bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and 13C NMR spectra of model compounds for poly(4‐bromostyrene)
Authors: Nguyên‐Trân Tuyet Mai , Lauprêtre Françoise , Jasse Bruno 
Published: April 2003

AbstractThe preparations of 2,4‐bis(4‐bromophenyl)pentane (1b) and 2,4,6‐tris(4‐bromophenyl)heptane (2b) are described. The study of the different isomers of 1b and 2b by 13C NMR allows a comparison of the various configurational sequences of these compounds in terms of their chemical shifts. Methyl, methylene, and aromatic C1 carbons of 1b and 2b could be deduced from the values obtained from corresponding polystyrene model compounds by a mere translation. From the aromatic C1 chemical shifts it was possible to propose an assignment of the corresponding triads of poly(4‐bromostyrene).
Thermodynamics of hydrogen bonding polymer‐solute interactions by inverse gas chromatography
Authors: DiPaola‐Baranyi Giuseppa , Guillet James E. , Jeberien Hans‐Edwin , Klein Joachim 
Published: April 2003

AbstractThe gaschromatographic retention behaviour of a series of solutes with potential hydrogen bonding activity has been studied, using polyethylene, poly(ethylene‐vinyl acetate), poly(vinyl acetate), and poly(ethylene glycol) as stationary phases. Measurements were performed at various temperatures above the melting point and/or glass transition temperature of the polymers and the slopes of the ln V versus 1/T‐functions (where V is the specific retention volume) were used to calculate partial molar heats of solution (ΔHs). Correspondingly, the temperature dependence of the activity coefficient can be used to calculate partial molar heats of mixing (ΔH̄1infin;) of the solute at infinite dilution in the polymer. Based on a “homomorph” concept with the inherent assumption of additive group contributions to the total interaction energy, hydrogen bonding energies of polymer‐solute systems could be separated using polyethylene on one hand and appropriate model solutes on the other hand as reference materials.
Effect of UV light on the system styrene/maleic anhydride at −196°C
Authors: Bartoň Jaroslav , Capek Ignác , Tiňo Jozef 
Published: April 2003

AbstractThe effect of UV light (λ > 300 nm) on the system styrene/maleic anhydride/solvent (acetone or chloroform) in the presence and/or absence of the alternating styrene/maleic anhydride copolymer was studied by the ESR method at −196°C. It was found that the concentration of paramagnetic species increased with the time of irradiation. The intensity of the ESR spectra at −196°C did not change when the light was cut off. By analysis of the ESR spectra of the systems studied the methyl (aH = 2,3 mT), dichloromethyl (aH = 1,66 mT), and acetyl (aH = 0,52 mT) radicals as well as the radicals A and D (aHα = 2,25 mT, aHβ = 3,19 mT) and (aHβ = 1,1 mT), respectively, were identified.
The effect of stereochemical structure on the viscoelastic behaviour of poly(ethyl methacrylate)
Authors: Hrouz Jaroslav , Ilavský Michal , Spěváček Jiří , Trekoval Jiří 
Published: April 2003

AbstractThe low‐frequency viscoelastic behaviour of three stereoregular samples of poly(ethyl methacrylate) (PEMA) in the main transition region was investigated. The main effect of tacticity in the transition from the syndiotactic sample to the isotactic one consists in a shift of the main transition region (or of the glass transition temperatures, Tg) to lower temperatures by ≈ 70 K. The temperature dependence of the shift factor of all samples could not be adequately described by the single Williams‐Landel‐Ferry (WLF) equation within the whole range of temperatures; in the range T>Tg+60K, isotactic PEMA exhibited the largest departures from the WLF equation. In all cases, departures from the WLF equation could be quantitatively described in terms of the temperature dependence of the Andreade coefficient β. The temperature dependence of the Andreade compliance, JA, was also most pronounced for the isotactic sample. Vertical correction of the complex modulus G*, with WLF horizontal shifts preserved, led to the lowest activation energy ΔH for the isotactic sample, which means the highest magnitude of secondary relaxation mechanism in this sample. The birefringence measurement showed that the molecular nature of the deformational birefringence is independent of the tacticity of the sample and does not vary in the range Tg+25K<T<Tg+100K. In all the characteristics mentioned here, parameters of a conventional sample obtained by radical polymerization approached those of the syndiotactic sample.
Condensation polymerization of 2,2′‐diiodobiphenyl‐4,4′‐dicarbonyl dichloride with some mono‐ and diamino compounds
Authors: Banihashemi Ahmad , Oboodi Mohammad Reza 
Published: April 2003

AbstractSeveral potentially thermostable polyamides were prepared. 2,2′‐Diiodobiphenyl‐4,4′‐dicarboxylic acid and its diacid chloride 1 were synthesized. The latter was condensed with several amines, e.g., aniline, p‐toluidine, p‐chloroaniline, and 2‐aminopyridine, to prepare model compounds of polyamides testing the reactivity of the diacid dichloride 1 towards various amines, and to compare their spectra with those of the polymers. The polyamides themselves were prepared by solution and melt condensation of diacid chloride 1 with the following diamines: p‐phenylenediamine, m‐phenylenediamine, 2,6‐diaminotoluene, benzidine, bis(4‐aminophenyl)‐methane, 4,4′‐diaminobiphenyl sulfone, and 3,3′‐diaminobenzophenone. The solubility of the polyamides in different solvents and their inherent viscosities were also measured. The values of the inherent viscosity were in the range of 0,1–1,9. The UV, IR, and 1H NMR spectra of the prepared polyamides were recorded. The melting points of the polymers were found to be higher than 360°C and the thermogravimetric curves showed that the polymers are stable up to 400°C in air.
Vinyl polymerization, 367. Polymerization of methyl methacrylate initiated with sodium polyethylenephosphate in the presence of an aqueous solution of copper(II) chloride
Authors: Imoto Minoru , Ouchi Tatsuro , Sakae Masatoshi , Yamamoto Hiroyuki 
Published: April 2003

AbstractPolymerization of methyl methacrylate (MMA) initiated with the system of sodium polyethylenephosphate (PEP‐Na), copper(II) chloride, and water was carried out. The effect of the mass of each component on the conversion of MMA was studied. The polymerization proceeded through a radical mechanism. The overall activation energy was found to be 54,5 kJ·mol−1. The formation of a complex of Cu(II)‐ion with PEP‐Na and water was confirmed by electronic absorption spectra. The initiation mechanism was discussed.
Präparative Mehrschritt‐Trennverfahren mit entmischenden Flüssigkeiten
Authors: Kuhn Rainer 
Published: April 2003

AbstractMulti‐step fractionation methods using demixing solvents have been used to determine the chemical distribution of binary copolymers as well as block‐ and graft‐copolymers. Four variations of these multi‐step fractionation methods are described: Cumulative fractionation, successive fractionation, semicumulative fractionation, and head‐tail type of fractionation. The ability of these fractionation methods is demonstrated by investigating two‐block copolymers of styrene and butadiene which have different chemical compositions and by fractionating a chlorinated polyethylene. Using the head‐tail fractionation procedure, one obtains a middle fraction with a compositional heterogeneity of less than 2%. The results show that the chemical compositional distributions of all chemical heterogeneous copolymers can be determined by the method of fractionation with demixing solvents provided the corresponding homopolymers can be separated into different phases. This type of separation procedure has been applied to 60 different polymer systems and should be applicable to many more polymer systems.
Distinction entre les phénomènes d'agrégation et de micellisation présentés par des copolymères amphipathiques. Cas des copolymères polystyrène/polyvinylpyridinium en milieu aqueux
Authors: Selb Joseph , Gallot Yves 
Published: April 2003

AbstractHydrophobic‐hydrophilic polystyrene/poly(4‐vinyl‐N‐ethylpyridinium bromide) (poly‐(l‐phenylethylene)/poly[l‐(N‐ethyl‐4‐pyridinio)ethylene bromide]) block or graft copolymers were synthesized. These copolymers are well defined products, and are homogeneous in mole‐ cular weight and composition. They were obtained by quaternization, with ethyl bromide, of the nitrogen atoms of pyridine units of polystyrene/poly(4‐vinylpyridine) block or graft copolymers. In dilute solution in a selective solvent for polyelectrolytic polyvinylpyridinium moities (water + salt), there is multimerization, i. e. presence of particles constituted by several macromolecules. Light scattering and ultracentrifugation measurements show that this multimerization is not the expected “micellization”, i.e. an “association” phenomenon due to the amphiphilic character of the copolymer, but corresponds Lo an “aggregation” phenomenon, resulting from incomplete dissolution of the product at the molecular scale.
The polymerization of isobutyl vinyl ether by trifluoroacetic acid
Authors: Bolza F. , Treloar F. E. 
Published: April 2003

AbstractThe polymerization of isobutyl vinyl ether (IBVE) initiated by trifluoroacetic acid (TFA) in 1,2‐dichloroethane and in 1,2‐dichloroethane/carbon tetrachloride mixtures has been studied over the temperature range −2,5°C to 35°C. Provided that the ratio [IBVE]/[TFA] did not exceed 88 and that 2·10−4 mol·1−1 < [TFA] < 4·10−3 mol·1−1 polymerization was the only detectable reaction, and the initial rate of reaction R0 was equal to k[IBVE]2[TFA]. The activation energy of the rate = (34 ± 2) kJ · mol−1 and the activation energy of the molecular weight = − (11,9 ± 0,5) kJ · mol−1. When [TFA] < 1·10−4 mol/l, no reaction was detectable. The polymers produced had molecular weights less than 4400; the only transfer is by monomer and this is the main chain‐breaking step. The reaction was unaffected by the addition of water for [H2O] < [TFA]. The rate depended on the solvent dielectric constant, but in a manner suggestive of a dipole‐dipole reaction. A mechanism is proposed for the reaction in which the reactive intermediates are trifluoroacetate esters solvated by monomer.
Die thermische polymerisation von methylmethacrylat, 3. Verhalten des ungesättigten dimeren bei der polymerisation
Authors: Brand Elisabeth , Stickler Manfred , Meyerhoff Günther 
Published: April 2003

AbstractThe thermal polymerization of methyl methacrylate is accompanied by the formation of appreciable amounts of an unsaturated dimer (H‐1). The behaviour of H‐1 during homopolymerization in presence of an initiator at 60, 80 and 100°C and during copolymerization with MMA in presence of an initiator at 60°C are investigated. The rate of (H‐1)‐homopolymerization is very low. The transfer constant to monomer H‐1 is about CH‐1 = 3·10−3 at 80°C as received from Pn‐determinations. The termination is essentially by disproportionation. The copolymerization parameters as resulting from polymerizations with labeled MMA at 60°C are rMMA = 1,8 and rH‐1 = 0,33, respectively.
Functional metal‐porphyrazine derivatives and their polymers, 5. Peroxidatic oxidation of guaiacol by Fe(III)‐3,4,3′,4′,3″,4″,3‴,4‴‐octacarboxyphthalocyanine (Fe(III)‐oaPc) and Fe(III)‐oaPc/polyelectrolyte systems
Authors: Shirai Hirofusa , Maruyama Akio , Konishi Mitsugi , Hojo Nobumasa 
Published: April 2003

AbstractThe oxidation of guaiacol by the Fe(III)‐oaPc/H2O2 system is studied by using a stopped flow spectrophotometer. The maximum rate of oxidation reaction by this system amounts to about 1000 times that in the absence of H2O2. The kinetic investigation indicates that the reaction can be regarded as “an ordered two‐substrates reaction” and that the oxidation reaction proceeds according to the peroxidase‐like mechanism. The reaction is inhibited by adding cyanide. The structure of oxidation products is also discussed. The catalytic action of Fe(III)‐oaPc in the presence of various polyelectrolytes such as poly(vinylamine) is also investigated, varying the pH values, and the environmental effect of the polymers in their catalytic behavior is discussed.
The influence of spherulitic size on the environmental stress cracking of low density polyethylene
Authors: Shanahan M. E. R. , Chen‐Fargheon C. , Schultz J. 
Published: April 2003

AbstractThe influence of morphology in a low density, high melt index polyethylene was studied with particular reference to environmental stress cracking (ESC). Test samples of the polyethylene were molded under constant conditions, only the subsequent rate of cooling to room temperature being changed. Several techniques were used to study the resultant polymer including ESC tests, X‐ray diffraction, optical microscopy and constant strain rate stress/strain tests. It was found that the faster the polymer was cooled after molding, the smaller was the typical diameter of the spherulites and the greater the resistance to stress cracking. A hypothesis is proposed to explain the differences in terms of the ease with which a crack can propagate, assuming that propagation is easier in amorphous material than within spherulites.
Mechanism of the methyl methacrylate polymerization photo‐induced by benzoin derivatives
Authors: Merlin André , Fouassier Jean‐Pierre 
Published: April 2003

AbstractDeoxybenzoin and 2,2‐dimethoxy‐2‐phenylacetophenone (α,α‐dimethoxydeoxybenzoin) were used to initiate the polymerization of MMA in solution. It is shown that hydrogen donating solvents enhance the rate of polymerization. Laser spectroscopy experiments lead to a better insight in the photophysical processes in the excited states. Irradiation of these molecules under various conditions results in the generation of radicals capable of initiating the polymerization. Rate constants of the sensitizer quenching by MMA are determined. Two models are proposed for the initiation of the MMA photopolymerization in solution.
Melting and crystallization behaviour of random copolymers from adipic acid, trans‐3‐hexenedioic acid and 1,16‐hexadecanediol
Authors: Maglio Giovanni , Marchetta Carlo , Palumbo Rosario 
Published: April 2003

AbstractCopolyesters derived from adipic acid, trans‐3‐hexenedioic acid and 1,16‐hexadecanediol were prepared and investigated by means of X‐ray diffraction and DSC techniques. From the X‐ray results an isomorphous replacement of the saturated and unsaturated diacid units has been suggested. The equilibrium melting temperature T and the heat of fusion ΔHf were slightly dependent on the copolyester composition. The crystallization process was analyzed by means of Hoffman's kinetic crystallization theory for a lamellar type crystal growth. The values of the free energy of formation of a nucleus of critical dimensions ϕ* and the free energy of folding σe were found to decrease regularly with increasing amount of double bonds, varying from 110 to 83 kJ/mol for Δϕ* and from 171 to 127 erg/cm2 for σe. This effect has been interpreted on the basis of an increase of chain flexibility owing to the presence of the trans double bonds.
Melting temperatures and enthalpies of polyethers, 2. Poly(octamethylene oxide)
Authors: Marco Carlos , Fatou José Gómez , Bello Antonio , Blanco Amparo 
Published: April 2003

AbstractThe dependence of the melting temperature on the crystallization temperature for low molecular weight fractions of poly(octamethylene oxide), (poly(oxyoctamethylene)), in the range from Mn = 3400 to Mn = 9 000, is analyzed. It is found that in this molecular weight region, the extrapolated linear relation melting temperature Tm vs. crystallization temperature Tc, for high levels of crystallinity yields an equilibrium temperature, which is in good accord with theoretical expectations; meanwhile the Tm vs. Tc relation for low levels of crystallinity leads to higher equilibrium temperatures. The equilibrium melting temperature corresponds to 356 K for Mn = 9 000 and the enthalpy of fusion was found to be 60,5 cal/g (= 253 J/g).
Darstellung und [η]‐M̄‐Beziehung von Mikrogelen aus polyvinylalkohol
Authors: Arbogast Wolfgang , Horvath Andreas , Vollmert Bruno 
Published: April 2003

AbstractMicrogels were prepared by crosslinking of poly(vinylalcohol)s with different molecular weights (saponification degree: 88 mole‐%) with glutaraldehyde in aqueous solutions. The degree of crosslinking was varied between 0 and 10% (i.e. 10 crosslinks per 100 structural units). Viscosity measurements showed that the viscosity number [η] of the microgels decreases considerably with increasing degree of crosslinking — as to be expected with increasing mean density of the random coils: The mean coil volume in aqueous solution shrinks by introducing 10 crosslinks per 100 structural units to 1/10 of the primary volume. A comparison of the logarithmic [η]‐M̄‐plots of our microgels showed a linear decrease of the exponent a, from a = 0,73 (uncrosslinked) to a = 0,16, with increasing degree of crosslinking. By extrapolation, with a degree of crosslinking of 13% (i.e. 13 cross‐links per 100 structural units of polymer chain), it was found that [η] becomes independent of the molecular weight of the primary PVAl‐samples.
Bildung von Cyclopentenylverbindungen beim Metathese‐Abbau von modifiziertem 1,4‐Polybutadien
Authors: Hummel Klaus , Heiling Peter , Karaoulis Christos , Kathan Wolfgang , Stelzer Franz 
Published: April 2003

AbstractThis investigation deals with metathesis degradation products of modified 1,4‐polybutadiene (poly(1‐butenylene)) which have not been taken into consideration as yet, e.g. substituted cyclopentene and linear isomerization products. Substituents were introduced into 1,4‐poly‐butadiene either by partial bromination with N‐bromosuccinimide followed by a Grignard‐Wurtz reaction or by reaction with the corresponding methyl compound and dicumyl peroxide. Polymers with 2‐methylbenzyl, 4‐methylbenzyl, 4‐chlorobenzyl, 4‐methoxybenzyl, 2‐naphthylmethyl, 2,4,6‐trimethylphenyl, 1‐naphthyl, 9‐anthryl, and 9‐phenanthryl substituents were degraded by metathesis with 4‐octene using WCl6/(CH3)4Sn as a catalyst and were analyzed by gas chromatography/mass spectrometry and by liquid chromatography.
X‐ray and neutron small‐angle scattering of random coil polymer solutions
Authors: Koyama Ryuzo 
Published: April 2003

AbstractSmall‐angle scattering curves of random coil polymer solutions are calculated from the general scattering theory of solutions by making use of a previous calculation of the Yvon‐Born‐Green integral equation for the radial distribution function of the solute polymer molecules. The calculated scattering function is a monotonously decreasing function of the scattering angle at low polymer concentration, and it has a minimum and a maximum at high concentration, where the polymer interaction is repulsive. For large scattering angle, the reciprocal values of the scattering function increase almost linearly with sin2(θ/2), where θ is the scattering angle. This calculated result is in qualitative agreement with recent experimental results of X‐ray and neutron small‐angle scatterings of polymer solutions.
Darstellung von neuen makromolekularen stoffen aus derivaten der 3‐aminocrotonsäure und dimaleinimiden
Authors: Haug Theobald 
Published: April 2003

AbstractCross‐linked polymers are formed by a new addition polymerization of dimaleinimides with bis(3‐aminocrotonic acid)‐esters, ‐amides, or ‐nitriles. Model reactions show that the derivatives of 3‐aminocrotonic acid add to the electrophilic double bond of maleinimide. The resulting succinimid derivatives rearrange thermally to the corresponding pyrrolinones. At higher temperatures, especially in the presence of an excess of maleinimide, a second molecule of maleinimide is added to the pyrrolinone. Some properties of moulded and casted polymers are described.
Ternary copolymerization of carbon dioxide with epoxybutanes
Authors: Inoue Shohei , Matsumoto Kunio , Yoshida Yasuhiko 
Published: April 2003

AbstractThe ternary copolymerization of carbon dioxide with 1,2‐epoxybutane and other epoxybutane isomers using the diethylzinc/water system as catalyst was carried out to investigate the relative reactivity between epoxides. cis‐2,3‐Epoxybutane was much more reactive than trans‐2,3‐epoxybutane in the copolymerization with carbon dioxide. The copolymer obtained from the reaction of carbon dioxide and cis‐2,3‐epoxybutane upon hydrolysis gave threo‐2,3‐butanediol, indicating the exclusive inversion of configuration in the ring‐opening of the epoxide. In the formation of cyclic carbonate as a byproduct of the copolymerization, cis‐2,3‐epoxybutane and trans‐2,3‐epoxybutane exhibited a similar reactivity.
Untersuchungen zur kettenspaltung und entstehung von π‐bindungen in der vinylkette von polystyrol in lösung unter sauerstoff‐ und lichteinfluß
Authors: Woliński L. 
Published: April 2003

AbstractThe influence of the solvent on chain degradation of polystyrene (PS) as well as the formation of π‐bonds in the vinyl chain is investigated, the latter caused by irradiation of PS‐solutions with long wave UV light (λ ≥ 270 nm) and reactions of singlet‐oxygen O2 (1Δg). Unambiguous qualitative proof could be given for chain degradation of polystyrene under the given experimental reaction conditions. Quantitative considerations though, based on different oxygen content in the respective solutions, different tension of the macromolecular chain and/or different contraction of the macromolecular coils proved to be not tenable or incomplete. It is shown that under the given experimental conditions formation of π‐bonds in PS results from a reaction of chlorine radicals with PS molecules. The kinetics of π‐bond formation in CCl4 and CHCl3 solutions is investigated by light scattering measurements. The conclusions aim at a quantitative determination of the saturation state in the formation of π‐bonds in both solutions.
The action of tin compounds in condensation‐type RTV silicone rubbers
Authors: van Der Weij Frederik Willem 
Published: April 2003

AbstractThe vulcanization of RTV (=room temperature vulcanizing) silicone rubbers under the action of organotin compounds is investigated. The mechanism for the cure is inferred from the chemical properties of a variety of relevant organotin compounds and is illustrated with the reactions that occur when dialkyltin dicarboxylates (A) are used as catalysts. The resulting organotin hydroxide (B) is shown to be the actual catalyst. With tetraethoxysilane (2) it forms organotin silanolates (D). Silanolysis of this compound results in the formation of a new siloxane linkage and recovery of the actual catalyst. Alkoxysilanes in which part of the alkoxy groups is replaced by siloxy groups, appear to be more reactive than the initial alkoxysilanes. At elevated temperatures side‐reactions like condensation of silanols with alcohols under the action of organotin compounds become increasingly prominent. Heating during cure effects, that part of the silanols becomes blocked by alkoxy groups. The mechanical properties of the resulting rubbers are usually far from optimum. During heating of cured rubber in a confined atmosphere, i.e., in the presence of the alcohol formed during cure, condensation of silanols with alcohol occurs too. Because these are equilibrium reactions, this process finally leads to complete degradation of the rubber.
Redox polymerisation, 5. Kinetics of the polymerisation of acrylonitrile and methyl methacrylate initiated by the system cyanoacetic acid‐Mn(III)(acac)3 in DMF and DMSO
Authors: Haragopal Mahadevan , Mahadevan Venkatanarayana 
Published: April 2003

AbstractPolymerisation of acrylonitrile and methyl methacrylate initiated by the system cyanoacetic acid‐Mn(III)(acac)3 is investigated in DMF and in DMSO at 25–35°C. Kinetics of reduction of the complex by cyanoacetic acid shows the formation of a mixed ligand complex whose decomposition yields the primary radicals. Efficient initiation of polymerisation by these radicals followed by exclusive mutual termination accounts for the kinetics of polymerisation. Rate and equilibrium parameters are evaluated and their significance discussed.