bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison between different ways to obtain molecular weight distributions of PVC and a study on the anomalies of PVC in tetrahydrofuran solutions
Authors: Andersson Kent B. , Holmström Arne , Sörvik Erling M. 
Published: April 2003

AbstractClassical methods for determinations of molecular weight distribution of PVC have been compared with gel permeation chromatography (GPC) measurements. Two PVC samples representing extreme values of polydispersity for common commercial resins, have been characterized by GPC and precipitation fractionation, using the tetrahydrofuran/H2O system. The concept of universal calibration and a correction for incomplete resolution have been applied to GPC data. Intrinsic viscosities and molecular weight averages have been determined both for the fractions and the original polymers.Different ways to calculate molecular weight distributions from the fractions have been compared. It was found that the modified BEALL method using the SCHULZ distribution function for the fractions, gives the most accurate molecular weight distribution if spurious peaks could be eliminated. Among the methods using molecular weight averages for the whole polymer in combination with a distribution function, the SCHULZ distribution function showed the best agreement with GPC. Distribution functions based on one molecular weight average only seemed to give less satisfactory results.Association of PVC molecules in tetrahydrofuran causes anomalous behaviour during the fractionation procedure and with other characterization methods. It was found that the amount of aggregates increases with syndiotacticity. To avoid the undesired influence of such supermolecular structures a heat treatment of the PVC solutions was used. The deviation from linearity in log [η] vs. log Mw plots was thus found to be due to aggregation and not to long chain branching.
Reaktionen mono‐ und bifunktioneller thiocarbonsäuren mit mono‐ und bifunktionellen isocyanaten oder isothiocyanaten
Authors: Kricheldorf H. R. , Leppert Elmar 
Published: April 2003

AbstractThiocarbonsäuren reagieren mit Isocyanaten oder Isothiocyanaten wesentlich schneller als Carbonsäuren, wobei primär Carbamidsäure‐carbonsäurethioanhydride und Carbonsäure‐thiocarbamidsäurethioanhydride entstehen, die sich nur in einigen Fällen in der Kälte isolieren lassen. In der Wärme entstehen vor allem Carbonsäureamide, mit aromatischen Isocyanaten auch Diarylharnstoffe, Carbonsäuren und Arylisothiocyanate. α,ω‐Dithiocarbonsäuren liefern mit Diisocyanaten oder Diisothiocyanaten in der Kälte Poly‐[thiocarbonylimino‐(6‐oxo‐hexamethylene)] („Polythioanhydride”︁) oder beim Erhitzen Polyamide vom Nylon‐Typ. Durch Umsetzung von 6‐Isocyanato‐ oder 6‐Isothiocyanatothiohexansäure‐trimethylsilylester mit Alkohol oder Phenol läßt sich oberhalb von 200°C Nylon‐6 mit Molekulargewichten bis zu 10000 gewinnen.
Stabile polysauerstoff‐radikale. I. Synthese von polymerisationsfähigen monomeren mit sterisch behinderter freier oder geschützter phenolischer hydroxylgruppe
Authors: Braun Dietrich , Maier Bertold 
Published: April 2003

AbstractAls Ausgangsverbindungen für die Darstellung von stabilen Polysauerstoff‐Radikalen dienten neue Monomere mit sterisch behinderter freier oder geschützter phenolischer Hydroxylgruppe, deren Synthese in der vorliegenden Arbeit beschrieben wird: 2,6‐Di‐(tert‐butyl)‐4‐vinylphenol wurde durch Decarboxylierung von 3‐[3,5‐Di‐(tert‐butyl)‐4‐hydroxyphenyl]acrylsäure in 80 bis 90 proz. Ausbeute erhalten. 2,6‐Di‐(tert‐butyl)‐4‐isopropenylphenol wurde durch eine GRIGNARD‐Reaktion von 3,5‐Di‐(tert‐butyl)‐4‐hydroxyphenylmethylketon mit Methylmagnesiumjodid und anschließende Dehydratisierung des gebildeten tertiären Alkohols mit neutralem Aluminiumoxid in 90 proz. Ausbeute synthetisiert. [2,6‐Di‐(tert‐butyl)‐4‐isopropenylphenyl]‐methyläther wurde aus 3,5‐Di‐(tert‐butyl)‐4‐methoxybenzonitril durch zwei GRIGNARD‐Reaktionen mit Methylmagnesiumjodid über die bisher unbekannten Zwischenstufen 3,5‐Di‐(tert‐butyl)‐4‐methoxyphenylmethylketon und 2‐[3,5‐Di‐(tert‐butyl)‐4‐methoxyphenyl]‐2‐propanol und anschließende Dehydratisierung des tertiären Alkohols mit 89 proz. Phosphorsäure in 64 proz. Ausbeute erhalten.
Photopolymerization sensitized by metal acetylacetonate
Authors: Kaeriyama Kyoji , Shimura Yukio 
Published: April 2003

AbstractPhotopolymerization of styrene and methyl methacrylate has been examined for twelve metal β‐diketonates. Mn(acac)3 and Co(acac)3 have a large sensitizing effect. In the photopolymerization of styrene sensitized by Co(acac)3, conversion increases linearly with time up to 10% conversion. Since sensitization is high in the wavelength region of charge transfer absorption and low in ligand field region, photoreduction of Co(III) to Co(II) is suggested during the formation of initiating radical.With the use of Mn(acac)3, photopolymerization rate of styrene was very high. The reduction of Mn(III) to Mn(II) was ascertained by ESR if 1‐methylstyrene was added as a radical scavenger. Without any radical scavenger, however, Mn(III) did not undergo reduction in benzene solution. In both cases of Co(acac)3 and Mn(acac)3, the initiation is by acetylacetonyl radical dissociated from the chelate. The central metal ion is simultaneously reduced. The initiation process is exactly the same as the thermal initiation.
Thermal degradation of copolymers of methyl methacrylate and butyl acrylate, 3. Residual polymer
Authors: Grassie N. , Fortune J. D. 
Published: April 2003

AbstractThe residual material after thermal degradation of copolymers of methyl methacrylate and butyl acrylate, covering the entire composition range, has been investigated. High methacrylate copolymers remain soluble in carbon tetrachloride. Increasing acrylate content makes the residue increasingly insoluble. The absorption which appears in the IR spectrum of the residual polymer at 1560 cm−1 is associated with the formation of a carboxylate ion whereas a shoulder on the carbonyl peak at 1760 cm−1 is ascribed to lactone formation. Absorption at 1605 cm−1 in the IR spectrum and in the 420–227 nm region of the UV spectrum are attributed to conjugated carbon‐carbon unsaturation.Chain scission in low acrylate copolymers and crosslinking in high acrylate copolymers are both closely associated with the acrylate content of the copolymer but there is no one to one relationship between chain scission and carbon dioxide production as there was in the methylmethacrylate/methyl acrylate copolymer system.
Esterification of benzenecarboxylic acids with ethylene glycol, III. Kinetics of esterification of 2‐hydroxyethyl hydrogen terephthalate with ethylene glycol catalyzed by zinc oxide
Authors: Krumpolc M. , Málek J. 
Published: April 2003

AbstractKinetics of esterification of 2‐hydroxyethyl hydrogen terephthalate (III) with ethylene glycol (II) catalyzed by zinc oxide was studied in an open system at initial molar ratios III/II from 1:13 to 1:25 and at 180–190°C. A mathematical model of the kinetics was suggested, involving irreversible consecutive, competitive, and equilibrium reactions. As verified by calculation with a digital computer, the model agrees well with the experimental data over the whole range of III conversions into bis(2‐hydroxyethyl) terephthalate (IV) and ethylene di[p‐(2‐hydroxyethoxycarbonyl)benzoate] (dimer V). The individual reaction steps are assumed to be the reaction of III with II to form IV (k1), the condensation of IV giving V and II (k2), the reverse transformation of V into IV under the action of II (k3), the reaction of III with IV yielding V (k4, the condensation of III to ethylene p‐carboxy‐benzoate p‐(2‐hydroxyethoxycarbonyl))benzoate (dimer VI) (k5), and the reaction of VI with II to give V (k6). The values of reaction constants determined at the III to II initial molar ratio of 1:19,5, at 190 ± 0,1°C, and zinc oxide concentration of 0,002 mol · kg−1 are: k1 = 0,031, k2 = 0,054, k3 = 0,075, k4 = 0,18, k5 = 0,19, and k6 = 0,11 mol · kg−1 · h−1; the equilibrium constant K (k2/k3) at 190°C corresponds to a value of 0,72. The analytical method was based on the successive extraction of the individual reaction components from one sample and on their polarographic determination.
Thermal degradation of copolymers of methyl methacrylate and butyl acrylate, 4. The reaction mechanism
Authors: Grassie N. , Fortune J. D. 
Published: April 2003

AbstractThe major products and most of the minor products of the thermal degradation of copolymers of methyl methacrylate and butyl acrylate covering the whole composition range have been accounted for in terms of a complex series of radical processes with a common initiation step.
The electroinitiated polymerization of N‐vinylcarbazole with zinc bromide, II. Kinetics of polymerization
Authors: Phillips D. Colin , Davies D. H. , Smith J. D. B. 
Published: April 2003

AbstractThe electroinitiated polymerization of N‐vinylcarbazole (VCZ) in acetone solvent at 25°C with zinc bromide, as catalyst, and platinum electrodes was investigated in detail. The polymerization rate was found to be directly dependent on current strength, zinc bromide concentration and the initial water content of the solvent.The molecular weights of the formed polymers (1000–6000) are independent of current strength, zinc bromide concentration and degree of conversion of monomer to polymer, but are affected by water, monomer concentration, and by the type of electrodes used. The chemical composition of the polymer is invariant with current strength, zinc bromide concentration, degree of conversion, and electrode material but does vary slightly with the water content of acetone.
The thermodynamics of polymerisation of aldehydes and cyclic ethers. Part III: Oxepane and 1,3‐dioxepane
Authors: Busfield W. K. , Lee R. M. 
Published: April 2003

AbstractThe equilibrium between gaseous monomer and amorphous polymer has been studied for oxepane and 1,3‐dioxepane between 38°C and 92°C. From the equilibrium pressures of monomer the ΔH°gc and ΔS°gc values have been calculated. Thermodynamic data for the vaporisation of each monomer have also been measured and have enabled values of ΔH1c° and ΔS1c° for the polymerisations to be calculated.For oxepane:

and for 1,3‐dioxepane:
Calculation of the carbon‐13 chemical shifts of the methylene carbons of meso and racemic 2,4‐dimethoxypentanes as model compounds of poly(vinyl methyl ether)
Authors: Ando Isao , Kondo Masahiro , Ikuta Tetsuo , Nishioka Atsuo 
Published: April 2003

AbstractThe 13C chemical shifts of the methylene carbons of meso and racemic 2,4‐dimethoxypentanes were calculated by the CNDO/2 method. The results were in fairly well accordance with the experimental results of poly(vinyl methyl ether). The cis form of the side chain was more stable than the trans form.
Esterification of benzenecarboxylic acids with ethylene glycol, 4. Kinetics of the initial stage of polyesterification of terephthalic acid with ethylene glycol catalyzed by zinc oxide
Authors: Krumpolc Miroslav , Málek Jaroslav 
Published: April 2003

AbstractThe initial stage of polyesterification of terephthalic acid (1) with ethylene glycol (2) catalyzed by zinc oxide was studied kinetically in heterogeneous as well as homogeneous phase in an open system at initial mole ratios of 2 to 1 ranging from 10 to 77 and at temperatures from 180 to 196°C. A mathematical model of the kinetics was suggested which, as verified by computer calculations, is valid for all systems characterized by the initial mole ratio of 2/1 ≧ 10 and over the whole range of transformations of 1 up to the equilibrium between bis(2‐hydroxyethyl) terephthalate (4) and 1,2‐bis[p‐(2‐hydroxyethoxycarbonyl)benzoyloxy]ethane (dimer 5). The kinetically important reaction steps in the initial stage of polyesterification are the esterification of 1 with 2 yielding 2‐hydroxyethyl terephthalate (3) (k1), the esterification of the latter with 2 to form 4 (k2), the condensation of 4 giving dimer 5 (k3), the glycolysis reaction of the latter fo form 4 (k‐3), the condensation of 1 with 4 yielding 1‐(p‐carboxybenzoyloxy)‐2‐p‐(2‐hydroxyethoxycarbonyl) [benzoyloxy]‐ethane (dimer 6) (k4), the condensation of 3 to give dimer 6 (k5), and that of 3 with 4 to form dimer 5 (k6), and the esterification of dimer 6 with 2 yielding dimer 5 (k7). In the heterogeneous phase of the polyesterification of 1, the favoured reactions are the condensation reaction of 3 and that of 3 with 4 to form dimer 6 and dimer 5, respectively; in the homogeneous phase the condensation of 1 with 4 leading to dimer 6 is the kinetically preferred reaction. Optimum values of the rate constants k1k7 are presented. The equilibrium constant k3/k−3, determined at the 2/1 initial mole ratio of 12,5 and 190°C, corresponds to a value of 0,85. An analytical method is presented based on the successive extraction of the five reaction components from one sample of the reaction mixture and on their polarographic determination.
The chemical shifts and the conformations of linear hydrocarbons, 2
Authors: Ando Isao , Nishioka Atsuo 
Published: April 2003

AbstractThe proton chemical shifts of methyl and methylene groups along the chains of some linear hydrocarbons with carbon numbers 9, 16, 22 and 30, were calculated by using POPLE's approximation and Monte Carlo method.Contrary to the single peak obtained by averaging the chemical shifts of specified methylene protons for 100 Monte Carlo chains, double peaks were obtained by plotting the distribution of the chemical shifts of the methylene protons without averaging.These results could interpret the experimental behavior of the proton chemical shifts of some linear hydrocarbons in α‐chloronaphthalene solution.
Über die polymerisation von 1,3‐dithiolan‐2,4‐dionen
Authors: Kricheldorf Hans R. , Bösinger Klaus , Schwarz Gerd 
Published: April 2003

Abstract1,3‐Dithiolan‐2,4‐dione (5) sind destillierbare Monomere, die aus 2‐Halogencarbonsäuren leicht zugänglich sind. Basische Katalysatoren können eine rasche Polymerisation zu Polyestern der 2‐Mercaptocarbonsäuren, Poly(thioalkylencarbonyle), (9) bewirken, wobei sich rel. mol. Massen um 80000 erreichen lassen. Während primäre Amine und andere protische Nucleophile als Initiatoren wirkungslos sind, steigt die katalytische Aktivität aprotischer Basen mit zunehmender Basizität, da die wirkungsvollste Startreaktion aus einer CH‐Deprotonierung am Monomeren resultiert. Die thermische Decarboxylierung führt ebenfalls zur Polymerisation, doch wird mit steigender Temperatur in zunehmendem Maße 1,4‐Dithian‐2,5‐dion (10) gebildet. Der thermische Abbau der Polyester zu 10 erfolgt bevorzugt am Kettenende. Ein rascher Abbau der Polyester wird aber auch schon bei Raumtemperatur und selbst unter wasserfreien Bedingungen von starken Basen, wie z. B. tertiären Aminen und Alkoholaten, bewirkt.
The vibrational spectra of some ethylene‐propylene copolymers
Authors: Fraser Graham V. , Hendra Patrick J. , Walker John H. , Cudby Michael E. A. , Willis Harry A. 
Published: April 2003

AbstractIR‐ and RAMAN spectra of ethylene‐propylene copolymers are given, and their significance is discussed in terms of the structure of the “crystalline” units. It is concluded that vibrational spectroscopy is applicable to the structural diagnosis in this case, and that the addition of small amounts of propylene to ethylene alters the crystallinity in blocks of the latter to the less normal form containing only one chain per unit cell. In these particular cases, at lower ethylene concentrations normal crystallisation seems to occur in both ethylenic and propylenic sectors.
Phase diagram and structural study of polystyrene‐poly(ethylene oxide) block copolymers, 2. Systems polystyrene‐poly(ethylene oxide)/solvent of the poly(ethylene oxide) block
Authors: Gervais Monique , Gallot Bernard 
Published: April 2003

AbstractBy means of low angle X‐ray scattering and differential scanning calorimetry, we have drawn the phase diagrams of block copolymers from styrene and ethylene oxide in the presence of a preferential solvent for poly(ethylene oxide) (PEO). Such systems exhibit two liquid crystalline structures in terms of temperature and solvent concentration.A lamellar structure with crystallized PEO chains (LCC) exists at temperatures below about 40°C and for solvent concentrations ranging from 0 to a value characteristic of the copolymer studied. For higher solvent concentrations and temperatures up to about 170°C a structure with method PEO chains is found.We have shown that in the LCC structure the chains of PEO crystallize in two layers; the solvent forms a third layer located between the PEO layers. This crystalline structure confirms the structure already proposed for the systems styrene‐ethylene oxide copolymer/diethyl phthalate.As the solvent concentration is increased, the thickness of the solvent layer increases, separating the PEO layers but without dissolving them; when the thickness of the PEO layers is high enough, the chains of PEO may crystallize on a lower thickness the number of folds being increased by one.We have studied the influence of the composition and relative molecular mass of the copolymer as well as the influence of the nature of the solvent on the variation of the structural parameters with solvent concentration.
“Entanglement” concept and chain conformations in bulk amorphous polymers
Authors: Privalko Valery P. , Lipatov Yuri S. 
Published: April 2003

AbstractIt is shown that the presently available information on the structure of bulk amorphous polymers is consistent with the concept of the existence of a substantial amount of short‐range segmental order. It is suggested that the sharp change of molecular‐weight dependence of NEWTONian viscosity of polymer melts with the approach to the critical “entanglement” molecular weight Mc is brought about mainly by the transition from the extended‐chain conformation of the macromolecules into the statistically folded‐chain conformation. Finally, empirical relationships are obtained which relate the values of polymer packing coefficients in the crystalline state as well as the “best” numerical values of Mc with molecular parameters of a polymer.
Collagen‐Poly(methyl methacrylate) graft copolymers: Effect of aqueous organic solvent system and salts on copolymer composition
Authors: Rao K. Panduranga , Joseph K. Thomas , Nayudamma Y. 
Published: April 2003

AbstractCollagen‐poly(methyl methacrylate) (PMMA) graft copolymers were prepared in a number of aqueous/organic solvent systems and in the presence of neutral salts using ceric ammonium nitrate as initiator. The composition of the collagen‐methyl methacrylate graft copolymers was studied by hydrolyzing the collagen backbone and measuring the molecular weights of the grafted PMMA branches. In water/methanol grafting media the molecular weights of the PMMA branches showed a maximum at a methanol concentration of 25% and then decreased with further increase in methanol concentration. Even though the percent grafting registered a sharp fall with increasing concentration of methanol, the number of grafting sites remained more or less constant and was almost the same as that obtained in aqueous medium. Other aqueous/organic solvent systems gave more grafted chains than those prepared in water alone, and these were of lower molecular weight. Anions such as sulphate and chloride were found to have more influence than nitrate in decreasing the number of grafting sites.
Molecular weight determination of isotactic polypropylene by high‐sensitivity ebulliometry
Authors: Parrini Paolo , Vacanti Marcella Sacchini 
Published: April 2003

AbstractThe use of a new differential ebulliometer and the determination of the number average molecular weight of unfractionated isotactic polypropylenes is described; the results were reproducible and of satisfactory accuracy. Application of a thermopile with 150 junctions and of suitable devices for the regularity of boiling allowed measurements of number average molecular weights M̄n up to 100000 in good agreement with results obtained by other methods.In this way it is possible to measure M̄n directly, e.g. for reliable determinations of M̄w/M̄n also for polymer samples with low molecular weights and/or wide molecular weight distributions.
Kinetics and mechanism of cationic epoxide copolymerization
Authors: Entelis Sergey G. , Korovina Galina V. 
Published: April 2003

AbstractThe kinetics and mechanism of copolymerization of epoxyalkanes [epoxypropane (2a), 1‐chloro‐2,3‐epoxypropane (2b), and 2,3‐epoxy‐1‐propyl nitrate (2c) (glycide nitrate)] with tetrahydrofurane by BF3 were investigated. Kinetic and molecular weight regularities were established and copolymerization constants were determined. The formation of cyclic tetramers of the epoxyalkanes was found to be a characteristic feature of homo‐ and copolymerization. Reactions yielding double bonds at the end and hydroxylic groups and such hindering chain growth were investigated.From a large class of phenomena the hypothesis was derived that the growing polymer chain represents a “cyclic” zwitterion and the active center is an ion pair. A number of facts in favour of the carbonium nature of the polymerization centers was established.
Vinyl polymerization, 314 Polymerization of vinyl monomers photosensitized by 1,4‐bis(pentamethylene)‐2‐tetrazene
Authors: Sugiyama Kazuo , Nakaya Tadao , Imoto Minoru 
Published: April 2003

AbstractThe photopolymerization of vinyl monomers can be sensitized by 1,4‐bis(pentamethylene)‐2‐tetrazene (1). The kinetics of the photopolymerization was investigated in the case of styrene (St). The rate of polymerization was found to be proportional to the one half power of the concentration of 1 and to the first power of the concentration of St. A plausible mechanism proposed for the overall reaction is discussed in the light of the experimental results.
Redox polymerization kinetics of vinyl polymerization initiated by the v5 +/cyclohexanone system in aqueous sulphuric acid
Authors: Mohanty Trijama R. , Singh Baishnab C. , Nayak Padmalochan 
Published: April 2003

AbstractKinetics of the vinyl polymerization of acrylonitrile initiated by the redox system cyclohexanone/V5 + were investigated in aqueous sulphuric acid in the temperature range of 35—50°C and the rates of polymerization and of V5 + disappearance etc. were measured. From the result it was concluded that the polymerization reaction is initiated by an organic free radical arising from the V5 +‐cyclohexanone reaction and terminated by V5 + ions. A suitable kinetic scheme was proposed and the various rate and energy parameters were evaluated.