bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of crosslinked poly(N‐vinyl‐2‐pyrrolidone) by calorimetry and by NMR
Authors: Tenhu Heikki , Sundholm Franciska , Bjorksten Johan 
Published: April 2003

AbstractAqueous solutions of poly(N‐vinyl‐2‐pyrrolidone) are converted to gels by reaction with potassium peroxydisulfate K2S2O8. The degree of crosslinking in the gel fractions depends on the amount of persulfate used. The degree of crosslinking is related to the amount of non‐freezing bound water in the gels by means of differential scanning calorimetry in the temperature range from −50°C to + 170°C. The chemical nature of the bonds formed during gelation is studied by 1H and 13C NMR Spectroscopy and by swelling tests. NMR measurements point to the formation of aliphatic sidechains as well as crosslinks in the gelation. The swelling tests give low values for the number of crosslinks, hence the formation of branched chains strongly influences the properties of the gels. In contrast to what was expected no carboxyl groups are found in the gels.
Epitaxy of helical polyolefins: Polymer blends and polymer‐nucleating agent systems
Authors: Lotz Bernard , Wittmann Jean‐Claude 
Published: April 2003

AbstractHelical polyolefins (polypropylene (PP) and poly(1‐butene)) (PB‐1) possess crystallographic faces in which the side‐groups form well aligned rows. These structural features are shown, through a number of examples, to interact with linear polymers (polyethylene (PE) and polyamides) and nucleating agents. These interactions explain, on the basis of characteristic epitaxial relationships, the mutual activity of certain pairs of crystalline polymers and the hitherto puzzling “universality” of some nucleating agents towards both linear (i.e. PE‐like) polymers and helical polyolefins.
Homogeneous Ziegler‐Natta catalysis: Efficiency improvement of vanadium catalyst systems by tributyltin hydride for the ethylene/propylene/diene terpolymerization
Authors: Giannetti Enzo , Mazzocchi Romano , Albizzati Enrico , Fiorani Tiziana , Milani Federico 
Published: April 2003

AbstractThe effect of tributylin hydride on different vanadium‐based homogeneous catalytic systems for the ethylene/propylene/diene (EPD) terpolymerization was studied. Productivity improvements were always observed. Studied on the composition of the polymerization residues as well as on the interaction between single components of the catalytic system were also carried out. The results are interpreted on the basis of the enhanced oxidation of the vanadium(II) species by radical intermediates resulting from the reaction between tin hydrides and the chlorinated organic activator.
Induction of metachromasia and circular dichroism in some dyes by sulfated bael gum polysaccharide and its anticoagulant property, 1
Authors: Pal Medini Kanta , Bhattacharyya Ashoke Kumar 
Published: April 2003

AbstractBael (Aegle marmelos) gum polysaccharide (AMA), a polyacid polysaccharide with a high equivalent weight (2091) was shown to exhibit a very weak chromotropic character and to fail to induce a metachromatic spectral shift of the dye toluidine blue. Sulfation of the polysaccharide to a carboxylate/sulfate mole ratio of 1 (AMA‐S2; equivalent weight 698) largely enhances the chromotropic character. AMA‐S2 shows a blue shifted metachromasia with toluidine blue (TB) and pinacyanol chloride (PCYN), and a red shifted J‐band with N,N′‐diethylpseudoisocyanine chloride (PIC). Mixtures of AMA‐S2 with both PCYN and PIC exhibit a strong circular dichroism in the visible range of the respective dye/polyanion system. The anticoagulant property of the Bael gum polyasaccharide also improves with its sulfation, as expected.
Synthesis of new polynaphthalimidophenylquinoxalines and their copolymers
Authors: Korshak Vasilij V. , Krongauz Jergienija S. , Belomoina Natasha M. , Jediński Zbigniew , Kowalski Bogdan , Paliwoda Adam 
Published: April 2003

AbstractA series of novel polyphenylquinoxalines containing naphthalimide structures in the chain were prepared by reacting 3,3′‐diaminobenzidine, 3,3′,4,4′‐tetraaminodiphenyl ether and 3,3′,4,4′‐tetraaminodiphenyl sulfone with the two new monomers of N,N′‐bis(4‐benzoylcarbonylphenyl)‐4,4′‐(1,3‐phenylenedioxy)‐di‐1,8‐naphthalenedicarboximide (3a) and N,N′‐bis(4‐benzoylcarbonylphenyl)‐4,4′‐[isopropylidenebis(1,4‐phenyleneoxy)]‐di‐1,8‐naphthalenedicarboximide (3b). The obtained polymers exhibit high decomposition temperatures, their Tg values being, however, below 300°C. Their solubility in common solvents, e.g. chloroform, is excellent, but their molecular weight is low. Higher molecular weight products were obtained by copolymerization of 3a, b with N,N′‐bis(4‐benzoylcarbonylphenyl)‐1,8 : 4,5‐naphthalenetetracarboxdiimide (3c) yielding films and fibers with good mechanical properties.
Syntheses of macrocyclic oligoesters from 5‐hydroxymethyl‐2‐furancarboxylic acid
Authors: Hirai Hidefumi , Naito Katsuyuki , Hamasaki Taihei , Goto Minoru , Koinuma Hideomi 
Published: April 2003

AbstractNew macrocyclic oligoesters 3a – d, containing furan rings, were synthesized by condenzation of 5‐hydroxymethyl‐2‐furancarboxylic acid (1) using 2‐chloro‐1‐methylpyridinium iodide (2) as condensing agent. Water‐insoluble products were separated by GPC and characterized by IR, NMR, MS, and elemental analysis. The product distribution was found to depend remarkably on the reaction conditions. When the mole ratio of 2 to 1 was 1,65 in pyridine was solvent, the cyclic trimer 3a and the tetramer 3b were obtained, both in more than 30% yield. In addition higher cyclic oligoesters (3c – d), linear oligoesters (5b – e), and the polyester (6) were formed. When a large amount of tributylamine was used as a scavenger of hydrogen halides in toluene as solvent, the polyester was the main product. Condensation in hexane in place of toluene, yielded the linear oligoesters as main products. A mechanism is proposed for the formation of the cyclic oligoesters.
Recherche de télomères à activité pharmacologique potentielle, 6. Introduction de moleécules relais entre le principle actif et la chaine télomère
Authors: Bauduin Gérard , Bessière Jean‐Marie , Martel Jacques , Piétrasanta Yves 
Published: April 2003

AbstractReactions of insertion of components serving as bridges between a pharmacologically active constituent and a water‐soluble telomeric chain, were carried out. Model compounds containing hydroxyl, amine or carboxylic functions were studied. In each case a bifunctional compound could be found, which is capable of reacting with the model. The resulting products could be fixed on a telomer. The results with the model compounds were applied to the fixation of the carboxylic drug indometacin.
Propylene polymerization on titanium‐magnesium catalysts, 3. Influence of the products resulting from the interaction of trialkylaluminium with aromatic esters on the activity and stereospecificity
Authors: Sergeev Sergei A. , Bukatov Gennadii D. , Zakharov Vladimir A. 
Published: April 2003

AbstractThe influence of the conditions of interaction between AlR3 and aromatic esters (D) and of the products formed on the activity and stereospecificity of the actalytic system TiCl4/ethyl benzoate/MgCl2 + Al(i‐Bu)3 + D in propylene polymerization was studied. An increase of the polymerization temperature above 60°C leads to a decrease in the activity of the titaniummagnesium catalyst (TMC) and in the isotacticity of the polypropylene produced. A preliminary interaction of AlR3 with D at elevated temperatures diminishes the isotacticity of the polymer and has no influence on the activity of TMC. IR spectroscopy was employed to study the influence of the temperature and time of AlR3 interaction with the esters as well as that of the composition of AlR3 (AlEt3 or Al(i‐Bu)3) on the process of reduction of these esters. Reduction products such as aldehydes, ketones, and primary alkoxy derivatives of aluminium cannot provide of high stereopecificity of TMC. High stereospecificity is rather thought to be provided by the interaction of active sites with a free ester or tertiary alkoxy derivaties of aluminium. The contribution of each of these processes depends on the catalyst composition and on the polymerization conditions.
Thermodynamic and hydrodynamic properties of aliphatic polyesters, 3. Analysis of osmotic and light scattering data of poly(β‐propiolactone) in 2,2,2‐trifuloroethanol in terms of a universal scaling law for the osmotic pressure in the excluded volume limit
Authors: Rosenvasser Daniel , Figini Rubén V. 
Published: April 2003

AbstractOsmotic and light scattering data of poly(β‐propiolactone) in 2,2,2‐trifluoroethanol, a thermodynamically very good solvent, are analyzed in terms of a universal scaling law for the osmotic pressure in the excluded volume limit. The polymolecularity correction function to calculate osmotic pressures from light scattering data is deduced and a numerical method to treat simultaneously all the measured osmotic pressures at different concentrations is developed. It is shown that, for a given concentration, provided the molecular weight of the polymer species together with its radius of gyration is known, the osmotic pressure of its dilute and semidilute solutions can be calculated.
A small angle neutron scattering study of an oligo(oxytetramethylene)
Authors: Miller John A. , Cooper Stuart L. 
Published: April 2003

AbstractSmall angle neutron scattering experiments were performed on a blend of deuterated and protonated hydroxyl terminated oligo(oxytetramethylene)s. The oligomer had a number‐average molecular weight of 1000. The experimental data were fitted to a Debye function in order to obtain the radius of gyration of the chains. The measured radius of gyration, which was corrected for molecular weight distribution, was found to compare well with the values reported in the literature for poly(oxytetramethylene) in a theta solvent, as measured by viscosity methods and extrapolated to a molecular weight of 1000. Thus, this short oligomeric species has a random coil configuration. The weight‐average molecular weight determined from the SANS data was 1540, compared with a value of 1450 determined from high performance liquid chromatography. This implies that no isotopic segregation of the deuterated and protonated species occurs.
Structural studies on molecular complexes of polyethers, 3. Urea‐polyether complexes
Authors: Suehiro Kazuaki , Urabe Akira , Yoshitake Yoshiharu , Nagano Yoshiaki 
Published: April 2003

AbstractComplexes of urea with polyethers, \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{&#x02010;&#x02010;} [\left( {{\rm CH}_2 } \right)_m {\rm O\rlap{&#x02010;&#x02010;} ]}_n$\end{document} (m = 2–4, 6, 8–10), were prepared, and their crystal structures and decomposition temperatures were studied. The crystal structures of the complexes with polyethers (m ≥ 3) are similar to those of n‐alkanes, so‐called urea adducts. Only poly(oxyethylene), (m = 2), presents a complex of a different type of crystal structure. The decomposition temperatures of the complexes are in the range of 134 to 144°C and change in parallel with the melting points of polyethers themselves against the number of CH2 groups in the monomeric units.
Functional polymers, 32. 5‐Methoxy‐ and 5‐hydroxy‐2H‐benzotriazol‐2‐yl mono‐ or disubstituted resorcinols or phloroglucinols
Authors: Xi Fu , Basset Walter , Vogl Otto 
Published: April 2003

AbstractFour new 5‐methoxy‐2H‐benzotriazol‐2‐yl mono‐ or di‐substituted resorcinols and phloroglucinols 5a, b and 6a, b were synthesized by reaction of resorcinol or phloroglucinol with 4‐methoxy‐2‐nitrobenzenediazonium chloride in a 1:1 or 1:2 mole ratio and subsequent reductive cyclization with zinc and sodium hydroxide. The methoxy groups of all four compounds were cleaved with dry hydrogen bromide gas in dimethylformamide leading to the corresponding hydroxyl derivatives 7a, b and 8a, b in nearly quantitative yields. Unlike the reaction of phloroglucinol with a large excess of 2‐nitrobenzenediazonium chloride, which gave the trisubstituted product, with 4‐methoxy‐2‐nitrobenzenediazonium chloride no phloroglucinol derivative with three 5‐methoxy‐2H‐benzotriazol‐2‐yl groups could be obtained. All the resulting products were characterized by their IR, 1H, and 13C NMR, and UV spectra. The resorcinol derivatives (both methoxy‐ and hydroxy‐) Showed λmax of 345 nm and an absorption coefficients as high as 4 · 104 l · mol–1 · cm−1, and the phloroglucinol derivatives a λmax of 350 nm and an absorption coefficient as high as 4,5 · 104 l · mol−1 · cm−1.
Dynamic and static light scattering from critically branched polymer solutions
Authors: Kajiwara Kanji , Burchard Walther , Kowalski Michael , Nerger Dittmar , Dušek Karel , Matějka Libor , Tuzar Zdeněk 
Published: April 2003

AbstractCritically branched polyurethanes of varying molecular weight were prepared from poly(oxypropylene)triol and methylenedi‐p‐phenylene diisocyanate with and without solvent. The static/dynamic light scattering from DMF solutions of these samples was measured. The results were discussed in terms of the classical (Flory‐Stockmayer, FS) and percolation theory of gelation; the bulk‐polymerized sample obeyed the FS process, whereas the solution‐polymerized samples were better described by the percolation process.
Polyphenylene als Ausgangssubstanz für leitfähige Materialien
Authors: Simitzis Johannis , Dimopoulou Chrysoula 
Published: April 2003

Abstractp‐Polyphenylens were synthesized from benzene with the catalytic systems AlCl3/CuCl2/H2O and FeCl3/H2O under various conditions; also o,m,p‐polyphenylenes were synthesized from biphenyl with the catalytic system AlCl3/CuCl2. A method was described for estimating the amounts of polyphenylenes and oligophenylenes, formed during the polymerization of benzene. The synthesized polyphenylenes were characterized by their melting points, elemental analysis, IR‐analysis and X‐ray studies. The polyphenylenes, except for the material synthesized with FeCl3/H2O, are crystalline. The materials synthesized with FeCl3/H2O were amorphous and contained a greater amount of chlorine. The polyphenylenes exhibit electrical conductivities, according to which they can be classified as semiconductors. The importance of three factors, which also influence the value of the electrical conductivity of the polyphenylenes, namely the crystallinity, the presence of chlorine and the structure (p‐ or o,m,p) of the polyphenylenes is stressed.
Halbleiter‐Materialien aus der Pyrolyse von Polyphenylenen
Authors: Simitzis Johannis , Dimopoulou Chrysoula 
Published: April 2003

Abstractp‐Polyphenylenes and o,m,p‐polyphenylenes are pyrolyzed at various temperatures up to 1500°C in a nitrogen atmosphere. The weight loss during the pyrolysis and the residues of pyrolysis are studied by gravimetric measurements, elemental analysis, X‐ray analysis and electrical conductivity. The results of the measurements are interpreted by correlating the mechanism of pyrolysis with the structure and the numerical values of the electrical conductivity of the corresponding residues of pyrolysis. The maximum temperature of pyrolysis has a very important meaning for the electrical conductivity of the residues of pyrolysis, where has the polymerization conditions of the various polyphenylenes play only a secondary role. Three ranges of the temperature are distinguished (up to 600°C, 600 – 800°C, above 800°C), in which the corresponding residues of the pyrolysis are novel semiconductor materials with different structures and properties. Also the significance of chlorine as dehydrogenation agent is explained; chlorine contributes to the connection of neighbouring macromolecules; thus the presence of small amounts of Cl in polyphenylenes in the first temperature range of the pyrolysis seems to be suitable.
Etude de la polycondensation linéaire de polymères précurseurs α,ω‐bifonctionnels avec des agents de couplage bifonctionnels de faible masse molaire
Authors: Gnanou Yves , Chaumont Philippe , Lutz Pierre , Hild Gérard , Rempp Paul 
Published: April 2003

AbstractChain extension reactions involving α,β‐bifunctional precursor polymers and bifunctional coupling agents of low molecular weight were investigated both theoretically and experimentally. The number and weight molecular weight distributions were calculated, and computer simulations were performed, neglecting the weight of the coupling agent with respect to that of the precursor polymer. Examples of such chain extension reactions include the polycondensation of “living” α,β‐dicarbanionic polystyrene with 1,4‐bis(bromomethyl)benzene, and the reaction of poly(oxyethylene)glycol with a low‐molecular‐weight diisocyanate. The characterization of the resulting polymers yields results that are in satisfactory agreement with the theoretical expectation.
Water‐insoluble dextrans by grafting, 2. Reaction of dextrans with n‐alkyl chloroformates. Chemical and enzymatic hydrolysis
Authors: Chaves Manuel Sánchez , Arranz Félix 
Published: April 2003

AbstractThis work deals with the modification reaction of dextran with ethyl and butyl chloroformate using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analyses. The reaction rate was found to increase in the following order: N,N′‐dimethylaniline < pyridine < triethylamine. The presence of cyclic carbonates was observed when triethylamine was used as catalyst. A linear dependence of the reaction rate on polymer and pyridine concentrations and a more complex dependence on the n‐alkyl chloroformate concentration were found. Reaction rate and yield decrease with increasing amount of LiCl in the solvent medium and increase with increasing chain length of the n‐alkyl chloroformate. The activation energy was found to be 64 kJ/mol (15,3 kcal/mol). The equilibrium water content (EWC) values decreases progressively when either the content of carbonate groups or the side chain length increases. The hydrolysis in the heterogeneous phase showed that the time required for the polymer solubilization is dependent upon the nature of the carbonate groups, the temperature as well as the pH value of the medium. Dextranase was found to be inactive in the hydrolysis of water‐insoluble modified dextrans. However, the hydrolysis takes place when water‐soluble modified dextrans were used.
Copolymerization of monomethyl maleate and ‐fumarate with styrene
Authors: Rätzsch Manfred , Büttner Birgit , Steinert Volker 
Published: April 2003

AbstractThe copolymerization of monomethyl maleate (MMM) or monomethyl fumarate (MMF) with styrene is investigated. The dependence of the copolymerization rates on the composition of the monomer mixture and the monomer reactivity ratios r are determined. An identical structure of the MMM and MMF polymer radicals was found, that is the k21‐values of both copolymerization systems are equal (monomer 1 ≡ styrene; monomer 2 ≡ MMM or MMF). From this knowledge the difference of the copolymerization rates between MMM and MMF can be attributed to the k12‐values.
The effect of specific interactions on the sorption equilibrium in the polymer/mixed solvent system
Authors: Pouchlý Julius , Z̆ivný Antonín 
Published: April 2003

AbstractUsing the theory of association equilibria, equations are derived for preferential and total sorption into the coil for a ternary system containing inert liquid A, self‐associating liquid B and polymer C, capable of specific interactions with component B. Due to strong interactions, the assumption of random mixing is not valid for this system. In preceding work differences between experiment and prediction based on the classical Flory‐Huggins equation were formally described by the introduction of a ternary interaction term. For this particular system the ternary term may be interpreted as a consequence of the decrease in the entropy of mixing, caused by strong association of component B. On the contrary, if this component is bound to the polymer at the same time, the ternary term decreases. The equations derived in the paper lead to a reasonable fit with experimental data of the system benzene (A)/alcohol(B)/poly(methyl methacrylate)(C).
13C NMR study of O‐(2‐hydroxypropyl)cellulose
Authors: Kimura Keiichiro , Shigemura Takeo , Kubo Masao , Maru Yasumitsu 
Published: April 2003

AbstractThe proton‐decoupled signal of methyl carbons of O‐(2‐hydroxypropyl)cellulose (HPC) (1b, m ≥ 1) was found to be split into two peaks. The results of experiments on lanthanide shift and the dependence of the relative intensities of both peaks on the molecular weight of poly(oxypropylene) [poly(propylene oxide)] (PPO) indicated that the low‐field peak results from the terminal hydroxypropyl groups and the high‐field peak from the inside oxypropylene units. From the ratio between the intensities of the two peaks and the molar substitution (MS) (average number of oxypropylene units per anhydroglucose (AHG) unit), the degree of substitution (DS) (average number of hydroxyl groups substituted per AHG unit) was calculated. This new method could be applied to samples of low‐MS to which the conventional method based on the 1H NMR technique alone was inapplicable. From the analysis of 13C NMR spectra of HPC samples differing in MS, an authentic structural picuture of the HPC molecule could be proposed.
Etude des proprietés électro‐optiques des l'ADN par biréfringence électrique à faible champ, 3. Anisotropie optique et polarisabilité électrique
Authors: Marion Christian , Roux Bernard , Perrot Brigitte , Bernengo Jean‐Claude 
Published: April 2003

AbstractThe field dependence of the birefringence fraction corresponding to the well‐defined long relaxation mechanism was studied for DNA. A typical saturation curve was obtained and when analysed this phenomenon gave the parameter Δn3,s from which it was possible to calculate the electrical and optical polarizability anisotropies. The results were analyzed along the lines of recent theories and experimental data.
The influence of the penultimate chain element on monomer transfer in living polymerization
Authors: Pu Zhou , Yan Deyue , Tang Weifung 
Published: April 2003

AbstractThe influence of the penultimate chain element on the monomer transfer in living polymerization was treated according to Elias' kinetic scheme. The Laplace transformation and a graphic method are used to obtain the exact solution of the molecular weight distribution functions. The numerical results are discussed and compared with the molecular weight distribution curve for which a penultimate effect was not considered.
Studies on the water induced plasticization behavior of nylon 4. The influence of crystallinity and radiation crosslinking
Authors: Jin Xigao , Ellis Thomas S. , Karasz Frank E. 
Published: April 2003

AbstractThe influence of crystallinity and radiation crosslinking on the water induced depression of the glass transition temperature in Nylon 4 [poly(2‐pyrrolidone)] has been investigated by differential scanning calorimetry. Radiation crosslinking was effective in preventing exothermic events associated with crystallization during the measurement of the incremental change in heat capacity (ΔCp); a parameter necessary for the theoretical evaluation of the depressed glass transition temperature. ΔCp, when normalized to account for fractional crystallinity, was found to deviate substantially from a linear two phase relation. A simple three phase representation of morphology is proposed to account for this deviation, and assumptions have been made regarding the distribution of plasticizer, leading to good agreement between the theoretical and experimentally observed depressions of the glass transition temperature.