bluuebunny/crossref_metadata_2025 huggingface dataset:
Persilylierung von Cellulose, Amylose und Polyvinylalkohol
Authors: Bredereck Von Karl , Strunk Klaus , Menrad Hubert
Published: April 2003

Es wird über die Darstellung von Tris‐O‐trimethylsilyl‐cellulose, ‐amylose und Polyvinyltrimethylsilyläther durch Umsetzung von Cellulose, Amylose und Polyvinylalkohol mit N‐Trimethylsilylacetamid berichtet.
Syntheses and polymerisation of methyl 12‐ and 18‐vinyloxystearates
Authors: Tewari G. N. , Chatterjee P. C. , Aggarwal J. S.
Published: April 2003

Methyl 12‐ and 18‐vinyloxystearates were prepared by vinyl transetherification with ethyl vinyl ether. Stannic chloride initiated cationic polymerisation of these monomers in cyclohexane yielded colourless viscous liquids having a degree of polymerisation of about 20. The ester groups in the polymers were hydrolysed to give the corresponding polyacids and were reduced to give the corresponding polyols.
Dye‐sensitized photopolymerization of methylmethacrylate in nonaqueous media
Authors: Maiti Sukumar , Saha Mihir K. , Palit Santi R.
Published: April 2003

The dye‐sensitized photopolymerization of methylmethacrylate by visible light in nonaqueous media especially benzene has been investigated using long chain aliphatic amines as activators. For the typical system, eosin/cetyl dimethylamine/methylmethacrylate in benzene, the rate of polymerization has a square root dependence on light intensity and direct proportionality on monomer concentration, while with respect to eosin and cetyl dimethylamine, it passes through a maximum, indicating their dual role as both initiator and retarder. The molecular weight decreases with increase in light intensity and eosin concentration, and also with decrease in monomer concentration. However, the molecular weight passes through a maximum with cetyl dimethylamine concentration. Electrondonating groups attached to the benzene nucleus in the halogenated fluorescein dye stuffs accentuate the sensitizing action of dye stuffs, while electron‐withdrawing groups deactivate it. The greater the chain length and the greater the amount of N‐substitution in the long chain aliphatic amines, the greater is the activating influence. The effect of combination of dye stuffs as well as the effect of solvents on the rate of polymerization are also discussed. With increase in amine concentration, the average number of amino end groups per chain is reduced. The presence of hydroxyl end groups has also been demonstrated in systems containing alcohols. Presence of oxygen or air in the polymerization systems is always accompanied by an inhibition period and reduction in rate of polymerization. The overall activation energy has been found to be 20 kcal/mole. For the effect of different variables on the rate of polymerization and molecular weight tentative mechanisms following a free radical course have been suggested.
Unperturbed dimension of polystyrene from viscosity measurements in cosolvent media
Authors: Deb P. C. , Palit Santi R.
Published: April 2003

The method proposed by DEB and CHATTERJEE1 for the determination of unperturbed dimension of a polymer from solution viscosity data in different solvents and molecular weight has been applied to four fractions of polystyrene in a series of cosolvents consisting of varying amounts of acetone and cyclohexane. The solubility characteristics of these cosolvents, particularly the optimum solvent composition, have been examined with respect to the thermodynamic theory of R. L. SCOTT.
Temperature dependence of solution viscosity of polymers in solvent‐nonsolvent systems
Authors: Sastry K. S. , Patel R. D.
Published: April 2003

The temperature dependence of viscosity for a dilute polymer solution is given by the equation η = A·eQ/RT. The value of Q and A for polybutene‐1 and polyisobutylene in pure solvent and solvent‐nonsolvent systems have been obtained. Variation of the apparent energy of activation of viscous flow Q, with concentration c has been discussed according to the equation.

where Q0 is the value for the solvent, M is the molecular weight of the polymer and Ke is a constant. The change in sign of Ke observed for both the polymers in the solvent‐nonsolvent systems is discussed.

The dependence of the preexponential term A on concentration is discussed according to the equations

where A0 is the value for the solvent, Ka, K, α, and β are parameters depending on the polymer and solvent. The dependence of entropy of activation ΔS on molecular weight and concentration has been discussed for both the polymers.
Studies on addition polymerization in mixed solvent system. Part III. Chain transfer of glycols in the polymerization of methyl methacrylate
Authors: Bhaduri Gopal Chandra , Nandi Uma Shankar
Published: April 2003

The role of different glycols for the overall kinetics and particularly for the chain transfer step in the addition polymerization of methyl methacrylate has been studied. The polymerization of methyl methacrylate has been carried out in the homogeneous phase using mixed solvent systems at 60 and 80°C. The degree of polymerization has been found to decrease owing to chain transfer and dilution but after a certain concentration, it gradually increased with increasing glycol concentration. This increase in the degree of polymerization has been attributed to a reduced termination rate resulting from the coiling of the growing polymer chain at higher glycol concentrations. The chain transfer constants of glycols have been found to increase with the size of the alkyl groups indicating thereby that the chain transfer probably occurs via the abstraction of an H atom from the alkyl group and not from the OH group of the glycols.
Note on the effect of γ‐irradiation on the melting behavior of polyethylene single crystals
Authors: Takamizawa Kan'Ichiro , Fukahori Yoshihide , Urabe Yoshiko
Published: April 2003

Polyethylene single crystals were prepared from isoamyl acetate solutions, whose thickness was 200 Å. They melted without significant reorganization during the heating process of DTA measurements. Irradiation with doses up to 100 Mrads scarcely affected the melting point and heat of fusion of the crystals. In case of pressed aggregates of the single crystal, the increase of the melting point by irradiation was observed. The effect of irradiation became even stronger with melt‐crystallized samples. The increase was interpreted in terms of interlamellar crosslinking. It is possible that the melting point of irradiated single crystals increases if the lamellae are in close contact.
Der nachweis der kettenstruktur von aus p‐kresol und formaldehyd aufgebauten mehrkernverbindungen. IV. Durch kernmagnetische resonanz‐spektren
Authors: Eichhoff Von Hans‐Joachim , Kämmerer Hermann , Weller Dieter
Published: April 2003

Von 17 phenolischen, aus p‐Kresol und Formaldehyd aufgebauten Mehrkernverbindungen mit einem Molekulargewicht bis 986 wurden die kernmagnetischen Resonanz‐(1H‐NMR)‐spektren aufgenommen. Die gefundenen Bereiche der Signale sind: für die Methylprotonen von δ = 2,13 bis 2,44 ppm, die Methylenbrückenprotonen von 3,61 bis 4,01 ppm und die aromatischen Protonen von 6,45 bis 7,74 ppm. Die Signale der Protonen der phenolischen Hydroxylgruppe haben keine charakteristischen chemischen Verschiebungen; sie konnten manchmal erst nach Lösungsmittelwechsel erkannt und im Bereich von 5,45 bis 11,03 ppm gefunden werden. Bei höhermolekularen Verbindungen lassen sich die in der Kette endständigen Methyl‐ und Methylenbrückenprotonen von den anderen unterscheiden. Die Flächenintegrale der einzelnen Signale stimmen mit der angegebenen chemischen Struktur überein. Die NMR‐Spektren erlauben auch, den Reinheitsgrad der untersuchten Verbindungen abzuschätzen. Die aus den Synthesewegen abgeleiteten Strukturen, die mit den zugehörigen IR‐Spektren übereinstimmen, können durch die NMR‐Spektren weitgehend bestätigt werden.
The unperturbed dimensions of poly(styrene‐co‐dimethylitaconate)
Authors: Veličkoviča Jovan , Jovanović Dragan , Vukajlović Jovanka
Published: April 2003

The changes of free rotation around the carbon‐carbon bonds in statistical chains of poly(styrene‐co‐dimethylitaconate) samples of different average composition were evaluated in terms of the σ‐parameter, the ratio of the end‐to‐end distance of the coil in the unperturbed state to the same distance in a freely rotating chain. Samples of copolymers were carefully fractionated and fractions of identical composition selected for viscosity and light scattering measurements were subjected to the KURATA‐STOCKMAYER extrapolation procedure, and KΘ and σ evaluated in terms of composition. Always between values of 2.17 and 2.02 for the parent homopolymers, σ goes through a slight minimum at about 33 mole‐% of styrene. The phenomenon seems to stress the significance of electrostatic forces between opposite and neighbouring substituents of the poly(dimethylitaconate) chain which are comparable to the mutual incompatibility of unlike monomer residues in the copolymer chain.
Ringschlußreaktionen an aromatischen polymeren
Authors: Lorenz Von G. , Gallus M. , Giessler W. , Bodesheim F. , Wieden H. , Nischk G. E.
Published: April 2003

Aus 4.4′‐Dichlordiphenylsulfon und dem Dikaliumsalz der 5‐Hydroxy‐anthranilsäure in Dimethylsulfoxid wurde 4.4′‐Bis‐(4‐carboxy‐3‐amino‐phenoxy)‐diphenylsulfon erhalten und in polaren Lösungsmitteln wie N‐Methylpyrrolidon (NMP) oder N.N‐Dimethylacetamid (DMA) mit aromatischen Dicarbonsäurechloriden zu hochmolekularen Polyamiden mit freien Carboxylgruppen umgesetzt. Diese Polyamid‐carbonsäuren ließen sich in NMP unter Zusatz von Dehydratisierungsmitteln wie Thionylchlorid, Phosphoroxidchlorid oder Phosphorpentoxid in hochmolekulare Polybenzoxazinone überführen. Mit aromatischen Aminen wurden daraus N‐arylsubstituierte Polychinazolone mit besonders guter Löslichkeit in organischen Lösungsmitteln hergestellt. Ebenfalls N‐arylsubstituierte Triazolmodifizierte Polybenzimidazole wurden aus 3.5‐Bis‐(4‐arylamino‐3‐aminophenyl)‐4‐aryl‐1.2.4‐triazolen und aromatischen Dicarbonsäurechloriden in NMP mit nachfolgendem Erhitzen der offenkettigen Polyamid‐amine unter Wasserabspaltung erhalten. Die Ringschlußreaktionen werden an Hand von IR‐Spektren erörtert.
Zum fällungsverhalten von mischungen polymerhomologer substanzen. II.
Authors: Klein Von J. , Wittenberger U.
Published: April 2003

Das Entmischungsverhalten von definierten Polymermischungen wurde im System Polystyrol/Benzol/Methanol bei 25°C durch die Analyse der Gelphasen, die sich bei bestimmten Überschreitungen (30, 60 und 90%) des Gleichgewichts bilden, untersucht. Dabei ergab sich, daß in erster Linie die hochmolekulare Komponente aus der Lösung „herausgedrückt”︁ wird, aber auch die niedermolekulare Komponente eine Löslichkeitsverminderung erfährt. Diese Löslichkeitsbeeinflussung nimmt mit zunehmendem Konzentrationsverhältnis cB/cA und mit abnehmendem Molekulargewichtsverhältnis MA/MB zu, in guter Übereinstimmung mit Fällungstitrations‐Experimenten. Ein Einfluß von Menge und Zusammensetzung der Gelphase auf die Zusammensetzung der Solphase kann nicht festgestellt werden.

Die statistisch‐thermodynamischen Theorien werden in ihrer gegenwärtigen Form diesem Entmischungsverhalten der verdünnten polydispersen Lösung offenbar nicht gerecht. Gegenwärtig sollte daher der Beschreibung mittels empirisch bestimmbarer Aktivitätskoeffizienten der Vorzug gegeben werden. Im Rahmen einer kurzen Diskussion der Folgerungen für die Polymerfraktionierung wird gezeigt, daß die Löseverfahren in ihrer Trennleistung den Fällungsverfahren überlegen sein müssen.
Synthese und chemische eigenschaften einiger copolymerisate von 8‐hydroxy‐5‐vinyl‐chinolin‐derivaten. 1. Teil: Darstellung der monomeren
Authors: Manecke Von Georg , Aurich Hans‐Peter
Published: April 2003

8‐Hydroxy‐5‐acetyl‐chinolin und Derivate, von denen einige in 2‐Stellung methyl‐ und/oder in 7‐Stellung bromsubstituiert sind, wurden als äthyl‐ und Benzyläther mit Natriumborhydrid reduziert. Die Carbinole ergaben bei der Pyrolyse die Vinylverbindungen.
The radiation induced reactions of aqueous polyethylene oxide solutions. I. Theory of gelation
Authors: Stafford J. W.
Published: April 2003

Dilute deaerated aqueous polyethylene oxide solutions have been irradiated with 60Co γ‐rays. The concentration dependence of the gel dose, the dose required for gelation, was found to vary with the initial molecular weight of the polymer used. For low molecular weight polymer, with increasing polymer concentration the gel dose fell rapidly to its lowest value at the critical concentration, ccrit, and thereafter increased. High molecular weight material showed similar behaviour below ccrit, but the gel dose varied little with addition of polymer for concentrations not far above ccrit. These results are interpreted in terms of a proposed theory which considers the intermolecular crosslinking process to be diffusion controlled below ccrit, and to depend on the packing of discrete, non‐interpenetrating polymer molecules not far above ccrit. Literature data on the radiation induced gelation of deaerated aqueous polyvinyl alcohol solutions can also be satisfactorily treated with the proposed theory.
Polymerization of epoxyorganosilanes. II. Asymmetric selective polymerization of epoxyorganosilanes
Authors: Khanh Pham Huu , Koinuma Hideomi , Inoue Shohei , Tsuruta Teiji
Published: April 2003

The asymmetric selective polymerization

In PINO's words : stereoselective polymerization, cf. J. Polymer Sci. C 16 (1968) 3265.

of epoxyethyltrimethylsilane (ETMS) and of (2.3‐epoxypropoxy)trimethylsilane (EPOS) were studied using a catalyst system formed by an organometallic compound reacted with an optically active reagent. Optically active polymers were obtained in both cases but the asymmetric selectivity of EPOS polymerization was low, considering the weak optical activity of glycidol derived from the hydrolysis of recovered monomer. Concurrently, this experiment permitted us to deduce that dextrotatory EPOS has the same configuration as dextrorotatory glycidol.

A polymer of EPOS was submitted to a series of reactions leading to a polymer identical to polypropylene oxide (PPO). The optical behaviour of this polymer, studied in comparison with PPO, also confirmed the relation between the absolute configuration of EPOS and its optical rotation sign. This is the first example, in which the absolute configuration can be determined by utilizing the asymmetric selective polymerization.
Chain growth in the base catalyzed hydrogen transfer polymerization of acrylamide to poly(β‐alanine)
Authors: Camino Giovanni , Guaita Marino , Trossarelli Luigi
Published: April 2003

Yields and reduced specific viscosities of the products of the sodium tert‐butoxide catalyzed hydrogen transfer polymerization at 100°C of acrylamide in 1‐methyl‐2‐pyrrolidone have been determined as a function of time of polymerization. The results conclusively prove a stepwise chain growth mechanism since the early stages of the reaction.
EDA‐komplexe als kettenüberträger. I. Die übertragungswirkung von tetrachlorkohlenstoff bei der styrolpolymerisation als funktion der monomerkonzentration
Authors: Olaj Von O. F.
Published: April 2003

Das System Styrol/CCl4 zeigt eine Abhängigkeit der Übertragungskonstante C vom Molverhältnis Überträger (Ü) : Monomerem (M) ; bei 95°C sinkt C um ca. 20%, wenn [Ü]/[M] von 0,36 auf 1,76 steigt; eine Kettenlängenabhängigkeit von C kommt als Ursache nicht in Frage. Folgende Deutung wird gegeben: CCl4 liegt in Styrol in zwei Formen unterschiedlicher Übertragungsaktivität vor, in einer freien Form mit der Übertragungskonstante CF und in Form eines EDA‐Komplexes mit der Übertragungskonstante CX, wobei CCl4 als Acceptor und Styrol als Donator fungiert. Die relativen Anteile beider Formen verschieben sich bei Änderung der Zusammensetzung des Systems. Für kleine Komplexbildungskonstanten K (K beträgt bei Raumtemp. ca. 6 · 10−2l/Mol) gilt für die „formale”︁ Übertragungskonstante C

Da in einem binären System die Summe [Ü] + [M] ≈︁ const., muß C eine lineare Funktion von [M] sein. Dies ist in der Praxis ausgezeichnet erfüllt und trifft selbst dann in guter Näherung zu, wenn [M] durch Verdünnung des Systems mit einem indifferenten Lösungsmittel (Cyclohexan) verkleinert wird, wo C selbst bei [Ü]/[M] = const. auf Grund der Dissoziation des Komplexes abnimmt. Durch Extrapolation von C auf [M] = 0 erhält man CF (0,010 bei 95°C, 0,005 bei 60°C); aus der Neigung der Geraden läßt sich abschätzen, daß CX das 5–10 fache von CF beträgt.
Anionic polymerization of aldehydes. I. Initiation reaction of aldehyde polymerization with sodium naphthalene
Authors: Mita Itaru , Yabe Seizo , Imai Isao , Kambe Hirotaro
Published: April 2003

The initiation mechanism of the polymerization of aldehydes by sodium naphthalene was studied. From the analysis of the reaction products of a mixture of excess sodium naphthalene and formaldehyde it was deduced that the initiation reaction of the formaldehyde polymerization was not an electron transfer but an addition of monomer to the catalyst, leading to the formation of a polymer dianion from two molecules of the ion radical. In the case of acetaldehyde no polymer was formed with this catalyst at −78°C. Main reaction product of an equimolar mixture of the initiator and acetaldehyde was aldol, the anion of which can not initiate the polymerization of the monomer.
Eine synthetische matrizenreaktion einer mischung von acrylsäureestern phenolischer mehrkernverbindungen; modell einer replicapolymerisation
Authors: Kämmerer Von Hermann , Hegemann Günter
Published: April 2003

Mischungen der Acrylsäureester phenolischer Mehrkernverbindungen sowie zunächst unveresterter Verbindungen wurden einer synthetischen Matrizenreaktion unterworfen. Die so erhaltenen Verbindungsgemische ließen sich mit Lithiumborhydrid reduzierend spalten, so daß neben den wiedergewonnenen phenolischen Mehrkernverbindungen Oligoallylalkoholmischungen entstanden. Deren Konzentrationsverhältnisse waren mit einer geringen Streuung die gleichen wie jene der Acrylsäureester oder der phenolischen Mehrkernverbindungen in den Ausgangsmischungen.
Copolymerizations of 3.3‐bis(chloromethyl)oxacyclobutane with β‐propiolactone and γ‐butyrolactone by lewis acids: “Two‐state“ polymerization mechanism
Authors: Ito Koichi , Inoue Toshihide , Yamashita Yuya
Published: April 2003

A “two‐state” polymerization mechanism is proposed to explain the previously reported abnormal sequence distributions in the copolymers from 3.3‐bis(chloromethyl)oxacyclobutane (BCMO) and β‐propiolactone (PL) prepared with SnCl4 or BF3OEt2 as catalyst. Long BCMO sequences are formed by the normal cationic mechanism, whereas formation of long PL sequences is explained by the “coordinated” cationic mechanism, which assumes the polymerization of PL molecules which are coordinated to the catalyst. The lactone monomers coordinate to the catalyst or to the propagating cation through the carbonyl oxygen atoms, and this is supposed to be an important factor for controlling the operation of the two mechanism. β‐butyrolactone (BL) is particularly strongly coordinated and so produces alternating copolymers with BCMO.
Synthèse et caractérisation de copolymères biséquencés de différents méthacrylates d'alcoyle
Authors: Ailhaud Par Henry , Gallot Yves , Skoulios Antoine
Published: April 2003

On a synthétisé à l'aide de la technique de polymérisation par voie anionique des copolymères biséquencés de divers méthacrylates d'alcoyle dont la chaîne latérale hydrocarbonée comporte de 1 à 18 atomes de carbone. On a opéré sous atmosphère inerte, en milieu tetrahydrofuranne; l'initiateur utilisé était le diphénylméthylsodium ou le diphénylméthylpotassium. On a montré que la copolymérisation est indépendante de l'ordre d'introduction des monomères dans le milieu réactionnel.

Les échantillons ont été soumis à une précipitation fractionnée à l'aide de couples solvant/précipitant choisis à dessein. On a caractérisé les différentes fractions par diffusion de la lumière, osmométrie et analyse élémentaire. On a montré que la plupart des copolymères bruts ainsi préparés ne renfermaient pas d'homopolymère et que les fractions recueillies avaient une polydispersité très faible en masse et en composition.
Bulk and solution polymerization of vinyl‐monomers in the presence of a chain transfer agent. Part I. vinyl chloride
Authors: Vidotto G. , Brugnaro S. , Talamini G.
Published: April 2003

The effect of carbon tetrabromide transfer both in bulk and 1.2‐dichloroethane solution polymerization of vinyl chloride has been investigated at 50°C. In heterogeneous systems the presence of carbon tetrabromide rises the initial polymerization rate, but reduces or eliminates, respectively, the autocatalysis of the reaction. On the other hand, in homogeneous systems, carbon tetrabromide exhibits a weak retarding action.

In both homogeneous and heterogeneous polymerization, carbon tetrabromide has a strong effect as chain transfer agent and its transfer constant deduced from the molecular weight of the polymers obtained in homogeneous systems is 4.70. The results are discussed based on a model recently proposed by the authors.
The mechanism in the asymmetrically selective oxidation of 3.4‐dihydroxyphenylalanine catalyzed by the poly‐L‐lysine‐copper(II) complex
Authors: Nozawa Tsunenori , Hatano Masahiro
Published: April 2003

In the oxidation of 3.4‐dihydroxyphenylalanine (DOPA) the effect of the asymmetrical structure in poly‐L‐lysine‐copper(II) complex (PLL‐Cu(II)) on the asymmetrical selectivity ratio was investigated at various reaction temperatures and various preparation conditions of the catalyst, or by addition of catechol or phenylalanine. From the comparison of the asymmetric selectivity with the structure of the catalyst, the combination of two or more asymmetric cupric complex units was considered as the cause for the asymmetrically selective catalysis, where α‐helical structure may serve to hold the two or more cupric complex units in a special steric configuration. Moreover a plausible mechanism for the asymmetrically selective oxidation was discussed by the evidence from the addition effects of catechol or phenylalanine and by the asymmetrically selective interaction between PLL‐Cu(II) and DOPA. Then, the mechanism seems to be confirmed by an inspection with a molecular model.
Etude du gonflement de gels réticulés préparés par copolymérisation séquencée anionique
Authors: Weiss Par Paul , Herz Jean , Rempp Paul
Published: April 2003

Das Quellungsverhalten von vernetzten Gelen, die auf anionischem Wege hergestellt wurden, wurde untersucht. Der Quellungsgrad der Gele im Gleichgewicht ist stark strukturabhängig und durch die Bedingungen ihrer Herstellung beeinflußt. Die experimentell erhaltenen Werte des Quellungsgrades stehen in guter Übereinstimmung mit den für ideale Gele aus den strukturellen Parametern berechneten Werten. In einigen Fällen allerdings wurden Abweichungen beobachtet, die durch die Gegenwart von freien Kettenenden oder von Kupplungen (Knoten mit Funktionalitätswert 2) oder von beiden zugleich verursacht werden. In diesen Fällen kann kein Idealmodell die Eigenschaften der Gele erklären.
Sources of error in bulk polymer densities determined by the gradient column technique
Authors: Blackadder David A. , Keniry John S.
Published: April 2003

Sources of error in the determination of the density of bulk‐crystallized polyethylene in gradient columns have been reconsidered. Preferential absorption of any one column liquid can lead to gross differences between the apparent polymer densities as determined in different columns. It is therefore important to select column liquids which have about the same swelling power for the polymer. Samples of very high specific surface should be avoided, though the threshold for significant errors of this kind is unlikely to be crossed in practice. Finally, water should not be used as a column liquid in connection with polyethylene measurements because water‐rich mixtures may not wet the polymer completely. The principles emerging from this work are likely to be of general application.
Polymerization in the presence of organoaluminum compounds and Azobisisobutyronitrile
Authors: Gaylord Norman G. , Maiti Sukumar
Published: April 2003

The rate of decomposition of azobisisobutyronitrile (AIBN) in methyl methacrylate styrene, and a styrene/methyl methacrylate mixture and the rate of polymerization of the monomers are enhanced in the presence of organoaluminum halides. The monomer‐RxAlXy interaction influences the rates of both AIBN decomposition and monomer polymerization as well as the polymerization mechanism. The copolymerization of styrene and methyl methacrylate yields alternating copolymers in the presence of AIBN/RxAlCly and random copolymers in the presence of AIBN alone. The AIBN/RxAlCly activated copolymerization occurs in the dark but is accelerated in visible light.
The mechanism of the initiation reaction of the cationic polymerization of tetrahydrofuran by stable cationic salts
Authors: Yamashita Yuya , Kozawa Shigeyuki , Hirota Masahiro , Chiba Kazumasa , Matsui Hisashi , Hirao Akira , Kodama Mikio , Ito Koichi
Published: April 2003

The mechanism of the initiation reaction for the polymerization of cyclic ethers and lactones by triethyloxonium‐, acetyl‐ and dioxolenium‐salts was studied.

Triethyloxonium salts initiate the polymerization of cyclic ethers simply by the alkyl exchange reaction. Cyclic esters react with triethyloxonium salts at both ether and carbonyl oxygens but the polymerization proceeds by the acyl‐oxygen fission. The kp value of the polymerization of THF by triethyloxonium salts is almost constant independent of gegenanion. Acetyl cation initiates the polymerization of THF partly by bonding mechanism, but dioxolenium salt initiates completely by bonding.
The dissolution and stability of cellulose triacetate in acetone
Authors: Cowie J. M. G. , Ranson R. J.
Published: April 2003

The solubility behaviour of primary cellulose acetate in acetone has been investigated and it has been found that samples with a degree of substitution (DS) between 2.80 and 2.90 can be completely dissolved by first cooling the polymer‐liquid mixtures to about 190°K then warming to ambient. The efficiency of this process deteriorates rapidly for DS of 2.90–3.0 when only partial solution can be effected. Upper and lower critical solution temperatures have been estimated for these solutions, which provide an indication of the extent of total miscibility for the system. Approximate values for the enthalpy of fusion, together with glass and melting temperatures have been determined by means of a differential scanning calorimeter. The data suggest that acetone can dissolve the smaller crystallites and the associated amorphous regions in the fully acetylated material, but cannot dissolve the larger well ordered regions, unless the sample contains a significant number of hydroxyl groups.
Polymer deformation. XVIII. Biaxial deformation of polyoxymethylene
Authors: Singhania A. K. , Geil P. H.
Published: April 2003

Biaxial deformation of bulk polyoxymethylene was studied by electron microscopy and small‐ and wide‐angle X‐ray diffraction. The deformation was carried out in two ways: simultaneous and sequential. Effects of subsequent annealing were also studied. Simultaneously deformed specimens show a large degree of fibrillity at deformation as low as 1.1 × 1.1. Y‐shaped fibrils and the tendency of some of the fibrils to bend back on themselves by more than 180° do not appear to be explainable by current postulates concerning the formation of fibrils. The deformation appears to be quite inhomogeneous on a microscopic scale. Small‐angle X‐ray patterns show the tendency of lamellae to become parallel to the surface of the film as deformation proceeds. On annealing the overall relaxation is nearly complete. The fibrillar networks collapse completely leaving no striated structure. Small‐angle X‐ray patterns show relaxation of the lamellae. During sequential deformation micronecks form during the first draw. These either split or collapse during the second draw depending upon local bulk shrinkage. On annealing, most fibrils again disappear.
Copolymerisation von Acrylnitril und α‐Chloracrylsäuremethylester
Authors: Dankovics Von A.
Published: April 2003

Die Copolymerisation von Acrylnitril und α‐Chloracrylsäuremethylester in Emulsion wurde kinetisch untersucht. Umsatz, Grenzviskosität, spezifisches Gewicht, Zusammensetzung der Copolymeren und Induktionsperiode wurden bestimmt.

Die Wahrscheinlichkeit für die Verteilung von Acrylnitril‐ und α‐Chloracrylsäremethylester‐Kettensegmenten wurde in Abhängigkeit von der Zusammensetzung des Monomeren gemisches bestimmt. Es wurde gezeigt, daß die aus den beiden Monomeren aufgebauten Makromoleküle aus unregelmäßig angeordneten, kurzen Sequenzen bestehen.

Ferner wurde gezeigt, daß der Umsatz der Quadratwurzel der α‐Chloracrylsäuremethylester‐Konzentration direkt proportional ist. Die Induktionsperiode nimmt mit der Erhöhung der α‐Chloracrylsäuremethylester‐Konzentration ab.

Der Umsatz hängt vom pH‐Wert des Reaktionsmediums ab. Bei pH > 7 ist die Reaktionsgeschwindigkeit sehr niedrig.
Umlagerungen bei der durch Lithiumbutyl initiierten Polyreaktion der Diene Isopren und Butadien
Authors: Gebert Wolfgang , Hinz Jürgen , Sinn Hansjörg
Published: April 2003

Bei der Reaktion von Lithiumbutyl mit Isopren in Diäthyläther entstehen Lithiumnonenyle, die bei der Zersetzung mit Wasser 36% 2‐Methylocten‐(1) und die cis‐trans‐Isomeren des 3‐Methyl‐octens‐(2) im Verhältnis 63:1 ergeben.

Nach Entfernung des Diäthyläthers vom Lithiumnonenyl durch Abkondensation nach wiederholterZugabe von n‐Heptan werden die Kohlenwasserstoffe im Verhältnis 26 : 74 gefunden, während nach erneuter Zugabe von Diäthyläther wieder das Verhältnis 36 : 64 auftritt.

Das Verhältnis der verschiedenen isomeren Lithiumnonenyle ist vom Lösungsmittel abhängig. Die Isomeren lagern sich reversibel um; auch in Diäthyläther findet in erheblichem Umfange 1.4‐Addition von Isopren an Lithiumbutyl statt.

Während bei −10°C für die Polyreaktion des Isoprens mit Lithiumbutyl als Initiator die Geschwindigkeitskonstanten

gefunden werden, betragen die entsprechenden Werte für die Polyreaktion des Butadiens

Das kinetisch erfaßbare Assoziationsverhalten von Lithiumpolyisoprenyl wird durch

beschrieben, während Lithiumpolybutadienyl durch

beschrieben wird.

Die Vermutung, daß primär immer 1.4‐Verknüpfung erfolgt, deren Produkt dann unter der Wirkung des Initiators isomerisiert, wird gestützt durch die Zunahme der 1.4‐cis‐Struktur mit fallender Initiatorkonzentration:

Initiatorkonz.
1.4‐cis‐Struktur

Mol/l
Isopren
Butadien

3·10−2
80%
35%

5·10−5
95%
70%

<10−5
98%
–

Die bewiesene Umlagerung löst den Widerspruch zwischen postuliertem Primärschritt und gefundenen Produktstrukturen. Die Initiatorabhängigkeit der Stereoselektivität wird mit Hilfe einer Geschwindigkeitskonstanten ki, cis = 105 ± 10 I/Mol·sec der Isomerisierungsreaktion simuliert.
Feldionen‐ und Elektronenstoß‐Massenspektrometrie von Polymeren und Copolymeren. II. Polyisobuten, Polystyrol, Polypropen, Polystyrolperoxid, Polyvinylchlorid
Authors: Hummel D. O. , Düssel H. J. , Rübenacker K.
Published: April 2003

Als Beispiele für verschiedene Abbaumechanismen wurden Polyisobuten, Polystyrol, Polypropen, Polystyrolperoxid und Polyvinylchlorid in einem Massenspektrometer mit kombinierter Feld‐ und Elektronenstoßionenquelle pyrolysiert. Aus der Zusammensetzung der Primärfragmente lassen sich Abbaumechanismen herleiten, die teilweise noch nicht bekannt waren oder über die bekannten hinausgehen. Der Abbau von Polyisobuten und Polystyrol geschieht durch statistische Kettenbrüche und Retropolymerisation. Die mannigfaltigen Primärfragmente des Polypropens lassen sich durch statistische Kettenbrüche, «back‐biting» und Retropolymerisation erklären. Die thermische Spaltung des Polystyrolperoxids geschieht jeweils zwischen zwei Sauerstoffatomen; die Fragmente stabilisieren sich durch Sekundärreaktionen. Alterungsvorgänge, an diesem Beispiel studiert, lassen sich massenspektrometrisch nachweisen, bevor sie IR‐spektrometrisch manifest werden. Beim PVC wurde gezeigt, daß zahlreiche schwerere Bruchstücke, überwiegend Aromaten und Alkylaromaten, als «Primär»‐Fragmente anzusehen sind.
Calculation of particle sizes in emulsion polymerization systems
Authors: Watterson John Grant , Parts Adolf Gustav
Published: April 2003

Calculations of the particle size number distribution resulting from emulsion polymerization have been carried out for a model of the system used previously by the authors. The sum of the lifetimes of the growing molecules which a particle has contained, is used as the measure of its size. The resulting curves indicate an increase in the breadth of the distribution with increasing time.
The influence of irradiation and hydration on the transport properties of isotropic and anisotropic membranes
Authors: Williams J. L. , Schindler A. , Peterlin A.
Published: April 2003

The influence of quaternization on the transport properties of water and sodium chloride under reverse osmosis conditions has been examined for alternating copolymers of styrene and 4‐vinyl pyridine. These results demonstrate quite clearly a linear relationship between log P as a function of salt rejection or reciprocal hydration. Such a relationship seems to be quite general for ionic polymers. Also, results with irradiation demonstrate that tensile properties of these copolymers can be improved by about 60% at an optimum dose of about 9 megarads. In addition, the directional permeability of graded membranes has been demonstrated for an alternating copolymer where a gradient of quaternization was imposed on the membrane. Both the water and salt flux were higher along the quaternization gradient than in the reverse orientation of the membrane.
Etude en solution diluée des propriétés du polystyrène ramifié en étoile
Authors: Meunier Jean‐Claude , van Leemput Robert
Published: April 2003

The solution properties of monodisperse four and six branch star‐polystyrene samples have been investigated by viscosimetry, osmometry and light‐scattering.

The ⊖ temperature measured by the temperature dependence of the second virial coefficient in cyclohexane is lower than 34.8°C and the expansion of the coil is decreased by branching.

The behaviour of the branched polymer is controlled by the number and the length of the branches and no unique relation exists between hydrodynamic and geometric parameters.

Average molecular weight data measured by light‐scattering are systematically lower than those obtained by osmometry.
Vinyl polymerization with dimethylaniline/cupric nitrate system
Authors: Sato Tsuneyuki , Takada Masaki , Otsu Takayuki
Published: April 2003

A study of vinyl polymerizations initiated with the system of dimethylaniline (DMA) and cupric [Cu(II)] nitrate has been made. This initiator system was found to induce the polymerization of vinyl monomers having an electron‐attracting substituent such as methyl methacrylate (MMA) and acrylonitrile, but it does not initiate the styrene and vinyl acetate polymerizations. The rate of polymerization (Rp) of MMA with this system was expressed by the following Eqs., depending upon the Cu(II) concentration used:

The apparent activation energy for this polymerization was found to be 16.5 and 14.4 kcal/mole for the above two Cu(II) concn. ranges, respectively. The polymer of MMA obtained by this system was found to contain an endgroup similar to dimethylaniline, probably a methylanilinomethyl group, from the determination of its UV spectrum.
Üuber poly‐[3 (bzw. 5)‐vinyl‐pyrazol‐derivate] und ihr metallionenbindungsvermögen
Authors: Schenck Hans‐Uwe , Manecke Georg
Published: April 2003

Durch radikalische Lösungspolymerisation wurden Homopolymere von 3(bzw. 5)‐Vinylpyrazol‐derivaten erhalten und deren Eigenschaften untersucht. Durch Copolymerisation von 2,5 Mol‐% Bis‐[3(bzw. 5)‐vinyl‐5(bzw. 3)‐pyrazolyl]‐keton mit 3(bzw. 5)‐Vinyl‐5(bzw. 3)‐pyrazol‐carbonsäureäthylester (I) bzw. 3(bzw. 5)‐Vinyl‐4.5(bzw.3)‐pyrazol‐dicarbonsäuredimethylester (II) wurden Harze dargestellt, die nur begrenzt quellbar sind und die durch Verseifung in Poly‐[vinyl‐pyrazol‐carbonsäure]‐harze (Harz A1 und Harz A2) überführt wurden. Diese Harze stellen hochkapazitive Chelatharze dar. Es wurde das Metallionenbindungsvermögen für Cu2⊕, Ni2⊕, Zn2⊕ und Mg2⊕ und die Aufnahmegeschwindigkeit in Abhängigkeit vom pH‐Wert im Bereich von pH 1 bis pH 5,5 untersucht.
Intramolecular phase transitions of block copolymers in solution from viscosity — temperature studies
Authors: Urwin J. R. , Girolamo M.
Published: April 2003

Intrinsic viscosity against temperature plots for two sequence block copolymers of isoprene and styrene in decalin and methyl cyclohexane confirm the general behaviour of these polymers in preferential solvents. The operative parameters are the mol. wt., composition and ⊖ temperature of the less soluble polymer in the particular solvent. The STOCKMAYER‐FIXMAN relation [η]M = Φ0(A + 0.51 BηM)is obeyed, for a particular composition, at all temperatures, but the unperturbed dimensions in the block appear to drop significantly at temperatures below the transition temperature. Since the constant Φ0 is influenced by the segmental distribution, the drop in unperturbed dimensions may be considered to reflect the conformation change from the phase‐mixed to phase‐separated form. The characteristic ratio, C∞ = 〈r2〉0/nl2, which is calcd. from K in the KUHN‐MARK‐HOUWINK Eq. determined directly from [η]0 (⊖ = 44°C in methyl ethyl ketone) is identical with that obtained by extrapolation using the STOCKMAYER‐FIXMAN relation at 46°C. Moreover, C∞ may be calcd. directly from C∞Block = xC∞PS + (1 − x) C∞PI after taking account of the isomeric composition of the polyisoprene.
Effects of triphenyl phosphite on the radical polymerization of acrylonitrile
Authors: Ogawa Takeshi , Taninaka Takumi , Takada Hiroshi , Minoura Yuji
Published: April 2003

In the polymerization of acrylonitrile initiated with α,α′‐azobisisobutyronitrile, triphenylphosphite exhibited two different effects on the rate of polymerization, a decreasing effect and an increasing effect. The decrease is due to the phosphoranyl radical formed by the addition of a 2‐cyanopropyl radical to triphenylphosphite. The increase is due to the formation of a weak n‐π complex between triphenylphosphite and acrylonitrile, which was confirmed from the UV absorption spectra. Triphenylphosphite had no significant effect on the molecular weight of the polymer. The phosphorus content in the polymer was small (0.02–0.06%), the number of phosphorus units in one polymer chain being 1–4.
Imidazole catalyses in aqueous systems. VII. Enzyme‐like catalytic hydrolyses of phenyl esters by copolymers containing imidazole and carboxylate functions
Authors: Kunitake Toyoki , Shinkai Seiji
Published: April 2003

The catalytic hydrolysis of phenyl esters — 3‐acetoxy‐N‐trimethylanilinium iodide (ANTI), 3‐nonanoyloxy‐N‐trimethylanilinium iodide (NNTI), and p‐acetoxybenzoic acid (ABA) — was conducted at 30°C in an aqueous system using polymer catalysts containing a phenylimidazole unit. The hydrolysis of ABA with a negatively charged polymer catalyst followed second‐order kinetics, whereas the catalytic hydrolysis of the cationic substrates proceeded according to MICHAELIS‐MENTEN kinetics. The cationic substrates appear to be bound at the polymer catalytic site by electrostatic forces when the polymer contained the imidazole and carboxylate functions. The substrate binding behavior of the polymer catalysts was explicable by considering the conformational characteristics of the catalytic site. NNTI showed a binding tendency greater than that of ANTI because of its enhanced hydrophobic character due to the long acyl chain. The presence of the carboxylate group at the catalytic site facilitates the intra‐complex reaction for the cationic substrates.
Syntheses and reactions of functional polymers. LXIII. Syntheses of phenyl polystyryliodonium salts
Authors: Yamada Yorinobu , Okawara Makoto
Published: April 2003

The syntheses of polystyrenes containing iodonium structure were investigated. It was found that phenyl polystyryliodonium bisulfate was quantitatively prepared from polystyrene iodosoacetate and benzene in the presence of conc. sulfuric acid. In a similar way, cross‐linked phenyl‐ and thienyl‐polystyryliodonium salts were synthesized. Anion exchange reaction of phenyl polystyryliodonium bisulfate with sodium bromide and potassium thiocyanate was also studied.
Application of dye techniques in the study of chain‐transfer properties of thiols
Authors: Roy Kamal Kumar , Pramanick Dinabandhu , Palit Santi R.
Published: April 2003

Dye techniques (dye partition technique in particular) have been found to be simple and sensitive methods for studying the chain transfer properties of substituted thiols containing ionic or ionogenic groups (amenable to dye test). These are: 2‐Mercapto ethanol, 2‐mercapto ethylamine hydrochloride, and thioglycolic acid. Ctr values obtained by this method are found to agree fairly well with those obtained from conventional DP methods. ARRHENIUS parameters and some thermodynamic functions have been evaluated from experimentally determined Ctr values. Existence of a negative temperature coefficient is found for the transfer process of the thiols with PMMA radicals. Transfer potency of the thiols is found to be dependent on their structure. Thus Cs value for 2‐mercapto ethylaminehydrochloride with MMA is found to be least in the present series which can be accounted for the presence of a strong electron accepting group in the thiol which vehemently opposes the electron transfer from the thiol to the electron accpeting PMMA radical in the transition state.
Universal calibration procedures in gel permeation chromatography. Examination of poly(dimethyl siloxane) in a theta solvent
Authors: Dawkins John V. , Hemming Malcolm
Published: April 2003

Gel permeation chromatography calibrations for polystyrene standards and poly‐(dimethyl siloxane) fractions have been obtained with polystyrene gel using o‐dichlorobenzene at 87°C. Intrinsic viscosity‐molecular weight data show that, at this temperature, o‐dichlorobenzene is a theta solvent for poly(dimethyl siloxane) but a good solvent for polystyrene. The KUHN‐MARK‐HOUWINK exponents are 0.50 and 0.73 for poly(dimethyl siloxane) and polystyrene respectively. This significant difference in polymer/solvent interaction allows assessment of various universal calibration procedures. Comparison of the experimental poly(dimethyl siloxane) data with curves calculated from a polystyrene calibration suggests that the most suitable calibration procedures use the hydrodynamic volume or the perturbed dimensions given by the FLORY‐FOX equation. Calibration procedures based on the unperturbed dimensions or on the perturbed dimensions derived from the PTITSYN‐EIZNER equation are not valid when the difference in the KUHN‐MARK‐HOUWINK exponents is large. For experimental calibrations with fractions, the position of molecular weight and hydrodynamic volume calibrations may depend on the choice of average molecular weight. The influence of fraction polydispersity on the plots is discussed.
An electron spin resonance study of the radiation damage of polysulphone
Authors: Lyons Arthur R. , Symons Martyn C. R. , Yandell John K.
Published: April 2003

ESR studies of γ‐irradiated polysulphone (prepared from 2.2′‐bis(4‐hydroxyphenyl)‐propane and 4.4′‐dichlorodiphenyl sulphone) and its model compounds (diphenyl sulphone, 2.2′‐diphenyl propane, diphenyl ether), suggest that the majority of radicals produced in the polymer are formed by the subsequent reactions of hydrogen atoms released from the pendant methyl groups by the action of the γ‐radiation. Cyclohexadienyl‐type radicals are produced in quantity together with phenoxy and ArṠO2 radicals. Supporting evidence for the mechanism is obtained from studies of the hydrogen atom bombardment of the polymer.
Aqueous polymerization of acrylamide initiated by acidic thiourea/potassium bromate redox system
Authors: Shukla J. S. , Misra D. C.
Published: April 2003

The aqueous polymerization of acrylamide initiated by bromate/thiourea redox system has been studied in acidic media at 25 ± 0.2°C in a nitrogen atmosphere.

The rate of polymerization has been found to vary with the first power of the potassium bromate concentration within the range 0.75·10−2 to 2.0·10−2 mole·1−1 and nearly with the first power of the hydrochloric acid concentration within the range 2.85·10−2 to 8.55·10−2 mole·1−1. However, the rate of polymerization is independent of the thiourea concentration, but varies with the first power of the monomer concentration within the range 6.0·10−2 to 10.0·10−2 mole·1−1. The initial rate increases but the maximum conversion decreases as the temperature increases within the range 19 to 35°C.

The over all energy of activation has been found to be 22.9 kcal·mole−1 within the temperature range mentioned above. Water miscible organic solvents and mono‐ and dibasic salts show the same effect as given by MISRA et al. The effect of cationic and anionic surfactants has been found to increase and decrease the rate of polymerization (Rp) respectively, however non‐ionic detergents have no effect on the (Rp).
The asymmetrically selective hydrolysis of phenylalanine esters catalyzed by poly‐L‐lysine/copper(II) complexes
Authors: Nozawa Tunenori , Akimoto Yoshihiro , Hatano Masahiro
Published: April 2003

The poly‐L‐lysine/copper(II) complex was found to exhibit the asymmetrically‐selective catalysis on the hydrolysis of phenylalanine esters at pH 7. The reaction rate showed a first order dependence on the ester concentration for the initial part of the hydrolysis. Tetraaquocopper(II) ion and bis(bipyridyl)copper(II) ion had no catalytic activity on the hydrolysis at pH 7. The catalytic activity was discussed on the basis of the stability constant data of these complexes.
Untersuchungen zur copolymerisation von pyrrolidon und caprolactam
Authors: Schirawski Günter
Published: April 2003

Pyrrolidon und Caprolactam werden im Temperaturbereich von 70–200°C in Masse anionisch copolymerisiert. Die mit steigender Polymerisationstemperatur abnehmende Polymerisationsneigung des Pyrrolidons führt trotz hoher Monomerkonzentrationen zu immer niedriger liegenden Pyrrolidongehalten. Für 70, 110, 150 und 2OO°C werden die Copolymerisationsparameter ermittelt.
Sequenzanalyse bei trioxocan/dioxolan‐copolymeren durch NMR‐spektroskopie unter zusatz von lanthaniden‐komplexen
Authors: Fleischer Dietrich , Schulz Rolf C.
Published: April 2003

Zusatz des paramagnetischen Lanthanidenchelats Eu(DPM)3 zur Meßlösung eines Trioxocan/Dioxolan‐Copolymeren ermöglicht im kernmagnetischen Resonanzspektrum die Bestimmung der Bruttozusammensetzung und verschiedener Sequenzen. Das sehr reaktionsfähige Trioxocan (TOC) polymerisiert zu Beginn bevorzugt (rTOC = 78, rDOL = 1,7); Dioxolan (DOL) wird im weiteren Verlauf der Reaktion wahrscheinlich durch Transacetalisierungsreaktionen in das Polymere eingebaut bis zu einer nahezu statistischen Verteilung der Grundbausteine.
Über die Wechselwirkung des Katalysators und Cokatalysators mit dem Monomeren und Polymeren bei der kationischen Polymerisation des Isobutylens. I. Modellstudium der primären Deuterierung und isomerisierung des triisobutylens durch das system AlBr3/DBr
Authors: Kříž Jaroslav , Marek Miroslav
Published: April 2003

Der zeitliche Verlauf der Isomerisierung und der Deuterierung in verschiedene Stellungen des 1.1‐Dineopentyläthylens durch das System AlBr3/DBr in Heptan entspricht der Konkurrenz zwischen der Reaktion des Deuterons und der des AlBr3 allein mit dem Substrat. Es wird diskutiert, in welcher Weise dieser Effekt bei der kationischen Polymerisation des Isobutylens zur Geltung kommen kann.
Some reaction variables in the aqueous solution synthesis of titanium polythioethers
Authors: Carraher Charles E. , Nordin Robert J.
Published: April 2003

Titanium polythioethers of the form below were prepared from Cp2TiCl2 and dithiols by the solution method.
magnified image

The following reaction variables were studied and reported on: molar ratios of the base, Cp2TiCl2 and dithiols and concentration of the reactants, stirring time and volume of the aqueous phases.

Polymer yield seeks a maximum around a molar ratio of Cp2TiCl2:dithiol:base of 1:1:2.