bluuebunny/crossref_metadata_2025_split huggingface dataset:
Beitrag zur polymeranalogen umsetzung der cellulose zu cellulosenitrat
Authors: Thinius Von K. , Thümmler W. 
Published: April 2003

AbstractDurch 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:
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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

AbstractIn 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

AbstractAbsolute 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

AbstractBei 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

AbstractPolymerization 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

AbstractThe 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

AbstractBinding 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

AbstractThe 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

AbstractAbsorption 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

AbstractThe 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

Abstract1,4‐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

AbstractEmpirical 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

AbstractThe 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

AbstractThe 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

AbstractThermal 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractAddition 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

AbstractLinear 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

AbstractA 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.