bluuebunny/crossref_metadata_2025 huggingface dataset:
Gelchromatographie. 1. Mitt. Trennung von oligomeren
Authors: Heitz Von W. , Ullner H. , Höcker H.
Published: April 2003

Vernetzte Polymere werden hergestellt und ihre Eignung zur gelchromatographischen Trennung von Gemischen von Oligomeren geprüft; im einzelnen wurden untersucht: mit Isocyanaten modifiziertes Sephadex; Polymethyl‐und Polybutylmethacrylat, vernetzt mit Glykoldimethacrylat bzw. mit Polyäthylenoxid‐dimethacrylat; Polyvinylacetat, vernetzt mit n‐Butandioldivinyläther; Polystrol, vernetzt mit Divinylbenzol; ferner Silicagel.

Der Einfluß der Molekülgestalt auf das Elutionsvolumen wurde geprüft. Die Elutionsvolumina von p‐Oligophenylenen, die eine stäbchenförmige Molekülgestalt besitzen, sind größer als die von Oligourethanen gleichen Molekulargewichts; o‐ und m‐gewinkelte Oligophenylene zeigen gegenüber p‐Oligophenylenen nur sehr geringe Unterschiede in den Elutionsvolumina. Es wird geschlossen, daß die Wechselwirkung der zu trennenden Substanzen mit dem Gel einen wichtigen Einfluß auf die Trennung ausübt.
The initiation mechanism of polymerization by the system AlEt3/H2O
Authors: Ueshima T. , Fujii T. , Saegusa T. , Furukawa J.
Published: April 2003

The reaction between H2O and triethylaluminum Al(Et3) as well as the initiation mechanism of the polymerization by the system AlEt3/H2O have been examined by means of tritiated water, Considerable amount of tritium from tritiated water remained in the system AlEt3/H2O prepared at room temperature. Heat treatment of the system causes both the extensive decrease of tritium content and loss of catalyst activity. Polymers of styrene and isobutyl vinyl ether prepared by the system AlEt3/H2O were found to be radioactive. These findings have been taken to assume that acid hydrogen does exist in the system AlEt3/H2O and is directly responsible for the initiation of cationic polymerization.
Treatment of the effect of excluded volume and deduction of unperturbed dimensions of polymer chains. Configurational parameters for cellulose derivatives
Authors: Flory Paul J.
Published: April 2003

Methods currently used for deducing unperturbed dimensions of polymer chains from intrinsic viscosities are examined and the hazards of linear extrapolation of plots of [η]2/3/M1/3 against either M2/3/[η]1/3 or M/[η] for this purpose are pointed out. Applications of this procedure to cellulose derivatives have led to erroneous results. Proper interpretation of newer data substantiated earlier conclusions to the effect that these chains tend to be more highly extended than those of other polymers, and that their unperturbed dimensions vary markedly from one solvent medium to another.
Syntheses of new chelate‐polymers and its catalytic activities
Authors: Nose Yoshinori , Hatano Masahiro , Kambara Shu
Published: April 2003

Some new polymeric ligands of β‐diketone type were synthesized and the catalytic effects of their copper chelates on the decomposition reaction of hydrogen peroxide and the oxidation reaction of ascorbic acid were measured in comparing with that of monomeric chelates of the same structure. The two polymeric ligands described as the following formulae (I) and (II) with thousands of molecular weight were prepared by the reaction of dimethyl‐terephthalate, bisacetyl derivatives and sodium dispersion. magnified image

In the chelation reactions between the polymeric ligands and cupric ion, two reaction methods, i.e. homogeneous and interfacial, were compared in regard to the extent of the chelation. In the homogeneous reaction by using tetrahydrofuran as a reaction medium the extent of the chelation could not be over 50% of the theoretical value. On the other hand, the chelate formation was carried out quantitatively at the interface between benzyl alcohol solution of the ligands and aqueous solution of cupric salt.

In the measurements of the catalytic activity of the copper chelates for the decomposition reaction of hydrogen peroxide, it was found that the catalytic activity is in the decreasing order of:

The same results were observed for the oxidation reaction of ascorbic acid. On the basis of structural analyses, the catalytic activity of the chelates was assumed to depend on the bond strength between the ligand and cupric ion.
Polymerization by transition metal derivatives. VII. Investigation of the polymerization of isoprene by phenylmagnesium bromide and cobalt fluoride
Authors: Delheye G. , Dawans F.
Published: April 2003

Studies were carried out on the polymerization of isoprene with the catalytic system formed by unsolvated phenylmagnesium bromide and cobalt fluoride. The experiments pointed out the important role of some oxygented compounds, such as water or alcohol. Under the given conditions, the rate of polymerization of isoprene increases with increasing concentration of cobalt and varies drastically when the alcohol concentration is varied the molecular weights and the microstructure of the polymers obtained remain unchanged by addition of controlled amounts of alcohol to the catalyst system.
Polymerization of acenaphthylene initiated by iodine
Authors: Giusti P. , Puce G. , Andruzzi F.
Published: April 2003

The kinetics of iodine initiated polymerization of acenaphthylene has been followed dilatometrically at 0, 20 and 30°C. in (CH2Cl)2 using a semi‐open technique. Experiments in vacuum dilatometers fitted with electrodes have been also carried out in order to follow the conducativity at the same time as the conversion. The general features of this polymerization are analogous with those of iodine initiated polymerization of styrene (S‐shaped time‐conversion curves, high reaction order with respect to the iodine concentration, co‐catalysis by hydrogen iodide). The slowness of the reaction and the low conductivity in the steady‐state suggest that it is a pseudocationic reaction.
Ein elektronenspinresonanzverfahren zur bestimmung von reaktionskonstanten kurzlebiger radikale bei der polymerisation
Authors: Fischer Von Hanns
Published: April 2003

Es wird gezeigt, daß durch ESR‐Untersuchungen an kurzlebigen Radikalen während der Polymerisation unter Anwendung eines Durchflußverfahrens reaktionskinetische Konstanten bestimmt werden können. Dazu werden allgemeine Eigenschaften des Durchflußsystems diskutiert und als Beispiel Messungen bei der Polymerisation von Acrylsäure in wäßriger Lösung mit CH3‐Radikalen als Starter behandelt. Aus den Ergebnissen folgt, daß Reaktionskonstanten ähnlich aufgebauter Kettenradikale mit zunehmender Kettenlänge kleiner werden.
Polymerisation of tetrahydrofuran (part III)
Authors: Sims D.
Published: April 2003

The effect of epichlorohydrin [ECH] on the polymerisation of tetrahydrofuran with phos phorus pentafluoride has been studied. The rate of polymerisation has been found to depended on [M] and increases linearly with [ECH] up to a maximum where [ECH] = 0.27 [PF5], after this point no increase in the rate of polymerisation occurs. It has been suggested that the active catalyst is formed by the reaction of PF5 and ECH and a mechanism is proposed.
Über die darsterung von poly‐1,2,4‐oxadiazolen und poly‐1,2,4‐oxadiazolinen
Authors: Batzill Von W. , Funke W.
Published: April 2003

Es wurde die Darstellung von Poly‐1,2,4‐oxadiazolen und von Poly‐1,2,4‐oxadiazolinen aus Diamidoximen und Dicarbonsäuredichloriden bzw. Dialdehyden untersucht. Die Cyclisierung warde in einer Reaktionsstufe oder nach Isolierung der entsprechenden Poly‐(O‐acyloyIamidoxime) durchgeführt. Die isolierten, harzartigen Produkte besaßen Polykondensationsgrade von etwa 5 Grundbausteinen.
Beitrag zur bestimmung von hydroxylzahlen in ungesättigten polyesterharzen
Authors: Heidel Von Klaus , Dittmann Walter , Stürzenhofecker Franz
Published: April 2003

Eine Reihe von Methoden zur Bestimmung der Hydroxylzahl wurde auf ihre Brauchbarkeit an ungesättigten Polyesterharzen geprüft. Als allgemein anwendbares, sclinell und bequem durchführbares Verfahren erwies sich. die durch p‐Toluolsulfonsäure katalysierte Acetylierung in Äthylacetat. Die Acetylierung in Pyridin erfordert Iängere Reaktionszeiten und bedingt wegen der schlechten Endpunktserkennung bei der Titration, eine breitere Streming. Bei Perchlorsäure als Acetylierutigskatalysator muß die Reaktionszeit für jedes Harz erst genau ermittelt werden.
Orientierte aufwachsung von polyamiden auf KCI‐spaltdflächen. I. Orientierte aufwachsung des polyamids, der ϵ‐aminocapronsäure (6‐nylon)
Authors: Fischer Von E. W. , Williems J.
Published: April 2003

Die orientierte Aufwachsun (Epitaxie) des Polyamids der ϵ‐Aminocapronsäure auf(001)‐Spaltflächen von Kaliumchlorid wurde licht‐ und elektronenmikroskopisch untersucht. Mittels Elektronenbeugung konnte festgestellt werden, daß das Polyamid mit den (020)‐Ebenen (Rostebenen) auf der KCl‐Oberfläche aufwächst. Dabei bilden die Kettenachsen einen Winkel von ca. 19° mit den Kanten der Würfelflächen des KCl, so daß sich insgesamt vier Aufwachssysteme mit verschiedener Orientierung ausbilden. In Richtung der a‐Achsen des Polyamidoitters stimmen die Perioden von Gast‐ und Trägergitter bis auf 0,33 Å überein. Die Aufwachsschichten bestehen aus dünnen Fibrillen, in denen die Ketten mit einer Periode von ca. 100 Å gefaltet sind. Auch andere Polyamide (6,6‐; 6,10‐; 7‐ und 8‐Nylon) sowie Polyacrylnitril und Polyurethan wachsen epitaktisch auf (001)‐ KCl auf.
Elektrolytisch initiierte polymerisation von caprolactam
Authors: Gilch Von Heinz , Michael Dietrich
Published: April 2003

Die anionisch aktivierte Polymerisation von Caprolactam wurde durch Elektrolyse initiiert. Durch eine Schmelze von Caprolactam, die lsocyanat als Aktivator und ein Alkalisalz enthielt, wuide ein clektrischer Strom geschickt. Dabei entstand an der Kathode ein Alkalilactam, das die Polymerisation auslöste und emen Polyamidäberzug auf der Kathode bildete. Die Polyamidbildung wurde in Abhängigkeit von den Reaktionsbedingungen untersucht.
Beitrag zur polymeranalogen umsetzung der cellulose zu cellulosenitrat
Authors: Thinius Von K. , Thümmler W.
Published: April 2003

Durch Veresterung von Cellulose mit Gemischen aus wasserfreier Salpetersäure und Chlorkohlenwasserstoffen, insbesondere Dichlormethan, können in sehr kurzer Reaktionszeit bei Temperaturen zwischen 0 und ‐30°C Cellulosenitrate mit 13,8 bis 14% N hergestellt werden. Die Umsetzung verläuft polymeranalog. Die auf diese Weise gewonnenen, im Reaktionsgcmisch unlöslichen Cellulosenitrate können zur exakten Bestimmung des Durchschnittspolymerisationsgrades von Cellulosen verschiedener Provenienz herangezogen werden. In chlorierten Kohlenwasserstoffen und einigen anderen indifferenten Verdünnungsmitteln dissoziiert die hochkonzentrierte Salpetersäure gemä:
magnified image
Die Nitronium‐Ionen sind das eigentliche nitrierende Agens. Sie reagieren mit großer Geschwindigkeit mit den Hydroxylgruppen der Cellulose. Die auf diese Weise hergestellten hochveresterten Cellulosenitrate sin 1 außerordentlich stabil und einwandfrei in den ihrem Versterungsgrad entsprechenden Lösungsmitteln löslich.
2,6,8‐trioxaspiro(3,5)nonane preparation, polymerization and polymer propertiess
Authors: Watanabe Kazuo , Sugihara Toshiharu
Published: April 2003

In this paper are described the preparation of 2,6,8‐trioxaspiro(3,5)nonane (I) which has two different and polymerizable rings in one molecule, its cationic polymerization, and some properties of the polymer. I was Prepared by the action sodium hydroxide on 5‐bromomethyl‐5‐hydroxymethyl‐1,3‐dioxan, which was obtained from pentaerythritol monobromide and paraformaldehyde in the presence of hydrochloric acid. The polymerization of I was carried out in methylene chloride by using BF3. (C2H5)2O as a catalyst, giving highly crystalline polymers (m.p., 220‐225°C.). The results of IR‐analysis of the polymer, together with its solubility and melting properties, indicated that the polymerization occurred primarily through ring opening of the oxetane ring in the monomer without appreciable extent of cross‐linking by opening of the 1,3‐dioxan ring. The thermal stability of the polymer was examined both in air and nitrogene atmosphere. 5‐Methylene‐1,3‐dioxan besides formaldehyde was detected in the pyrolysis products, the formation of which was reasonably explainable by the cleavage of the main chain of the polymer through the so‐called β‐scission mechanism.
The effects of ionizing radiation on the molecular weight of crystalline polypropylene
Authors: Geymer D. O.
Published: April 2003

Absolute molecular weight measurements were obtained on samples of crystalline polypropylene before and after irradiation vac. Some of the chain fracture was produced directly by the radiation, and some occurred days later by a reaction between trapped free radicals and atmospheric oxygen when the ampoules were opened to remove the polymer. The latter reaction is the cause of the abnormally large decrease in the molecular weight of polypropylene when it is irradiated to low doses vac. and subsequently exposed to the atmosphere. This observation raises questions as to the validity of many polymer irradiation studies where care is not taken to destroy the radicals before allowing the irradiated polymer to contact oxygen.

When the trapped free radicals in irradiated polypropylene were destroyed with methyl mercaptan prior to the admission of air, scission yields became normal and the gelation dose decreased markedly. The radiochemical yields of chain fractures and crosslinks at 35°C. are G(chain fracture) = 0.62 and G(crosslinks) = 0.50 when oxidation is not permitted.
Über die möglichkeit der bildung makrocyclischer polyoxyniethylene. 29. mitt über polyoxymethylene1
Authors: Jaacks Von Volker
Published: April 2003

Bei der kationischen Polymerisation von 1,3,5‐Trioxan in Cyclohexan entstehen Polyoxymethylene, welche partiell thermisch stabil und alkalibeständig sind, ohne daß irgendwelche bekamiten stabilen Endgruppen nachgewiesen werden konnten. Möglicberweise handelt es sich hierbei um Makrocyclen.
Role of cocatalysts in polymerizations initiated with benzyl derivatives of transition metals, 1. Polymerization of ethylene
Authors: Martineau Dominique , Dumas Philippe , Sigwalt Pierre
Published: April 2003

Polymerization of ethylene initiated in naphta solution by Zr(CH2C6H5)4 at 200°C under high purity conditions showed a cocatalytic effect of water with a maximum rate for a mole ratio H2O/Zr close to 0,1. No activity was observed for the hypothetical compound (C6H5CH2)3ZrOZr(CH2C6H5)3. Ethylene polymerization was also initiated with supported catalysts obtained by reaction of Zr(CH2C6H5)4 with silicium oxide or pre‐dried aluminium oxide with an increase of activity (by a factor of 5). The resulting polyethylenes were found to be virtually linear with 1,5 CH3 groups for 1000 C atoms and with melting points of 134 – 136,5°C. They have high molecular weights with very broad distribution. These results were interpreted by a mechanism involving Ziegler‐like active centers.
Study of the nature of radical polymerization of methyl methacrylate with “aged” chromium(II) acetate/benzoyl peroxide
Authors: Hungenberg Klaus‐Dieter , Bandermann Friedhelm
Published: April 2003

The polymerization of methyl methacrylate (MMA) in DMF with “aged” chromium (II) acetate (Cr(Ac2)) and benzoyl peroxide (BPO), previously formulated as a living radical polymerization, was investigated. The reaction between Cr(Ac)2 and BPO gives besides N‐methylformamidomethyl benzoate (3) the N‐methylformamidomethylchromium(III) cation (6) as intermediate, which itself may react with BPO with the formation of additional free radicals as compared with the thermolysis of BPO. Thus, the polymerization of MMA in this system could be shown to be a normal radical one with free and uncomplexed radicals. The increase of the degree of polymerization with aging and monomer conversion is explained by the decreasing rate of the radical forming reactions and the onset of the gel effect.
Chemische synthese verzweigter polysaccharide, 10. Polymere mit amidartig gebundenen mono‐ und oligosaccharid‐seitenketten
Authors: Emmerling Winfried N. , Pfannemüller Beate
Published: April 2003

Binding of mono‐, di‐, and oligosaccharides by amide linkage to polymers carrying carboxylic or amino groups was studied with synthetic polymers (poly(acrylic acid), poly(vinylamine)) and polysaccharide derivatives (e.g. chitosan). Suitable methods are described which allow a variation of the number and lenght of the attached saccharide branches. In the absence of salt, all products with a degree of substitution (DS) < 1 show polyelectrolyte behaviour. Compared with the unsubstituted polyelectrolytes, for the branched polymers a substantial increase of the viscosity was observed within a certain range of branch density. In the case of glucose side chains, the maximum viscosity was found near DS = 0,1. In the case of maltose side chains, this maximum of the viscosity occurred at higher DS. A similar but smaller increase in the viscosity was observed in 0,1 M NaCl solution. The results are explained by a shielding of the backbone charges from the counterions and by an additional chain stiffening effect resulting from hydrogen bonds, i.e., ring formation between the amide linkage and adjacent free carboxylic or amino groups.
The compatibility of poly(butyl acrylate) with chlorinated polyethylene
Authors: Chai Zhikuan , Walsh David J.
Published: April 2003

The compatibility of poly(butyl acrylate) (PBA) with chlorinated polyethylene (CPE) was studied using dynamic mechanical measurements and light scattering turbidimetry. For around 50 wt.‐% and above chlorination of CPE they were found to be miscible and show a lower critical solution temperature upon heating. It was found that a favourable heat of mixing of oligomeric analogues could not be taken as a guarantee of the compatibility of the corresponding polymers: the heat of mixing of PBA with cereclor 45 (chlorinated paraffin, 45, 7 wt.‐% CI) is negative, but the corresponding polymers PBA/CPE3 (48,0 wt.‐% CI) are immiscible. When the Flory equation of state theory is applied to the system, a large negative interaction entropy parameter Q12 must be introduced to counterbalance the large negative interaction energy parameter X12, obtained from the heats of mixing of PBA with cereclor. The simulated spinodals are flat‐bottomed. However, if a much smaller negative X12 is adopted, the spinodal calculated will have more curvature. Kinetic constraints on the migration of molecules during phase separation were observed when the molecular weight exceeded certain limits and this could affect the observed cloud point diagram.
Chiral configuration in the complexes of poly (Nε‐alkyl‐L‐lysine)s with alkylamino azo dyes
Authors: Yamamoto Hiroyuki
Published: April 2003

Absorption and circular dichroism (CD) spectra were measured on the complexes of poly(Nε‐alkyl‐L‐lysine)s and alkyl azo dyes. Absolute configuration of the complexes was examined by the exciton chirality method. Most complexes show S‐chirality of the transition dipole moments of dyes. Increased hydrophobic properties of both dye molecule and polypeptide side‐chains change the chirality of dye from common S‐ to uncommon R‐chirality. The induced CD results are discussed from the point of view of hydrogen bonding, electrostatic, and hydrophobic properties of both dyes and polypeptides.
Orientierungsverhalten von segmentierten polyetherurethanen in abhängigkeit von der dehnung und den verwendeten lösungsmitteln
Authors: Hoffmann Karin , Bonart Richard
Published: April 2003

The solvent influence on two‐ phase structures resulting from drying films of segmented polyetherurethanes of different hard segment contents and molecular weights was investigated by infrared dichroism measurements of the orientational behaviour of the hard segments. A low density of physical crosslinking and/or minor association in solution leads to a lamellae structure resulting in an inhomogeneous distribution of stress at elongation. The formation of lamellae is impeded, if the solution shows pronounced formation of associates. Destruction of the lamellae can be monitored by studying the orientational behaviour for repeated deformations and by means of orientation‐extension‐hysteresis experiments. Stress‐strain diagrams exhibit no contradictions to the discussed structural transformations by the influence of different solvents.
Metathesis degradation of polymers obtained by grignard‐wurtz reaction of partially α‐brominated 1,4‐polybutadiene
Authors: Hummel Klaus , Kathan Wolfgang
Published: April 2003

1,4‐Polybutadiene was partially brominated at the methylene groups with N‐bromosuccinimide. Then, by means of Grignard‐Wurtz reactions, the following substituents were introduced: isopropyl, butyl, pentyl, cyclohexyl, phenyl, 4‐methylphenyl, 4‐ethylphenyl, 3,4‐dimethylphenyl, 4‐isopropylphenyl, 4‐fluorophenyl, 3‐trifluorophenylmethyl, 4‐chlorophenyl, benzyl, 2‐methylbenzyl, and 4‐methylbenzyl. The modified polymers (ca. 20% of the units substituted) were degraded to low molecular products with E‐4‐octene in the presence of the catalyst WCl6/(CH3)4Sn. The degradation products were separated by gas chromatography and identified by mass spectrometry. Isomeric substituents, isomeric units, and isomeric segments in the polymers could be distinguished. — In Grignard‐Wurtz reactions, transfer reactions with toluene as solvent and simultaneous reactions with two Grignard reagents (4‐methylphenyl and 4‐methylbenzyl compounds) were also investigated.
Influence of the structure of chlorophenyl 2,3‐epoxypropyl ethers on their reactivity in ionic polymerization
Authors: Stolarzewicz Andrzej
Published: April 2003

Empirical correlation equations could be derived for comparison of the relative reactivities of a homologous series of chlorophenyl 2,3‐epoxypropyl ethers in cationic polymerization initiated by SnCl4, and in anionic polymerization initiated by KOH. These equations include a conformation constant, Sk, accounting for the interaction between the oxirane ring and the aromatic substituent. For the anionic polymerization the saponification number must be introduced additionally into the correlation equation to account for a side reaction between initiator and substituent.
High conversion copolymerization, 2. Styrene/maleic anhydride copolymer composition studies
Authors: Capek Ignác , Juraničová Viera , Bartoň Jaroslav
Published: April 2003

The free radical initiated copolymerization of styrene with maleic anhydride at high conversions is studied. The data of the fractional conversion of the comonomers, of the fractional copolymerization rate, of the instantaneous and cumulative composition of the copolymer for the copolymerization of an equimolar mixture of styrene and maleic anhydride in ethyl methyl ketone (at 60°C) and in 1,4‐dioxane (at 120°C) up to high conversions as a function of the reaction time (resp. conversion) are presented. Negligible differences at 60°C, but significant ones at 120°C were found between the experimentally measured fractional compositions and those calculated according to the integrated form of the copolymer composition equation (Mayo‐Lewis equation), using the published values for the copolymerization reactivity ratios.
Molecular weight distributions of poly(methyl methacrylate) produced at high viscosities
Authors: Bogunjoko Julius S. T. , Brooks Brian W.
Published: April 2003

The molecular weight distribution of poly(methyl methacrylate), which is produced by the free‐radical polymerisation of methyl methacrylate, is influenced by the presence of poly(methyl methacrylate) which is dissolved in the monomer prior to the polymerisation. An experimental technique has been devised which permits a distinction to be made between polymer which is present at the start of the reaction and the polymer which is formed by the reaction. Mathematical analyses of alternative reaction schemes have been made. These predicted changes that would occur in the molecular weight distribution of the new polymer when the solution viscosity increased. Comparison with experimental measurements of molecular weights makes possible the distinction between the alternative reaction schemes. The results are compatible with a reaction mechanism in which the mobilities of the growing radicals are not influenced equally by the solution viscosity. The results are not those which would be expected by the simple inclusion of primary radical termination in the reaction scheme. In some cases, analysis by gel permeation chromatography showed that the molecular weight distribution of the poly(methyl methacrylate) formed by the reaction is bimodal. This is consistent with predictions from the mathematical analysis.
Chemical modification of polydienes, 2. Properties of polybutadiene and nitrile rubbers grafted with poly(tetrahydrofuran)
Authors: Gordon Cameron G. , Duncan Alexander W. S.
Published: April 2003

Thermal analysis by differential scanning calorimetry (DSC) indicated that graft copolymers of poly(tetrahydrofuran) (PTHF) on a nitrile rubber containing 39 wt.‐% acrylonitrile have a two‐phase morphology comprising crystalline PTHF and amorphous rubber. In rubbers with an 18 wt.‐% acrylonitrile content the PTHF is more compatible with the rubber and exerts a plasticising effect; crystallinity of the PTHF is not as well developed. cis‐1,4‐Polybutadiene and PTHF are partially miscible and in grafts on these two the melting endotherm of the latter was not detected. The relative values of the solubility parameters of PTHF and the three rubbers are consistent with this behaviour. All graft copolymers have a fairly low thermal stability and begin to decompose under N2 below 200°C. Degradation appears to be initiated at the PTHF grafts. Graft copolymers of PTHF with nitrile rubbers are less resistant to petroleum than the ungrafted rubbers.
Parameters of the generalized exponential function for the molar mass distribution of the polystyrene standard NBS 706
Authors: Chiantore Oscar , Guaita Marino
Published: April 2003

The experimental molar mass distribution of the polystyrene standard NBS 706, as determined by high performance size exclusion chromatography, has been fitted with the generalized exponential function, whose parameters have been evaluated by a computer procedure. Comparison is made with the Schulz‐Zimm and logarithmic normal distributions, and the consistency of the different average molar masses is discussed.
Phase behaviour of liquid crystalline side chain polymers
Authors: Frenzel J. , Rehage G.
Published: April 2003

The phase behaviour of liquid crystalline side chain polymers is investigated by different experimental methods.PVT‐ and DSC‐measurements as well as X‐ray and optical investigations show that additionally to the known factors from low molecular weight liquid crystals the flexibility of the polymer backbone influences the liquid crystalline properties of the phase. Fixing a mesogenic side chain to a polymer backbone leads to a stabilisation or even a generation of a liquid crystalline phase in comparison to the corresponding low molecular weight liquid crystals. — The liquid crystalline phases which are known from low molecular weight liquid crystals are also found for liquid crystalline polymers (nematic, chiral‐nematic, smectic). In contrast to low molecular weight liquid crystals the phase transformations smectic to crystalline and chiralnematic to smectic show strong time dependences for polymeric substances. — A crystallization of the liquid crystalline side chain polymers is observed, when the polymer main chain is so flexible, that the mesogenic groups can form a crystalline order. The crystallization process leads for a smectic sample to a layer lattice structure. From X‐ray investigations one can conclude that the smectic arrangement of the mesogenic side chain exhibits a preorder for the crystalline structure. As known from other substances the crystallization rate depends on temperature and pressure. — The transformations in the liquid crystalline region are first‐order transformations and obey the Clausius‐Clapeyron equation. At lower temperatures all liquid crystalline polymers solidify to anisotropic glasses. Below the glass transition temperature nematic or smectic states of order are frozen‐in and preserved in this way.
Lyotropic and thermotropic liquid‐crystalline phase formation from fractions of a semiflexible cellulosic polymer
Authors: Bhadani Suraj N. , Tseng So‐Lan , Gray Derek G.
Published: April 2003

The benzoic acid ester of (2‐hydroxypropyl)cellulose (BzPC) was prepared and fractionated from acetone solution by precipitation with methanol‐water (85:15, by volume). The fractions were characterized by low‐angle laser light scattering in tetrahydrofuran, and by size exclusion chromatography with a low‐angle laser light scattering detector. Dilute solution viscosities were measured in acetone and benzene, and the results were interpreted on the basis of a worm‐like chain model for BzPC. The critical concentrations of polymer necessary to form lyotropic cholesteric phases in acetone and benzene were found to decrease as the molar mass of the polymer increased, reaching a limiting volume fraction of ≈ 0,35 for high molar mass fractions. The experimental results were compared with the prediction of recent theories for the formation of liquid crystalline phases from semiflexible polymers; the chain parameters required by the theories were estimated from dilute solution viscosities. The fractions of BzPC also showed a thermotropic transition from liquid crystalline phase to isotropic melt. The transition temperature increased sharply with increasing molar mass to reach a limiting value of 176°C.
Biodegradable random copolypeptides of β‐benzyl L‐aspartate and γ‐methyl L‐glutamate for the controlled release of testosterone
Authors: Asano Masaharu , Yoshida Masaru , Kaetsu Isao , Nakai Katsuyuki , Yamanaka Hidetoshi , Yuasa Hisako , Shida Keizo , Suzuki Keiji , Oya Masanao
Published: April 2003

The random copolypeptides of β‐benzyl L‐aspartate (β‐Bz L‐Asp) and γ‐methyl L‐glutamate (γ‐Me L‐Glu) were synthesized and implanted subcutaneously in rats. It was found that the resulting copolypeptides are degraded and also have good biocompatibility in vivo. On the basis of these results, poly(β‐Bz L‐Asp‐co‐γ‐Me L‐Glu) was tried to be used as a material for a drug delivery system. Copolypeptide‐testosterone composites were prepared at a pressure of 200 kg/cm2 in the presence of a slight amount of dichloroethane. The in vivo release rate of testosterone from copolypeptide‐drug composites was about 5,5 times higher than that in vitro. The in vivo release rate remained relatively constant over a period of 90 days at 0,22 mg/day. The serum testosterone concentration in castrated rats was 0,40 ng/ml and the value went up to 6,8 ng/ml after the biodegradable copolypeptide‐testosterone composite was implanted and was kept constant for the duration of test.
Polymerization of lactams, 58. Nonactivated polymerization of 2‐pyrrolidone in the presence of higher lactams
Authors: Chuchma František , Roda Jan , Králíček Jaroslav
Published: April 2003

Addition of a higher lactam (ε‐caprolactam or 8‐octanelactam) to the nonactivated polymerization of 2‐pyrrolidone, initiated with potassium tert‐butoxide or the isolated potassium salt of 2‐pyrrolidone, does not lead to the formation of a copolyamide. Only a marked decrease of polymerization rate is observed and the maximum rate of 2‐pyrrolidone homopolymerization shifts to a lower temperature. The possible causes of this interesting phenomenon are discussed.
29Si NMR‐untersuchungen an polykieselsäureestern
Authors: Marsmann Heinrich C. , Meyer Ehler , Vongehr Manfred , Weber Ernst F.
Published: April 2003

Linear and branched siloxanes were prepared by partial hydrolysis of silicon tetrachloride and by esterification of the products of hydrolysation with methyl and ethyl nitrite. 29Si NMR spectra made it possible to distinguish between the isomers of each oligomer up to the heptamer. Linear relationships between the 29Si chemical shifts of the ethyl and the methyl esters on one hand and between the ethyl esters and the poly(silicic acid)s on the other hand were observed. However, due to the different effect of neighboring building units, there are only poor relationships between the 29Si data of the esters and the chloro derivatives.
Chemical synthesis of polysaccharides, 2. A synthetic polysaccharide having two hydroxyl groups in its repeating unit, 4‐deoxy‐(1→6)‐α‐D,L‐xylo‐hexopyranan
Authors: Okada Masahiko , Sumitomo Hiroshi , Hishida Yasuhito
Published: April 2003

A new D,L‐polysaccharide, 4‐deoxy‐(1→6)‐α‐D,L‐xylo‐hexopyranan (3), containing two hydroxyl groups in its repeating unit was synthesized, starting from 3,4‐dihydro‐2 H‐pyran‐2‐carbaldehyde (4) (Acrolein dimer). The monomer, a bicyclic acetal, 3(a),4(a)‐bis(benzyloxy)‐6,8‐dioxabicyclo[3.2.1]octane (1) was prepared from the starting material via six step reactions. The cationic ring‐opening polymerization of 1 was effectively achieved by using antimony pentachloride or trifluoromethanesulfonic acid as initiators to afford the polyacetal 2 with number average molecular weights of up to 1,2 · 105. Debenzylation of 2 with sodium metal in liquid ammonia gave rise to a white powdery polymer identified as 3 by 13C‐NMR spectroscopy. The synthetic polysaccharide 3 melting in the range of 90 to 103°C was found to be soluble in dimethyl sulfoxide and water, and insoluble in other common organic solvents. Water sorption of 3 was measured at different relative humidities between 32 and 97% and compared with those of natural dextran and a synthetic polysaccharide having an analogous structure.
Oligo(thiophénylènes‐1,4) α,ω‐difonctionnalisés, 4. Effects de la structure sur la miscibilité avec le polyundécanamide. Propriétés des mélanges
Authors: Daccord Gérard , Sillion Bernard , Thibert Cyrille
Published: April 2003

From several types of polyamides (3, 4, 5, and 6) containing blocs of 2, 4, 6, and 14, 7 thio‐1,4‐phenylene units blends with polyundecanamide (2) were prepared. Their miscibility, thermal properties, mechanical properties, and methane permeability were studied and related to the chemical structure of the additives. The thermal stability of the polyamide was found to be improved for all kinds of blends. The miscibility of the thio‐1,4‐phenylene blocs incorporated into the copolymers is higher than the theoretical prediction for the unmodified blocs. Increasing of Young's modulus and decreasing of methane permeability were observed when the thio‐1,4‐phenylene blocs are partially miscible.
Propriétés physicochimiques d'une série de polystyrènes deutériés en solution dans le tétrahydrofuranne
Authors: Lapp Alain , Strazielle Claude
Published: April 2003

The physicochemical properties of a series of deuterated polystyrenes were investigated in tetrahydrofuran by viscosity, light scattering (LS), on line LS‐GPC, and size exclusion chromatography (GPC). The viscosity laws and unperturbed dimensions of deuterated (PSD) and “hydrogenated” (PSH) polystyrene were compared. There are small but distinct differences in the solution behaviour of PSH and PSD. Some optical properties of partially D‐labelled polystyrenes were investigated.
Studies on the adiabatic polymerisation of acrylamide
Authors: Thomson Ross A. M. , Ong Chin Kee , Rosser Christine M. , Holt John M.
Published: April 2003

Kinetic parameters, obtained isothermally, have been used in the quantitative description of the polymerisation of acrylamide under virtually adiabatic conditions. The equations which have been derived relate the temperature rise on reaction to the decrease in reactant concentration during the course of reaction, taking account of the various energies of activation and frequency factors involved, whose values may be chosen as required. The approach used has been to find the value of the overall activation energy which gives the best agreement between theoretical and experimental temperature‐time plots. Good agreement has been obtained between these when a value of 74,5 ± 0,9 kJ · mol−1 was chosen for the overall activation energy for the persulfate‐initiated polymerisation of acrylamide using a wide range of initiator and monomer concentrations. This gives a value of 135,5 kJ · mol−1 for the activation energy for the thermal decomposition of the persulfate ion, which is in good agreement with the literature. Interesting implications are discussed in the context of the nature of the product formed during the course of the polymerisation.
Kinetics of the addition reaction of sec‐butyllithium onto bis(1‐phenylvinyl)benzenes
Authors: Leitz Edgar , Höcker Hartwig
Published: April 2003

Divinylidene compounds such as bis(1‐phenylvinyl)benzenes not being anionically homopolymerizable add sec‐butyllithium (sBuLi) to form biscarbonionic species. The reaction can be treated as a consecutive addition reaction. For 1,3‐bis(1‐phenylvinyl)benzene the rate constants of the first and second addition step of sBuLi are both 1,98 · 10−2 1/(mol · s); for 1,4‐bis(1‐phenylvinyl)benzene the rate constant for the first step is 2,06 · 10−2 1/(mol · s) and that for the second step is 1,51 · 10−3 1/(mol · s) (in toluene as solvent, with an excess of sBuLi at 20°C). The overall activation energy of the individual steps is 60 kJ/mol, the frequency exponent being between 8 and 9.
Lamellar crystalline structure of star‐shaped block copolymers with an amorphous block of polystyrene and two crystallizable blocks of poly(ethylene oxide)
Authors: Gervais Monique , Gallot Bernard , Jérǒme Robert , Teyssié Philippe
Published: April 2003

Star‐shaped block copolymers S(EO)2 with two poly(ethylene oxide) chains (PEO) linked to the same end of a polystyrene chain (PS) exhibit a lamellar liquid crystalline structure, with crystallized and folded PEO chains, in the dry state as well as in the presence of a preferential solvent of the PS block at temperatures below about 50°C. Refolding of the PEO chains was studied in terms of the PS swelling degree and in terms of the PEO content of the copolymers. A difference in length of the PEO chains was suggested, probably resulting from the different nature of the sites that initiate the EO chain polymerization. To investigate the effect of the number of the PEO chains fixed to the PS block, two block copolymers S(EO)2 and SEO of the same relative molecular mass and composition were studied.
Gruneisen parameter for polyamides
Authors: Warfield R. W. , Kayser Eleonore G. , Hartmann Bruce
Published: April 2003

For the five aliphatic polyamides, poly(caprolactam), poly(ω‐aminoundecanoic acid), poly(ω‐aminododecanoic acid), poly(hexamethylene adipamide), and poly(hexamethylene sebacamide), experimental values were obtained of the thermodynamic properties: molar volume, volume thermal expansion coefficient, isothermal bulk modulus, and molar heat capacity. These properties were combined to form the dimensionless ratio known as the Gruneisen parameter. All of the experimental properties were analyzed in terms of molecular components using the method of additive properties. It was concluded that the hydrogen bonding found in polyamides produces a highly localized region of very low Gruneisen parameter.
The solid‐state polymerization, physical properties, and crystal structures of diacetylene mixed crystals
Authors: Enkelmann Volker
Published: April 2003

Suitable substituted diacetylenes, 2,4‐hexadiynylene di‐p‐toluenesulfonate (1a) and 2,4‐hexadiynylene di‐p‐fluorobenzenesulfonate (1b), were cocrystallized to form substitutional solid solutions. By solid state polymerization of mixed crystals of 1a and 1b single crystals of the corresponding copolymers were obtained. The polymerization rate can be varied over a wide range by admixture of the comonomer 1b in the lattice of 1a. The crystal structures of monomer 1b and of the corresponding polymer, 2b, were determined. It was found that the packing of the reactive triple bond systems is identical in both monomers. Comonomer 1b acts as a defect site with a high probability of chain termination.
Synthesis of macromolecular antioxidants by reaction of aromatic amines with epoxidized polyisoprenes, 2. Kinetics and mechanism of model reactions
Authors: Jayawardena Shanthilal , Reyx Danièle , Durand Dominique , Pinazzi Christian Pierre
Published: April 2003

Kinetic and thermodynamic parameters were determined for the reaction of the unsymmetrical oxiranes 3,4‐epoxy‐methylheptane (1) and 1,2‐epoxy‐3‐ethyl‐2‐methylpentane (4) with aniline in o‐dichlorobenzene. A kinetic scheme involving two elementary reactions agrees well with the experimental results obtained for the phenol catalysed reactions. The thermodynamic parameters, especially the entropy, lead to the proposal of a concerted transfer mechanism allowing for the observed normal and abnormal addition reactions.
The propagation rate‐constants for the cationic polymerisation of acenaphthylene and styrene in nitrobenzene
Authors: Holdcroft Geoffrey E. , Plesch Peter H.
Published: April 2003

Rate measurements of the polymerisation of acenaphthylene in nitrobenzene at 298 K by PhCO+ SbF6− gave kp+ = 23,2 ± 2 dm3 · mol−1 · s−1 which confirmed our previous value with yet another initiator. Under the same conditions we obtained kp+ = 188 ± 9 dm3 · mol−1 · s−1 for styrene. The completeness of initiation was indicated by a count of carbonyl groups by spectroscopy. The conductivity measurements indicated that [Pn+] is independent of time and that there is no ion‐pairing. The DPD of the polymers was unimodal and the DP independent of m0 and c0. Exploratory experiments showed that HClO4 and CF3SO3H in nitrobenzene are not useful for kp+ determinations. In an Appendix a detailed treatment is given of how the impurity content of solvent and monomer can be determined by kinetic measurements.
Cationic polymerization of 1‐azabicyclo[4.2.0]octane, 1 alkylation
Authors: Matyjaszewski Krzysztof
Published: April 2003

The rate constants of the reaction of 1‐azabicyclo[4.2.0]octane (1) with different alkyl esters or halides were measured using 1H NMR and UV spectroscopy as well as conductometric methods. The reactivities of the alkylating agents were found to decrease with increasing nucleophilicity of the derived anions (CF3SO⊖3 > I⊖ > Br⊖ > picryl⊖ > Cl⊖). Reactivities of all ethyl derivatives, except ethyl chloride, are higher than the reactivity of the 1‐alkyl‐1‐azoniabicyclo[4.2.0]octane cation (2), which means that for these compounds the rate constant of initiation is higher than that of propagation. The reactions proceed much slower in methanol than in nitrobenzene due to the strong donor‐acceptor interactions between methanol and 1. Attempts to observe covalent active centers directly by NMR spectroscopy in the polymerization mixture or to detect them kinetically, were unsuccessfull. The reactivity of ethyl triflate, modelling the hypothetical active center, was found to be 2.104 times higher than the reactivity of ions 2. This is ascribed to the high strength of the bond in the cation 2, not sufficiently compensated by the strain of the four‐membered ring.
Investigation of the structure of polymers of the polyphenylene type by 13C NMR spectroscopy
Authors: Urman Yakov G. , Teplyakov Mikhail M. , Alekseeva Swetlana G. , Khotina Irina A. , Slonim Izrael Ya. , Korshak Vasilii V.
Published: April 2003

The structure of a number of polymers of the polyphenylene type, prepared by polycyclocondensation of aromatic diketones and their acetals was investigated by 13C NMR spectroscopy. The spectra provide a means to determine the content of 1,3,5‐trisubstituted benzene rings and defective β‐methylchalcone fragments, as well as the endgroups.
Initiation mechanism of free‐radical polymerization of methyl methacrylate by p‐substituted N, N‐dimethylanilines
Authors: Tsuda Kazuichi , Kondo Shuji , Yamashita Keiji , Ito Kiyohiko
Published: April 2003

In order to investigate the initiation mechanism of the polymerization of MMA by N, N‐dimethylaniline (DMA), p‐substituted DMA's were prepared and used for a kinetic study. Electron donating groups increase and electron withdrawing substituents decrease the over‐all rate of polymerization. Moreover, different kinds of amines were examined as initiators. The results were related with the Hammett equation and the ionization potential of the amines. The solvent effect and the composition of the initiator complex were investigated. From these results, it is concluded that the initiating species is a 1:1 electron transfer complex of DMA with the monomer methyl methacrylate.
Evaluation of kinetic parameters resulting from photostabilized degradation of poly(2,6‐dimethyl‐1,4‐phenylene oxide) films in the absence and presence of zinc bis(O,O′‐diisopropyldithiophosphate)
Authors: Chandra Ramesh
Published: April 2003

Light scattering was used to evaluate the resulting changes in molecular weight, root‐mean‐square radius of gyration, degree of polymerization, number of chain scissions per single chain kngth, degree of degradation, specific rate constant, energy of activation, enthalpy, entropy and free energy of activation for the photo‐oxidative degradation of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (poly(oxy‐2,6‐dimethyl‐1,4‐phenylene)) film, both in the presence and absence of 0,1 wt.‐% zinc bis(O,O'‐diisopropyldithiophosphate) (ZnDTP) as photostabilizer, undergoing random chain scission and crosslinking processes in the temperature range 313–363 K with light of wavelength 365 nm. The inhibitive action of ZnDTP was discussed from the viewpoint of the amount of gel fraction.
Investigation of exothermic polymer blends by neutron scattering
Authors: Jelenič Jernej , Kriste Rudolf G. , Oberthür Radulf C. , Schmitt‐Strecker Sigrid , Schmitt Burghard J.
Published: April 2003

Provided a polymer is soluble, i. e., molecularly dispersed in another polymer irrespective of the molecular weight of the components, the solution is exothermic. By increasing the temperature two effects, both unfavourable to mixing become larger: (i) the excess entropy of mixing caused by contact interaction and (ii) the total effect from the difference of the free volumes of the pure components. So, an upper miscibility gap occurs. The thermodynamic properties of the mixture cannot be derived from the properties of the pure components. They can be described by the corresponding states theory of Prigogine, Flory, and Patterson with suitable values for the contact energy and contact entropy parameters X12 and Q12. The temperature of separation can be predicted from measurements on the mixture at low temperatures.
Catalytic effects of cationic polymeric liposomes on the alkaline hydrolysis of aniomic phenyl esters
Authors: Kitano Hiromi , Katsukawa Makoto , Ise Norio , Dorn Klaus , Ringsdorf Helmut
Published: April 2003

Alkaline hydrolyses of anionic phenyl esters such as 4‐acetoxy‐3‐nitrobenzoic acid and 4‐butyryloxy‐3‐nitrobenzoic acid were examined in the presence of cationic and polymeric liposomes, liposomes of low molecular weight compounds, and micelles. All the additives accelerate the reaction due to the hydrophobic interaction between substrates and additives and the electrostatic interaction both between substrates and additives and between OH− and additives. In the Arrhenius plots of the reactions catalyzed by the liposomes, discontinuous regions were observed due to the phase transition of liposomes from the gel state to the liquid crystal state. Activation parameters ΔH≠, ΔS≠ and ΔV≠ for these reaction systems were evaluated. Both ΔS≠ and ΔV≠ values increase upon the addition of cationic liposomes and micelles. These results were attributed to the desolvation of the activated complex by the strong electrostatic affinity to the cationic colloidal additives.