bluuebunny/crossref_metadata_2025_split huggingface dataset:
A spectroscopic and quantitative characterization of various fractions of the heterogeneous polymer system (EPDM‐g‐maleic anhydride)‐g‐polyamide 66 using high resolution 13C solid state NMR and IR techniques
Authors: van der Velden G. , Nelissen H. , Veermans T. 
Published: April 2003

AbstractThe structure of EPDM grafted onto polyamide 66 has been analyzed with high resolution solid state 13C NMR and IR spectroscopy. Details about the EPDM rubber include the amount of rubber incorporated in this blend, the sequence analysis of the EPDM rubber and an estimate of the type and amount of termonomer used (in this case only trans 1.4‐hexadiene). The sample contains 20% EPDM rubber, 6% polyamide 66 grafted onto EPDM rubber and 74% neat polyamide 66. Some evidence has been obtained via IR spectroscopy for the presence of cyclic imide groups, derived from grafted maleic anhydride groupings. No evidence for the use of a coupling agent could be obtained from either the 13C SPE‐MAS spectra of the interphase enhanced polyamide 66 or from the isolated rubber phase.
Structure and properties of polyamide 6 modified by N‐trialkylsilylcaprolactam
Authors: Mateva R. , Mateev M. , Delev O. 
Published: April 2003

AbstractThe physical behavior ofpolyamides of type N 6 with different contents of N‐trialkylsilylcaprolactam (SL) has been investigated by mechanical spectrometry, differential scanning calorimetry and wide‐angle X‐ray scattering. The copolymers have been obtained by an anionic polymerization in bulk under isothermal conditions. The presence of a bulky substituent at the nitrogen atom of the amide group plays an essential role for the number of the hydrogen bonds as well as for the formation of physical and chemical bonds. This bonds results in significant changes of the physical behavior of the modified polyamides. These changes have been studied.
Polymerization of N‐ethylmaleimide with cyclic ketene O,N‐acetals as catalyst
Authors: Fernández S. , Letsch J. , Klemm E. 
Published: April 2003

AbstractIsopropylidene‐3,4,4‐trimethyl‐oxazolidine 3 is an initiator for the radically and anionically induced polymerization of N‐ethylmaleimide (NEMI) (Scheme 2). An electron transfer from the CT‐complex of NEMI/3 leads to the radical anion/radical cation pair. In THF (ϵ=7.58) diradicals result from these processes, connected with a radical homopolymerization of NEMI (experiment A). The polymerization is inhibited by TEMPO and not by H+‐ions (experiments B and G). In NEMI as “solvent” (experiment E), which possesses a high dielectric constant, we postulate an anionic mechanism for the NEMI homopolymerization. The polymerization also takes place in the presence of TEMPO and it is inhibited by H+‐ions (experiments F, C).
Self‐diffusivity of diblock copolymers in solutions in neutral good solvents
Authors: Anastasiadis S. H. , Chrissopoulou K. , Fytas G. , Appel M. , Fleischer G. , Adachi K. , Gallot Y. 
Published: April 2003

AbstractThe composition, f, and concentration, ϕ, dependence of the self‐diffusion coefficients of diblock copolymers in solutions in a common good solvent have been investigated by pulsed‐field‐gradient nuclear magnetic resonance and photon correlation spectroscopy. The difference in the entanglement characteristics of the parent homopolymers was found to be very important in determining the diffusion coefficients. The investigation on toluene solutions for a series of poly(styrene‐b‐isoprene) diblocks, possessing almost similar molecular weights and compositions ranging from 0.18 to 0.74, showed that the dependence of the diffusivity on diblock composition f conforms with the progressive transition from the Rouse to the entanglement regime at different concentrations due to the different critical molecular weights for entanglement of the parent homopolymers. The same idea can account for the diblock composition dependence of the self‐diffusivity for poly(styrene‐b‐butadiene) diblocks. Moreover, the self‐diffusivities for three poly(styrene‐b‐methyl methacrylate) diblocks in toluene are insensitive to copolymer composition (0.35 to 0.69) in accord with the very similar entanglement characteristics of the two blocks.
Synthesis of highly stereo‐ and regio‐regular isotactic poly(phenylglycidylether) using ionic coordinative initiators
Authors: Ronda J. C. , Serra A. , Mantecón A. , Cádiz V. 
Published: April 2003

AbstractRacemic and optically active 3‐phenoxy‐1,2‐epoxypropane (phenylglycidylether, PGE) were polymerized in an ethereal solvent by an initiator system formed by combination of aluminum isopropoxide with one of four different zinc salts (chloride, bromide, iodide and acetate) in several ratios. Conversions and molecular weights of the isotactic polymer fraction are clearly related to the coordinating ability as a Lewis acid of the salts. Using water as co‐initiator, the non‐stereoselective sites are inactivated and therefore conversions and molecular weights of isotactic polymer increase. Both racemic and enantiomerically pure PPGEs show similar X‐ray patterns but some differences in the DSC plots are observed. Conversions, molecular weights and degrees of crystallinity of the isotactic polymer fraction obtained were studied and related to the polymerization conditions and the reaction mechanism.
Synthesis of block copolymers by nitroxyl‐controlled radical polymerization
Authors: Steenbock M. , Klapper M. , Müllen K. , Pinhal N. , Hubrich M. 
Published: April 2003

AbstractThe homopolymerization of methyl methacrylate (MMA) in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) is described and compared to the TEMPO‐mediated polymerization of styrene. Furthermore, the formation of block copolymers between MMA and styrene from polystyrene chains with TEMPO fragments as end groups is examined. The degree of block formation is estimated by GPC analyses. ESR experiments are performed on the polystyrene chains to study the scission behavior of the TEMPO fragments.
Recrystallization of HDPE in HDPE/iPP quenched films
Authors: Yan S. , Petermann J. , Yang D. 
Published: April 2003

AbstractEpitaxial crystallization behavior of HDPE/iPP double layers under quenching and annealing conditions has been studied by means of transmission electron microscopy (TEM). The results obtained from bright field TEM observations indicate that in the as‐quenched state the HDPE that is in direct contact with the surface of the oriented iPP substrate recrystallizes in the form of oriented crystallites dispersed on the iPP substrate. The electron diffraction results show that besides the two normally observed epitaxial orientations between HDPE and iPP, there is also a special orientation with [001]HDPE ‖ [001]iPP. The HDPE which is in contact with the clean surface of a glass slide crystallizes in small lamellae with random orientation. In the boundary region, the epitaxially crystallized HDPE small lamellae stop right on the boundary of the oriented iPP film. If the quenched samples are annealed at 128°C (below Tm of HDPE) for 2 h, the small HDPE crystals grow to thick lamellae in both areas. But only the epitaxial orientation of HDPE with [001]HDPE ‖ [101]iPP has been observed.
Lipase‐Catalyzed ring‐opening polymerization and copolymerization of 15‐pentadecanolide
Authors: Uyama H. , Kikuchi H. , Takeya K. , Kabayashi S. 
Published: April 2003

AbstractEnzymatic ring‐opening polymerization of a 16‐membered lactone, 15‐pentadecanolide (PDL), has been carried out in bulk using various lipases of different origin as catalyst. The polymerization with Pseudomonas fluorescens lipase (lipase PF) catalyst afforded the corresponding polyester in high yields. The rate of the polymerization catalyzed by lipase PF at a temperature lower than 45°C was very small, whereas the polymerization at higher polymerization temperature (≥60°C) proceeded much faster. Lipase derived from Pseudomonas cepacia was also active for the polymerization of PDL. The polymerization catalyzed by Candida cylindracea lipase at high temperature (75°C) afforded the polymer with molecular weight up to 2.0 x 104. The polymerization behavior of PDL through lipase catalysis has been compared with that of ε‐caprolactone (ε‐CL). PDL showed an enzymatically higher polymerizability than ε‐CL, despite the smaller ring‐strain of PDL, which is due to the stronger recognition of PDL by lipase. Enzymatic copolymerization of PDL with other lactones using lipase PF catalyst produced copolymers with molecular weight of several thousands. From 13C NMR analysis, the diad sequence distributions were determined.
Self‐compacting smectic polymers. An unusual temperature dependence of interlayer distance for side chain polysiloxanes in sm a and sm b phases
Authors: Kozlovsky M. V. , Haase W. 
Published: April 2003

AbstractA prominent reduction of the layer thickness, d1, in the Sm A and Sm B phases with increasing temperature has been observed for a series of side chain polymers. The maximum decrease in d1 value for one of the copolymers is ∼7Å; i.e. 15% of its total value. The influence of the chemical structure of the main chain and side groups on the effect has been studied. Models have been proposed for packing of mesogenic side groups at different temperatures.
Fractionation of partially stereoregular poly(propylene oxide) from acetonitrile solution
Authors: Colak N. , Akgün A. 
Published: April 2003

AbstractPartially stereoregular poly(propylene oxide) (PPO) samples synthesized using Pruitt‐Bagett catalysts (PBC) were fractionated at 40°C and 70°C from acetonitrile solution by adding small portions of water. The formed polymer‐rich phases were clear liquids except the first three fractions obtained at 40°C; those were solids. The fractions were characterized with their viscosity average molecular masses and melting points. Results showed that the procedure described in the present report fractionates partially stereoregular PPO on the basis of molecular weight, independent of their tacticity.
Liquid crystalline block and graft copolymers
Authors: Fischer H. , Poser S. 
Published: April 2003

AbstractSince the first reports on the combination of liquid crystalline polymers in block (1985) and graft (1986) copolymers with amorphous and semi‐crystalline polymers, the scientific interest has been focused on understanding how the size and type of the mesophase displayed by the liquid crystalline part(s) affects the LC → isotropic transition and the order in the LC domains themselves with respect to the morphology displayed. An overview of the work that has been done so far will be given, as well as a closer discussion of the interaction between morphology and LC phase behavior as evaluated on a large number of very well defined LC side group block copolymers. Furthermore, applications and results of mechanical and optical investigations are discussed.
Influence of the elimination temperature on light emitting devices prepared from poly(p‐phenylene vinylene)
Authors: Herold M. , Gmeiner J. , Schwoerer M. 
Published: April 2003

AbstractWe report detailed measurements on the thermal conversion of the tetrahydrothiophene prepolymer to poly(p‐phenylene vinylene) (PPV) and show the influence of the elimination conditions on the properties of PPV and on light emitting devices (LEDs) prepared in the configuration ITO/PPV/Al. Electroluminescence correlates with a diode behavior in the current—voltage characteristic and can be observed for PPV heated at a minimum temperature of 130°C. Increase of the elimination temperature results in a red‐shift of both the photoluminescence and electroluminescence spectra by ≈10 nm, which enables us to control the color of our LEDs in a small range. We have observed that refered to the brightness of the devices the optimum elimination temperature is 160°C, and we show that a further increase of temperature does not improve the properties of PPV‐ LEDs.
The characteristics of polydienes obtained with lanthanide‐based catalysts
Authors: Iovu H. , Hubea G. , Hurst S. J. 
Published: April 2003

AbstractPolyisoprene and polybutadiene samples, prepared from the respective monomers using lanthanide‐based catalysts, have been analyzed in terms of microstructure, glass transition temperatures and stabilities to thermo‐oxidative degradation. Quantitative determination of 1,4‐cis/trans, 1,2‐ and 3,4‐contents have been made from the IR spectra of the polymers. Attempts to use 1H and 13C NMR and Raman spectroscopy to analyze the microstructure of the materials has at best proved only partially successful. TGA and IR spectroscopy have been used to study the influence of catalyst residue on the thermo‐oxidative degradation of the polymers.
Morphology of a conducting polymer and its relation to the electronic properties
Authors: Paschen S. , Carrard M. , Senior B. , Chao F. , Costa M. , Zuppiroli L. 
Published: April 2003

AbstractWe have investigated the morphology of a heavily disordered conducting polymer, polypyrrole doped with large polymeric anions. An extensive microscopy study (scanning electron microscopy, atomic force microscopy and transmission electron microscopy) together with previously obtained information on the samples' electronic properties conveys to us the following image: the observed globules of diameters between 10 and 100 nm originate from the polymeric dopants forming coils with the doping centers concentrated on the coil surfaces and the polypyrrole surrounding the whole. In this way polypyrrole‐rich “sheets” run through the whole sample and guarantee the electrical continuity which prevails even in samples with polypyrrole volume fractions as low as several per cent. For the first time, the building block of the “fractal” cauliflower structure, observed also in many other electrochemically prepared conducting polymers, could be identified.
Evaluation of equation‐of‐state parameters and the description of PVT‐data
Authors: Rudolf B. , Ougizawa T. , Inoue T. 
Published: April 2003

AbstractFor three different equation‐of‐state theories the characteristic parameters of two polymers were calculated, and the ability of the theories to describe PVT‐data using these parameters was investigated. The comparison between the different theories shows that, concerning the description of PVT‐data, the modified cell model of Dee and Walsh is not only superior to the theory of Flory, Orvoll and Vrij and that of Sanchez and Lacombe as reported before, but also to the theory of Simha and Somecynsky and the open cell model of Zhong, Wang and Lu. Finally, simple formulae are given to calculate the characteristic parameters of the latter two theories from those of the theory of Flory, Orwoll and Vrij.
Biphasic polystyrene ionomers neutralized by bifunctional organic counterions
Authors: Dulac L. , Bazuin C. G. 
Published: April 2003

AbstractThe evidence for biphasic morphology in lightly sulfonated polystyrene (PS‐SSA) ionomers neutralized by bifunctional organic cations (namely, 1,6‐hexanediamine or HDA) is established by comparing their dynamic mechanical behavior, as a function of ion content and degree of neutralization, with that for metal‐neutralized biphasic ionomers. The trends as a function of ion content regarding the transition temperatures and intensities of the HDA‐neutralized ionomers parallel what is observed for metal‐neutralized ionomers, in particular polystyrene‐based ones. A small‐angle X‐ray scattering peak, identified as an “ionomer peak”, is observed in the PS‐SSA‐HDA ionomer of the highest ion content studied. Furthermore, it was observed that partial neutralization affects the cluster phase more strongly than the matrix phase. This can be explained by the contribution of the acid groups to the matrix Tg, and their ability, when present in large amounts, to affect the ionic interaction strength or facilitate ion hopping, which influences primarily the cluster Tg.
Problems relating to long period determination in polyethylene shish‐kebab structures
Authors: Michler G. H. , Naumann I. , Baltá Calleja F. J. , Ania F. 
Published: April 2003

AbstractThe X‐ray long periods from high molecular weight injection molded polyethylene (PE) with a shish‐kebab structure have been compared with values derived from electron micrographs. It is shown that while small angle X‐ray scattering (SAXS) presents two long periods, the direct measurements from transmission electron microscopy (TEM) furnish only the lower SAXS periodicity. In an attempt to clarify this discrepancy of results, laser light diffraction and Fourier transformation of electron micrographs have been undertaken. Using this method two long periods are found in all regions investigated. Results are discussed in terms of the role played by the structured or “weakly crystalline” interlamellar parts, containing a lower electron density, which are neglected by the small angle scattering of X‐rays and which give rise in particular regions to larger scattering periodicities.
Comparison of the viscoelastic properties of syndio‐ and isotactic polypropylenes
Authors: Eckstein A. , Friedrich C. , Lobbrecht A. , Spitz R. , Mülhaupt R. 
Published: April 2003

AbstractThe viscoelastic properties of fourteen syndio‐ and isotactic polypropylenes (PPs) were measured in the molten state at several temperatures by means of oscillatory rheometry. Metallocene catalysis allows the control of molecular mass of both PP families and provides narrow molecular mass distributions (MMD) with a polydispersity of about 2. The validity of the Arrhenius and WLF equations for PP was checked. Syndio‐ and isotactic PP follow Arrhenius behavior but exhibit different activation energies of flow. From the dynamic shear moduli, viscoelastic parameters were determined and correlated with molecular mass. The dependence of the zero shear viscosity on the weight average molar mass exhibits the well‐known scaling relation. Stereoregularity has an important effect on the viscoelestic behavior of PP melts.
Anisotropic surface eruptions on polymerized diacetylene crystals
Authors: Shivshankar V. , Sung C. , Kumar J. , Tripathy S. K. , Sandman D. J. 
Published: April 2003

AbstractSurface eruptions that are approximately 0.5 μm in diameter at the base and about 700 Å in height have been observed by atomic force microscopy on single crystals and films of polydiacetylenes of the alkylurethanes of 5,7‐dodecadiyn‐1,12‐diol when the polymerization is performed using 60Co gamma radiation in the presence of air. The eruption process is associated with monomer polymerization and is anisotropic, as the eruptions are found only on the (100) face of single crystal specimens. Crystals having surface eruptions are irreversibly converted from blue to red at room temperature on exposure to a single pulse of 532 nm laser light while crystals lacking eruptions do not undergo this change.
Phase inversion with gel/sol/gel‐treatment — a new technology for the formation of hollow‐fiber membranes at a wet spinning process
Authors: Albrecht W. , Weigel Th. , Paul D. 
Published: April 2003

AbstractThe preparation of hollow‐fiber membranes with high asymmetric morphology by a wet spinning process by phase inversion of polymer solutions with a nonsolvent medium is normally connected with the formation of a relatively dense unwelcome skin. One possibility to eliminate this disadvantage is a phase inversion process with gel/sol/gel‐treatment, whose physicochemical peculiarities are descibed in this paper. In the gel/sol/gel‐treatment an initially wet hollow‐fiber membrane is contacted with a solvent and subsequently with a nonsolvent again. Such a technology causes a second phase inversion at the outer surface of the hollow‐fiber membrane. Results about parameters influencing the gel/sol/gel‐process are presented as an illustration for the treatment of polyacrylonitrile hollow‐fiber membranes with a special structure. In conclusion, first ideas of the mechanism of this process are formulated.
Unique morphology of poly(azomethine ethers) sheared in the liquid crystalline state
Authors: Dean D. , Geil P. H. 
Published: April 2003

AbstractThe morphology and electron diffraction patterns of sheared films of a series of aliphatic‐aromatic poly(azomethine ethers) with n = 1,4 and 7–10 CH2 units in the aliphatic segment have been characterized by transmission electron microscopy. The films were prepared by shearing in the liquid crystalline (nematic) state. In all cases, lamellae ca. 400 Å thick and more or less perpendicular to the shear direction and perpendicular to the substrate were obtained. Annealing increases the lamellar thickness and overall order. Redrawing of annealed, sheared samples of n = 10 suggests they consist of chain folded lamellae. Electron diffraction (ED) yielded h0l single crystal patterns in all cases, except for n = 1, which yielded orthorhombic, fiber‐like patterns. The h0l patterns suggest a planar, single crystal orientation over the entire sample. Annealing sheared samples above the crystal‐liquid crystal transition temperature resulted in reorientation of the molecules (from parallel to perpendicular) with respect to the substrate. ED patterns changed accordingly from h0l to hk0. Sheared samples with n = 4 gave both orthorhombic and monoclinic diffraction patterns.
Syntheses and spectroscopic pH titrations of naphthol‐labeled poly(methacrylic acid)s
Authors: Itoh Y. , Ogura K. , Hirota T. , Hachimori A. , Abe K. 
Published: April 2003

AbstractPoly(methacrylic acid) (PMA) and poly(acrylamide) (PAAm) with a small mole fraction of naphthol (NpOH) residues were prepared by polymerization of methacrylic acid or acrylamide with three position isomers, methacryloylaminonaphthol. The substituent effect on the apparent pK values (pKobsd), determined by spectroscopic pH titrations in aqueous solution, was observed for the NpOH‐labeled PAAm. The electrostatic surface potential (ψ) for PMA was calculated from the difference in the pKobsd values for the labeled PMA and PAAm. The obtained ψ value decreased as the spacing between the OH moiety and the polymer main chain increased. This clearly indicates that the ψ value is a sensitive function of the distance from the polyion surface.
Properties of ultra‐high‐molecular polyethylene and related polymerization‐filled composites produced by solid‐state extrusion
Authors: Beloshenko V. A. , Kozlov G. V. , Varyukhin V. N. , Slobodina V. G. 
Published: April 2003

AbstractThe structural, shrinkage and mechanical characteristics were studied of specimens of ultra‐high‐molecular polyethylene (UHMPE) and polymerization‐filled composites UHMPE‐Al and UHMPE‐bauxite produced by plunger extrusion of powder material. It is shown that the dependence of the strain–stress characteristics of UHMPE and its composites on the extrusion ratio varies considerably in the presence of a filler. Mechanisms explaining the behavior of the polymer material under study are proposed.
Electroluminescent stilbenoids – electrochemically generated luminescence in solution and organic light emitting devices on a polymer blend basis
Authors: Kelnhofer K. , Knorr A. , Tak Y.‐H. , Bässler H. , Daub J. 
Published: April 2003

AbstractOrganic light‐emitting diodes based on molecularly doped polymer blends have been fabricated and characterized using donor–acceptor substituted stilbenoids as active dye components for hole transport, electron transport and emission. A Comparison of the electrochemically generated luminescence (ECL), the photoluminescence (PL) and the electroluminescence (EL) of the organic light‐emitting devices (OLEDs) is given.