bluuebunny/crossref_metadata_2025_split huggingface dataset:
The vibrational spectra of some normal polyolefins
Authors: Fraser Graham V. , Hendra Patrick J. , Chalmers John M. , Cudby Michael E. A. , Willis Harry A. 
Published: April 2003

AbstractThe IR and RAMAN spectra of several normal isotactic polyolefins are presented and the effect of cooling is studied. The structural implications of side‐chain and main‐chain crystallization are discussed.
Étude par relaxation du carbone‐13 des mouvements segmentaires de la poly(vinyl‐2 pyridine)
Authors: Chachaty Claude , Forchioni Alain , Ronfard‐Haret Jean‐Claude 
Published: April 2003

AbstractLes mouvements segmentaires de la poly(vinyl‐2 pyridine) (PV2P) en solution dans CDCl3 et CD3OD ont été étudiés par mesure du temps de relaxation T1 des carbones‐13. Le temps de relaxation de ces carbones est pratiquement indépendant de la masse moléculaire et de la tacticité du polymère. Il est cependant un peu plus long pour les carbones des cycles que pour ceux de la chaîne, ce qui suggère un mouvement lent de libration de ces cycles autour de l'axe Cα—C5. Dans le cas de la forme polyélectrolyte de la PV2P (ion pyridinium) on note un accroissement sensible de la rigidité de la chaîne du fait de la répulsion qui s'exerce entre les cycles chargés positivement. Des expériences complémentaires de R.P.E. indiquent que les protons α de la chaîne se situent dans le plan des cycles pyridyles, ce qui permet de définir la position d'équilibre de ces derniers par rapport à la chaîne.
Optically active hydrocarbon polymers with aromatic side chains, 4. Stereospecific homo‐ and copolymerization of phenyl‐α‐olefins
Authors: Carlini Carlo , Ciardelli Francesco , Pini Dario 
Published: April 2003

AbstractThe polymerization of optically active phenyl‐α‐olefins, such as (R)‐4‐phenyl‐1‐hexene (1) and (S)‐5‐phenyl‐1‐heptene (2), has been performed by TiCl3/(“ARA”) or VCl4/Al[CH2CH(CH3)2]3 catalyst. 2 gives polymers which are amorphous at room temperature; no evidence of stereoregularity is obtained by IR investigation, whereas 1H‐NMR spectra seem to give some indication of steric order. By contrast, the polymers from 1, which are largely insoluble in boiling solvents, are crystalline at X‐ray examination according to an isotactic structure. The copolymerization of 1 with 4‐methyl‐1‐pentene (3) gives statistical copolymers which appear to be coisotactic. This is confirmed by crystallinity at X‐ray examination, IR and optical activity data.
Optically active hydrocarbon polymers with aromatic side chains, 5. Conformational and chiroptical properties of stereoregular polymers of phenyl‐α‐olefins
Authors: Carlini Carlo , Ciardelli Francesco , Lardicci Luciano , Menicagli Rita 
Published: April 2003

AbstractThe chiroptical properties of stereoregular polymers of optically active 4‐phenyl‐1‐hexene (1) and 5‐phenyl‐1‐heptene (2) as well as of the copolymers of 1 with 4‐methyl‐1‐pentene (3) were investigated. The comparison of the rotatory power and of the CD spectra in the spectral region of the π→π* electronic transitions of the aromatic chromophore of these polymers with the corresponding properties of optically active phenylalkanes allows the conclusion that the macromolecules of the homopolymer of 1 as well as of its copolymer with 3 contain chain blocks in helical conformation with a predominant direction of the screw. No evidence of this type was obtained for the polymers from 2. Conformational analysis based on molecular models shows that in the case of 1 having R absolute configuration, the favoured direction of the screw is the right handed one as found for poly[(R)‐4‐methyl‐1‐hexene]. The relationships between the conformation of the macromolecules and CD of the phenyl chromophore between 275 and 185 nm are consistent with previous results concerning copolymers of styrene with optically active α‐olefins.
Beitrag zur hydroxymethylierung von hydroxyphenylenmethylen‐verbindungen sowie IR‐ und UV‐spektroskopische untersuchungen dieser verbindungen
Authors: Kämmerer Hermann , Niemann Wilhelm 
Published: April 2003

AbstractEs wurden höhermolekulare α‐Brom‐ bzw. α‐Methyl‐ω‐hydroxy[(2‐hydroxy‐5‐methyl‐1,3‐phenylen)methylene] nach LEDERER und MANASSE dargestellt; die höchste erreichte rel. mol. Masse betrug rund 700. Mit steigender rel. mol. Masse wuchsen Zahl und Anteil der Nebenprodukte, so daß die Reinigung bis zur dünnschichtchromatographischen Reinheit immer verlustreicher wurde und die Ausbeuten auf 10–15% abfielen. Einige der Nebenprodukte wurden isoliert; ihre Konstitution wurde aufgeklärt und durch IR‐ und UV‐Messungen bestätigt. Tetrasubstitutionsbanden, Methylengruppen‐ und Hydroxylgruppenbanden der IR‐Spektren wurden eingehend untersucht. Die HUNTERsche Beziehung wurde bestätigt und ihre allgemeinere Gültigkeit aufgezeigt.
Dimerization and polymerization of butadiene with zero‐valent nickel and protonic acids
Authors: Furukawa Junji , Kiji Jitsuo , Konishi Hisatoshi , Yamamoto Kazuyoshi , Mitani Shin‐Ichi , Yoshikawa Susumu 
Published: April 2003

AbstractThe behavior of hydridonickel coordination compounds as catalysts for the oligomerization and polymerization of butadiene in various solvents was studied. In the presence of alcohol bis(tricyclohexylphosphine)chlorohydridonickel (4, X = Cl) (HNiCl[P(C6H11)3]2) catalyzes the linear dimerization. With hydridotetrakis(phosphite)nickel(1+) (2) ([HNi{P(OR)3}4]+), which is prepared from tetrakis(phosphite)nickel (1) (Ni[P(OR)3]4) and trifluoroacetic acid, dimerization occurs in sec‐alcohol but there is no reaction in tert‐alcohol. The main product is 2‐methylenevinylcyclopentane (8). The other products are 4‐vinylcyclohexene (10), 1,5‐cyclooctadiene (5), 1,3,7‐octatriene (7) and 1,3,6‐octatriene (9). The hydridonickel coordination compound, prepared with inorganic acids, does not afford the dimers but the 1,4‐trans polymer.
Investigations on the initiation mechanism of the acrylonitrile/butadiene alternating copolymerization in the presence of organometallic catalysts
Authors: Kuran Witold , Pasynkiewicz Stanisław , Florjańczyk Zbigniew 
Published: April 2003

AbstractThe alternating copolymerization of acrylonitrile and butadiene in the presence of organo‐aluminum compounds of the type RAlCl2 could be shown to be initiated by free radicals formed by cleavage of the AlR bond. The R• and radicals were detected under polymerization conditions by ESR spectroscopy, and the presence of the R groups in the copolymer and co‐oligomers could be confirmed by NMR and IR spectroscopy, and by elemental analyses. The results were discussed in terms of an initiation mechanism previously postulated by the authors.
Column fractionation of poly(oxymethylene diacetate)
Authors: Olcese Tito , Ackermann J. , Radici P. , Bianchi Umberto 
Published: April 2003

AbstractA column fractionation technique for poly(oxymethylene diacetate) is described. Fractionation is achieved by using a single solvent, N,N‐dimethylformamide, at a gradually increasing temperature.The mode of introduction of the crystallizable polymer into the column is a decisive factor for the reproducibility and efficiency of fractionation. Best results are obtained by introducing the polymer as a gel phase.
Syntheses and properties of new aromatic‐aliphatic copolyimides
Authors: Iwakura Yoshia , Yang Chin‐Ping , Uno Keikichi 
Published: April 2003

AbstractAromatic aliphatic copolyimides (19a–m) containing pyromellitdiimide and glutar‐ or succinimide rings in the main chain were synthesized by a two‐step reaction of specified dianhydrides (5a, b) with primary diamines (11a–h). In the first step, poly(amic acid)s (17/18) having pyromellitdiimide rings were prepared by the reaction of 2,2′‐pyromellitdiimido‐diglutaric or disuccinic anhydride (5b, 5a) with 11a–h in polar solvents. In the second step, the conversion of 17/18 to the copolyimides 19a–m was carried out either thermally or by chemical means. 5b and 5a were synthesized by the reaction of pyromellitic anhydride with glutamic or aspartic acid, respectively. No gelation was observed during a long period of storage of the poly(imidoamic acid)s 17/18 in polar solvents at room temperature. For their conversion to copolyimides, a dehydrating agent such as acetic anhydride and a catalyst such as pyridine were applied successfully. The copolyimides gave clear, tough and flexible films from DMSO solution. They show excellent stabilities at high temperatures and against oxidative degradation. IR spectra, solubilities, TG analyses and the formation of the new copolyimides were studied and compared with those of corresponding model compounds.
Thermodynamic studies based on corresponding states theory for solutions of polystyrene in ethyl methyl ketone
Authors: Nakajima Akio , Hamada Fumiyuki , Yasue Kenji , Fujisawa Koichi , Shiomi Tomoo 
Published: April 2003

AbstractThe polymer solution theory on the corresponding state principle developed by FLORY was examined by comparing the thermodynamic parameters calculated theoretically with experimental results. The osmotic pressure of the polystyrene/ethyl methyl ketone system was determined for solutions of polymer concentrations 10 to 30% at 10 to 55°C. Using X12 and Q12 parameters best fitting to these data, the calculated parameters were compared with experimental results. Both the entropy parameter ψ1 and enthalpy parameter χH, 1 were negative and decreased with increasing temperature. FLORY'S theory elucidates appreciably well the thermodynamic quantities with the use of the adjustable parameters X12 and Q12, but there seems to remain still some disagreement with experimental results. SHULTZ‐FLORY'S method for determining the Θ‐temperature was discussed based on this theory.
Heats of dilution of atactic polystyrene in ethyl acetate
Authors: Baba Yoshihiro , Katayama Haruyoshi , Kagemoto Akihiro 
Published: April 2003

AbstractThe heats of dilution and the volume change for the system polystyrene/ethyl acetate were measured. It was shown that the values of the interaction heat parameter as well as those of the excess volume change their positive sign to a negative one at about the same molar mass of the polymer. This is explained in terms of drastic changes of the conformation of the polymer molecules as soon as a certain molar mass is attained.
Pentad tacticity of polymethacrylonitrile through 13C‐NMR spectroscopy
Authors: Inoue Yoshio , Koyama Kenji , Chûjô Riichirô , Nishioka Atsuo 
Published: April 2003

AbstractThe pentad stereochemical placements in polymethactylonitrile were analyzed by using proton‐decoupled natural abundance FOURIER transformed 13C‐NMR spectra. The data of pentad microtacticity were used to examine the stereospecific polymerization mechanisms. Two types of polymethacrylonitrile were used. The relative intensities of pentad peaks for the polymer prepared with free radical catalyst by bulk polymerization at 80°C were reasonably interpreted by the BERNOULLIan model. Those for the polymer, prepared with diethylmagnesium in toluene at 70°C, may be described by both the stereoblend model and the firstorder MARKOVian model, but not by BERNOULLIan model.
Crystallization of polypeptides in the course of polymerization, 6. Effect of the heteroatom attached to the β‐carbon on the crystal growth
Authors: Kōmoto Tadashi , Ōya Masanao , Kawai Tōru 
Published: April 2003

AbstractIn order to examine the growth mechanisms of polypeptides with a heteroatom, S, on the β‐ and γ‐carbons which give the α‐conformation and the α‐helical conformation, resp., in the course of a heterogeneous polymerization, we have studied kinetics of the heterogeneous polymerization of S‐methyl‐L‐cysteine N‐carboxy anhydride (NCA), S‐benzyloxycarbonyl‐L‐cysteine NCA and L‐methionine NCA initiated by butylamine in acetonitrile and the morphologies of the resultant polymers. As was anticipated, it has been verified that poly‐(S‐substituted‐L‐cysteines), which take only the β‐structure as the ordered form, gave the chain‐folded crystals. In all the cases studied, long lath‐like crystals formed in the early stages of polymerization thickened into round rod‐like fibers as the polymerization proceeded. A possible model was proposed for the growth mechanism of these polymer crystals, taking into account the cross‐β‐structure. It has been revealed that poly(L‐methionine) with the α‐helical structure gave the extended chain crystals.
Estimation of the rate constant of termination by the monomer in the anionic polymerization of methyl methacrylate
Authors: Löhr G. , Müller A. H. E. , Warzelhan V. , Schulz G. V. 
Published: April 2003

AbstractBased on the assumption that the termination reaction in the anionic polymerization of methyl methacrylate in THF with cumyl cesium as initiator is exclusively caused by the monomer, the termination rate constant kt(±) for the ion‐pairs of polymethylmethacrylcesium is estimated by analyzing the molecular weight distribution (MWD) of polymer samples prepared at different temperatures under otherwise identical reaction conditions. The activation energy of the termination reaction of the ion‐pairs is found to be about 11 kcal/mol (46 kJ/mol). – The relatively broad MWD of the non‐deactivated chains (the so called internal nonuniformity) reveals the existence of ion‐pairs with different reactivity.
Polyreaktionen in orientierten Systemen, 3. Polymerisation ungesättigter Benzylidenaniline mit flüssig‐kristallinen Eigenschaften
Authors: Perplies Eberhard , Ringsdorf Helmut , Wendorff Joachim H. 
Published: April 2003

AbstractDie Acrylsäure‐ und Methacrylsäureester 3a–m wurden synthetisiert und auf ihr nematogenes Verhalten untersucht. Zwei Monomertypen wurden zur Untersuchung des Polymerisationsverhaltens herangezogen. Dabei zeigte sich, daß die Polymerisationsgeschwindigkeit beim übergang vom nematischen in den isotropen Bereich sprungartig ansteigt. In Abhängigkeit von der Darstellungsweise des Polymeren ergaben sich Unterschiede in der Struktur. Polymere, die bei 20°C in Lösung dargestellt werden, sind amorph, während Lösungsmittel‐polymerisate, die bei −78°C hergestellt und anschließend getempert wurden, eine Struktur aufweisen, die mit der der Polymeren aus der nematischen Phase nahezu übereinstimmt. Diese Tatsache kann als Hinweis dafür angesehen werden, daß bei tiefen Temperaturen Monomer‐aggregate in Lösung vorliegen.
ESR investigations of γ‐irradiated sulfur‐containing vinylpolymers
Authors: Mönig Hans , Ringsdorf Helmut 
Published: April 2003

AbstractThe formation and behaviour of radiation‐induced free radicals in statistical copolymers of ethoxyvinylthiomethane (1a) with N‐vinylpyrrolidone (2) (1:2,5) and of ethylthiovinylthiomethane (1b) with 2 (1:3,5) has been studied using electron spin resonance spectroscopy. After a γ‐irradiation of the copolymers at 77K Cα‐radicals in the vinylpyrrolidone moieties could be detected. Investigations on the behaviour of these radicals with an annealing procedure revealed that only in the copolymer (3b) with the dithioacetal group a transfer reaction of hydrogen atoms to the Cα‐radicals in the vinylpyrrolidone moieties occurs. This process may be regarded as a repair mechanism.
Untersuchungen zur ringöffnenden Polymerisation der 2‐Imino‐1,3‐oxazolidine
Authors: Kieser Manfred , Hamann Karl 
Published: April 2003

AbstractEs wurde die ringöffnende, zu Poly(ureylenäthylen)en (Polyäthylenharnstoffen) führende Polymerisation der 2‐Imino‐1,3‐oxazolidine untersucht.Aus 3‐Phenyl‐2‐phenylimino‐1,3‐oxazolidin (1) und sauren Verbindungen ließen sich kristalline Addukte isolieren, die aber nur dann als Initiatoren für die Polymerisation von 1 wirksam waren, wenn die saure Komponente mit dem Iminostickstoff koordiniert war.Die kinetische Untersuchung der Polymerisationsreaktion ergab, daß keine Induktionsperiode auftritt und die Reaktion nach einem Zeitgesetz pseudo 1. Ordnung verläft, was für eine bimolekulare Reaktion des geschwindigkeitsbestimmenden Schritts der Polymerisationsreaktion spricht.Diese Ergebnisse ließen sich mit denen in Einklang bringen, die für die Ringöffnungsreaktion der Iminooxazolidine mit organischen Säuren im niedermolekularen Bereich gefunden wurden.
Study of the isothermal bulk polymerization of methyl methacrylate by differential scanning calorimetry
Authors: Malavašič Tatjana , Vizovišek Ivan , Lapanje Savo , Može Adolf 
Published: April 2003

AbstractCourse and kinetics of the isothermal bulk polymerization of methyl methacrylate were studied by differential scanning calorimetry. The initiator used was 2,2′‐azoisobutyronitrile. The polymerization was investigated at temperatures between 70 and 90°C at constant initiator concentration, 5,2.10−2 mol dm−3. The heat of polymerization at 70°C is −52,3 kJ/mol (−12,5 kcal/mol) and decreases, i.e. becomes more negative, with increasing temperature. Initial rate constants for the polymerization were also determined and from them the overall activation energy, 77 kJ/mol (18,4 kcal/mol), which is in good agreement with the literature value. Another series of polymerization experiments were performed at 80°C with variable amounts of the initiator. The heat of polymerization found is −52,8 kJ/mol (−12,6 kcal/mol) and depends only slightly on the initiator concentration. The overall rate of polymerization at low degrees of conversion depends on the square root of the initiator concentration. These findings thus corroborate the conclusion reached by other authors that differential scanning calorimetry is a useful method for studying the kinetics of polymerization.
Viscosities of dilute solutions of poly(tetrahydrofurfuryl methacrylate)
Authors: Zafar Mukhtar Mohammed , Mahmood Ruqia 
Published: April 2003

AbstractThe intrinsic viscosities of seven fractions (from M̄n = 1,69.105 to M̄n = 6,13.105) of poly(tetrahydrofurfuryl methacrylate) in eleven solvents at temperatures between 30° and 50° show the following order: tetrachloroethane > dichloroethane > tetrahydrofuran > chloroform > benzene > bromobenzene > ethyl acetate > carbon tetrachloride > methyl pentyl ketone > acetone > 2‐hydroxymethyltetrahydrofuran. Values of HUGGINS slope constants range between 0,34 to 0,48 for the unfractionated polymer and the magnitudes of a and k in the expression [η] = kMa show little variations with temperature in case of good solvents whereas the opposite is observed in case of poor solvents. The theta temperature for 2‐hydroxymethyltetrahydrofuran containing 20% methanol is 31,2 ± 0,3° and 3,49, 5,72, and 4,97 are the values for K0.104, (r/M)1/2.109 and (r/Z)1/2.108, respectively.
Stereoselective copolymerization of racemic α‐olefins with ethylene by isospecific Ziegler‐Natta catalyst
Authors: Ciardelli Francesco , Locatelli Paolo , Marchetti Massimo , Zambelli Adolfo 
Published: April 2003

AbstractCopolymers of ethylene with racemic and optically active 3,7‐dimethyl‐1‐octene (3,7‐DM‐1‐O) have been prepared in the presence of ZIEGLER‐NATTA isospecific catalysts. The copolymers of racemic 3,7‐DM‐1‐O have been separated in fractions having optical activity of opposite sign by chromatography on optically active poly[(S)‐3‐methyl‐1‐pentene]. The degree of separation obtained is very close to that found for the isotactic homopolymer of 3,7‐DM‐1‐O. The fractional precipitation of both types of copolymers has been also carried out in order to obtain information on the distribution of the comonomers. The results exclude a mere steric control by the growing chain end. The stereoselectivity can be better explained on the basis of the presence of asymmetric catalytic complexes, which are stereospecific in the isotactic sense.
New light on an old polymerisation. The polymerisation of styrene by HClO4 in methylene chloride
Authors: Pepper David Charles 
Published: April 2003

AbstractProblems of interpretation of the mechanisms in the polymerisation of styrene by HClO4 in CH2Cl2, especially of chain propagation are discussed and experimental results from recent studies of the bimodal molecular weight distributions found in polymers prepared at 0 C and below, and of the kinetics of the rapid, non‐stationary, precursor polymerisation at −80 C and other low temperatures are presented. The former indicate simultaneous, but independent, propagation at 0 C by pseudo‐ionic and ionic species. The latter reveal the transient existence at low temperatures of an ionic species (absorbing at 340 nm) identified as the (poly)styryl carbenium ion. The measurements permit estimates of the free‐ion propagation rate constant at −80 C to −45 C, and suggest the unexpected conclusion that propagation by ion pairs is several fold faster than by free ions. Both species however appear to be not simple, but strongly complexed by monomer. It is speculated also that monomer complexation of the perchloric acid initiator plays an important rôle in determining whether pseudo‐ or true ionic mechanisms predominate.
Cationic polymerization of aliphatic olefins: Highlights of latest developments at the university of akron
Authors: Kennedy J. P. 
Published: April 2003

AbstractThe cationic copolymerization of isobutylene and β‐pinene (2(10)‐pinene) yields random copolymers which exhibit interesting physical properties. E.g., high molecular weight copolymers containing isobutylene/β‐pinene in the ratio of 90/10 and 97/3 are sulfur‐vulcanizable ozone‐resistant elastomers. Copolymer synthesis was accomplished with Friedel‐Crafts halides e.g., C2H5AlCl2, BF3, etc. using ethyl chloride diluent at low temperatures. The structure of the copolymers was determined by NMR spectroscopy. The reactivity ratios of isobutylene and β‐pinene are stongly affected by temperature, however, are much less sensitive to the particular Lewis acid used. Interestingly, with C2H5AlCl2, the individual reactivity ratios become equal to unity below ca. −100°C, i.e., the copolymerization becomes azeotropic.The mechanism of cationic olefin polymerizations induced by various alkylaluminum compounds has been investigated by model reactions. The rate of the reactions. The rate of the reaction

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is strongly affected by the nature of the (CH3)3CX and the CH3X solvent (X=Cl, Br. I). Unexpectedly, the sequence of rates of this reaction was found to be (CH3)3CCl>(CH3)3CBr>(CH3)3Cl. Further, an intensive study of the 2,4,4‐trimethyl‐1‐pentene/(CH3)3Al/(CH3)3CCl model system gave a series of important mechanistic insights. E.g., if an alkylaluminum compound having a β‐hydrogen in respect to aluminum is used as the coinitiator e.g., (C2H5)3Al, [(CH3)2CHCH2]3Al, etc., rapid hydridation terminates the reaction: