bluuebunny/crossref_metadata_2025_split huggingface dataset:
Das thermische Verhalten von Isopren‐Styrol‐Zweiblockcopolymeren
Authors: Schneider Hans‐Adam , Hurduc Natalia , Caşcaval Constantin N. , Riess Gérard , Marti Salvatore 
Published: April 2003

AbstractInvestigations by pyrolysis‐gas chromatography (P‐GC) and by thermogravimetry (TG) on styrene‐isoprene two‐block copolymers demonstrated that the thermal behaviour of these copolymers is influenced mainly by the microstructure of the polyisoprene (PI) block. Generally, the PI blocks with a higher content of vinylic 1,2‐microstructures show a lower content of volatile products in P‐GC and a slower weight loss in TG, suggesting an apparent higher thermostability. All copolymers show in P‐GC the main products of the corresponding homopolymers in an amount directly proportional to the respective content of the components in the copolymers. All results suggest an independent degradation of the two different blocks of styrene‐isoprene block copolymers.
Adiabatic polymerization of ε‐caprolactam in presence of lithium chloride, 1. Thermodynamic and Kinetic aspects
Authors: Alfonso Giovanni Carlo , Bonta' Giorgio , Russo Saverio , Traverso Anna 
Published: April 2003

AbstractThe activated anionic polymerization of ε‐caprolactam in presence of LiCl (up to 10 wt.‐%) is studied under quasi‐adiabatic conditions. The temperature increase of the system, after proper corrections for the heat exchange with the surroundings, allows to evaluate the enthalpies of polymerization δHp and to correlate their variations with the specific interactions of LiCl with monomer and polymer. The sharp decrease of −δHp as function of LiCl content is attributed to the stabilizing effect of the ion‐dipole interactions, which is higher for the monomer‐salt pair than for the polymer‐salt mixture. The initial rates of polymerization are enhanced by a few percents of added LiCl, with a maximum at about 3 wt.‐%. The relative influence of various physical factors on the polymerization kinetics and thermodynamics is discussed.
Solid state polymerization of a nitrophenoxy disubstituted diacetylene
Authors: McGhie Andrew R. , Lipscomb George F. , Garito Anthony F. , Desai Kirit N. , Kalyanaraman Palaiyur S. 
Published: April 2003

AbstractThe solid state polymerization of the disubstituted diacetylene 1,6‐bis(2,4‐dinitrophenoxy)‐2,4‐hexadiyne by thermal annealing at 130°C to yield high quality polymer single crystals is reported. This compound is unique in that it polymerizes by thermal annealing but not under ordinary x‐ray conditions, thus allowing determination of the crystal structures of both the monomer and polymer by x‐ray diffraction. The conditions for solid state polymerization and the structural changes during polymerization were investigated. In addition, the kinetics of polymerization were studied by differential scanning calorimetry. An induction period with activation energy EA(slow) = 139,7 ± 3 kJ/mol (33,4 ± 0,7 kcal/mol) is followed by a rapid polymerization regime with activation energy EA(fast) = 132,2 ± 6 kJ/mol (31,6 ± 1,5 kcal/mol) during which first order kinetics are obeyed. The total heat of polymerization is − ΔHp = 134,7 ± 6 kJ/mol (32,2 ± 1,5 kcal/mol). After polymerization, a disordering phase change takes place with continued isothermal annealing which becomes clearly evident at isothermal annealing temperatures higher than 130°C.
Polymerization of ethylene catalyzed by titanocene systems, 2. Catalytic systems Cp2 TiRCl/oxyaluminium compounds
Authors: Cihlář Jaroslav , Mejzlík Jiří , Hamřík Oldřich , Hudec Pavel , Majer Josef 
Published: April 2003

AbstractEthylene polymerization, catalyzed by Cp2TiEtCl or Cp2TiMeCl and cocatalyzed by oxyaluminium compounds, formed via hydrolysis of AlEtCl2, AtEt2Cl, AlEt3, AlMeCl2, AlMe2Cl, AlMe3, and AlEt(OBu)Cl, was studied. The cocatalytic activity of oxyaluminium compounds was found to decrease with increasing number of alkyl substituents in the corresponding alanes. The only inactive cocatalyst from the oxyaluminium compounds studied is the one formed via hydrolysis of AlEt(OBu)Cl. Oxyaluminium compounds from methylalanes are substantially less active than those from ethylalanes. If the same aloxane cocatalyst is employed, the catalytic activities of both Cp2TiEtCl and Cp2TiMeCl are similar. The molecular weight distributions of polyethylene are narrow for the systems Cp2TiRCl/(oxyaluminium compounds from AlEtCl2); fairly broader distributions were found for systems Cp2TiRCl/(oxyaluminium compounds from AlMeCl2). Systems with oxyaluminium compounds from dialkyl‐ or trialkylalanes yield polyethylene with distinctly bimodal distribution curves. The mechanism of ethylene polymerization catalyzed by titanocene systems cocatalyzed by oxyaluminium compounds is discussed.
Polybutadiènes hydroxytéléchéliques, 4. Microstructure des polybutadiènes hydroxytéléchéliques radicalaires observée par 1H NMR à 350 MHz et mécanismes de propagation
Authors: Pham Quang‐Tho 
Published: April 2003

AbstractThe examination by 1H NMR spectroscopy at 350 MHz of commerical hydroxytelechelic polybutadienes Arco R45M® allows the quantitative determination of the in‐chain vinylcentered triads and the 4 types of hydroxylated vinyl chain ends. Vinyl primary radicals as well as macroradicals were found to propagate with penultimate and pen‐penultimate effects.
2‐hydroxyethylierung von oligo(iminoethylen)en und deren überführung in oligo[N‐(2‐chlorethyl)iminoethylen]e
Authors: Mannschott Christian , Höcker Hartwig , Kern Werner 
Published: April 2003

AbstractOligo[N‐(2‐chloroethyl)iminoethylene]s (8) were synthesized as potential antitumor agents like their low molecular weight analogues. It was found that oligo(iminoethylene)s (5) can be 2‐hydroxyethylated with ethylene oxide and subsequently transformed into oligo[N‐(2‐chloroethyl)iminoethylene hydrochloride]s (14) with thionyl chloride. The stability of the free oligomers 8 was found to decrease with the number of N‐2‐chloroethyl groups in the molecule.
The relation between phase transition and crystallization behavior of 1,4‐trans‐poly(butadiene)
Authors: Finter J. , Wegner G. 
Published: April 2003

AbstractThe crystallization behaviour of pure 1,4‐trans‐poly(butadiene) (1,4‐PTBD) from dilute solutions in heptane and its relation to the phase transition phenomena in the solid state is investigated. Depending on whether the nucleation occurs in the high‐temperature modification II or the low‐temperature modification I two different regimes of crystallization behaviour are observed which in turn determine the crystal thickness as well as the phase transition and annealing behaviour of the crystals. The equilibrium phase transition temperature (I–II) is 356 K, the corresponding enthalpy is 144 J.g−1; the equilibrium melting temperature is 437 K and the enthalpy of melting is 69 J.g−1. The surface free energy terms are obtained relating the crystal thicknesses measured by SAXS and DSC to the temperatures of phase transition and melting, resp. Following Hoffman's theory of nucleation and growth the theoretical curves for the rate of nucleation and crystal growth are calculated and compared to the experimental results.
The cleavage of β‐ketoesters with sodium tert‐butoxide. Reactivation of a pseudoterminated propagation centre in the anionic polymerization of methacrylates
Authors: Lochmann Lubomír , Trekoval Jiří 
Published: April 2003

AbstractEthyl 2,2,4‐trimethyl‐3‐oxopentanoate is cleaved with sodium tert‐butoxide into simple esters, part of which is substituted with sodium in the α‐position. Reaction mixtures arising in this way from this ketoester or from some other ones rapidly induce the polymerization of methyl methacrylate. The role of such a cleavage in the reactivation of the pseudoterminated propagation centre in the anionic polymerization of methacrylates is discussed.
Immobilization of trypsin on poly(methyl methacrylate‐co‐2‐acryloylamino‐2‐methylpropanesulfonic acid)
Authors: Nithianandam Varadalambedu Srinivasan , Srinivasan Kalathur Sabdham Vangepuram , Joseph Koithara Thomas , Santappa Mushi 
Published: April 2003

AbstractTrypsin was immobilized on a copolymer of methyl methacrylate and 2‐acryloylamino‐2‐methylpropanesulfinic acid. The resulting immobilized trypsin shows 25% of the soluble enzyme specific activity. The pH optimum of the immobilized trypsin is shifted to a higher value by 1,1 units. The pH stability of the immobilized trypsin is better than that of the soluble enzyme, whereas the temperature stability of the soluble and the immobilized enzyme is almost identical.
Volumes spécifiques de polystyrènes en étoile à l'état liquide
Authors: Sarazin Dominique , FrançOis Jeanne 
Published: April 2003

AbstractSpecific volume measurements carried out on linear and star‐shaped liquid polystyrene versus the number average molecular weight, Mn scaling between 5000 and 2.106, are in good agreement with a review of the experimental results of others. These results confirm the occurrence of a loss of volume per monomeric unit above a molecular weight of 10000 already observed for polystyrene in solution. We attribute the influence of this specific volume variation against Mn on the thermal dilatometric coefficient α = (1/v)dv/dT and the temperature of vitrous transition. We also attempted to give an explanation for this phenomenon.
Phase distribution chromatography (PDC) as a method for the investigation of polymers in solution, 2. Flow‐equilibrium
Authors: Greschner Georg S. 
Published: April 2003

AbstractThe dynamical region of the measured calibration curves is investigated using the results of the theory published previously. The kinetic constants of the flow‐equilibrium are calculated from the measurements according to two different models for a spontaneous polymer diffusion of the transported P‐mer from sol into gel of the Phase Distribution Chromatography (PDC)‐column. The corresponding lateral concentration profiles in the gel are found by analytical integration of Fick's second law under the corresponding boundaries. An energetic model of this flow‐equilibrium is stated, giving the activation enthalpy and ‐entropy of the rediffusion of the polymer from gel into sol after some retardation time in the gel. The influence of the gel mass of the column on its resolution is briefly investigated. Since the measurements show that the resolution of the PDC‐column vanishes in the vicinity of the theta point, spreading phenomena in the column can be investigated by means of analysis of the corresponding PDC elution curves. The results give a basis for the numerical computation of the molecular weight distribution of narrowly distributed polystyrenes from PDC elution curves at sufficiently low column temperatures. The PDC‐separation effect is opposite to that of gel permeation chromatography (GPC).
Electric dipole moment of ethylcellulose, in 1,4‐dioxane and in benzene
Authors: Araki Kazuo , Imamura Yoshio 
Published: April 2003

AbstractThe electric dipole moments per repeating unit of ethylcellulose (EC) of various molecular weights were determined by dielectric measurements at 1 kHz (μL) and at 1 MHz (apparent moment, μH) in 1,4‐dioxane and benzene. The numerical values were μL = 5,23 D (= 17,45.10−30 C·m) and μH + 2,72 D (= 9,07.10−30 C·m) for 1,4‐dioxane, and μL = 4,81 D (= 16,04.10−30 C·m) and μH = 2,42 D (= 8,07.10−30 C·m) for benzene, respectively. μL and μH were almost independent of the molecular weight in both solutions. The persistence dipole moment μq was estimated to be 13,6 D (= 45,36.10−30 C·m) in 1,4‐dioxane, and 13,4 D (= 44,70.10−30 C·m) in benzene, respectively, and the flexibility of the EC chain was discussed.
Polymer conformation and NMR chemical shifts, 3. Calculation of conformational energies on alternating acrylate‐styrene copolymers
Authors: Tanabe Tsuneaki , Koinuma Hideomi , Hirai Hidefumi 
Published: April 2003

AbstractConformational energies of meso and racemic dyads of four alternating copolymers composed of methyl methacrylate or methyl acrylate with styrene or α‐methylstyrene are computed by an empirical force field method as a function of the rotational angles about the skeletal bond pair within each of the dyads. The patterns of the energy contour surfaces of poly(methylacrylate‐alt‐styrene) and poly(methyl methacrylate‐alt‐α‐methylstyrene) resemble respectively those of the corresponding homopolymers, i.e. poly(styrene) or poly(methyl acrylate) and poly(α‐methylstyrene) or poly(methyl methacrylate). On the other hand the energy maps of poly(methyl methacrylate‐alt‐styrene) and poly(methyl acrylate‐alt‐α‐methylstyrene) containing an α‐methyl group in either of the monomeric units, greatly differ from those of the homopolymers of the component monomers. For all the alternating copolymers, the ḡ state is more than 5 kcal/mol higher in energy than the lowest energy state, as it was for the homopolymers. The cutoff distance, employed as a tentative measure of the solvent effect in the calculation of nonbonded interaction, gives a significant effect on the conformational energy, especially of the meso‐tt state. Bond interaction parameters for various pairs of substitutents in the copolymers are evaluated from the calculation and they are compared with those determined from the conformational analysis of the homopolymers to check whether or not they are generally applicable to conformational analysis of polymers. Furthermore, conformational probabilities are calculated by the matrix method using the data of the energy calculation.
Beiträge zur polymerisation von 2‐isopropenylnaphthalin, 3. Anionische homopolymerisation von 2‐isopropenylnaphthalin
Authors: Engel Dieter , Schulz Rolf C. 
Published: April 2003

AbstractThe anionic homopolymerization of 2‐isoprenylnaphthalene with butyllithium in tetrahydrofuran at –78°C is described. The refractive index increment amounts to dn/dc = 0,2084 ml/g for these polymers in toluene at 25°C and wavelength λ = 436 nm. Determination of the molecular weights by light scattering yielded values between 13 000 and 270 000. The second virial coefficients also determined by light scattering measurements are comparable with the corresponding data of poly(α‐methylstyrene). A calibration curve is given for gel permeation chromatography of the poly(2‐isoprenylnaphthalene)s, whose polymolecularity indexes Mw/Mn lie between 1,06 and 1,2. Their intrinsic viscosity/molecular weight relationship is [η] = 1,43·10−2 M0,663. From 1H NMR of the α‐methyl group fractions of isotactic triads between 30 and 55% are evaluated. The glass transition temperature extrapolated to infinite molecular weight is Tg∞ = 221°C. Above 300°C fast degradation by monomer formation is observed.
Hot drawing of surface growth polyethylene fibers, 2. Effect of drawing temperature and elongational viscosity
Authors: Smook Jan , Torfs Jan C. M. , Pennings Albert J. 
Published: April 2003

AbstractA distinct improvement of the tensile properties of “surface growth” polyethylene fibers can be realised by drawing at elevated temperatures. The optimal drawing temperatures were found in the range of 120–150°C. Drawing in the hexagonal phase above 150°C does not lead to an increase of strength. Elongational viscosity measurements revealed extremely high values in the order of 1011–1012 Poise. Activation energies between 75–95 kJ/mol were determined from the temperature dependence of elongational viscosity. The observed drawing behaviour is discussed in relation to the morphological changes that occur during drawing.
Lösungs‐ und verdünnungswärmen von polyethylenglykolen in wasser und benzol, 1. Experimentelle ergebnisse
Authors: Koller Johann , Killmann Erwin 
Published: April 2003

AbstractDissolution and dilution enthalpies of poly(ethylene glycol)s were measured in water and benzene, resp., by microcalorimetry. The enthalpies depend on both solute concentration and molar mass, indicating interactions between hydroxyl endgroups, ether groups and solvent molecules. Low molar mass samples form hydrogen bonds between hydroxyl and ether groups at solute concentrations of 0,003 g/cm3 and higher. High molar mass samples form intermolecular associates through dispersion forces at concentrations above 0,06 (benzene) and 0,1 g/cm3 (water).
Optically active hydrocarbon polymers with aromatic side chains, 10. Synthesis and properties of homopolymers and copolymers of 6‐vinylchrysene
Authors: Chiellini Emo , Solaro Roberto , Ciardelli Francesco 
Published: April 2003

AbstractThe synthesis of 6‐vinylchrysene (1) starting from chrysene is described. The study of the polymerizability of 1 by conventional radical, cationic, and Ziegler‐Natta procedures indicates the tendency of 1 of give head‐to‐tail polymeric products with a similar degree of polymerization independent of the catalytic system. Copolymers of 1 with optically active (−)‐menthyl acrylate (2), (−)‐menthyl methacrylate (3), and (S)‐4‐methyl‐1‐hexene (4), were also prepared. No apparent copolymerization of 1 with optically active alkyl vinyl ethers occurred by cationic initiation. Spectroscopic and chiroptical properties are presented to support the formation of copolymer macromolecules. Finally, the differential dichroic absorption measurements allow one to stress that in optically active vinylaromatic copolymers the extent of preferential asymmetry, induced by the dissymmetric field of units derived from the optically active nonaromatic comonomer, increases with increasing bulkiness and polarizability of the vinylaromatic comonomer.
Application de la réaction de métathèse à la synthèse de prépolymères α,ω‐bifonctionnels. 1: Cométathèse entre le cyclooctadiène‐1,5 et l'hexène‐3 dioate de diméthyle
Authors: Reyx Danièle , Campistron Irène , Heiling Peter 
Published: April 2003

Abstractα,ω‐Dimethoxycarbonyl substituted polyenes were synthesized by co‐metathesis between 1,5‐cyclooctadiene (1) and dimethyl 3‐hexenedioate (2) by use of the catalytic system WCl6/Sn(CH3)4. The ability of 2 for co‐metathesis with 1 was proved by determination of the distribution of low molecular weight products in terms of reaction time and 2/1 mole ratio. For these studies, high values of 2/1 ratios (0,5–4) were chosen in order to obtain lowest molecular weight co‐metathesis products (3b–3e). Metathesis involved preferentially the double bonds in the neighbourhood of the ester groups. At lower values of the 2/1 ratio (0,012–0,061) α,ω‐difunctional prepolymers (3i) were synthesized.
The behaviour of poly(2,3‐epoxypropyl methacrylate) in dilute solution
Authors: Mrkvičková Libuše , Kálal Jaroslav , Bednář Bohumil , Janča Josef 
Published: April 2003

AbstractHomopolymers of 2,3‐epoxypropyl methacrylate with various molecular masses were prepared by solution polymerization with 2,2′‐azoisobutyronitrile as initiator. The effect of polymerization conditions on the molecular parameters (weight‐ and number‐average molecular masses MW and Mn intrinsic viscosity [η]) and the tacticity of the resulting poly (2,3‐epoxypropyl methacrylate)s was investigated. For unfractionated polymers, the constants of the Mark‐Houwink equation for 1,4‐dioxane and tetrahydrofuran were determined. Gel permeation chromatography was tested as a tool for the determination of the Mw and Mn values.
Melting behaviour of native 1,4‐trans‐isotactic‐polypentadiene obtained by inclusion polymerization in perhydrotriphenylene
Authors: Farina Mario , Silvestro Giuseppe Di 
Published: April 2003

AbstractThe extrapolated melting point of native 1,4‐trans‐isotactic‐polypentadiene obtained by inclusion polymerization in pre‐irradiated perhydrotriphenylene is 104°C, 10 K higher than that of a long‐annealed conventional polymer. The WAXS spectrum corresponds to that of the already known paracrystalline structure; this notwithstanding, its heat of melting is 20–70% higher than that of polypentadiene crystallized from solution or from the melt. The native polymer shows noteworthy superheating phenomena and is not able to induce crystallization of high‐melting crystals from the melt. This behaviour is consistent with that predicted for extended‐chain polymeric crystals. This conclusion is supported by the absence of definite peaks in the SAXS spectrum of the native polymer.
Autoxidation reactions of polystyrene derivatives
Authors: Ohkatsu Yasukazu , Tanaka Tetsuo , Tsuruta Teiji 
Published: April 2003

Abstractp‐Isopropylstyrene was homopolymerized or copolymerized with styrene using AIBN as initiator in benzene at 50°C. The resulting polymers were easily oxidized by oxygen to produce polymers having hydroperoxy groups. The oxidized polymer was found to have considerably different solubility from the original polymer. Kinetic evaluation of the oxidation reactions of poly(p‐isopropylstyrene) showed that the tertiary hydrogen of the isopropyl group present at the pendant aromatic ring was more susceptible to the oxidation reaction than the main chain methine hydrogen. The rate constants of these two oxidation reactions were found to be 4,0 · 10−4 mol−1/2 · l1/2 · sAutoxidation reactions of polystyrene derivatives1/2 and 2,5 · 10−4 mol−1/2 · l1/2 · s−1/2, respectively. These values were much smaller than that for the tertiary hydrogen atom of the isopropyl group of cumene (3,21 · 10−3 mol−1/2 · l1/2 · s−1/2, at 68°C), a low molecular weight model compound.
Disordering of helix of oxidized L‐methionine containing copolypeptides
Authors: Aiba Sei‐ichi , Minoura Norihiko , Fujiwara Yukihiko 
Published: April 2003

AbstractThe solid‐state conformation of copolymers of oxidized L‐methionine [L‐Met(O)] with L‐methionine (L‐Met) and/or L‐alanine (L‐Ala) was studied by IR spectroscopy and circular dichroism (CD). The results from the IR spectra in the region of 900−330 cm−1 are compared with data obtained by CD experiments. A film cast from the solution of a copolymer containing L‐Met(O) had a new trough between 205 and 210 nm in the solid‐state CD spectra and new IR absorption bands at 815 and 680 cm−1, while oxidizing the film of an L‐Met containing copolymer after casting did not induce a significant change in IR and CD spectra. It seems that the film cast from the solution of an L‐Met(O) containing copolymer exhibits the feature of a random coil as well as of an α‐helix. From the CD spectra of the film on immersion in water, it was deduced that the helix of the film became gradually disordered and hence the film was dissolved in water.
Metalloesters, 8. Esters of diacids and oligo(carboxylic acid)s (oligomers of methyl methacrylate) substituted in α‐position with an alkali metal. Their stability and IR Spectra
Authors: Lochmann Lubomír , Trekoval Jiří 
Published: April 2003

AbstractEsters of diacids and oligo(carboxylic acid)s substituted in α‐position with Li, Na, or K (models of the propagation site in the anionic polymerization of methyl methacrylate (MMA)) were prepared, and their IR spectra were recorded. In the range 1600 – 1800 cm−1, their absorption of the Mt+ group in benzene solution was reflected in a band between 1630 and 1645 cm−1, depending on the counterion. In the presence of THF or of tert‐butoxide of the same alkali metal this band appears between 1626 and 1660 cm−1. Coordination of the more remote alkoxycarbonyl group (e.g., in γ‐position) to the counterion is demonstrated by a band near 1712 cm−1; its absorbance is much lower in the presence of THF. In solution, the metalloesters undergo autocondensation, the rate of which increases dramatically with the number of monomeric units. Thus, in benzene at 25 °C ethyl 2‐lithioisobutyrate is stable for more than a week, whereas the half life of dimethyl 2‐lithio‐2,4,4‐trimethylglutarate (Li‐dimer, 3b) is <24 h, and the Li‐trimer (5a), Li‐tetramer (5b), and Li‐pentamer (5c) completely decompose in less than 4 min under these conditions. The decomposition may be slowed down by adding tert‐butoxide of the same alkali metal. In THF the decomposition proceeds much more quickly. The properties of models used in this study are compared with those of the propagation site in the anionic polymerization of MMA.