdel‐Razik E. A. 
Published: April 2003

AbstractHomogeneous thermal graft copolymerization of acrylonitrile (AN) onto ethyl cellulose (EC) by using ammonium persulfate (APS) as free radical initiator was carried out in the toluene: DMSO solvent system. Many variables affecting the grafting parameters were studied. The effect of using comonomer pairs of acrylonitrile and acrylamide on the grafting yield was examined. Different techniques such as IR and NMR were used. A Trommsdorf effect was observed in certain systems. The rate of graft copolymerization of acrylonitrile onto EC was determined as Rp=0.16% min—1. The higher carbonyl content of thermooxidized EC showed lower grafting yield. The mechanism of the grafting reaction is discussed.
Electrochemical solution properties of poly(vinylbenzyltrialkylammonium) salts
Authors: Wandrey C. , Zarras P. , Vogl O. 
Published: April 2003

AbstractPoly(vinylbenzyltrialkylammonium) salts with alkyl groups having 1 to 8 carbon atoms on the ammonium nitrogen atom were synthesized. The polymers are soluble in water but have different solubility when low molecular salts such as sodium chloride are added. The reduced solution viscosity in water showed typical polyelectrolyte behavior. Larger alkyl groups make the polymers much less soluble and even insoluble in water. The polymers are still soluble in methanol. To study the counterion‐polyion interactions in semidilute and dilute solution the electrical conductivity and counterion activity were investigated in a range of low polyelectrolyte concentration (10−6<cp10−3 monomol/l). With decreasing concentration, below the overlap concentration, a rapid increase of the equivalent conductivity occurred followed by a maximum. The electrochemical solution properties were found to be influenced by the size of the substituents of the cationic group.
Study of polytetrafluoroethylene crystallization
Authors: Ferry L. , Vigier G. , Vassoille R. , Bessede J. L. 
Published: April 2003

AbstractCrystallization of polytetrafluoroethylene (PTFE) from the melt state has been studied by wide angle X‐ray scattering (WAXS), small angle X‐ray scattering (SAXS) and differential scanning calorimetry (DSC) experiments, supported by scanning electron microscopy (SEM) observations. Isothermal crystallization of PTFE (between 315 °C and 325 °C) is analyzed and compared with PTFE cooled at 1 °C/min taken as the reference. We establish a TTC (time, temperature, crystallization) diagram and point out the time and temperature dependence of both crystallite thickness and crystallinity. It appears that the crystallization occurs in a very narrow temperature range. We assign the morphological changes to different crystal growth regimes in the range of study.
On the deformation of hard elastic polymers — applicability of the coil‐strand‐transition model
Authors: Wittkop M. , Kreitmeier S. , Göuritz D. 
Published: April 2003

AbstractThe applicability of the coil‐strand‐transition model to describe the deformation of hard elastic polymers was studied by deformation and relaxation tests of hard elastic polyethylene and hard elastic polypropylene samples in different liquids. It was found that within the model the calculated values of the fibril diameter, the contribution of surface stress and the total stress are in agreement with measurements. The dominance of energetic contributions to the stress was also confirmed.
Reaction of glycidyl ethers with ε‐caprolactam
Authors: Tänzer W. 
Published: April 2003

AbstractPhenyl glycidyl ether (PGE) as well as ε‐caprolactam (CL) can be polymerized by cationic initiators. For the present work, Mg(ClO)4ċ2 H2O was used. The formation of different oligomer structures depends strongly on the reaction conditions if both monomers are oligomerized in a one‐pot reaction. HPLC,13C‐NMR and FT‐IR studies showed that not only were homooligomeric products of PGE formed, but also products from phenyl glycidyl ether and ε‐caprolactam. Homopolymerization of CL does not occur. Mixtures of diglycidyl ether of bisphenol A (DGEBA) and CL in the presence of catalytic amounts of magnesium perchlorate yield clear and homogeneous castings withTg=96 to 100°C. These networks include <10% dioxane‐ and water‐extractable products.
Structural and dynamical studies of 13C‐labeled polyethylene adsorbed on the surface of silica gel by high‐resolution solid‐state 13C NMR spectroscopy
Authors: Inoue D. , Kurosu H. , Chen Qun , Ando I. 
Published: April 2003

Abstract13C CP/MAS NMR spectra of 10% 13C‐labeled polyethylene adsorbed on the surface of silica gel were measured by means of high‐resolution solid‐state 13C NMR. From these experimental results, it was found that adsorbed polyethylene has immobile and mobile parts. In the immobile part, the polyethylene takes the trans conformation as the major conformation and gauche as the minor conformation, and in the mobile part fast transition between trans and gauche conformations occurs. Futhermore, in order to elucidate the dynamics of the polyethylene, 13C spin‐lattice relaxation times T1 were measured. It was found that the molecular motion of the polyethylene in the mobile part is strongly restricted, compared with the noncrystalline component of polyethylene in bulk.
Optically active and highly threodiisotactic poly(triphenylmethyl crotonate) with conformational chirality
Authors: Ute K. , Asada T. , Nabeshima Y. , Hatada K. 
Published: April 2003

AbstractPolymerization of triphenylmethyl crotonate with a 9‐fluorenyllithium/(S,S)‐(+)‐2,3‐dimethoxy‐1,4‐bis(dimethylamino)‐butane complex in toluene at −78°C gave a highly threodiisotactic polymer. The polymer had a trimodal distribution of molecular weight (MW); the highest‐MW part showed a small negative optical rotation and the other two showed positive rotation. The middle‐MW fraction (DP=21.5, M̄w/M̄n=1.07) had an [α]D of +53.3°. The optical rotation of this fraction decreased gradually in chloroform at 60°C while the GPC curve of the fraction remained unchanged. The loss of optical activity was ascribed to the racemization through helix sense reversal of the polymer chain. The rate of the decrease in optical rotation obeyed first‐order kinetics. From the rate constants at 50 and 60°C, the activation enthalpy for the helix reversal was determined to be 28.4 kcal/mol.
Catalysis on polymer supports
Authors: Schlick S. , Bortel E. , Dyrek K. 
Published: April 2003

AbstractWe present an overview of the synthesis, physical characterization and catalytic properties of polymer‐supported reagents and consider the major advantages and drawbacks in the use of polymeric supports for synthesis and catalysis. The most important development in recent years appears to be the characterization of polymeric supports by thermal analysis, advanced spectroscopic and scattering methods, and electron microscopy. As a result, the mechanism of catalytic activity is better understood; the challenge remains to prepare supported catalysts with good mechanical properties, and high chemical stability at elevated temperatures, and to prevent the loss of often pricey catalysts such as rhodium during numerous catalytic cycles.
Glass transition in ethylene‐vinylacetate copolymers analyzed by combined dielectric and X‐ray scattering experiments
Authors: Holzer B. , Strobl G. 
Published: April 2003

AbstractWe studied the peculiarities of the glass transition in semicrystalline polymers by simultaneous temperature‐dependent small angle X‐ray scattering experiments and dielectric relaxation studies on ethylene‐vinylacetate statistical copolymers. Properties of the β‐relaxations, which represents the glass transition of these systems, change systematically with the comonomer content and the temperature. The broadening of the dielectric loss spectra, indicative of large variations in the sequence mobility in the amorphous regions, increases with the crystallinity, and on approaching Tg also explicitly with decreasing temperature. While the first effect is due to the special structure of the disordered regions, where the presence of fixed entanglements and loops results in motional restrictions, the temperature effect near Tg may reflect the increase in the correlation length of the β‐process.
The structure of the hard domains in trans,trans‐HMDI‐based polyurethane elastomers
Authors: Nigar M. , Blackwell J. , Chvalun S. N. , Seneker S. D. , Schmelzer H. G. 
Published: April 2003

AbstractX‐ray methods have been used to investigate the structure of the hard domains in polyurethane elastomers based on trans, trans‐dicyclohexylmethane 4,4′‐diisocyanate (HMDI) with butanediol as the chain extender. The crystalline hard segments become oriented on stretching the films at room temperature, although the degree of crystallinity remains relatively low. The ordering is improved considerably by annealing the films for several hours at 130–190°C: the fiber diagram contains 25 sharp Bragg reflections which are indexed by a triclinic unit cell with dimensions a=5.1 Å, b=10.2 Å, c=37.5 Å, α=115.2°, β=84.9°, and γ=94.2°. The cell contains dimer units of two chains which are probably staggered along the c axis direction in the bc plane. In the samples annealed for shorter periods of time, a second less abundant crystal structure is observed that coexists with the first. This second structure is also triclinic with a more extended fiber repeat of c=41.3 Å and is slowly converted to the contracted form on further annealing. Molecular models show that in the extended form the butanediol units have the all‐trans conformation, whereas in the contracted form they probably have the tg+tg−t or tg−tg+t conformations, which have lower potential energies than the all‐trans form. The chains in both the extended and the contracted conformations are able to form a network of intermolecular hydrogen bonds, and in this regard the structures are very similar to those reported previously for the analogous diphenylmethane diisocyanate (MDI)‐based elastomers. Thus the higher melting points for the HMDI‐based hard segments are most likely due to hydrophobic interactions between the dicyclohexyl methanes that are stronger than those between the diphenyl methanes of the MDI‐based elastomers.
Surface modification of polyethylene fibers treated in an oxygen microwave plasma
Authors: Plawky U. , Londschien M. , Michaeli W. 
Published: April 2003

AbstractThe surface modification of a commercial polyethylene fiber treated in an oxygen low temperature microwave plasma was investigated. The change in surface chemistry was analyzed with electron spectroscopy for chemical analysis. A controlled state of oxidation of the fiber surface was reached by variation of gas flux, process pressure and microwave energy. The oxygen was incorporated into the fiber surface in the form of functional groups. In the determined treatment range, a change in surface morphology as a result of the plasma treatment was not observed with electron microscopy. The higher oxygen content in the fiber surface increased the fiber‐matrix adhesion as shown by mechanical tests.