bluuebunny/crossref_metadata_2025_split huggingface dataset:
Etude du couplage chromatographie d'exclusion‐diffusion de la lumière, 1. Dispositif expérimental et étude de polystyrènes «références»
Authors: Beltzung Laure , Strazielle Claude 
Published: April 2003

AbstractThe possibilities of coupling size exclusion chromatography with light scattering (GPC‐DDL) are studied. The continuous light scattering detector is a modified (laser He‐Ne excitation) classical light scattering apparatus Fica 42000, equipped with a flow cell of low capacity (120μl). With this cell, a detection of the scattered light is obtained only at an angle of 90°. The light scattering detector is coupled with a GPC apparatus (packed with 10 μm gel particles). The precision, reproducibility and limitation to obtain molecular weight distribution curves of “standard” linear polystyrenes are studied.
Etude du couplage chromatographie d'exclusion — diffusion de la lumière, 2. Application a quelques problèmes particuliers
Authors: Beltzung Laure , Strazielle Claude 
Published: April 2003

AbstractA continuous light scattering detector coupled to a gel permeation chromatography (GPC) instrument (GPC‐LS), as described in the preceding paper, is used to determine the hydrodynamic structure factor g′ of branched polystyrene samples and to establish the viscosity law for poly(methyl methacrylate), poly(vinyl chloride), and poly(vinyl acetate) by comparing the results from GPC‐LS and GPC analysis (with molar mass calibration with linear, monodisperse polystyrene samples).
Precipitation studies of polystyrene from solution
Authors: Lau Ming Yan , Poh Beng Teik 
Published: April 2003

AbstractThe precipitation behaviour of polystyrene from solution was studied for the ternary system of polymer/solvent/precipitant, the solvent being toluene or ethyl methyl ketone and the precipitant methanol. The relationships between the efficiency of precipitation and temperature of precipitation, concentration of the solution, molecular weight of the polymer, and the solvent system were investigated. The optimum volume ratio of the polymer solution to precipitant, in order to obtain maximum efficiency of precipitation for a particular system, was derived from graphical plots. The results indicated that the efficiency increases with increasing concentration of the solution, molecular weight of polymer, and thermodynamically “poorer” solvent, but decreases with increasing temperature between 200 K and 300 K. It was also observed that a plot of the efficiency of precipitation versus the volume ratio of polymer solution to precipitant passes through a maximum for all the systems studied. The optimum volume ratio of polymer solution to precipitant exhibits a similar behaviour just as in the case of the efficiency of precipitation. Information obtained from this study enables one to select the best combination of the parameters affecting precipitation, in order to produce a high yield of precipitate of polystyrene at a relatively low cost of solvent and precipitant for a particular temperature of precipitation.
Beitrag zur Diskussion um die Morphologie von polyacetylen
Authors: Weßling Bernhard 
Published: April 2003

AbstractWe analysed by raster electron microscopy Luttinger‐polyacetylene as a powder and as a film, both in pristine and (SbF6−‐electrochemically) doped form. The samples had been intensively washed with MeOH/HCl. One sample had, according to the results of transmission electron microscopy, fiber morphology. All samples show globules as primary structure arranged in clusters (in powder), mono‐layers, or chains (in film) (which previously led to “fibril theory”). The primary spherical particles have diameters from 0,02–0,05 μm. The “fibril” sample has very small spherical primary particles, which may develop using low catalyst amounts. Our results support that the conductivity characteristics is governed by phenomena antiparallel to the chain direction (change‐transfer‐complexes).
13C NMR spectroscopy of 2‐formamido‐2‐methylpropyl acrylate and poly(2‐formamido‐2‐methylpropyl acrylate)
Authors: Reddy Boreddy S. R. , Arshady Reza , George Maurice H. 
Published: April 2003

AbstractThe synthesis and characterization of 2‐formamido‐2‐methylpropyl acrylate (FMPA) is reported. 13C NMR spectra of FMPA in CDCl3, CD3OD, DMSO‐d6, DMF‐d7, and D2O exhibit two pairs of lines for all seven carbon atoms at room temperature; the ratio of the two conformers varies moderately with solvent (21 : 79 to 41 : 59). The conformers are believed to involve strong internal hydrogen bonding which is not completely broken even by the addition of trifluoroacetic acid to CDCl3 (1/1, v/v). However, the pairs of lines coalesce in turn as the temperature is raised to 120°C in DMSO‐d6. FMPA was polymerized at 35°C in DMF and CHCl3, using a free radical initiator and the polymer was characterized by 13C NMR spectroscopy.
Functional metal‐porphyrazine derivatives and their polymers, 12. Synthesis and properties of polyimides containing a metalphthalocyanine ring and a pyridyl group
Authors: Shirai Hirofusa , Takemae Yoshitaka , Kobayashi Kesayoshi , Kondo Yoshiyuki , Hirabaru Okikazu , Hojo Nobumasa 
Published: April 2003

AbstractA novel class of polyimides (6a – c) containing Mt(II)‐phthalocyanine rings was synthesized by solution condensation in N‐methyl‐2‐pyrrolidone of Mt(II)‐[2,9, or 10(or 2,16, or 17)bis(3,4‐dicarboxybenzoyl)]phthalocyanine dianhydride [Mt(II)‐dahPc: Mt(II) = Co(II), Ni(II), and Cu(II)] with 2,6‐diaminopyridine, followed by thermal imidation. The polyimides showed room temperature dc‐conductivities in the range of 10−12 − 10−9 Ω−1 · cm−1, and, after quaternization of the pyridine group, the conductivities increased by 1 to 3 orders of magnitude.
Interaction of cross‐linked polyacrylic acid with cetyltrimethylammonium bromide
Authors: Musabekov Kuanyshbek , Abilov Zharylkasyn , Beisebekov Marat 
Published: April 2003

AbstractThe interaction of cross‐linked copolymers of acrylic acid with divinylbenzene (PAA‐C‐L) with the micelle‐forming surface‐active cetyltrimethylammonium bromide (CTMAB) is studied. It is shown that the ion‐exchange interaction of PAA‐C‐L with CTMAB at small degrees of polyelectrolyte cross‐linking is analogous to the interaction of linear polyacrylic acid with CTMAB. The total quantity of surface‐active substances (SAS) bound to PAA‐C‐L increases with an increase of the SAS concentration in the solution, with the pH of the medium, and with the quantity of the binding agent in the ion exchange resin.
Complex formation between bovine serum albumin and poly(acrylic acid) as studied by viscometry, circular dichroism, and fluorescence spectroscopy
Authors: Kuramoto Noriyuki , Sakamoto Munenori , Komiyama Jiro , Iijima Toshiro 
Published: April 2003

AbstractThe complex formation between bovine serum albumin (BSA) and poly(acrylic acid) (PAA) in water was studied by viscosity measurements. It was found that at a BSA/PAA mole ratio of 233 the reduced viscosity of the solution shows a minimum, indicating that binding take place nonspecifically on the BSA surface. Circular dichroism (CD) spectra indicate that BSA does not suffer conformational alteration by the presence of PAA. Fluorescence spectroscopic studies were performed on 1‐anilinonaphthalene‐8‐sulfonate(ANS)‐BSA systems in presence of monocarboxylic acids or PAA. Again, in contrast to the hydrophobic binding of the monoacids, it was found that PAA binds to BSA nonspecifically on the surface.
Sodium metatungstate, a new medium for binary and ternary density gradient centrifugation
Authors: Plewinsky Bodo , Kamps Rainer 
Published: April 2003

AbstractSodium metatungstate, Na6[H2W12O40] is presented as a new medium for density‐gradient centrifugation. This electrolyte may be used in aqueous, aqueous sodium chloride, or in methanol solutions. The sedimentation behaviour of sodium metatungstate in binary (Na6[H2W12O40]/H2O) and in ternary (Na6[H2W12O40]/NaCl/H2O) systems is presented and discussed. Practical examples are presented from macromolecular chemistry (Sedipur), biochemistry (DNA), and mineralogy (sodium‐aluminium mica).
Quasielastic light scattering studies of the pressure‐induced denaturation of lysozyme
Authors: Nyström Bo , Roots Jaan 
Published: April 2003

AbstractThe pressure‐induced denaturation of lysozyme in acetic acid/acetate buffer at pH = 4,0 was studied in the pressure range 1 – 4500 atm (0,10 · 106 – 456 · 106 N/m2) by photon correlation spectroscopy. The hydrodynamic radius RH, initially independent of pressure, was at moderate pressures observed to pass through a minimum. At higher pressures, in the transition region, RH upon pressure denaturation was approximately 9%. This increase was significantly smaller than those reported from quasielastic light scattering measurements on lysozyme solutions utilizing chemical agents and temperature as denaturants. Speculative arguments for this behaviour are presented. Upon releasing the pressure the return of RH was not reversible. The influence of pressure on the mutual diffusion coefficient was studied for a low and a high concentration. The results indicate that there exist enhanced intermolecular interactions at higher concentrations.
Investigation of polyesters of adipic acid and sebacinic acid with hydroquinone by pyrolysis‐mass spectrometry
Authors: Aguilera Carlos , Lüderwald Ingo 
Published: April 2003

AbstractThe structure and thermal degradation behaviour of polyesters of adipic acid and sebacinic acid with hydroquinone were investigated by direct pyrolysis in the ion source of a mass spectrometer. Poly(oxyadipoyloxy‐1,4‐phenylene) (1) and poly(oxyebacoyloxy‐1,4‐phenylene) (2) undergo a cleavage of the ester bond as a very selective thermal degradation reaction (Eq. (iii)). In order to differentiate the thermal and electron impact induced degradation reactions of these polyesters the fragmentation pathways of corresponding low molecular weight esters were followed.
Syntheses and thermodynamic studies on the protonation behaviour of polymers containing acylpiperazinyl units in the backbone or in the side chain of a vinyl polymer
Authors: Barbucci Rolando , Casolaro Mario , Ferruti Paolo , Tanzi M. Cristina , Grassi Lucia , Barozzi Chiara 
Published: April 2003

AbstractLinear poly(1,4‐piperazinediyl‐1‐oxotrimethylene) (1), in which amido and tertiary amino groups regularly alternate along the macromolecular chain, the isomeric poly[1‐(1‐piperazinyl‐carbonyl)ethylene] (8) for polyvinylic structure and its N‐methylated derivative, poly{1‐[(4‐methyl‐1‐piperazinyl)carbonyl]ethylene} (3), were prepared and characterized. Their protonation behaviour was investigated in aqueous solution by potentiometric and calorimetric techniques. In all cases the basicity constants were found to decrease linearly with α (the degree of protonation), whereas the enthalpy changes show a different behaviour toward protonation. The thermodynamic values indicate the important role of hydrophobic interactions.
New divinylidene compounds and their reaction with electron transfer reagents
Authors: Bastelberger Thomas , Thu Cuc Tran , Höcker Hartwig 
Published: April 2003

AbstractSome new divinylidene compounds, 1,3‐bis[4‐(β‐styryl)phenyl]propane (2b), 1,6‐bis[4‐(β‐styryl)phenyl]hexane (2d), 2,6‐bis(β‐styryl)pyridine (1b), and 1,5‐bis(β‐styryl)naphthalene (1c), were prepared. Their reaction with electron transfer agents was investigated and compared with that of homologous divinylidene compounds. The cyclic oligomers formed after protonation were separated and characterized spectroscopically. In general, no preferential formation of isomers is observed. The cyclic dimer, however, is the main product of the electron transfer reaction of 1b and 1c.
Etude des propriétés électro‐optiques de i' ADN par biréfringence électrique à faible champ, 1. Théorie, appareillage et exploitation des résultats
Authors: Marion Christian , Roux Bernard , Bernengo Jean‐Claude 
Published: April 2003

AbstractElectric birefringence (or Kerr effect) measurements can give, in principle, important informations on the optical, electrical and hydrodynamical properties of macromolecules. The theoretical basis of the Kerr effect is reviewed here so as to be applied to the determination of some molecular parameters of DNA such as optical and electrical polarizability anisotropies, permanent dipole moment, and rotatory diffusion constant. It is necessary to conduct the measurements at very low electric fields. The original device used and the methods for the analysis of the experimental data are described.
Photoinitiated degradation of poly(diacetylene)s in solution by random chain scission
Authors: Müller Michael A. , Wegner Gerhard 
Published: April 2003

AbstractPoly(diacetylene)s dissolved in common organic solvents undergo random chain scission, if irradiated by UV‐light. The pure polymers and their solutions are, however, stable, if they are photoirradiated within the main‐absorption band of the polymer backbone. The usual triplet sensitizers, especially in the presence of oxygen, and radical donors such as 2,2′‐azoisobutyronitrile (AIBN) enhance the rate of photodegradation. Suitable dyes are able to sensitize the chain‐scission in the visible regions as well. Random chain scission occurs also in the dark, but only at temperatures above room temperature and is enhanced by the addition of radical‐donors, e.g. AIBN. A mechanism of chain scission, induced by the attack of a radical to a multiple bond of the polyconjugated backbone of the polymer is proposed.
The rubber elastic behaviour of crosslinked polymers and a critical consideration of theoretical concepts
Authors: Gebhard Georg , Gleim Wolfgang , Rehage Günther , Schwarz Jürgen 
Published: April 2003

AbstractThe elastic properties in simple elongation have been investigated under various aspects for a series of elastomers, which were crosslinked randomly in the bulk state. The results are compared with different theoretical concepts for explaining the deviations from predictions of the simple statistical theory of rubber elasticity. The results do not favour clearly any one of the theoretical concepts under discussion.
Equation of state for linear polymer melts: the chemical structure parameter and its relationship to the characteristic volume, packing densities, characteristic bulk modulus and glass transition temperature
Authors: Roszkowski Zbigniew 
Published: April 2003

AbstractIt is shown that the three‐parameter equation of state for linear polymer melts, although consistent with the theorem of corresponding states, contains no information about the chemical structure of the polymer chain. This information is now included in the equation via a fourth parameter representing the structure. The relations between the chemical structure parameter and the characteristic volume of the polymer, its dense packing, characteristic bulk modulus, and glass transition temperature are deduced. It is demonstrated that the properties of the polymer are influenced by the compressibility of the polymer chain, which was not taken into account in the mechanical‐statistical approaches to the equation of state for liquid polymers. It is also shown that the dense packing of a polymer is almost equal to the close packing of spheres. The determination of the parameters of the four‐parameter equation requires the knowledge of the van der Waals volume of the constitutional repeating unit and p V T data for the liquid polymer, including the glassy transition region. This region should be investigated under cooling conditions considered as isochronal, the time of viscoelastic relaxations assumed to be zero.
Linear and star‐shaped hybrid polymers, 3. An improved purification procedure for coupling products of oligosaccharides by amide linkage
Authors: Ziegast Gerd , Pfannemüller Beate 
Published: April 2003

AbstractA convenient method for binding saccharides to natural and synthetic substances, polymers and low molecular weight compounds, consists in coupling via an amide linkage. For this purpose aldonolactone or amino groups are introduced at the reducting end of the saccharides which allows coupling to a great variety of amino and carboxyl groups containing compounds. Purification with the usual ion‐exchange resins based on polystyrene proved unsatisfactory for oligosaccharides due to adsorption effects and reduced ion‐exchange capacity. Excellent results on each step of conversion are obtained by chromatography on a cross‐linked poly(acrylamide) gel (Bio‐Gel P‐4 and P‐10) containing a small amount of carboxylic groups introduced by moderate saponification. The new procedure combining the effect of molecular size fractionation and ion‐exchange chromatography offers a wide field of application.
Tailor made partially substituted poly(iminoethylene) and derivatives in activated ester hydrolysis
Authors: Everaerts Albert , Samyn Celest , Smets Georges 
Published: April 2003

AbstractLinear poly(iminoethylene) (polyethyleneimine) (l‐PEI) was transformed into three types of branched polymers, which differ by the length and nature of the side groups, and their degree of substitution. By reaction with (1‐benzyloxycarbonyl‐2‐methylaziridine) (N‐benzyloxycarbonyl‐propyleneimine) (Z‐PI) followed by HBr‐acidolysis, N‐2‐aminopropyl derivatives of PEI with different degrees of substitution were obtained (1‐S‐y‐PEI). The synthesis of polymers with 2‐(2‐aminopropylamino)propyl groups was carried out by first partial acetylation of 1‐PEI, subsequent treatment twice with Z‐PI followed by HBr‐acidolysis, and finally deacetylation with 6 N HCl at 100°C (2‐S‐y‐PEI). Finally, reaction of I‐PEI with Z‐5‐aminopentyl tosylate gave polymers containing 5‐aminopentyl side groups (C5‐S‐y‐PEI). The catalytic activities of these three types of polymers were compared in the hydrolysis of p‐nitrophenyl acetate and 4‐acetoxy‐3‐nitrobenzoic acid. The reactions were followed under the conditions of pseudo‐first order kinetics, for which [Catalyst] ≫ [Substrate], and also under the conditions of Michaelis‐Menten complex formation kinetics, for which [Substrate] > [Catalyst]. The results indicate that the optimum catalytic activity is determined by the length of the spacer by which the primary amino groups is linked to the main chain, resulting in the following order of activity: (2‐S‐y‐PEI) ≈ (C5‐S‐y‐PEI) > (1‐S‐y‐PEI).
Die kristallstruktur von oligo[(2‐hydroxy‐1,3‐phenylen)methylen]en
Authors: Paulus Erich , Böhmer Volker 
Published: April 2003

AbstractThe crystal structure of three tetranuclear phenolic compounds – 6,6′‐bis (2‐hydroxy‐5‐methylbenzyl)‐4,4′‐dimethyl‐2,2′‐methylenediphenol (1), 6‐(2‐hydroxy‐3,5‐dimethylbenzyl)‐6′‐(2‐hydroxy‐5‐methylbenzyl)‐4,4′‐dimethyl‐2,2′‐methylendiphenol (2), and 6‐(3‐tert‐butyl‐2‐hydroxy‐5‐methylbenzyl)‐6′‐(2‐hydroxy‐5‐methylbenzyl)‐4,4′‐dimethyl‐2,2′‐methylene‐diphenol (3) –, was determined by single crystal X‐ray analysis. Intramolecular hydrogen bonds between all hydroxyl groups of adjacent phenolic units are found for all molecules. They are directed to the opposite end of the molecule by the ortho‐methyl or ortho‐tert‐butyl group in compounds 2 and 3, while no special orientation is found in 1. The conformation of the phenolic units is trans/trans (anti/anti) in 1 and cis/trans (syn/anti) in 2 and 3. Consequently, in the crystal lattice, 2 and 3 form cyclic dimers via intermolecular head‐to‐tail hydrogen bonds, while the molecules of 1 are arranged to chains of indefinite length by head‐to‐head and tail‐to‐tail hydrogen bonds.
Characterization of graft copolymeres of methyl cellulose and polyacrylamide by thermogravimetry
Authors: Kohli Krishna , Mukhopadhyay Sailes , Chatterjee Satya R. 
Published: April 2003

AbstractThermal stability and degradation kinetics of methyl cellulose, polyacrylamide and methyl cellulose grafted with different amounts of polyacrylamide were investigated by thermogravimetry. Polyacrylamide was found to be more stable than methyl cellulose. The thermal stabilities of the graft copolymeres lie in between these two extremes. The order of reaction, n, and energy of activation, E, of the thermal degradation were determined for all polymer samples. It was found that E for the degradation of polyacrylamide (41,4 kcal/mol = 173,2 kJ/mol) is higher than that of methyl cellulose (31,3 kcal/mol = 131,0 kJ/mol) and that E for the graft copolymers lies in between those of the two homopolymers. The over‐all reaction order of the degradation reactions was found to be unity for all polymer samples investigated.
Speckle patterns in small angle light scattering: A random phase screen approach
Authors: Holoubek Jaroslave , Sedláček Blahoslav 
Published: April 2003

AbstractThe basic features of scattering are shared by a number of closely related scatterer systems. The most elementary model for these systems in the random phase screen (RPS). In this article, predictions of the RPS theory are compared with the experimental data obtained by analysing scattered light speackle patterns from a film made of a semicrystalline polymer. On the basis of results obtained, it is possible (a) to classify speckle types depending on the illuminating conditions, (b) to measure speckle “smoothing” by determining the contrast of speckle intensity fluctuations, (c) to illustrate the relation between object and speckle movements in different geometries for simple types of sample movement (rotation, linear continuous translation and step‐wise translation). The experimental data tend to confirm the validity of RPS theory in the case of polymer films. It is indicated that under certain conditions the statistical, temporal and spatial coherence properties of the scattered light are sensitive to the detailed internal structure of the scattering medium.
Liquid phase peptide synthesis by fragment condensation on a soluble polymer support, 6. The influence of peptide‐chain lengths of Boc‐oligopeptides on the coupling efficiencies of their C‐terminal amino acids in coupling reactions with polymer‐bound amino acids
Authors: Isokawa Shizuko , Kobayashi Naoyuki , Nagano Ro‐ichi , Narita Mitsuaki 
Published: April 2003

AbstractThe influence of both the peptide‐chain lengths of Boc‐oligopeptides and the degree of crosslinking of polymer supports on the coupling efficiencies of the C‐terminal amino acids of Bocoligopeptides in the coupling reactions with terminal free amino groups of amino acids linked to polymer supports was investigated. The coupling efficiencies of Boc‐oligopeptides (consisting of 3 to 10 amino acid residues) relative to those of Boc‐Val‐OH or Boc‐Met‐OH were determined by competitive coupling reactions with amino acids anchored to soluble and crosslinked polystyrene supports, using four systems of coupling reagents dicyclohexylcarbodiimide (DCC) + 1‐hydroxy‐1 H‐benzotriazole, DCC + N‐hydroxysuccinimide, DCC + N‐hydroxy‐5‐norbornene‐2,3‐dicarboximide, and N‐ethoxycarbonyl‐2‐ethoxy‐1,2‐dihydroquinoline. In the coupling reactions on soluble polystyrene supports, containing 1 mol‐% of an amino acid (per styrene monomeric unit), and on poly(styrene‐co‐divinylbenzene (1%)), containing 1 or 10 mol‐% of an amino acid, little influence of peptide‐chain lengths was observed. In reactions with amino acids anchored to poly(styrene‐co‐divinylbenzene (2%)) (containing 2 or 20 mol‐% of terminal amino groups), an increase in peptide‐chain length of Boc‐oligopeptides was found to reduce remarkably the coupling efficiencies of their C‐terminal amino acids. With poly(styrene‐co‐divinylbenzene (2%))s as supports, it was detected that amino groups are present which are sterically inaccessible for peptide fragments such as Boc‐Ala‐Ala‐Leu‐Leu‐Leu‐OH and Boc‐Ala‐Ala‐Leu‐Leu‐Leu‐Pro‐Pro‐Leu‐Leu‐Leu‐OH.