bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymerization of N‐vinylcarbazole, 3. Studies of copolymerizations with methyl methacrylate and styrene
Authors: Bevington J. C. , Dyball C. J. , Leech J.
Published: April 2003

Copolymers of N‐vinylcarbazole (VCZ) with methyl methacrylate (MMA) and styrene (ST) were prepared using doubly‐labelled benzoyl peroxide as initiator and the relative numbers of benzoyloxy and phenyl end‐groups were determined. In the copolymers containing MMA, the ratios of the two types of end‐group are those expected for products of free radical polymerization. The copolymers of VCZ with ST contain benzoyloxy and phenyl end‐groups in proportions which correspond to those found in homopolymers of VCZ made in non‐radical polymerizations promoted by the peroxide.
Metalation of polystyrene and its model compound 1,3,6,8‐tetraphenyloctane by the sec‐butyllithium‐N,N,N′,N′‐tetramethylethylenediamine complex
Authors: Clouet Gilbert , Brossas Jean
Published: April 2003

1,3,6,8‐Tetraphenyloctane (1) the tetramer of styrene was metalated by a complex of sec‐butyllithium with N,N,N′,N′‐tetramethylethylenediamine in cyclohexane. The lithiated styrene tetramer was quenched with deuterium oxide, and the deuterated compounds were examined by mass, 1H NMR and IR spectrometry. The spectroscopic data revealed that the lithium atoms are placed chiefly at the aromatic ring. The meta/para distribution of metalated sites in the aromatic ring was found to be approximately 2:1. Polystyrene was lithiated with the same complex. The amount of lithium in the polymer could be varied over a wide range. It was found that each lithium atom in the polymer can be substituted by a functional group, thus permitting the introduction of a controlled number of functional groups. By use of this metalation technique, phosphonate groups could be introduced into the aromatic rings of polystyrene.
Isoprene dimerization
Authors: Clouet Francoise , Brossas Jean
Published: April 2003

The mixture of isomeric dimers obtained by the dimerization of isoprene, was analyzed. The study of dimer structures obtained after deactivation of the dianionic dimers by addition of a suitable reagent, revealed the nature of the intermediate and the weight of mesomeric forms of the initial radical anion in the case of an electron transfer initiation.
Synthesis and study of poly(oxine‐methylene)s
Authors: Patel B. S. , Patel S. R.
Published: April 2003

The work presented in this paper comprises synthesis and study of poly(oxine‐methylene)s

Systematic name: poly(8‐hydroxyquinolinediylmethylene)s.

. The synthesis is based on Friedel‐Crafts polyalkylation of 8‐quinolinol, commonly known as oxine, with dichloromethane in presence of anhydrous aluminium trichloride. Five polymer samples are prepared by varying molar proportions of the two monomers. The polymer samples are insoluble in commonly used organic solvents. They are soluble in acetic acid, formic acid, and in conc. sulfuric acid. The IR and UV spectral characteristics of the polymer samples are reported. Molecular weight of the polymer samples is estimated by conductometric titration in pyridine against standard sodium methoxide. Viscometric study is carried out both in formic acid and glacial acetic acid at 35°C. Solutions of polymer samples in formic acid show normal behaviour and those in glacial acetic acid show abnormal behaviour. Various empirical relations are applied to correlate these data in glacial acetic acid. Acetic acid containing water and simple electrolytes is used as a medium to suppress abnormal behaviour. The thermal properties of the polymer samples are also studied. All the results of analysis are adequately correlated. One oxine‐formaldehyde polymer sample was also synthesized for comparison.
Die Struktur kollagenähnlicher Homo‐ und Heteropolytripeptide, 4. Polytripeptide durch repetitive Peptidsynthese und Verbrückung von Oligopeptiden
Authors: Roth Werner , Heppenheimer Kurt , Heidemann Eckhart R.
Published: April 2003

Collagen‐ like oligopeptides of defined chain length were synthesized via the following tripeptides which were combined stepwise: Boc‐Gly‐L‐Pro‐L‐Pro‐OH (1), Boc‐Gly‐L‐Pro‐L‐Lys‐OH (2), Boc‐L‐Ala‐Gly‐L‐Pro‐OH (4), Boc‐Gly‐L‐Pro‐L‐Leu‐OH (6), and Boc‐L‐Ala‐L‐Hyp(OBz)‐Gly‐OH (9). Two methods for covalent bridging of three oligopeptides of the same sequence were applied resulting in the formation of polypeptides of type 22 or 23.
Infrared spectroscopic studies on polyethylene, 5. The measurement of chain branching on powder polyethylene specimens
Authors: Baker Clive , David Peter , Maddams William F.
Published: April 2003

The scope and limitations of the potassium bromide disc technique for the infra‐red determination of chain branching in small samples of polyethylene in powder form have been assessed. Many of the samples encountered have an average particle size, prior to grinding with potassium bromide, of about 100 μm and very satisfactory results have been obtained, but the presence of larger particles leads to poor quality discs and inferior results. The well established double beam technique proves suitable for removing the interfering methylene absorption and compensation with polymethylene in the form of a film rather than as a pressed disc is preferable. Difficulties were encountered in preparing branching standards in a uniform and fine powder form, to avoid variation of the absorption coefficient of the 1 378 cm−1 methyl band with particle size. Such powders are best obtained by precipitation from solution rather than by low temperature milling. Despite these problems chain branching measurements may be made with a precision of between 5 and 10% and an accuracy of about 15%.
Glass transition temperature of linear saturated and unsaturated polyesters
Authors: Cecere Giuseppe , de Candia Francesco , Palumbo Rosario
Published: April 2003

In the present paper we have investigated the role that the presence of trans double bonds plays on the glass transition temperature of linear polyesters. Experimental data indicate that the glass transition temperature is increased by an increase of the unsaturation concentration. The effect is not drastic but it is well detectable. This result is discussed taking into account the chain microstructure and the bulk structure effects.
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

The 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

The 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

Poly(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

Phenyl(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

The 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

Two 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

Lithium 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

The 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

2,4,6‐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

Hydrogenations 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

It 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

Crystallinity 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

The 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

Using 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

Products 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

Initiation 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

The 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

A 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

Et2Zn 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

The 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

The 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

Water‐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

The 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

The 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

Protected 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

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

Investigations 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

The 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

The 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

Ethylene 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

The 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

Oligo[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

The 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

Ethyl 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

Trypsin 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

Specific 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

The 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

The 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

Conformational 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

The 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

A 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

Dissolution 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

The 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

α,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.