bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and properties of a polyelectrolyte complex consisting of the three materials. [2‐(diethylamino)ethyl]dextran hydrochloride, sodium dextran sulfate, and poly(styrene sulfonate)
Authors: Kikuchi Yasuo , Sasayama Shizuko 
Published: April 2003

Abstract[2‐(Diethylamino)ethyl]dextran hydrochloride (EA) was reacted with a mixture of sodium dextran sulfate (DS) and poly(styrene sulfonate) (NaSS) to form a novel water‐water precipitate, a so‐so polyelectrolyte complex (PEC), comprising three biomedical materials. The mole ratios of (DS + NaSS)/EA in PEC's prepared at higher [H+] were greater than at lower [H+] except for those PEC's prepared in 5% NaOH solution. IR, elemental analyses, solubility measurements, and blood clotting tests for PEC's revealed that the molecular structure of the various PEC's differed according to the [H+], order of mixing in solution, though all PEC's were prepared from the same starting materials. It appears that the degree of dissociation and the conformation of DS, NaSS, and EA change with [H+] and that a different neutralization reaction occured in terms of different order of mixing. Blood clotting tests were performed on PEC tablets. It was found that PEC's suppressed the coagulation of blood compared with glass.
Determination of network structure by extraction and random degradation, 2. Experimental results: Functionality, inhomogeneity and efficiency of crosslinking
Authors: Hoffmann Martin 
Published: April 2003

AbstractExperiments on networks crosslinked by peroxides show that the amount of extracted molecules as well as the time needed for a dissolution of a network during random degradation and the molecular mass“Relative molecular mass” (systematic IUPAC name) is shortened to “molecular mass” throughout this paper.
of high molecular mass degradation products may be used to determine previously inaccessible structural details, such as molecular mass of the network chains, weight fraction of chains with one free end, functionality of the crosslinks, and inhomogeneity of crosslinking, i.e. the amount, the diameter, and the concentration of crosslinking units of anomalously and strongly crosslinked regions. In crosslinking of polydienes, chain splitting is negligible, but the functionalities of the crosslinks are abnormally high for low peroxide concentrations, because the peroxide radicals may connect more than two chains by polymerization. A relatively high spatial inhomogeneity of the concentration of crosslinking units occurs with polybutadienes, presumably because the radicals of this polymer have especially long life‐times so that they can polymerize sequences of polyfunctional crosslinks via kinetic chains with transfer reactions. In crosslinking of polyisoprene the apparent efficiency of this peroxide is about 1,0 if one takes into account not only the number of crosslinks, but also that of loops, and if one neglects transfer. The efficiency of this peroxide is ≫ 1 in the crosslinking of polybutadiene, because of pronounced transfer reactions.
Polymères thiocarboxyliques, 2. Synthèse par modification de polymères préformés
Authors: Haraoubia Rachid , Gressier Jean‐Claude , Levesque Guy 
Published: April 2003

AbstractDithioester groups were introduced into linear or crosslinked polystyrenes by Friedel‐Crafts reaction with ClCH2Si(CH3)3/CS2 or with ethyl chlorodithioformate, as well as thioamide groups by reaction with ethoxycarbonyl isothiocyanate. Treatment of several copolymers of acrylonitrile with ethanethiol and hydrogen chloride and subsequently with H2S led to copolymers with dithioester and thioamide groups in the side chains without cyclization. Most of these reactions occur without crosslinking.
Oxydation photothermique d'élastomères de polyuréthannes thermoplastiques, 2. Influence de la longueur d'onde et des conditions d'irradiation sur le jaunissement des polyuréthannes à structure aromatique
Authors: Gardette Jean‐Luc , Lemaire Jacques 
Published: April 2003

AbstractThe detrimental yellowing of aromatic polyurethanes by irradiation may be accounted for by two mechanisms based on the formation of different photo‐products. The first is observed at short wave lengths and proceeds through a photo‐Fries type reaction; the second mechanism is observed at longer wave lengths and involves quinoidic structures derived from primary hydroperoxides. These two paths may be differentiated by incorporation of well‐known additives into the polymer or by selection of various irradiation wave lengths.
Anomale röntgenstreuung zur erforschung makromolekularer strukturen
Authors: Stuhrmann Heinrich B. 
Published: April 2003

AbstractThe possibilities of anomalous X‐ray scattering for the investigation of semi‐ or noncrystalline macromolecular structures are discussed on the grounds of the first successful measurements of anomalous scattering of iron in dissolved hemoglobin. As anomalous scattering of this kind of material is limited to the near vicinity of the X‐ray absorption edges, the use of synchrotron radiation appears to be obligatory. The anomalous dispersion of the atomic form factors slightly increases with the atomic number. Anomalous dispersion is nearly doubled when going from the K‐absorption edge to the LIII‐absorption edge and from there to the Mv‐ absorption edge. Therefore, the use of anomalous dispersion in the soft X‐ray region is quite promissing. With the planned extension of the spectral range accessible to X‐ray diffractometers from 3 Å to 6 Å, one would get hold of the anomalous scattering of very important elements in macromolecular structures, like phosphorus, sulfur, and chlorine.
Structural studies on the Escherichia coli type‐27 capsular polysaccharide
Authors: Chakraborty Ajit K. 
Published: April 2003

AbstractThe primary structure of the Escherichia coli serotype K‐27 capsular polysaccharide has been investigated. The capsular polysaccharide was isolated from Escherichia coli strain E56b, serotype 08:K27(A):H‐. Using methylation analysis, characterization of oligosaccharides obtained by partial acid hydrolysis and enzymic degradation, as well as 1H nuclear magnetic resonance, the primary structure of the K‐27 glycan has been elucidated. The polymer was found to consist of tetrasaccharide repeating units of the following structure:
Inhibition of thermal and thermooxidative degradation of polystyrene by polyconjugated polymers with anthracene repeating units
Authors: Schopov Ivan , Jossifov Christo 
Published: April 2003

AbstractIt was found that three polyconjugated polymers with anthrancene repeating units slow down the thermal and thermooxidative degradation of polystyrene. This effect is explained by charge transfer complex formation between the radicals formed during the degradation of polystyrene and the polyconjugated polymers as donors.
Immobilisation du complexe de nickel de l'histidine L(+) sur des supports macromoléculaires hydrophiles
Authors: Spassky Nicolas , Reix Michel , Sepulchre Marie‐Odile , Guetté Jean‐Paul 
Published: April 2003

AbstractN‐(4‐vinylbenzyl)‐L‐histidine (5) and the corresponding methyl ester were synthesized by reacting L‐histidine or L‐histidine methyl ester with 4‐formylstyrene. N‐(4‐vinylbenzyl)‐L‐histidine methyl ester was radically copolymerized with various amounts of 2‐hydroxyethyl methacrylate and ethylene dimethacrylate, leading to resins of different degrees of hydrophilicity and crosslinking. After saponification of the histidine ester groups, the resins were chelated with Ni2+ salt in order to be used as polymeric catalysts in enantioselective ester hydrolysis reactions.
Etude de la structure ramifiée du polyéthylène basse densité par viscosité et diffusion de la lumière de fractions issues de la chromatographie d'exclusion gpc
Authors: Hert Marius , Strazielle Claude 
Published: April 2003

AbstractFractions of high density polyethylene (PEhd) and low density polyethylene (PEld) obtained from gel permeation chromatography were studied by viscometry and light scattering. The variations of the intrinsic viscosity [η], the molecular weight M̄w, and the radius of gyration Rg for PEhd and PEld were compared with one another and the relationships [η] vs M and Rg vs. M for PEhd were established. The dependence of structural parameters g = (Rg2)branch/(Rg2)linear and g′ = [η]branch/[η]linear on the molecular weight was determined for three samples of PEld.
Liquid crystalline main chain polymers with highly flexible siloxane spacers
Authors: Aguilera Carlos , Bartulin Juan , Hisgen Bernd , Ringsdorf Helmut 
Published: April 2003

AbstractThe synthesis and the phase behaviour of liquid crystalline main chain polymers are described. In these poly‐ and copolyesters the mesogenic units are linked by highly flexible oligodimethylsiloxane spacers. The comparison of their phase behaviour with that of polyesters known from the literature shows that dimethylsiloxane spacers as a replacement for alkyl spacers are leading to a drastic decrease of the transition temperatures. Depending on the length of the spacer glass transitions as low as −111°C can be achieved. The widths of the liquid crystalline phases thereby are retained up to a spacerlength of 13 oxydimethylsilanediyl (dimethylsiloxane) units. The homopolyesters mainly show smectic phases. In contrast to this nematic phases are found for copolyesters in which either the spacerlength or the mesogenic unit was varied. In one case a nematic phase was found over a temperature range of 311°C.
On the molecular weight determination by vapour pressure osmometry, 4. Experimental proof of the deviation of MVPO from Mn
Authors: Marx‐Figini Marianne , Tagliabue Marcelo , Figini Rubén V. 
Published: April 2003

AbstractThe kind of molecular weight average MVPO resulting from vapour pressure osmometry (VPO) measurements on solutions of paucimolecular polymer mixtures of different compositions is studied with a Hewlett Packard Model 302 B. Recent theoretical calculations which predicted that MVPO > Mn are confirmed. The experimentally found quotient MVPOMn is between 1,04 and 1,26, being the greater, the greater is the polydispersity of the mixture, which is agreement with the former mathematical derivations.
Polymer conformation and NMR chemical shifts, 7. Conformational analysis of random copolymers
Authors: Sato Kota , Koinuma Hideomi , Hirai Hidefumi 
Published: April 2003

AbstractA method is developed for the conformational analysis of copolymers with randomly distributed stereo‐ and comonomer‐sequences. The conformational probabilities of dyad sequences constituting a random copolymer chain are calculated as a function of the copolymer composition which is derived from the monomer reactivity ratios and the comonomer feed ratio. The applicability of this method is verified in the conformational analyses of poly(methyl acrylate‐co‐styrene) and poly(methyl methacrylate‐co‐styrene). The calculation indicates that the conformational stabilities of dyad sequences are scarcely dependent on the copolymer composition in the former copolymer, whereas they are susceptible to the composition in the latter copolymer. This conformational behavior apparently reflects the geometrical difference between the copolymers: the former is composed of two mono‐substituted monomers and the latter of sterically nonequivalent monomers, viz. mono‐ and di‐substituted vinyl compounds. The composition‐dependences of 13C NMR chemical shifts of these copolymers are interpreted, based on the conformational calculation by this method.
Application of spin trapping technique to radical polymerization, 20. Vinyl polymerization initiated by triphenylboron
Authors: Sato Tsuneyuki , Fukumura Naoki , Otsu Takayuki 
Published: April 2003

AbstractTriphenylboron was found to serve as an effective radical initiator for vinyl monomers without any participation of oxygen. The polymerization of methyl methacrylate (MMA) initiated by triphenylboron was studied kinetically in acetonitrile. The over‐all activation energy of the polymerization was calculated to be 60,3 kJ/mol. The polymerization rate (Rp) can be expressed as follows: Rp = k (Triphenylboron)0,9[MMA]1,8. Spin trapping studies revealed formation of phenyl radicals by decomposition of triphenylboron in the absence of oxygen. Decomposition of triphenylboron in toluene yielded o‐, m‐, and p‐methylbiphenyls, the isomer ratio of which was close to that observed in the decomposition of benzoyl peroxide in toluene. Furthermore, an ethanol solution of triphenylboron was found to give a very stable boron centered radical. From these findings, the initiation mechanism for the polymerization is proposed and discussed.
Functional monomers and polymers, 103. Synthetic application of polystyrene‐bound chloropyrimidine and chloropurine as dehydrating and desulfhydrating reagents
Authors: Kondo Koichi , Murakami Mikio , Takemoto Kiichi 
Published: April 2003

AbstractPoly{1‐[4‐(4‐chloro‐2‐oxo‐1,2‐dihydropyrimidin‐1‐ylmethyl)phenyl]‐ethylene} (1b) was pre‐pared by condensation of chloromethylated polystyrene and uracil and subsequent reaction with POCl3, and used as dehydrating and desulfhydrating reagent for the preparation of hydro‐xamates, acid chlorides, nitriles, and lactones. Other types of polymeric reagents, poly{1‐[4‐(2,6‐dichloro‐4‐pyrimidinylaminomethyl)phenyl]ethylene} (4) and poly{1‐[4‐(6‐chloro‐9(7)‐puri‐nylmethyl)phenyl]ethylene} (5) were prepared analogously. It was found that 1 b shows the highest activity in these syntheses as compared with the other polymeric reagents 4 and 5.
Asymmetric selective oligomerization of chloromethyloxirane
Authors: Tezuka Yasuyuki , Ishimori Michihiro , Tsuruta Teiji 
Published: April 2003

AbstractChloromethyloxirane (CMO) undergoes an asymmetric selective oligomerization with a binary catalyst system comprised of triethylaluminium and an optically active cobalt complex, N,N'‐disalicylidene‐(1 R)‐1,2‐cyclohexanediyldiaminatocobalt(II). A series of optically active oligomers obtained were isolated and characterized. Two kinds of linear oligomers were produced with respect to the end groups, namely epoxy‐ and halohydrin‐ended oligomers. A mechanism for the selective formation of linear oligomers by the present catalyst system is proposed.
Copolymerization of vinyl chloride and methyl acrylate catalyzed by ethylaluminium compounds
Authors: Florjańczyk Zbigniew , Kuran Witold , Sitkowska Jadwiga 
Published: April 2003

AbstractThe copolymerization of vinyl chloride (VC) and methyl acrylate (MA) in the presence of ethylaluminium compounds (C2H5AlCl2, (C2H5)2AlCl, and (C2H5)3Al) at low ethylaluminium compound (EAC)/MA mole ratios was investigated. An alternating copolymer was produced in this reaction when an excess of VC in the initial monomer feed was used. The addition of dibenzoyl peroxide (BPO) to the systems containing EAC resulted in an increase of the alternating copolymer yield. In polymerization systems containing EAC resulted in an increase of the alternating copolymer yield. In polymerization systems containing EAC combined with VOCl3 an enhancement of the alternating copolymer yield and formation of VC‐rich copolymers were observed. In the polymerization system with (C2H5)3AlVOCl3 a VC‐rich copolymer was the main product. It was concluded that VC‐rich copolymers are formed in the random radical copolymerization which occurs when most of EAC is complexed by the alternating copolymer chain. The structure of alternating and VC‐rich copolymers was studied in detail by means of 13C NMR spectroscopy.
Anionic and radical polymerization of p‐triphenyl‐ and p‐tributylgermyl‐styrenes
Authors: Hirao Akira , Shiraishi Yoshinobu , Martinez Francisco , Phung Hoang Minh , Nakahama Seiichi , Yamazaki Noboru 
Published: April 2003

AbstractAnionic polymerization of p‐triphenylgermylstyrene (1a) and p‐tributylgermylstyrene (1b) were investigated under high vacuum conditions (≈10−6 mbar). Both 1a and 1b were readily polymerized with sodium naphthalide, potassium naphthalide, or α‐methylstyrylsodium oligomers to form “living polymers”. The addition of α‐methylstyrene to these living systems gave the triblock copolymer, poly(α‐methylstyrene‐b‐p‐triphenylgermylstyrene‐b‐α‐methylstyrene). Both monomers were also polymerized radically with AIBN as initiator. Some physical properties of the resulting polymers were examined.
Electron transfer process in the microdomains of poly(sodium styrenesulfonate)‐poly(alkylene viologen) complexes
Authors: Ohno Hiroyuki , Hosoda Naohiro , Tsuchida Eishun 
Published: April 2003

AbstractThe electron transfer process in the microdomain of a polyion complex composed of poly(sodium styrenesulfonate), (syst. name: poly[sodium 1‐(4‐sulfonatophenyl)ethylene]), and poly(alkylene viologen)s 1 with 3 to 10 methylene groups between two adjacent viologen units was analyzed by means of voltammetry with a rotating disc electrode. Although the stability of 1 on the graphite electrode was improved by the formation of a polyion complex with poly(sodium styrenesulfonate), a smaller surface charge was observed in the polyion complex as compared with the electrode coated with poly(alkylene viologen) alone. Since the migration of the counter ion was clarified to be indispensable for the electron transfer in this case, the microdomain of polyion complexes should be formed by tightly‐shrunk polyelectrolyte chains. Furthermore, the electron transfer in the microdomain of the polyion complex is hardly detected, when the electrode is coated with an excess of the complex. The electron transfer strongly depended on the average distance between two adjacent redox sites in the matrix. These matrixes were suggested to be controlled by the subtle balance of hydrophobicity and charge density of 1.
Anwendung des komplexmodells zur beschreibung der bruttopolymerisationsgeschwindigkeit bei copolymerisationen mit ausgeprägter beteiligung von EDA‐komplexen
Authors: Braun Dietrich , Czerwinski Wojciech 
Published: April 2003

AbstractEquations are derived for free radical‐initiated copolymerization of monomers with significant charge‐transfer interactions, which describe the overall rate of polymerization. Both the simplified and the complete steady‐state principle has been applied. The equations obtained were examined with literature data for the monomer systems styrene/maleic anhydride and styrene/acrylonitrile. It is seen from the calculations that a nearly quantitative interpretation of experimental results including a wide range of monomer concentrations is feasible by means of the complete rate equation. In contrast, the simplified model does not even permit a qualitative interpretation of the experimental results.
Polymerization of acrylonitrile initiated by the redox system manganese (III) acetate/ethylene glycol
Authors: Samal Narayan C. , Mishra Ranu , Senapati Manjushree , Nayak Nrusingh C. , Patnaik Lalit N. , Rout Mahendra K. 
Published: April 2003

AbstractThe kinetics of polymerization of acrylonitrile initiated by the redox system manganese (III) acetate/ethylene glycol was studied in aqueous sulfuric acid medium in the temperature range from 30 to 40°C. The effect of varying the concentrations of monomer (M), acetic acid, and sulfuric acid and the addition of some electrolytes on the rate of polymerization (Rp) was investigated. Based on the experimental observations of the dependence of (Rp) on various parameters, a suitable kinetic scheme could be proposed. The plot of Rp2[M]2 vs. [M] was found to be linear, a striking general phenomenon observed for all the substrates we have studied in this laboratory.
UV‐photometrische analyse kationisch erzeugter polystyrole, 1. Nachweis des covalenten einbaus von acylresten aus aromatischen acylperchloraten
Authors: Kämmerer Hermann , Seyed‐Mozaffari Ahmad 
Published: April 2003

AbstractPolymerization of styrene was found not to take place with 4‐phenylazobenzoyl perchlorate in benzene solution. 4‐Biphenylcarbonyl perchlorate, however, initiates styrene polymerization under the same conditions leading to a product not containing acyl groups as indicated by UV spectroscopic analysis. 4‐Phenylazobenzoyl, 2‐naphthoyl, and 9,10‐dioxo‐2‐anthracenecarbonyl perchlorate (6b, 7b, and 8b), prepared form silver perchlorate and the corresponding acyl chlorides 6a, 7a, and 8a in styrene, were found to initiate the polymerization of styrene under anhydrous conditions at −25°C in the dark. By UV spectroscopy it could be shown that the resulting polymers contain covalently bound acyl groups. Their absorption bands correspond to those of model compounds 6c, 7c, 8c, and 7d, respectively. IR spectra of mixtures of polystyrene with model compounds show that incorporation of acyl groups can be detected by their carbonyl absorption in the region of 1680 – 1700 Cm−1 only in polystyrenes having molar masses <50 000.
Enthalpy of dilution of polystyrene/diethyl ketone
Authors: Fujihara Ichiro , Sakuta Takashi , Kagemoto Akihiro 
Published: April 2003

AbstractThe enthalpy of dilution at 298,15 K was measured for the system polystyrene/diethyl ketone with a recently constructed flow type microcalorimeter, and the heat interaction parameter, χh, was estimated. It was found that χh, for this system is very small and negative and that its absolute value decreases with increasing molecular weight of the polymer. By comparison with other ketone systems measured previously, it was found that a polar solvent makes the polystyrene molecule energetically stable in solution.
Acidolytic polymerization of N‐methyldodecanelactam
Authors: Puffr Rudolf , Tuzar Zdeněk , Mrkvičková Libuše , Šebenda Jan 
Published: April 2003

AbstractThe polymerization rate of 1‐methylazacyclotridecan‐2‐one (N‐methyldodecanelactam) (1) initiated with dodecanoic acid (2) can be described within the whole range of conversions in terms of the simple relation In ([1]0/[1]) = k[2]0t, in spite of the complexity of the overall reaction scheme. The rate constants (k) determined for 240, 260, and 280°C are 0,32, 1,21, and 3,4 kg · mol−1 h−1, respectively, and the constants of the Arrhenius equation are A = 6,6 · 1013kg · mol−1 h−1, E = 140 kJ · mol−1. The resulting poly(N‐methyldodecaneamide) (3) is a semicrystalline polymer (m.p. 65°C), soluble in polar organic solvents. The following constants of the Mark‐Houwink equation were determined for solutions of this polyamide: for 5000 < M̄w < 150 000 g · mol−1 at 25°C in THF (2‐propanol), K = 0,124 (0,161) cm3 · g−1, a = 0,59 (0,56); for 5 000 < M̄w < 80 000 g · mol−1 at ⊖‐temperature = 30,5°C in 1,4‐dioxane, K = 0,215 cm3 · g−1, a = 0,50. Analyses of molar masses, both theoretical and experimental (light‐scattering, GPC, osmometry, end groups), indicate that at the polymerization temperature of 280°C side reactions already take place, reflected in random cleavage and in branching of chains.
Synthesis and characterization of some aliphatic polyamides containing 4,4′‐azodiphenylene units
Authors: Chidambaram S. , Nanjan M. J. 
Published: April 2003

AbstractPolyamides containing azo groups were prepared by the phosphorylation method from 4,4′‐diaminoazobenzene and malonic, succinic, glutaric, adipic, azelaic, sebacic, or chlorosuccinic acid. The polymers were characterized by their viscosity and solubility, and by UV‐visible and IR spectroscopy, TG, and DTA.
Thermomechanical study of oriented poly(ethylene terephthalate): Effect of homogeneous deformation and moisture absorption
Authors: Rietsch François 
Published: April 2003

AbstractThe homogeneous drawing behaviour of poly(ethylene terephthalate) (PET) at T=80°C has been studied by glass transition temperature analysis. At the first stage of homogeneous drawing (draw ratios λp up to 3,0), the results as compared to the statistical Gibbs‐DiMarzio theory, suggest that the rate of the segmental motion increases with the draw ratio. In a second zone of moderate and high draw ratios (λp > 3) a non‐negligible loss‐entropy component occurs as predicted by the Gibbs‐DiMarzio theory of isovolume strained network chains. The moisture absorption at room temperature causes a decrease in glass transition temperature which is more pronounced at higher draw ratios.