bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemically initiated cationic polymerization of trioxane in acetonitrile. Part I
Authors: Mengoli Giuliano , Vidotto Graziano
Published: April 2003

Trioxane, dissolved in acetonitrile solvent containing tetrabutylammonium perchlorate as background electrolyte, has been polymerized under continuous current supply at the anode of an electrolytic cell with separated anodic and cathodic compartments. The polymerization rate and the molecular weight of the polymers obtained are functions of the current intensity and the reaction temperature.

At 20°C the reacting system presents a poor autocatalytic trend and may be described by the hypothesis of the steady state for the active species.

The thermal stability of the polyoxymethylenes obtained in acetonitrile solvent is improved by the electrochemical copolymerization of trioxane with 1,3‐dioxolane.
Polymerisation of vinyl monomers by transition metal benzyl compounds. Part II. Polymerisation of styrene by tetrabenzyl zirconium
Authors: Ballard D. G. H. , Dawkins J. V. , Key J. M. , Van Lienden P. W.
Published: April 2003

The polymerisation of styrene by tetrabenzyl zirconium in toluene in the dark at 30 and 40°C has been studied using kinetics, spectroscopic and radiochemical techniques. From the data obtained, together with information derived from molecular weight measurements, a mechanism has been obtained which is in accord with the experimental findings. The polymerisation is of the coordinated anionic type in which only one of the four zirconium benzyl bonds is activated for polymerisation. Each active metal centre grows only one chain and is terminated by a β‐hydrogen abstraction process or by a bimolecular reaction involving monomer. Transfer reactions are absent. Only a small fraction of the catalyst participates in polymerisation and the concentration of active polymerisation centres is very low. A complex between tetrabenzyl zirconium and coordinated monomer could not be detected experimentally. Values for the velocity constants for initiation, propagation and termination are determined.
Redox polymerisation, 2. Kinetics of the reaction initiated by the system cyclohexanone/Mn(III)
Authors: Devi N. Ganga , Mahadevan V.
Published: April 2003

Polymerisation of acrylonitrile and methyl methacrylate initiated by the system cyclohexanone/Mn(III) has been investigated at 30–35°C in perchloric acid and sulphuric acid media. The kinetics are consistent with the formation of an intermediate complex between the ketone and the oxidant whose decomposition leads to the initiating radical. In perchloric acid the termination is effected by the oxidant whereas in sulphuric acid primary radicals terminate growing chains. Rate and equilibrium constants have been determined and their significance discussed.
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

Classical 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

Thiocarbonsäuren 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

Als 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

Photopolymerization 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

The 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

Kinetics 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

The 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

The 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

The 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

The 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

The 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

The 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

1,3‐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

IR‐ 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

By 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

It 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

Collagen‐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

The 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

The 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

The 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

Kinetics 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.
Trans→cis photoisomerization of the stilbene residues in the side chains of copolymers from 2‐hydroxyethyl methacrylate and monomer containing stilbene residue
Authors: Mikeš František , Štrop Petr , Kálal Jaroslav
Published: April 2003

The rate of the trans→cis photoismerization of the stilbene residue was compared in the copolymer 3 from 2‐hydroxyethyl methacrylate (1) and trans‐N‐4‐(4‐nitrostyryl)phenylmethacrylamide (2a) with its low molecular weight analogue trans‐N‐4‐(4‐nitrostyryl)phenylisobutyramide (2b) in methanol, 2‐ethoxyethanol and in the binary solvents propanol/water and tert‐butyl alcohol/water. It was observed that the trans→cis photoisomerization of the stilbene residues was more rapid at 20°C in the side chains of the copolymer than for 2b in most solvents. This result may be interpreted on the basis of the quantum yield dependence for the trans→cis isomerization on the polarity of the medium where the isomerization takes place. Acceleration of the trans→cis isomerization of the stilbene residues in the side chains of the copolymer results from a decrease in the polymer microenvironment polarity as compared to the polarity of the solvent itself. This interpretation is supported by direct measurement of the polarity of the polymer chain microenvironment, based on the Kosower semi‐empirical polarity scale. The course of the trans→cis isomerization of 2b and 3 does not obey the equilibrium, first‐order reaction for all the solvents mentioned. The effect of preferential sorption of one of the components in binary solvents on the polymer coil and the effect of temperature on the photochemical trans→cis isomerization are discussed in connection with the experimental results.
13C‐kernresonanzspektren von ligninen, 2. Buchen‐ und fichten‐björkman‐lignin
Authors: Lüdemann Hans‐D. , Nimz Horst
Published: April 2003

Auf der Grundlage der in der ersten Mitteilung dieser Reihe beschriebenen Modellsubstanzen werden die Signale der 13C‐NMR‐Spektren von Buchen‐ und Fichten‐Björkman‐Lignin zugeordnet. Die Spektren liefern detaillierte Konstitutionshinweise, die im Einklang mit den Vorstellungen über die Biosynthese des Lignins und mit den Ergebnissen des Ligninabbaus sind. Die beiden Spektren zeigen außerdem charakteristische Unterschiede, die die 13C‐Spektroskopie zu einer geeigneten Methode für die Klassifizierung von Ligninen verschiedener pflanzlicher Herkunft macht.
Lösefraktionierapparatur für makromolekulare stoffe
Authors: Craubner Hans
Published: April 2003

Es wird eine Lösefraktionierapparatur für makromolekulare Stoffe beschrieben. Sie kann mit Schutzgas bei konstanten hohen und tiefen Temperaturen (bis 300°C), bei normalem oder erhöhtem Druck, sowie unter Vakuum betrieben werden.

Die Apparatur wurde durch Lösefraktionierung von Polyamid 6 (PA 6; [η] = 104cm3/g, Tm = 220°C, N = 12,4%) experimentell getestet. Mit Lösungsmitteln steigender Lösekraft (u.a. konz. Ameisensäure zwischen 20 und 90°C) wurde PA 6 in Fraktionen zerlegt. Bei einer Rückgewinnung von 100,0% beträgt der mittlere Trennfaktor φα = 1 und der Fraktionierwirkungsgrad Φ>99%. Die Viskositätszahl‐ und Schmelztemperaturverteilungen sind ungewöhnlich eng. In Verbindung mit einer linearen Lorenzkurve besteht für N Konzentrationsgleichverteilung.
Polymerisation of tetrahydrofurfuryl methacrylate in solution
Authors: Zafar Mukhtar Mohammed , Mahmud Ruqia
Published: April 2003

Radical polymerisation of tetrahydrofurfuryl methacrylate (1b) in chloroform benzene, bromobenzene, methyl benzoate, α‐bromonaphthalene, 1,2‐dimethylethylene phthalate, and in bulk at 60°C showed that only bromobenzene, methyl benzoate, α‐bromonaphthalene, and 1,2‐dimethylethylene phthalate have a rate‐enhancing effect. The values of kp, kt, and Ri, calculated from k/kt, kp/kt, and the measurement of the rate of polymerisation, have shown that probably kp is dependent on the nature of the solvent, whereas kt is related to the viscosity (kt.ηmix=constant) of the solvent/monomer mixture. There is on effect of solvent on the rate of initiation.
Some kinetic aspects regarding the solid state polymerisation of trioxane
Authors: Voigt‐Martin Ingrid
Published: April 2003

An attempt is made to correlate crystallographic changes arising during the radiation induced polymerisation of trioxane with the morphological changes observed during this process. Particular emphasis is placed on the differences which are noted with changing polymerisation time and temperature, so that both nucleation and growth could be discussed.
La fusion et la cristallisation du polypivalolactone
Authors: Prud'Homme Robert E. , Marchessault Robert H.
Published: April 2003

Des fibres orientées de polypivalolactone (PPL) ont été fondues dans un calorimètre enthalpique différentiel (DSC). Deux pics sont alors obtenus à des températures de 507 et 512 K. Ils correspondent à des phases formées de chaǐnes hélicoïdales et zig‐zag planaires respectivement, tel que démontré par la méthode des rayons‐X. Après la fonte et la recristallisation des ces měmes échantillons, deux pics de fusion sont révélés à des températures de 495 et 507 K. Ils correspondent à deux modifications cristallines différentes du PPL. Suivant les conditions de cristallisation et de recuit, chacune de ces deux modifications peut ětre isolée, ou un mélange des deux peut co‐exister.
Chemische charakterisierung des kettenaufbaus und kristallisationsverhaltens von copolymeren aus 3,3‐bis(chlormethyl)oxetan und β‐propiolacton
Authors: Wiemers Norbert , Wegner Gerhard
Published: April 2003

Aus 3,3‐Bis(chlormethyl)oxetan (1) und β‐Propiolacton (2) wurden durch kationische Polymerisation Copolymere hergestellt, in denen Propiolactoneinheiten bis zu einem Molenbruch von 0,16 eingebaut sind. Das Copolymerisationsverhalten wurde untersucht, und die Copolymerisationsparameter wurden bestimmt.

Die Copolymeren wurden kristallisiert und die Einkristalle hinsichtlich ihrer Zusammensetzung und Morphologie charakterisiert. Durch selektive Umesterung in den amorphen Bereichen der suspendierten Einkristalle wurde die Verteilung der aus β‐Propiolacton gebildeten Einheiten (PL) über den Kristall untersucht, und die Ergebnisse mit Abbauversuchen an den gelösten Copolymeren wurden verglichen. Bei der Polymerisation entstehen Copolymere, in denen Blöcke aus 3,3‐Bis(chlormethyl)oxetan‐Einheiten((—BCMO)n—) mit heterogen aus BCMO‐ und PL‐Einheiten zusammmengesetzten Sequenzen abwechseln. Die durchschnittliche Länge der homogenen BCMO‐Blöcke ist im untersuchten Mischungsbereich unabhängig von der Zusammensetzung der Monomermischung. In den lamellaren Einkristallen bilden die homogenen BCMO‐Blöcke die kristalline Phase, die BCMO‐PL‐Sequenzen werden in diè amorphen Bereiche gedrängt.
The cationic polymerization of ketene acetals and the preparation and characterization of poly(1,3‐diketones)
Authors: Dunn David J. , Plesch Peter H.
Published: April 2003

Various ketene acetals (1a–d) were prepared and their cationic polymerization under homogeneous and heterogeneous conditions, in bulk and in solution between ca. 100 and −100°C were investigated.

Most of the reaction products formed in solution were viscous pale yellow fluids or sticky red solids, whereas those formed in bulk with solid, sparsely soluble initiators were white waxes or powders. For all systems for which solubility of product permitted DP determinations, the highest DPs (ca. 20) were found from bulk polymerization with solid CdCl2. With a wide range of soluble initiators in different solvents over a wide range of concentrations, DPs greater than about 8 were exceptional.

It is suggested that there are at least five chain‐breaking reactions involving the growing dialkoxycarbenium ion \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\hbox{---} {\rm CH}_2 \hbox{---} \mathop {\rm C}\limits^ \oplus \left( {{\rm OR}} \right)_2 $\end{document} and evidence is presented which accounts for the high rate of chain‐breaking compared with that for other olefinic monomers.

Acid hydrolysis of the polymers yielded the corresponding poly(1‐oxoethylenes) (poly‐(1,3‐diketone)) (4a, b), and various derivatives of both the keto and enol forms of these were prepared.
Crystallization kinetics of natural rubber under stress
Authors: de Candia Francesco , Romano Gennaro , Vittoria Vittoria
Published: April 2003

In the present paper the crystallization kinetics of two networks of natural rubber was analyzed. The two networks were prepared following two different vulcanization techniques, as usual the first, and under swelling conditions the second.

The results are discussed at the molecular level and give some important information about the well known deviations from the Gaussian theory on rubber elasticity.
Synthèses de polyisoprènes et polybutadiènes téléchéliques à extrémités hydroxyles allyliques
Authors: Brossas Jean , Clouet Gilbert
Published: April 2003

Des polymères de bas poids moléculaire possédant des fonctions alcools allyliques aux extrémités des chaǐnes ont été synthétisés. Pour cela, nous avons préparé des polydiènes α,ω‐dicarbanioniques en utilisant le naphthalène‐lithium comme amorceur, et en effectuant la réaction de terminaison par addition d'oxygène. Afin de vérifier les structures obtenues, nous avons identifiées les dimères alcadiéniques correspondants. Par oxydation directe des extrémités carbanioniques, nous avons obtenu avec un bon rendement des polyalcadiènes α,ω‐diols à hydroxyles allyliques.
Polymerization of aromatic aldehydes, 11. Polymerization of 3‐(o‐formylphenyl)propionaldehyde and o‐phenylenediacetaldehyde
Authors: Tagami Sanae , Kunitake Toyoki
Published: April 2003

Polymerization of 3‐(o‐formylphenyl)propionaldehyde (4) and o‐phenylenediacetaldehyde (5) were performed with several ionic catalysts. The cationic polymerization of 4 yielded polyacetals which contained a seven‐membered cyclic unit (7) in mole fractions of 0,3–0,5. The uncyclized unit (6) contained the pendant aromatic aldehyde. Apparently, the aromatic aldehyde group reacted during the course of the intramolecular cyclization.

Polymerizations of 5 with BF3·O(C2H5)2, lithium tert‐butoxide, or Al(C2H5)3‐TiCl4 as catalysts, similarly gave polyacetals containing a seven‐membered cyclic unit (10) in mole fractions of 0,5–0,8. The extent of cyclization decreased with increase in temperature in the cationic polymerization, resulting in a difference of −7,5 kJ mol−1 (−1,8 kcal mol−1) between the activation energy of intramolecular cyclization and that of intermolecular propagation. The polymerization with Al(C2H5)3 as catalyst gave a polyester via propagation involving a hydride shift.
A chain folding model for poly(decamethylene oxide)
Authors: Fernandez‐Bermudez Salvador , Baltá‐Calleja Francisco José , Hosemann Rolf
Published: April 2003

The present paper deals with a small angle X‐ray diffraction study of poly(oxydecamethylene) [poly(decamethylene oxide)] (1) regarding the influence of the chemical nature of the macromolecule on the fold length value. Four fractions of 1 with different molecular weights, were crystallized and the highly diluted solutions of the crystals were deposited in layers just a few microns (μm) thick. These layers were investigated by means of X‐ray diffractometry. In all fractions the X‐ray long spacing, L, exhibits characteristic values which differs in the ratio of monomeric lengths. The crystal thickness predominantly corresponds to n=2 and 3 times half the value of the unit cell (13,75 Å), for crystallization temperatures Tc≤20°C. At higher temperatures these values increase to n=6. However, at Tc≈︁50°C n changes to n=7 or 8 and recovers the value n=6 at higher crystallization temperatures if the substance is still able to crystallize at these temperatures. The multiples of 13,75 Å obtained can be explained by a specific lateral packing of stems according to a proposed model which preserves the unit cell, excludes the oxygen atoms from the folds, and favours the idea of a regularly folded surface layer (4–5 atoms per fold, 2–3 Å thick) and of an ordered three dimensional suprastructure of oxygen atoms within the lattice. Similarly, the increase of the fold length on annealing occurs in steps equal to a whole number of repeating units along the molecular chain.
Studies on functional micelles, 2. Micellar effect on the preparation of cyclic dipeptide from thioalanine S‐dodecyl ester
Authors: Kawabata Yasuziro , Kinoshita Masayoshi
Published: April 2003

The condensation reaction of thioalanine S‐dodecyl ester (1a), catalyzed by pyridine, sodium hydroxide or alkyl amines, was carried out in aqueous media to give 3,6‐dimethyl‐2,5‐piperazinedione (2a) in good yield, although thioalanine S‐ethyl ester (1b) gave under the same reaction conditions only traces of cyclic dipeptide 2a. The specific accelerating effect was explained by a supposed matrix reaction on the micelle surface.
Gel permeation chromatography in mixed eluents. Effects of sorption on porasil gels
Authors: Berek Dušan , Bakoš Dušan , Bleha Tomáš , Šoltés Ladislav
Published: April 2003

The gel chromatographic behaviour of polystyrene standards in single and mixed eluents was compared using the polar inorganic carriers of the Porasil type. It was confirmed that the changes of the elution volume with injected polymer concentration are dependent on the thermodynamic quality of the solvent. In theta mixtures the elution volume changes only little in the studied range of injected concentrations.

Further it was shown that sorption phenomena in the system can play an important part. This fact is demonstrated by different courses of universal calibration curves for single good solvents and mixed theta solvents. Besides the adsorption of polymer onto carrier also the selective sorption of a mixed eluent component on gel and/or into polymer coils can take place, and this may lead to the change of the corresponding elution volume.
The proton chemical shifts and the stereochemical structures of poly(vinyl chloride)
Authors: Ando Isao , Nishioka Atsuo , Asakura Tetsuo
Published: April 2003

The proton chemical shifts of dyads, triads and tetrads of poly(vinyl chloride) were calculated as a function of racemic unit fraction in a chain by taking account of the diamagnetic contribution, magnetic anisotropy effect and polar effect, based on Pople's approximation. The electron densities on the hydrogen atoms in each of the model compounds for the dyad, triad and tetrad units were calculated by the CNDO/2 method. The statistical weights of the preferred conformations for any specified stereochemical configuration were calculated by generating a set of 100 Monte Carlo chains using Flory's matrix method. Thus the proton chemical shifts of methylene and methyne groups in each of the dyad, triad and tetrad units were calculated by averaging over the preferred conformations. Fairly good agreement between the calculated and the experimental values of the proton chemical shifts for the dyad and triad units were obtained, but some discrepancies were found in the case of tetrads especially mrm tetrads. The dependences of the proton chemical shifts of the dyad, triad and tetrad units upon the racemic unit fraction and on the temperature were discussed.
Polymere aus 6‐Acryloylamino‐2,3‐diphenylchinoxalin
Authors: Braun Dietrich , Quarg Gunter
Published: April 2003

6‐Acryloylamino‐2,3‐diphenylchinoxalin (5a) und 6‐Methacryloylamino‐2,3‐diphenylchinoxalin (5b) werden durch Umsetzung von 6‐Amino‐2,3‐diphenylchinoxalin (3) mit den entsprechenden Säurechloriden dargestellt. Die radikalische Polymerisation von 5a in Dioxan bei 60°C liefert Polymere mit Erweichungstemperaturen von 270–280°C. Die Polymerisationsgrade sind relativ niedrig.

Das Monomere 5a wird mit Methylmethacrylat radikalisch copolymerisiert. Die Copolymerisationsparameter betragen unter den oben genannten Polymerisationsbedingungen für 5a r1 = 3,09, für Methylmethacrylat r2=0,89. Die dargestellten Monomeren und Polymeren werden durch IR‐, NMR‐ und UV‐Spektren charakterisiert.
The photolysis of copolymers of methyl methacrylate and methyl acrylate
Authors: Grassie Norman , Scotney Alan , Davis Thomas I.
Published: April 2003

The photolysis of copolymers of methyl acrylate and methyl methacrylate, covering the entire composition range, is studied with the copolymers in the form of film and in solution, under vacuum and in an atmosphere of oxygen. In film under vacuum, copolymers with high acrylate contents become insoluble, and cross‐linking and chain scission may be separated by application of the Charlesby‐Pinner equation to sol‐gel separation data. Otherwise, the polymer remains soluble, chain scission predominates and may be measured by the changes in number average molecular weight. Differences in the characteristics of chain scission under the four sets of conditions are accounted for in terms of physical factors, such as glass transition temperatures and “cage” recombination of radicals, and chemically in terms of the alternative reactions available to the primary radicals involved.
Vinyl polymerization by metal complexes, 20. Initiation by vinylamine/vinyl alcohol copolymer · copper(II) systems
Authors: Kimura Keiichi , Inaki Yoshiaki , Takemoto Kiichi
Published: April 2003

The polymerization of acrylonitrile (AN) and of methyl methacrylate (MMA) initiated by various copper(II) chelates was studied in the presence of carbon tetrachloride. Several vinylamine (VAm)/vinyl alcohol (VA) copolymers with different contents of NH2 and OH bearing monomeric units were chosen as polymer ligands as well as polyvinylamine (PVAm)/poly(vinyl alcohol) (PVA) mixtures (of equal NH2 and OH group contents as the corresponding copolymers), PVAm, and PVA. The activity of the used polymer chelates to initiate the AN and the MMA polymerization was compared at various pH values of the reaction systems. For the polymerization of MMA, the VAm/VA copolymer systems showed a higher activity than the PVAm chelate containing the same amount of NH2 groups, contrary to the case of the polymerization of AN, where the polymerization activity showed a reverse behavior. The initiation mechanism is discussed.
Hydrolysis kinetics of terephthalic and 5‐sulfonatoisophthalic acid esters
Authors: Grobe Heinrich , Nissen Dietmar , Rossbach Volker
Published: April 2003

The saponification reaction of bis(2‐hydroxyethyl) terephthalate (3) and sodium 3,5‐bis(2‐hydroxyethoxycarbonyl)benzenesulfonate (6) was followed under pH‐stat conditions in the alkaline pH range (pH 8 to 10 at 50 to 80°C) to determine the consecutive reaction rate constants for the hydrolysis of the diesters and the intermediate monoesters. The observed overall reaction rate constants were split into the individual rate constants for the hydrolysis catalyzed by the solvent, the OH− ions, the SO groups and the COO− groups (k0, kOH−, kSO, kCOO−, respectively). No intermolecular catalysis by either the sulfonato or the carboxylato groups and no “autocatalysis” by the solvent was found. The activation parameters for the hydrolysis of the corresponding esters of both acids are equal; for the diesters 3 and 6: ΔH† = 73,7 (72,0) kJ mol−1 [17,6 (17,2) kcal mol−1], ΔG† = 103,8 (104,7) kJ mol−1 [24,8 (25,0) kcal mol−1], ΔS† = −89,6 (−97,6) J mol−1 K−1 [−21,4 (−23,3) cal mol−1 K−1]; for the monoesters [terephthalic acid mono(2‐hydroxyethyl) ester and 5‐sodiumsulfonatoisophthalic acid mono(2‐hydroxyethyl) ester]: ΔH† = 80,4 (78,7) kJ mol−1 [19,2 (18,8) kcal mol−1], ΔG† = 109,3 (109,7) kJ mol−1 [26,1 (26,2) kcal mol−1], ΔS† = −86,3 (−93,0) J mol−1 K−1 [−20,6 (−22,2) cal mol−1 K−1]. It is concluded that disorders in the fine structure of polyester fibers modified with sulfonato group containing comonomers may primarily be responsable for their lower hydrolytic stability and not any catalytic effects of these groups.
Preparation of graft and block copolymers by means of amide linkages
Authors: Gupta Satyendra Nath , Nandi Umashankar
Published: April 2003

Based on the reaction between acid chlorides and amines, two techniques were developed to prepare graft and block copolymers. In the first method poly(methyl methacrylate), (PMMA), containing chloroformyl groups was reacted with 2,2′‐azodiisobutyramidine (1) or 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane] (2) to give a polymeric initiator which, on thermal activation in the presence of acrylamide, produced graft and block copolymers, according to the position of the chloroformyl group on the PMMA backbone. In the second method, PMMA containing one terminal chloroformyl group was directly reacted with polyacrylonitrile containing two terminal amidine groups to produce a block copolymer.
Die Autoxidation von Cumol in Gegenwart von Chelaten monomerer und polymerer Schiffscher basen
Authors: Kurusu Yasuhiko , Storck Winfried , Manecke Georg
Published: April 2003

Es wurden einige Übergangsmetallchelate 2a–e, 4a,b und 6a,b monomerer und polymerer Schiffscher Basen (1, 3 und 5) aus Salicylaldehyd und 2‐Aminophenol, bzw. 2,4‐Diamino‐5‐hydroxyphenol, sowie aus 2,5‐Dihydroxyterephthalaldehyd und (2,4‐Diamino‐5‐hydroxyphenol) dargestellt und ihre katalytischen Eigenschaften für die Autoxidation von Cumol untersucht. Die Aktivität nimmt in der Reihenfolge Mn>Co>NI>Cu>Zn sowie mit steigendem Molekulargewicht der Schiffschen Base ab. Die Verbindungen katalysieren auch die Zersetzung von Cumolhydroperoxid; am wirksamsten erwiesen sich auch hier die Manganchelate.
Darstellung einiger oligomerer Cyclo{oligo[(2‐hydroxy‐1,3‐phenylen)methylen]}e. Spektroskopische Untersuchung ihrer Pseudorotation
Authors: Happel Günter , Mathiasch Bernd , Kämmerer Hermann
Published: April 2003

Es wird die Darstellung von Cyclo{tris[(2‐hydroxy‐5‐methyl‐1,3‐phenylen)methylen]‐(2‐hydroxy‐5‐tert‐butyl‐1,3‐phenylen)methylen} (4a), Cyclo{bis[(2‐hydroxy‐5‐methyl‐1,3‐phenylen)methylen]‐bis[(2‐hydroxy‐5‐tert‐butyl‐1,3‐phenylen)methylen]}(4b) und Cyclo‐{pentakis[(2‐hydroxy‐5‐methyl‐1,3‐phenylen)methylen]} (4c) beschrieben. Die IR‐Spektren zeigen, daß die phenolischen Hydroxygruppen der Vierringverbindungen 4a und 4b intramolekulare, vom Lösungs(CCl4)‐ oder Zerteilungsmittel (KBr) weitgehend unabhängige Wasserstoffbrücken bilden, die bei der pentameren Ringverbindung 4c schwächer sind. Anhand der 1H‐NMR‐Spektren läßt sich bei diesen Verbindungen eine Pseudorotation nachweisen. Die Massenspektren von 4a und 4b sind für verhältnismäßig hoch beständige Verbindungen charakteristisch, während die pentamere Verbindung 4c leicht einen Grundbaustein abspaltet und so wahrscheinlich eine Ringverengung eingeht.