bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solid‐liquid diagram of polyethylene‐perhydrotriphenylene mixtures. Congruent melting of an inclusion compound containing a macromolecular constituent
Authors: Farina Mario , Di Silvestro Giuseppe , Grassi Maria 
Published: April 2003

AbstractThe melting diagram of polyethylene‐perhydrotriphenylene mixturs shows the presence of an addition compound which melts congruently at 178,2°C. This adduct, whose structure was described as an inclusion compound, does not exist in the liquid phase and does not form mixed crystals with the pure constituents. An equation for the liquidus curve has been calculated on the basis of the Flory‐Huggins theory and fits the experimental data by placing the interaction parameter χ=0.
Reaction of (5S)‐1‐azabicyclo[3.1.0]hexane with boron trifluoride etherate. Formation of an adduct and polymerization
Authors: Yamashita Tetsushi , Nigo Masuhisa , Nakamura Nobuo 
Published: April 2003

AbstractThe ring‐opening polymerization of (5S)‐1‐azabicyclo[3.1.0]hexane (1) derived from L‐proline was attempted, by use of a catalytic amount of boron trifluoride etherate as an initiator, in order to obtain optically active polymers. Chiral polymers (2) were indeed easily formed when the above aziridine 1 was polymerized in bulk or in benzene. On the other hand, a stable BF3‐adduct was obtained in the form of colorless crystals when the dilute benzene solution (1%) of 1 was allowed to react with an excess of boron trifluoride etherate. The elemental analysis and the NMR (19F, 11B, and 13C) spectra of this adduct showed it to be a (5S)‐1‐azabicyclo[3.1.0]hexane‐boron trifluoride (1:1) complex (3). It was also found that the adduct initiated the polymerization of aziridine 1 more mildly than boron trifluoride etherate.
Asymmetric synthesis catalyzed by poly(α‐amino acid)s with a tertiary amino end group
Authors: Inoue Shohei , Kawano Yohji 
Published: April 2003

AbstractPoly(α‐amino acid)s having a 2‐(dimethylamino)ethylamido group at the carboxyl end were synthesized, and their catalytic activity in the asymmetric addition of 1‐dodecanethiol to isopropenyl methyl ketone was examined. By using monomeric derivatives, an optical yield of 11–31% was obtained, while polymeric catalysts gave much lower optical yield. The role of the conformation of the polymer catalysts is discussed.
Azoinitiatoren, 10. Co‐ und terpolymerisation von butadien und styrol mit phenyl(3‐vinylphenylazo)sulfid
Authors: Nuyken Oskar , Dorn Maximilian , Kerber Robert 
Published: April 2003

AbstractPhenyl(3‐vinylphenylazo)sulfide (2)—displaying not only the properties of an initiator (thermolysis) and a monomer (vinyl group) but also of a chain transfer agent (sulfenyl group)–was copolymerized with styrene in emulsion at 40°C and in bulk at 50°C. Terpolymerization with styrene and butadiene at 5°C in emulsion led to azo‐containing unsaturated polymers, which could be used for self crosslinking.
Chemische synthese eines mutagenen fragments der minus‐strang DNA des phagen ΦX 174
Authors: Schott Herbert 
Published: April 2003

AbstractThe chemical synthesis of the undecanucleoside decaphosphate d(A‐T‐T‐A‐A‐C‐C‐T‐C‐C‐T) is described. With the exception of the mutated nucleobase (marked by the asterisk), this fragment is complementry to a segment of the plus‐strand of DNA from the Phage ΦX 174. The “point‐mutated” DNA‐fragment is chemically synthesized in five condensation steps from the protected mononucleotides dpbzA(Ac), dpT(Ac), the dinucleoside phosphate d(MeOTr)bzA‐T, and the trinucleotide dpanC‐anC‐T(Ac) by the diester method.
Reversible uptake of molecular oxygen and carbon monoxide by polymeric Cu(I) and Pd(II) chelates of 2,3,6,7‐octanetetraone tetraoxime
Authors: Yukimasa Hidefumi , Sawai Hiroaki , Takizawa Takeo 
Published: April 2003

AbstractTwo kinds of coordination polymers were prepared from 2,3,6,7‐octanetetraone tetraoxime (1) and cupric acetate or bis(benzonitrile)palladium dichloride. The average molecular weigh of the Pd(II) chelate of 1 was found to be about 700–2500. The Cu(1) chelate of 1, obtained by treating the Cu(I) chelate of 1 with hydrazine hydrate in methanol under nitrogen, can reversibly take up and release molecular oxygen and carbon monoxide. The Pd(II) chelate of 1 can also reversibly take up carbon monoxide, but in lower yield.
Lithium amide catalyzed anionic polyaddition of 1,4‐divinylbenzene with N,N′‐diethylethylenediamine
Authors: Nitadori Yoshiaki , Tsuruta Teiji 
Published: April 2003

AbstractLithium amide catalyzed anionic polyaddition of N,N′‐diethylethylenediamine (6) to 1,4‐divinylbenzene (9) was carried out to obtain a new type of polyamine possessing a polymerizable vinyl group at the chain end, a so‐called “macromer”. Analyses of the reaction and of the resulting polyamine by means of 13C NMR and GPC revealed that this polyaddition reaction is a typical equilibrium reaction which is not accompanied with any side reactions, except with a possible cyclization reaction. The equilibrium constants K and their temperature dependence were determined and compared with those of model reactions. The rate constants k1 of the first step reaction and k2 of the second step were also determined independently.
Polymer retention mechanism in GPC on active gels, 1. Polystyrene in pure and mixed eluents
Authors: Campos Agustin , Soria Vicente , Figueruelo Juan E. 
Published: April 2003

AbstractThe elution behaviour of polystyrene (PS) on spherosil X0A 200 gel in twenty one eluents and its dependence on solvent goodness, as defined by the α exponent of the Mark‐Houwink equation, and solvent strength, ϵ0, have been studied. The interstitial volume, Vo, seems to depend solely on solvent goodness, being minimum for good solvents and maximum for solvent mixtures at Θ composition or close to it. By application of a network‐limited partition and adsorption mechanism, average pore radii of the gel, r, have been obtained. For ϵ0 > 0,45 a linear dependence with negative slope between r and ϵ0 exists, whereas for ϵ0 < 0,45 r values seem to display a joint dependence on ϵ0 and α·ϵ0 α = 0,17 is the limit for obtaining experimental PS elution curves, below that value the polymer being not recovered. A coefficient f, which allows the evaluation of relative distribution coefficients (Kp) is introduced and its numerical values determined for all the eluent systems. The f dependence on ϵ0 and αis similar to that followed by r. At high ϵ0 values partion effects will be mainly responsible for Kp values. However, at low ϵ0 values, besides partition, adsorption effects contribute to the increase of Kp values.
Synthesis and properties of poly(2,4,6‐trimethylstyrene)
Authors: Chaumont Philippe , Beinert Gérard , Herz Jean , Rempp Paul 
Published: April 2003

Abstract2,4,6‐Trimethylstyrene (3a) was found to be polymerizable anionically yielding well defined samples of poly(2,4,6‐trimethylstyrene) (4) with low polydispersity, provided the reaction is carried out at low temperature in a polar solvent. It could be demonstrated that the bulkiness of the trimethylphenyl substituents in this polymer is responsible for the somewhat enhanced rigidity of the chain, and for the increase of the glass transition temperature with respect to polystyrene and to some other methyl substituted polystyrenes.
Synthèse et propriétés d'oligomères dièniques partiellement et totalement hydrogénés
Authors: Camberlin Yves , Golé Jean , Pascault Jean Pierre , Durand Jean Pierre , Dawans François 
Published: April 2003

AbstractHydrogenations of several hydroxy‐terminated low molecular weight polybutadienes (PB) or non functional PB and one polyisoprene by homogeneous catalysis were studied. Hydrogenation of 1,4‐polybutadienes gave solid crystalline polymers. In the case of hydrogenated 1,2‐polymers a decrease of the glass transition temperature was noted, the hydrogenation leading to amorphous polymers. The rheological behaviour of oligomers was found to be Newtonian at low shear rates (≤ 100 s−1). The viscosity at Tg+100°C increased in every case with the hydrogenation rate. It was found that hydrogen bonding induced by hydroxyl groups has a great effect on the glass transition temperature but does not change the viscosity at Tg + 100°C.
Etude des solutions de polymères dans un mélange de solvants au voisonage de leur point critique de démixtion, 1. Système méthanol/cyclohexane/polyvinyl‐2 pyridine
Authors: Izumi Yoshinobu , Dondos Anastasios , Picot Claude , Benoît Henri 
Published: April 2003

AbstractIt is shown that small quantities of poly(2‐vinylpyridine) extensively change the coexistence curves of the two liquids methanol/cyclohexane, especially in the vicinity of the critical point of the two liquids. It is possible to observe as a function of temperature two domains of solubility separated by three domains of precipitation when the polymer has a molecular weight 200 000. Moreover the dimensions of the dissolved poly(2‐vinylpyridine) are abnormally high in the region of the critical point of the two liquids.
Relation between crystallinity degree and stability in solid state of high molecular weight poly(ethylene oxide)s
Authors: Bortel Edgar , Hodorowicz Stanisław , Lamot Ryszard 
Published: April 2003

AbstractCrystallinity degrees exert influence on the stability of high molecular weight poly(ethylene oxide)s, POE's, in solid state. It was found that the degradation of these POE's is connected with an increase of crystallinity degrees. Samples being prepared under the terms of the strontium carbonate initiated bulk polymerization, without stabilizer, degradated during 18 days just after the polymerization has been brought to an end, while at the same time the crystallinity degrees rose by 7‐20% up to an end value of about 70%. On the contrary the phenothiazine stabilized sample preserved its starting crystallinity degree during the whole time of investigation without suffering a significant degradation. The POE prepared by the calcium amide initiated solution‐precipitation polymerization at room temperature exhibited a higher starting crystallinity degree of about 70% and, as a consequence, it was stable during the whole time of investigation. Because the bulk polymerization must be carried out at least at 90°C, the POE formed crystallizes from the melt and a greater part of amorphous zones results than in the case of the solution‐precipitation polymerization, rendering the polymer less stable. The parameters established for the unit cell in the monoclinic system remained unchanged during the whole time of investigation in spite of changes in crystallinity degrees and molecular weights.
Thermal decomposition of acrylonitrile copolymers investigated by direct pyrolysis in the mass spectrometer
Authors: Ballistreri A. , Foti S. , Montaudo G. , Pappalardo S. , Scamporrino E. , Arnesano A. , Calgari S. 
Published: April 2003

AbstractThe thermal behaviour of copolymers of acrylonitrile containing up to 15 wt.‐% of methyl acrylate (MA), methyl methacrylate (MMA), vinyl acetate (VA), and vinyl bromide (VB) units, was investigated by gradually increasing the temperature of a polymer sample placed in the ion source of a mass spectrometer (MS). The resulting pyrolytic processes (time‐temperature resolved) were analyzed by detecting the volatile decomposition products formed. Several decomposition processes were ascertained. Bromine derivatives evolution from the VB copolymer chain occurs already at 160–200°C. The thermal decomposition of the pendant ester groups in the MA and MMA copolymers occurs in the temperature range of 200–260 °C. Typical polyacrylonitrile (PAN) decomposition fragments were detected in the 240–300 °C range in all the copolymers investigated. Acetic acid units are evolved from the VA copolymer simultaneously to the PAN thermal fragments. Heterocyclic compounds originated from the ladder structures appear beyond 300°C.
The anionic polymerization of methyl methacrylate with a bifunctional initiator
Authors: Warzelhan V. , Höcker H. , Schulz G. V. 
Published: April 2003

AbstractUsing a bifunctional initiator such as the tetrameric dianion of α‐methylstyrene for the anionic polymerization of methyl methacrylate the rate constant is found to increase with conversion approaching that observed with a monofunctional initiator while the tacticity of the polymers obtained changes from that of an almost ideally atactic to a highly syndiotactic polymer. The results are explained by the assumption of an intramolecular association of the two terminal ion pairs yielding a new active species and gradually dissociating with increasing degree of polymerization of the chain. Using a polymeric dianion of α‐methylstyrene as an initiator the association phenomenon is not observed.
Untersuchungen zur stereospezifischen pfropfung von butadien auf chloriertes polycyclopentadien
Authors: Heublein Günter , Freitag Werner , Mock Werner 
Published: April 2003

AbstractProducts with >90% of 1,4‐cis‐units in the grafted chains are obtained by employing suitable concentrations of cobalt complexes as an initiator component in the grafting of butadiene onto chlorinated polycyclopentadiene. Grafting efficiencies >90% can be achieved. In contrast to grafting without using cobalt complexes the reaction rate is faster. Suitable solvents are chlorobenzene, 1,2‐dichloroethane, or dichloromethane. Grafting efficiency, degree of grafting, and the molecular weights of the grafted chains are obtained by selective extraction of the grafts with pentane. The results suggest a cationic‐coordinative mechanism, in most cases accompanied by a “pure” cationic grafting.
Living anionic stereospecific polymerization of 2‐vinylpyridine, 1. Initiation of polymerization and stereoregularity of polymers
Authors: Soum Alain , Fontanille Michel 
Published: April 2003

AbstractInitiation of the polymerization of 2‐vinylpyridine by organomagnesium compounds in hydrocarbon solvents, was obtained without side reactions on the pyridine rings. The resulting active centres are unsymmetrical. They are stable and stereospecific, leading to living polymers with an isotacticity degree of about 0,9.
Oligomérisation anionique de l'éthylène, 4. Etude cinétique de la réaction amorcée par le complexe sec‐butyllithium‐tétraméthyléthylènediamine
Authors: Aldissi Matt , Schué François , Geckeler Kurt , Abadie Marc 
Published: April 2003

AbstractThe oligomerization of ethylene in hexane, initiated by sec‐butyllithium (sec‐BuLi) complexed with tetramethylethylenediamine (TMEDA) was studied. The half‐order reaction in [sec‐BuLi‐TMEDA] and [PELi‐TMEDA] (PELi = (polyethylene)lithium) supports the presence of aggregated dimer species. For the initiation as well as the propagation, a dissociation of these dimers (sec‐BuLi‐TMEDA)2 and (PELi‐TMEDA)2 has to be considered, the monomeric form being the only active one. The higher reactivity of sec‐BuLi compared to PELi can be explained partly by a secondary carbanionic structure compared to a primary one.
Synthesis of N‐(nitrophenyl)amine substituted diacetylene monomers
Authors: Garito Anthony F. , Horner Charles J. , Kalyanaraman Palaiyur S. , Desai Kirit N. 
Published: April 2003

AbstractA new class of nitroaniline derivatives of diacetylene monomers was synthesized for the study of the nonlinear optical properties of their solid state polymers. Several members provide further examples of solid state polymerization by thermal annealing.
Cationic vinyl polymerization by the initiator system diethylzinc/phosphoryl chloride
Authors: Biswas Mukul , Mishra Girish Chandra 
Published: April 2003

AbstractEt2Zn in combination with POCl3 induces the cationic polymerization of isobutyl vinyl ether and N‐vinyl carbazole at ambient temperature. The rate is directly proportional to [Et2Zn]. [POCl3] up to a mole ratio of unity of the components, and thereafter it decreases. At a fixed ratio of [Et2Zn]/[POCl3] the rate is second order in [Isobutyl vinyl ether]. Rate and [η] decrease in the presence of basic additives, pyridine, and water. Unlike the system Et3Al/POCl3, the present combination does not lead to any stereoregular poly(isobutyl vinyl ether) at ambient or lower temperatures. A cationic mechanism is proposed and an appropriate kinetic scheme is suggested.
Investigation of the polymerization of octanelactam initiated with hydrochloric acid
Authors: Bertalan György , Rusznák István , Ercsényi Ágnes , Anna Péter 
Published: April 2003

AbstractThe polymerization of octanelactame (1) initiated by HCl takes place according to the characteristic kinetic curves. Both characteristics, i.e., the fast initial and the extremely slow further stages, and the kinetic anomaly (in certain cases under otherwise identical conditions less polymer is formed at higher than at lower temperatures) can be interpreted easily on the basis of a mechanism already suggested by the authors. The two relevant chain growth reactions, i.e., lactam addition on \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\mathop {\rm N}\limits^ \oplus {\rm H}_{\rm 3} $\end{document}‐groups and the reaction between \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\mathop {\rm N}\limits^ \oplus {\rm H}_{\rm 3} $\end{document} and N‐acylamide groups, proceed through a tetrahedral intermediate in two directions, one of them being the known chain growth, the other one an amidine (or acylamidine) formation, in which the active groups, ensuring chain growth, desactivate. Both kinetic characteristics could be interpreted on the basis of the suggested mechanism, by measuring the amounts of amino and amidine groups with the progress of polymerization.
Synthese vernetzter lysin‐ und lysinpeptidgele
Authors: Eckstein Heiner , Schott Herbert 
Published: April 2003

AbstractThe syntheses of models of histones are described. The lysine derivative Nε‐Boc‐lysine methylester, the protected peptides (Lys(Z))5,(Lys(Boc))5‐Pro‐OtBu and the protected sequence 17–27 of the histone H1 of rabbit thymus, Pro‐Ala‐(Lys(Boc))4‐Ala‐Ala‐(Lys(Boc))2‐Pro‐OMe, were transferred via three different ways into insoluble gels. The first synthetic way started with acrylamides, obtained by the reaction of the active benzotriazol‐1‐yl acrylate (3) with Nα‐amino groups of the lysine derivative and of derivatives of lysine peptides. The acrylic peptides were copolymerized with tetramethylene dimethacrylate and thus transferred into insoluble gels. In a second way partially protected peptides were coupled with carboxylic groups of cross‐linked polyacrylic gels. The third way followed the principle of the solid phase peptide synthesis. Cleavage of the protecting groups resulted in lysine and lysine peptide gels, which resemble different models of histones. The peptide gels can be used both for column chromatographic investigations of the peptide‐nucleotide interaction and for affinity‐chromatography.
Studies with microgels as matrices for molecular receptor and catalytic sites: Reactivity of hydroxamic acids as pendant groups in water‐soluble microgels
Authors: Stacey Kenneth A. , Weatherhead Richard H. , Williams Andrew 
Published: April 2003

AbstractWater‐soluble microgels were prepared by emulsion copolymerisation of benzoic methacrylhydroxamic anhydride, methyl methacrylate, acrylic acid, and 2‐hydroxyethyl methacrylate with varying amounts of ethylene dimethacrylate as cross‐linking monomer (2,3–27 mole‐% in polymer feed). The reactivity of the copolymers to cleavage of 4‐nitrophenyl esters, after removal of the protecting benzoyl group, was compared with that of monomeric and linear polymeric hydroxamic acids. Pronounced activation was observed as the degree of ionisation of the hydroxyaminocarbonyl groups increased and the reactivity of these groups to be ionised was some 180‐fold higher than that of the initially ionised hydroxyaminocarbonyl groups; all the pendant hydroxyaminocarbonyl groups were active. The activation is attributed to increasing nucleophilicity of the hydroxamic ions caused by an increasingly negatively charged microenvironment rather than to an increasingly accessible microgel architecture as the pH is raised. No change is observed in the bulk of the microgel as the ionisation of the hydroxyaminocarbonyl groups and pH are increased. Polymers with high proportions of cross‐linking monomer feed are unreactive to 4‐nitrophenyl ester cleavage.
Study of the interaction between trans‐trans‐trans‐1,5,9‐cyclododecatriene and dinitrogen tetraoxide as a model reaction of polybutadiene rubber nitration
Authors: Kostov George , Slavcheva Juliana , Mladenov Ivan 
Published: April 2003

AbstractThe reaction of trans‐trans‐trans‐1,5,9‐cyclododecatriene (1) with dinitrogen tetraoxide in tetrahydrofuran solution was studied as a model reaction of polybutadiene nitration. The reaction products were characterized by means of chemical and physical methods and the reaction process is discussed from a kinetic point of view. Attempts were made to explain the reaction mechanism at the initial steps of the nitration. The similarity between the reaction products and the kinetic results with those observed in the reaction of polybutadiene rubber nitration shows 1 to be a convenient model.
Peroxo salts as initiators of vinyl polymerization, 5. Kinetics of polymerization of N‐vinyl‐2‐pyrrolidone by peroxodisulfate in aqueous solution. Effect of Ag+ and Cu2+ ions
Authors: Manickam Subramania Pillai P. , Subbaratnam Nagayanallur Ramanatha , Venkatarao Krishnarao 
Published: April 2003

AbstractThe kinetics of the polymerization of N‐vinyl‐2‐pyrrolidone by peroxodisulfate ion in aqueous solution in the presence and absence of metal ions Ag+ and Cu2+ is studied. The rate laws for the polymerization are established and the kp/kt1/2 values computed. A negative salt effect is observed for the Ag+ catalysed process, indicating the formation of a complex of the type AgS2O8− (aq). Cu2+ ions, however, are found to reduce the rate of polymerization.
Immobilisierung von Oligodesoxyriboguanylsäuren an vernetztem Polyvinylalkohol
Authors: Schott Herbert , Watzlawick Hildegard 
Published: April 2003

AbstractProtected homologs of deoxyriboguanylic acid are synthesized on a preparative scale by condensation of monomers according to the diester method. Oligomers with four and more monomeric units are isolated and bound to the free hydroxyl groups of an insoluble poly(vinylalcohol) gel via ester linkage with their 5'‐phosphate groups. The oligo(guanylic acid) gel, obtained after cleavage of the protective groups, is suitable for preparative template‐chromatography of nucleotide mixtures.
Zur molekularen Dynamik der Lösungsprozesse von Polystyrol in verdünnten Lösungen
Authors: Wolinski Leszek , Witkowski Konrad 
Published: April 2003

AbstractRelaxation times for the dissolution processes of polystyrene are determined by light scattering investigations. Characteristic frequency numbers of rotation diffusion and torsion oscillations of the solvent molecules are determined from the Rayleigh‐wings. A correlation is found between the relaxation times τt,k0 of the 3rd stage of the dissolution process of polystyrene in different solvents and the frequency numbers δ2 of the torsion oscillations of the solvent molecules. Hence, amongst the two kinds of molecular motion of the solvent molecules, torsion oscillations are effective in the dissolution process of the solute and their frequencies have to be considered as dynamically effective. Evaluation of solvents based on these considerations does not correspond to the hitherto used rules which solvents are thermodynamically good ones and which solvents are poor ones. As an example chloroform exhibits for polystyrene the shortest relaxation time of dissolution and therefore is considered to be amongst the best solvents whereas benzene with its long relaxation time would be considered to be a poor solvent for polystyrene.