bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phenyl‐2,4,6‐trimethylbenzoylphosphinates as water‐soluble photoinitiators. Generation and reactivity of OṖ(C6H5)(O−) radical anions
Authors: Majima Tetsuro , Schnabel Wolfram , Weber Wilhelm 
Published: April 2003

AbstractLithium‐ and magnesium phenyl‐2,4,6‐trimethylbenzoylphosphinates (TMPPL and TMPPM) are effective water‐soluble photoinitiators for the free‐radical polymerization of appropriate monomers such as acrylamide (AA) and methacrylamide (MAA) in aqueous solution. They are also capable of initiating the polymerization of other olefinic compounds such as styrene (St), methyl methacrylate (MMA) or acrylonitrile (AN) in water‐containing solvent mixtures such as 1:1 water‐acetonitrile mixtures. This is due to the fact that TMPPL and TMPPM undergo α‐scission with a rather high quantum yield (ϕ(α) ≈ 0,35) resulting in the formation of 2,4,6‐trimethylbenzoyl radicals and OṖ (C6H5)(O−) radical anions. The latter are very reactive toward olefinic monomers. Bimolecular rate constants kR+M/(L/(mol · s)) were determined by flash photolysis at room temperature, e. g. in neat water: 3,8 · 108 (MAA), 2,2 · 108 (AA), and in H2O/CH3CN (1:1, v/v): 1,8 · 107 (St), 1,2 · 108 (MMA), 8,4 · 107 (AN).
Whiskers of poly(4‐hydroxybenzoic acid) — preparative aspects
Authors: Kricheldorf Hans R. , Ruhser Frank , Schwarz Gert , Adebahr Thorsten 
Published: April 2003

AbstractPolycondensation of 4‐acetoxybenzoic acid (4‐ABA) at 300–400°C involves side reactions yielding a difficult to be hydrolyzed fraction of modified poly(4‐hydroxybenzoic acid) (poly‐HBA). Such side reactions are the formation of diphenyl ether groups, Fries‐rearrangement, formation of ketene or acetic anhydride and, possibly, isomerization to 3‐hydroxybenzoic acid. These by‐products not only influence the properties of poly‐HBA, they also affect the crystal growth of needle‐like crystals (whiskers). Even small amounts of free 4‐hydroxybenzoic acid poison the crystal growth of whiskers. The reaction conditions required for their preparation were optimized at 400°C. Fibrcus whiskers with lengths ≥ 100 μm and length/diameter ratios > 50 were only obtained at low monomer concentrations (≤0,05 mol/L). It is demonstrated by differential scanning calorimetry, wide‐angle X‐ray scattering and NMR spectroscopy that these whiskers are the chemically and physically most perfect form of poly‐HBA.
Polymers of carbonic acid, 6. Polymerization of trimethylene carbonate (1,3‐dioxan‐2‐one) with complexation catalysts
Authors: Kricheldorf Hans R. , Jenssen Jörg , Kreiser‐Saunders Ingrid 
Published: April 2003

AbstractNumerous bulk polymerizations of trimethylene carbonate (1,3‐dioxan‐2‐one, 2) were conducted at 90, 120 and 150°C. Tributyltin methoxide, tributyltin acetate, dibutyltin dibromide, tin(II) 2‐ethylhexanotate, bismuth(III) 2‐ethylhexanoate and zinc stearate were used as initiators. On the basis of GPC measurements with universal calibration, weight‐average molecular weights up to approx. 22000 were found. The chemical structure of the resulting polycarbonates was examined by elemental analyses and 1H NMR spectroscopy. In contrast to similar polymerizations of ethylene carbonate, either groups were never found. However, all polycarbonates contain a CH2OH end‐group. Furthermore, methylcarbonate, acetate, 2‐ethylhexanoate or stearate end‐groups were found. Cyclic oligomers were not detectable in the gel‐permeation chromatograms of reaction mixtures. IR spectra indicate complexation of the carbonyl group by the initiators. The reaction mechanism is discussed.
Mechanical behaviour of liquid‐crystalline polymers and their networks
Authors: Pakula Tadeusz , Zentel Rudolf 
Published: April 2003

AbstractLiquid‐crystalline polymers with mesogenic groups in the main chain and side chains as well as their networks are studied by the dynamic mechanical method. The homopolymers are compared with chiral copolymers of a similar chemical structure. Mechanical relaxation transitions are correlated with transitions observed by differential scanning calorimetry. In the nematic phase a flow‐thinning effect has been observed both for uncrosslinked polymers and for crosslinked systems. A possible molecular interpretation of the observed mechanical behaviour is discussed.
Polymers from multifunctional isocyanates, 6. Thermotropic di‐ and oligo(urethane)s from novel triad diisocyanatodiesters
Authors: Mormann Werner , Benadda Saria 
Published: April 2003

AbstractThe first examples of triad diisocyanatodiesters with a substituent in the central aromatic ring, namely methyl‐, trimethyl‐, tert‐butyl‐, and phenyl‐substituted 1,4‐phenylene bis(4‐isocyanato‐benzoates), and bis(4‐isocyanatophenyl) trans‐1,4‐cyclohexanedicarboxylate are described. The diisocyanatodiesters melt in the range of 160°C, give nematic mesophases and have a clearing transition above 300°C except for the phenyl‐substituted diisocyanate which exhibits a monotropic mesophase. Due to the more favourable aspect ratio of the mesogens thermotropic diurethanes were obtained by reaction with butanol and oligomeric thermotropic polyurethanes resulted from the reaction with butanol and diethylene glycol, triethylene glycol, or 3‐methyl‐1,5‐pentanediol. The phase behaviour of the urethanes in relation to their structure is discussed. The thermal stability of the urethanes is limited by the occurrance of urethane cleavage.
Properties of poly[N‐2‐(methyacryloyloxy)ethyl‐N,N‐dimethyl‐N‐3‐sulfopropylammonium betaine] in dilute solution
Authors: Huglin Malcolm B. , Radwan Mostafa A. 
Published: April 2003

AbstractPoly[N‐2‐(methacryloyloxy)ethyl‐N,N‐dimethyl‐N‐3‐sulfopropylammonium betaine] (1) which is an interesting polyzwitterion polymer by virtue of its “antipolyelectrolyte solution behaviour” has been prepared by free‐radical initiated polymerization in aqueous solution. Isothermal fractionation was conducted at 294 K employing formamide as solvent and acetone as precipitant. Twelve fractions covering a wide range of weight‐average molecular weight (215 000 ≤ M̄w ≤ 2 070 000) were used to characterise the polymer by light scattering, membrane osmometry and viscosity measurements. The Mark‐Houwink equations, established for 1 in two good solvents, 2,2,2‐trifluoroethanol (TFE) and 1,0 M aqueous NaCl solution, show that the polymer has a random coil configuration and that TFE is a thermodynamically better solvent than 1,0 M aqueous NaCl solution. The random coil configuration of 1 in TFE was confirmed from the dependence of the polymer dimensions on molecular weight.
Synthesis of poly(methyl methacrylate) macromonomers with phenolic functionality by group transfer polymerization and their use in polycondensation reactions
Authors: Heitz Thomas , Webster Owen W. 
Published: April 2003

AbstractMethyl 1‐trimethylsiloxy‐2‐[2,5‐bis(trimethylsiloxy)phenyl]vinyl ether (6) was used as the initiator for the group transfer polymerization (GTP) of methyl methacrylate (MMA) to give macromonomers with aromatic hydroxyl functions. Quantitative removal of the silyl‐protective groups was achieved by acidic or fluoride‐catalyzed cleavage to give the deprotected macromonomer 9. The reactivity of this macromonomer in polycondensation reactions was shown by the synthesis of a liquid‐crystalline main‐chain polyester with poly(methyl methacrylate) (PMMA) side chains (PES‐graft‐PMMA) (15) and a 4,4′‐isopropylidenediphenol‐based polycarbonate (PC‐graft‐PMMA) (19).
Living cationic polymerization of isobutyl vinyl ether with hydrogen iodide/metal acetylacetonate as initiating system
Authors: Sawamoto Mitsuo , Kojima Kazushige , Higashimura Toshinobu 
Published: April 2003

AbstractLiving cationic polymerization of isobutyl vinyl ether (IBVE) was achieved with hydrogen iodide/metal acetylacetonate [HI/M(acac)n] as initiating systems at −40°C in toluene or dichloromethane; the suitable M(acac)n complexes turned out to include Zn(acac)2, Fe(acac)3, and Al(acac)3. Thus, the number‐average molecular weights (M̄n) of the polymers increased proportionally to the monomer conversion, were regulated by the feed ratio of monomer to hydrogen iodide ([M]0/[HI]0), and were in good agreement with the calculated values on the assumption that one living polymer per molecule of hydrogen iodide is formed, while the molecular‐weight distributions of the polymers remained fairly narrow (M̄w/M̄n ≤ 1,2). An increasing concentration of M(acac)n accelerated the polymerization but did not influence the M̄n of the living polymers, thus indicating that the metal acetylacetonates serve as activators for the growing end derived from hydrogen iodide. When Mg(acac)2, and Sn(acac)4 were employed as M(acac)n with hydrogen iodide, polymerization hardly occurred at −40°C in dichloromethane.
Nematic elastomers, 1. Effect of the spacer length on the mechanical coupling between network anisotropy and nematic order
Authors: Kaufhold Wolfgang , Finkelmann Heino , Brand Helmut R. 
Published: April 2003

AbstractThe influence of the spacer length was investigated for the correlation between the network anisotropy and the order parameter of the mesogenic units. Stress‐optical measurements show that a closer coupling of the mesogenic moieties to the polymer backbone results in an increased interaction between the mechanical field and the mesogenic groups. The correlation between the phase transformation temperature TNI and the mechanical stress σ is represented using both, our experimental measurements and the derivation from the Landau‐de Gennes (LDG) formulation. From our results, it is possible, for the first time, to estimate the cross‐coupling coefficient U between the order parameter and the strain of a nematic elastomer. The analysis of the elastic properties of the elastomers suggests that non‐linear coefficients might become important to obtain quantitative agreement between theory and experiment.
Modification of membrane surfaces by plasma deposition of thin fluorocarbon films without affecting bulk properties
Authors: Clarotti Giorgio , Aoumar Abdallah Ait Ben , Schué François , Sledz Joseph , Geckeler Kurt Ernst , Flösch Dietmar , Orsetti André 
Published: April 2003

AbstractThe deposition of films from an argon plasma containing a mixture of ethylene oxide or hydrogen and perfluorohexane was tried to obtain very hydrophobic, less hydrophobic and intermediate coatings. This paper studies more extensively the deposition of a thin coating from a perfluorohexane and hydrogen plasma on polysulfone and polyhydroxybutyrate membranes to optimize their surface properties without affecting their filtering properties. The plasma deposition of smooth and very hydrophobic fluorocarbon coatings seems to increase the bio‐ and hemocompatibility of poorly biocompatible membranes. The treated substrates were characterized by measuring the mass variations, surface profilometry and contact angle measurements, as well as scanning electron microscopy and electron spectroscopy for chemical analysis.
13C NMR analysis of α‐olefins copolymers with 1,3‐butadiene obtained with zirconocenes/methylalumoxane catalysts
Authors: Galimberti Maurizio , Albizzati Enrico , Abis Luigi , Bacchilega Giancarlo 
Published: April 2003

AbstractEthylene copolymers with propene and/or 1,3‐butadiene were obtained using bis(η5‐cyclopentadienyl)zirconium dichloride (1) or ethylenebis[1‐3a, 7a‐η‐(4,5,6,7‐tetrahydro)‐1‐indenyl]zirconium dichloride (2) and methylalumoxane as catalytic systems. A detailed 13C NMR analysis of the copolymers was performed. The resonances in the olefinic region of the terpolymers were assigned to ethylene/butadiene/ethylene and propene/butadiene/ethylene sequences while the butadiene/propene sequence was ruled out. Analogously, no polymers were obtained from the polymerization of propene in the presence of 1,3‐butadiene. It is thus shown that the conjugated diene is an inhibitor for the polymerization of α‐olefins. The presence of trans‐1,2‐cyclopentane rings was detected both in the ethylene/butadiene copolymers and in the ethylene/propene/butadiene terpolymers. A different behaviour of the two catalysts was observed.
Synthesis and characterization of dextran radiocontrast carriers, 1. Ether methylamide derivatives
Authors: Paris Dominique , Meyer Dominique , Nigretto Jean Maxime 
Published: April 2003

AbstractThe synthesis of dextran radiocontrast carriers was undertaken to obtain derivatives expected to have slow and controlled biodegradation as well as slow extravascular diffusion features. The results presented here particularly concern derivatives including a methylamide spacer, prepared by condensation of the amine function of the contrast product with carboxymethylated dextran (CMD). The effect of various coupling reagents on the final yields is disucssed. Concerning the macromolecular features, all the synthesized products were characterized by acid‐base titration, elemental analysis, flame photometry, spectroscopic determinations and gel‐permeation chromatography. GPC showed that the carboxymethylation of dextran leads to some reticulation (doubling the molecular weights), whereas the coupling of CMD with the contrast compound does not alter the molecular weight and the polydispersity index of the products appreciably.
Chromophoric poly(vinyl alcohol derivative)s, 1. Synthesis and spectroscopical characterization of some poly(vinyl alcohol)s with alkoxyazobenzenecarbonyl substituents
Authors: Janietz Dietmar , Bauer Monika 
Published: April 2003

AbstractThe synthesis of new poly[(vinyl 4′‐alkoxyazobenzene‐4‐carboxylate)‐co‐(vinyl alcohol)]s 4a–c by Einhorn esterification of poly(vinyl alcohol) with 4′‐alkoxyazobenzene‐4‐carbonyl chlorides 3a–c prepared in two steps from 4′‐hydroxyazobenzene‐4‐carboxylic acid (1) is described. The degree of esterification is found to be about 85 mol‐%. Infrared, 1H and 13C nuclear magnetic resonance and ultraviolet spectroscopical data of the obtained polymers are determined.
Membrane of (polystyrene‐block‐polybutadiene‐block‐polystyrene)‐graft‐poly(2‐vinylpyridine) complexed with cobalt‐containing Schiff's bases for oxygen permeation
Authors: Hsiue Ging‐Ho , Yang Jen‐Ming 
Published: April 2003

AbstractA study of the complex formation of (polystyrene‐block‐polybutadiene‐block‐polystyrene)‐graft‐poly(2‐vinylpyridine) (SBS‐graft‐VP) graft copolymers with a cobalt‐containing Schiff's base (1) in chloroform solution is here reported. The facilitated transport of molecular oxygen in SBS‐graft‐VP membranes containing various cobalt‐containing Schiff's bases as fixed carriers of oxygen is studied including oxygen permeability in SBS‐graft‐VP membranes and oxygen‐binding ability to a cobalt‐containing Schiff's base. Due to the reversible absorption of oxygen to SBS‐graft‐(VP‐1), the permeation of oxygen is remarkable for the lower upstream pressure, which can be explained by a dual mode.
Microstructure determination of acrylonitrile/butyl methacrylate copolymers using 13C NMR spectroscopy
Authors: Kapur Gurpreet Singh , Brar Ajaib Singh 
Published: April 2003

AbstractAcrylonitrile/butyl methacrylate (A/B) copolymers were prepared in bulk with different comonomer feed ratios. The copolymer composition obtained from the total nitrogen content was used for calculating the reactivity ratios. Information about sequence distributions was obtained from 13C NMR spectroscopy. The relative amounts of A‐ and B‐centred triads were evaluated by using nitrile (CN) and carbonyl (CO) carbon resonances, respectively, and have been found to be in a good agreement with those expected theoretically.
Modification au deuxième degré de polymères époxydés, 3. Fixation de l'acide α‐naphtylacétique sur polyisoprène‐1,4 époxydé. Etude sur molécule modèle
Authors: Soutif Jean‐Claude , Klinpituksa Pairote , Brosse Jean‐Claude 
Published: April 2003

AbstractThe reaction of α‐naphthylacetic acid (1) (a plant growth stimulator) with 4,5‐epoxy‐4‐methyloctane (2) which reproduces the constitutional unit of epoxidized 1,4‐polyisoprene was studied. The rate of addition of the acid to the oxirane ring of 2 in chloroform with the tetramethylammonium salt of the acid 1 as catalyst increases with temperature, time, and concentration of the reagents.
Compatibility of tetramethyl polycarbonate and random poly(styrene‐co‐methyl methacrylate)s
Authors: Yu Dan , Hellmann Edit H. , Hellmann Gœtz P. 
Published: April 2003

AbstractPhase diagrams and concentration fluctations of blends of tetramethyl polycarbonate (TMPC)Polycarbonate of 2,2′,6,6′‐tetramethyl‐4,4′‐isopropylidenediphenol (tetramethyl derivative of bisphenol A).
and random copolymers P(SxMMA1−x) of styrene and methyl methacrylate were analyzed, using cast films and dry films. Phase separation was detected by light microscopy, DSC and small‐angle neutron scattering. Neutron scattering was also used to measure the structure of fluctuations in one‐phase as well as two‐phase states. The merits and problems of the various methods are discussed. Blends TMPC/P(SxMMA1−x) have high‐temperature miscibility gaps at x > 0,5. The copolymers interact non‐ideally, in a manner that had been observed before in their blends with PS and PMMA. An equation based on the classical theory but allowing diad effects describes the interaction parameters fairly well. It was used to calculate the interaction parameter of the immiscible homopolymer blend TMPC/PMMA which was also determined from the miscibility gap of a ternary blend TMPC/PMMA/P(SxMMA1−x).
Electroinitiated cationic polymerization of ε‐caprolactone using sacrificial anodes
Authors: Pierre Gérard , Limosin Danièle , Djelali Nacer‐Eddine 
Published: April 2003

AbstractThe polymerization of ϵ‐caprolactone is carried out with metallic cationic initiators generated electrochemically. V, Ti, Cr, Al and Hg cations gave rise to polymers with molecular weights in the range 1 000–13 000. Better yields and higher degrees of polymerization are obtained in the presence of [SbF6]− and [ClO4]− as anion of the supporting electrolyte, which is in accordance with the stability and the poor nucleophilicity of these anions.
Crosslinked polyethylene/polypropene blends, 1. Formation of insoluble parts, crystallization and melting
Authors: Chodák Ivan , Janigová Ivica , Romanov Andrej 
Published: April 2003

AbstractCrosslinked blends of low density polyethylene/isotactic polypropene (LDPE/iPP) were studied over the whole composition range. The degree of crosslinking was determined from the gel content and the degree of swelling. In the presence of a coagent an efficient crosslinking of polypropene can be observed in blends whereas in the absence of the coagent only the PE component is crosslinked.Thermal characterization of the blends by differential scanning calorimetry (DSC), i.e. heat of fusion, melting and crystallization temperatures suggest that the crosslinking results in the formation of a structure with molecules of both components being mutually connected. A two‐phase structure is still maintained and crosslinked molecules of polypropene (PP) and polyethylene (PE) are found at the interface.The effect of crosslinking on the rate of crystallization is different for PE and PP. This phenomenon is explained by the superposition of the influence of crosslinking on the rate of crystal growth and nucleation.
Propriétés rhéologiques à l'état fondu de mélanges binaires de polyéthylène et de polybutène‐1
Authors: Deri Fawaz , Lallam Abdelaziz 
Published: April 2003

AbstractThe dynamic rheological study on a series of binary blends obtained from low‐density polyethylene and poly(1‐butene) was carried out. From our results we can propose an analogical pattern which is able to simulate the rheological behaviour of the blend in the melt state. We have calculated the different parameters of the model and their variations with temperature, composition, mixing and frequency. We have demonstrated that:

The viscosity η0 and the mean relaxation time τ0 decrease with increasing temperature, while the parameter h of the distribution of relaxation times remains independant of the temperature.
Kneading operation gives rise to a drop of the τ0, η0 and h values compared to those products which have not been kneaded.
The viscosity η0 is the weighted sum of the blend components.
The viscosity η0 of the blend is a function of the molecular weight.
External silane donors in Ziegler‐Natta catalysis. An approach to the optimum structure of the donor
Authors: Härkönen Mika , Seppälä Jukka V. 
Published: April 2003

AbstractOur earlier work about alkoxysilanes as external donors in high‐activity Ziegler‐Natta catalysts is broadened with studies on the performance of some other oxygen‐containing silane compounds and with some studies on the effect of the structure of the hydrocarbon part of the alkoxysilane compounds: There are new informations about the optimum structure of an external silane‐type donor. The alkoxy group proved to be the best electron‐donating group, whereas the other oxygen‐containing electron‐donating groups tested worked less effectively. In some structures the oxygen atoms were sterically too hindered for effective deactivation. Some increase in the isotacticity was nevertheless observed even with the poor performance donors, which indicates that there could be a population of active centres that are very easy to deactivate. All the para‐substituted alkoxy phenyl silane donors tested gave polypropene with high isotacticity and activity. Therefore, we conclude that the nature of the substituent does not markedly affect the performance of the donor — at least as long as the substituent has not a sterically free electron‐donating group.
An investigation into the nature of the electrochemical and surface properties of polyacrylamides and a study of their adsorption onto the surface of papermaking woodpulps using alternating‐current polarography
Authors: Petzold James C. , Herrington Thelma M. 
Published: April 2003

AbstractA cationic polyacrylamide was examined using polarography, constant potential coulometry, photon correlation spectroscopy, electrocapillarity and potentiometric titrimetry. A polarographic response was found in differential‐pulse polarography (DPP), direct‐current and Kalousek modes at −1,7 V versus a silver/silver chloride electrode. In each case the magnitude of the response was a function of polymer concentration. However, it is thought that the response is not due to the polymer itself but impurities found with it. These were found to have a pK of 4,75. The polymer appears to develop a more open structure in LiCl solution (<0,0013 mol/L). The unwashed polymer was found to greatly increase the interfacial tension at the mercury drop, but this effect was considerably reduced on washing the polymer in 70% acetone solution. Hydrolysis of the polymer seems to occur at pH 10. The suppression of the negative tensammetric peak of poly(ethylene glycol) (PEG200) by a range of cationic polyacrylamides was used for their analysis in the determination of their adsorption onto the surface of woodpulp. The adsorption was found to be a function of both their cationicity and mean molar mass. The rate of hemicellulose desorption from the woodpulp appears to be pH dependent. The impurity is thought to be mainly adipamic acidSystematic name: 5‐carbamoylpentanoic acid.
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