bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bestimmung der ungestörten Dimensionen von Makromolekülen aus Lichtstreuungsmessungen unter Berücksichtigung der Molekulargewichtsverteilung
Authors: Bareiss Rolf E. , Bellido José 
Published: April 2003

AbstractEs werden die Formeln für die Polymolekularitätskorrekturfaktoren zweier Varianten des Baumann‐Verfahrens zur Bestimmung der ungestörten Dimensionen von Makromolekülen, welche eine Schulz‐Flory‐ bzw. eine logarithmische Normalverteilung der Molekulargewichte aufweisen, angegeben. Die experimentelle Prüfung mit Poly(α‐methylstyrol)‐,[Poly(1‐methyl‐1‐phenyläthylen)]‐Mischungen, welche in guter Näherung Schulz‐Flory‐ bzw. logarithmische Normalverteilungen der Molekulargewichte aufweisen, zeigt, daß sowohl für das Baumann‐Stockmayer‐Fixman‐ als auch für das Baumann‐Kurata‐Stockmayer‐Verfahren die lineare Extrapolation für Polymerhomologe mit beliebiger Breite der Molekulargewichtsverteilung möglich ist und zu den gleichen Werten für die ungestörten Dimensionen wie für Polymerhomologe mit enger Molekulargewichtsverteilung führt, wenn die Werte für das Gewichtsmittel des Molekulargewichts Mw und das z‐Mittel des Trägheitsradiusquadrats 〈S̄2〉z mit den entsprechenden Polymolekularitätskorrekturfaktoren qMw bzw. qsz multipliziert werden.
Functional monomers and polymers, 31. On the stereoregularity of vinyl polymers containing nucleic acid bases
Authors: Akashi Mitsuru , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractN‐β‐Methacryloyloxyethyl derivatives of adenine, thymine, uracil, and theophylline were polymerized at 60°C in various solvents, using azodiisobutyronitrile as an initiator, and the polymers obtained were further converted to poly(methyl methacrylate). From the high resolution NMR spectra of poly(methyl methacrylate) thus derived, the stereoregularity of the polymers originally prepared was determined. The NMR spectra measured at 150°C in dimethyl sulfoxide‐d6 showed three peaks based on α‐methyl protons, which were assigned to the components of the syndiotactic triad (S), heterotactic triad (H), and isotactic triad (I). In the free‐radical polymerization of these monomers containing nucleic acid bases at 60°C, the polymerization rate was found to be influenced by the sort of the bases and solvents used, while the stereoregularity of the polymers seems not to be affected by them.
Funktionelle monomere und polymere, 33. Synthese von stereoregulären vinylpolymeren mit nucleinbasen in den seitenketten
Authors: Inaki Yoshiaki , Takada Hiroshi , Kondo Koichi , Takemoto Kiichi 
Published: April 2003

AbstractStereoregular polymethacrylates containing adenine, uracil, or theophylline residues in the side chains (4a–c), were prepared starting from isotactic and syndiotactic poly[1‐(2‐bromoethoxycarbonyl)‐1‐methylethylene] (2) by reaction with the sodium salts of the corresponding nucleic bases. NMR‐ and UV‐spectroscopic studies of the polymers were carried out.
The oxidative coupling of 2,6‐xylenol catalyzed by polymeric complexes of copper, 1. Kinetic study of the catalysis by copper(II)‐complexes of partially aminated polystyrene
Authors: Schouten Arend Jan , Prak Nanno , Challa Ger 
Published: April 2003

AbstractThe oxidative coupling reaction of 2,6‐xylenol (3) catalyzed by copper(II) complexes of chemically modified polystyrene was investigated. Under the applied reaction conditions the main reaction product was 2,6,2′,6′‐tetramethyl‐1,1′‐dioxo‐4,4′‐bicyclohexa‐2,5‐dienylidene (4). It was found that the polymeric complexes behave quite different from the low molecular analogue and that these differences can mainly be ascribed to a better complexation of copper within polymer coils. It appeared that a Michaelis‐Menten description of the kinetics fits rather well when the concentration of the phenol was not too high.
NMR studies on the growing species of cyclic acetals in their cationic polymerization. 1H‐NMR spectra of oxycarbenium ions formed in some model reactions
Authors: Yokoyama Yasuaki , Okada Masahiko , Sumitomo Hiroshi 
Published: April 2003

AbstractThe ionic species formed in the reaction of 1,3‐dioxane with triethyloxonium salts were examined by 1H‐NMR spectroscopy under various conditions. The signal assignable to the protons of the positively charged end‐methylene group appeared at δ = 9,9–16,6 ppm, depending on temperature, solvents, and counter ions. The quenching of the ionic species with sodium ethoxide provided 1,3‐dioxane, 1,3‐diethoxypropane, and 3,5,9‐trioxaundecane. The removal of diethyl ether from the reaction mixture containing the ionic species shifted the end‐methylene proton signal to a higher magnetic field and favored the formation of 1,3‐dioxane in the quenching reaction. Similar phenomena were observed for the ionic species produced in the reaction of 1‐chloromethoxy‐3‐ethoxypropane with antimony pentachloride. These results indicate the oxycarbenium ionic nature of the ionic species formed in the above reactions. On the basis of these model reactions, the growing species of cyclic acetals in the cationic polymerization is discussed.
Thermischer Abbau von linearen polymeren unter nicht isothermen bedingungen
Authors: Schneider Ioan‐Adam , Hurduc Natalia 
Published: April 2003

AbstractBei der Untersuchung des thermogravimetrischen Verhaltens von linearen Polymeren unter nichtisothermen Bedingungen in Luft ergab sich, daß, ein einfacher Vergleich der Kurven aus der dynamischen Thermogravimetrie (TG und DTG) keine genaueren Aussagen bezüglich des thermischen Abbaues zuläßt. Erst ein Versuch, diese Kurven vor allem unter Berücksichtigung des Umsatz‐ und Aufheizgeschwindigkeitseinflusses kinetisch auszuwerten, führte zu deutlichen Unterschieden. Diesen entsprechend, baut unter den verwendeten Bedingungen anionisches PMMA nach einem Kettenmechanismus ab, wogegen beim anionischen PS zwei parallele Reaktionen ablaufen. Bei linearem PE ist der Abbau so kompliziert, daß keine näheren Angaben gemacht werden können.
Synthese und halbleitereigenschaften von phthalocyaninartigen polymeren mit Tetrathiafulvalen‐Einheiten
Authors: Koßmehl Gerhard , Rohde Michael 
Published: April 2003

Abstract4,5,4′,5′‐Tetracyano‐2,2′‐bi‐1,3‐dithiolylidene (tetracyanotetrathiafulvalene) (1) was found to react with metal acetylacetonates (2a–m) to give dark, insoluble, and infusible polymers 3a–m with phthalocyaninelike structure. The electrical conductivity of the polymers was investigated (σ298K < 6·10−5 Ω−1 cm−1), and a linear relationship between the logarithm of the electrical conductivity and the activation energy of the different polymers was found (compensation effect). Measurements of the thermoelectric power proved p‐conduction.
Free radical polymerization of unconjugated dienes, 17. Copolymerization of dimethyl 2,6‐dimethyleneheptanedioate with methyl methacrylate in benzene solutions
Authors: Casorati Ernesto , Martina Alfredo , Guaita Marino 
Published: April 2003

AbstractSince dimethyl 2,6‐dimethyleneheptanedioate (1) yields, by free radical polymerization in benzene solutions, soluble polymers without any residual unsaturated groups, the hypothesis is made that either the molecule of this monomer or the radical into which the molecule is converted by the attack of a growing chain has a pseudocyclic conformation. To test the validity of this hypothesis, 1 was copolymerized in benzene with methyl methacrylate. The values found for the reactivity ratios can be interpreted on the basis of conformations of the molecules of 1, in which the two unsaturated groups partially shield each other, in agreement with the hypothesis that the molecule itself has a preferred conformation prefigurating a cyclic structure.
Effet de la concentration sur la transition conformationnelle des copolymères séquencés et greffés
Authors: Dondos Anastasios , Benoît Henri 
Published: April 2003

AbstractIn this paper we have been studying the effect of concentration c on reduced viscosity ηsp/c for a triblock copolymer poly(methyl methacrylate)/polystyrene/poly(methyl methacrylate) and for a graft copolymer of the same nature.The temperature of the experiments has been chosen in the range where the conformation changes from a segregated form to a pseudogaussian one. For this temperature range ηsp/c is not a linear function of concentration but the points ηsp/c vs. c are situated on two straight line segments with a well defined intercept.We discuss the phenomenon in comparison to results obtained on mixtures of homopolymers. These results suggest a strong and anomalous dependance of molecular conformation on concentration.
Microstructure and melting point of stereoregular polymers. A tentative experimental correlation for isotactic polypropylene
Authors: Pavan Andrea , Provasoli Augusto , Moraglio Giovanni , Zambelli Adolfo 
Published: April 2003

AbstractFractions of predominantly isotactic polypropylene with varying stereoregularity were examined by NMR analysis and by hot‐stage optical microscopy, and the stereochemical composition and the melting point of each fraction were determined. From the stereochemical composition the average length of the isotactic stereoblocks is evaluated, and the experimental results are compared to the lengths calculated according to two statistical models of stereospecific propagation. The experimental melting points are then related to the experimental average lengths of isotactic stereoblocks, and the correlation is discussed.
Deuteron NMR relaxation and molecular motion of polystyrene in solution
Authors: Grandjean Jean , Sillescu Hans , Willenberg Bernd 
Published: April 2003

AbstractDeuteron relaxation times T1 of polystyrenes deuterated at the backbone (PS‐d3) and the phenyl ring (PS‐d5), respectively, have been measured in solutions of benzene and diethyl malonate as a function of concentration and temperature. We conclude that the motion of the phenyl ring is faster than that of the backbone, the difference being smallest at high temperatures around 180°C. The temperatures dependence is discussed in relation to the activation energies in polystyrene.
Cationic polymerization of styrenes by protonic acids and their derivatives, 4. Homo‐ and Co‐polymerizations of para‐substituted styrenes by CF3SO3H
Authors: Sawamoto Mitsuo , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

Abstractp‐Methyl‐ and p‐chlorostyrenes (pMeSt and pClSt) were polymerized by CF3SO3H in methylene chloride at 0°C and gave polymers with a bimodal molecular weight distribution (MWD). This indicates that the polymerizations involve two independent propagating species: a dissociated and a non‐dissociated species. Their selectivities toward monomers were compared in the copolymerizations of pMeSt and pClSt with styrene (St) by CF3SO3H in benzene, methylene chloride, and nitrobenzene solvents. Decreasing solvent polarity and the presence of a common‐ion salt ((n‐C4H9)4N+SO3CF−3) greatly increased the reactivity difference between the monomers. Thus the non‐dissociated species is more selective than the dissociated species. In contrast, the composition of pMeSt‐St copolymers produced by BF3O(C2H5)2 did not change with the solvent polarity. The difference in nature between the propagating species generated by CF3SO3H and by BF3O(C2H5)2 is discussed.
Über polyarylenalkenylene und polyheteroarylenalkenylene, 8. Synthesen und charakterisierung von poly(imidazo[4.5‐f]benzimidazol‐2,6‐diylvinylenarylenvinylen)en und einigen ihrer oligomeren
Authors: Manecke Georg , Brandt Lothar , Koßmehl Gerhard 
Published: April 2003

AbstractSome poly(imidazo[4.5‐f]benzimidazol‐2,6‐diylvinylenarylenevinylene)s (13aa–cc) were prepared via the Knoevenagel condensation starting from 2,6‐dimethylimidazo[4.5‐f]benzimidazole (4a) or its N1, N7 ‐dimethyl‐ and ‐diphenylderivatives (4b, c) and aromatic dialdehydes. Analogous reactions of 4a and 4c with monoaldehydes and of 2‐methylbenzimidazole with dialdehydes led to oligomer model compounds (6a–d, 8a–e, 9, 10a–d, 12) which were also prepared via another reaction type (Wittig reaction). The chemical structures were confirmed by elemental analysis, IR, and electronic spectra. The oligomers, in addition, were characterized by mass spectra and some were identified by independent synthesis. Electrical conductivities and thermical degradations of the polymers and of some of the oligomers were also investigated.
Herstellung, charakterisierung und lösungseigenschaften von einheitlichen styrol‐α‐methylstyrol block‐copolymeren
Authors: Rahlwes Dieter , Kirste Rudolf G. 
Published: April 2003

AbstractAn improved anionic polymerization technique for the preparation of highly uniform styrene/α‐methylstyrene linear two‐block copolymers is described. Three sets of samples with molecular weights M were prepared under equal experimental conditions, namely polystyrenes (2 · 105 < M < 3 · 106), poly(α‐methylstyrene)s (7 · 104 < M < 4 · 106), and block copolymers (2 · 105 < M < 2,5 · 106). Ultracentrifugation in a density‐gradient does not show any chemical heterogeneities in the block copolymers. The molecular polydispersity U = Mw/Mn–1 is U = 0,03 or less as estimated from GPC‐measurements. The high molecular and chemical homogeneity of the block copolymers and the optical similarity of the two segment types yield light scattering measurements which give molecular weights Mw, radii of gyration 〈r2〉1/2 and second virial coefficients A2 with almost the same accuracy as in the case of homopolymers. The radii of gyration and the intrinsic viscosities of the block copolymers give no evidence for any “intramolecular phase separation” in the good solvent toluene. The coil conformation corresponds closely to that of the homopolymers.
Functional metal‐porphyrazine derivatives and their polymers, 1. Synthesis of metal‐[2,9or10(or 2,16or17)bis(3,4‐dicarboxybenzoyl)]phthalocyanine derivatives
Authors: Shirai Hirofusa , Yagi Sadafumi , Suzuki Akira , Hojo Nobumasa 
Published: April 2003

AbstractThe diimide of metal‐[2,9or10(or 2,16or17)bis(3,4‐dicarboxybenzoyl)]phthalocyanine(diPc) (where i = imide) 2 or 3 were prepared from 3,4,3′,4′‐benzophenonetetracarboxylic dianhydride (BTDA) (1), phthalic anhydride (PA), urea, and metal salts such as CuCl2, CoCl2, and FeCl3 etc. at 170°C. In the case of copper, the diPc monomer 2 or 3 and the dimer 4 or 5 could be synthesized. Those copper complexes are stable to all of the chemical procedures. However, the core metals of Fe(III), Co(II), Ni(II) and Zn(II)‐diPc were partially removed in the acid treatment. Metal phthalocyanine derivatives which have four carboxyl groups in the peripheral site, metal‐[2,9or10(2,16or17)bis(3,4‐dicarboxybenzoyl)] phthalocyanine(daPc) (a = acid) 6 or 7, were synthesized by hydrolysis of the metal‐diPc. The metal‐daPc are soluble in water, in aprotic solvents such as N,N′‐dimethylformamide, and also in sulfuric acid. The physicochemical properties of some metal‐daPc derivatives were investigated.
Über die druckabhängigkeit der viskoelastischen und physikalisch‐chemischen eigenschaften von polymeren, 2. Spezifisches volumen und thermische ausdehnung einiger polymeren beim schmelzen und kristallisieren
Authors: Karl Veit‐Holger , Asmussen Frithjof , Ueberreiter Kurt 
Published: April 2003

AbstractMeasurements of specific volumes are described as function of temperature and pressure of melting or crystallizing linear polyethylene, isotactic polypropylene, and polyoxymethylene. A pressure range of 50 to 1600 bar permits determination of relative volume changes as function of temperature and pressure. Pressure influence on melting points, temperature hysteresis between melting and crystallization and their volume changes as well as the thermodynamic driving force of phase change have been investigated. Clausius‐Clapeyron's equation permits calculation of heats of crystallization.
Studies on polymerizations initiated by syncatalytic systems based on aluminium organic compounds, 6. Comparison with isobutene polymerizations initiated by ethylaluminium dichloride or aluminium trichloride
Authors: Maina Marcello Di , Cesca Sebastiano , Giusti Paolo , Ferraris Giuseppe , Magagnini Pier Luigi 
Published: April 2003

AbstractThe results of previous studies carried out on the polymerization of isobutene initiated by diethylaluminium halides plus halogens are compared with results obtained with other syncatalytic systems such as diethylaluminium chloride (or triethylaluminium) plus hydrochloric acid (or tert‐butyl chloride), as well as with results obtained with aluminium compounds such as ethylaluminium dichloride or aluminium trichloride which do not require co‐initiators to initiate the polymerization of isobutene. The kinetic data indicate clearly that the polymerization of isobutene initiated by syncatalytic systems is characterized by a relatively slow initiation and by the absence of important termination reactions and of transfer with monomer. In contrast to this, the polymerizations initiated by strong Lewis acids such as ethylaluminium dichloride or aluminium trichloride show a much faster initiation and stop at incomplete conversion which indicates that at least one efficient termination reaction is operative. It is also demonstrated that this termination reaction produces at least one substance which acts as a co‐initiator for the isobutene polymerization initiated by diethylaluminium halides or triethylaluminium.
A study on mechanism of excimer formation through fluorescence quenching for isotactic and atactic polystyrenes and poly(p‐methylstyrenes) in solution
Authors: Ishii Tadahiro , Handa Takashi , Matsunaga Satoru 
Published: April 2003

AbstractThe mechanism of excimer formation and deactivation for isotactic and atactic polystyrenes, and isotactic and atactic poly(p‐methylstyrenes) was studied by comparison of the rate parameters which were calculated from the fluorescence quenching and the decay time measurements of excimer emission band. The activation energy of excimer formation was obtained from the effect of temperature change on fluorescence intensity. The rate parameters of excimer formation for isotactic polymers are in the order of 109 s−1 and larger than those for atactic polymers. The activation energy for isotactic polymers is smaller than that for atactic polymers. These results show that isotactic polymers can form the excimer more easily than atactic polymers. The facility of excimer formation for isotactic polymers is interpreted as lower energy barrier required to achieve the excited excimer state.
Determination of the tacticity of polyacrylonitrile and its oligomers by 13C NMR spectroscopy
Authors: Balard Henri , Fritz Hans , Meybeck Jean 
Published: April 2003

Abstract13C NMR spectroscopy allows the determination of the microtacticity of polyacrylonitrile (PAN) and its models, the dimer, trimer, and tetramer of acrylonitrile (1a–c). In the case of the oligomers, the carbons of the chain are the most stereosensitive ones, but in the case of PAN it is the carbon of the cyano group. The 13C NMR spectrum of PAN composed of ten peaks which can be assigned to the ten possible pentad configurations.
Studies on chitin, 3. Preparation of pure chitin, poly(N‐acetyl‐D‐glucosamine), from the water‐soluble chitin
Authors: Kurita Keisuke , Sannan Takanori , Iwakura Yoshio 
Published: April 2003

AbstractPure chitin, poly(N‐acetyl‐D‐glucosamine), was successfully prepared by acetylating the partially deacetylated water‐soluble chitin with acetic anhydride‐pyridine or with acetic acid‐dicyclohexylcarbodiimide. Although enough selectivity between amino and hydroxyl groups was not shown, acetylation with acetic anhydride‐pyridine gave rise to the complete acetylation of amino groups and thereby O‐, N‐acetylated chitin was formed. The ester groups were then selectively transformed to hydroxyl groups by means of either hydrolysis or transesterification to give the pure chitin. Acetic acid‐dicyclohexylcarbodiimide system was found to enable one step complete and selective acetylation of amino groups under very mild conditions and it appeared to be superior to the others for the purpose.
Polymer induced aggregation of dye molecules. Influence of the attachment of dye molecules as side groups
Authors: Smets Georges J. , Simionescu Bogdan 
Published: April 2003

AbstractBy radical polymerization, 7‐(N‐acryloyl‐N‐methyl)‐3‐dimethyliminio‐3H‐phenothiazine chloride (1) has been transformed in the N‐substituted polyacrylamide carrying Azure B side groups, poly{1‐[N‐(3‐dimethyliminio‐3H‐phenothiazin‐7‐yl)‐N‐methylaminocarbonyl]ethylene chloride}. On addition of poly(acrylic acid) dye‐polymer interactions and metachromasy phenomena have been examined using absorption spectrometry.Similarly, 1 has been copolymerized with acrylic acid. Intramolecular functional interaction causes a bathochromic absorption band (652 nm) which persists partially on addition of poly(acrylic acid), and affects dye‐aggregation and metachromasy.
Diastereomere Alkene als Modelle für die 13C‐NMR‐Spektroskopie von Polymeren
Authors: Ritter Wolfgang , Elgert Karl‐Friedrich 
Published: April 2003

AbstractTrans‐3,4,7,8‐tetramethyl‐5‐decene is a low molecular weight model of poly‐2,5‐(2,4‐hexadiene). Eight resonance signals can be observed in the 13C NMR spectrum of the carbon double bond which are assigned to the relative configurations of the asymmetric carbon atoms. The configurational splitting can be described partially by additive constitutional and configurational shift parameters, which have been determined from a number of alkenes with up to four asymmetric carbon atoms. However, full additivity is not reached as the conformation of the substituents of the carbon double bond influences the shift differences due to the relative configurations of the asymmetric carbon atoms.
Diastereomere Alkane als Modelle für die 13C‐NMR‐Spektroskopie von Polymeren
Authors: Elgert Karl‐Friedrich , Ritter Wolfgang 
Published: April 2003

AbstractLow molecular weight alkanes, e.g. 3,7‐dimethylnonane, with two asymmetric carbon atoms are suitable models for the assignment of the configurational splitting in the 13C NMR spectrum of the alternating copolymer from ethylene and propylene, poly(1‐methyltetramethylene).
Synthesis and properties of aliphatic unsaturated polymers with 1,3,4‐oxadiazole‐2,5‐diyl units
Authors: Schopov Ivan , Vodenicharova Margarita 
Published: April 2003

AbstractTwo polymers built up of 1,3,4‐oxadiazole‐2,5‐diyl and vinylene resp. ethynylene groups (polymers 2 and 3) were prepared by polycondensation of fumaramide resp. acetylenedicarboxamide with hydrazine sulfate in polyphosphoric acid. 2 and 3 exhibit the properties of conjugated polymers—dark colour, semiconductivity, and paramagnetism. The electric conductivity measurments were performed on pellets and on thin films in sandwich and surface cells. The comparison of the semiconducting properties of the polymers mutually and with poly‐p‐xylylidene leads to the conclusion that the trans‐double bond is a better building unit for conjugated semiconductive polymers than the triple bond and the 1,3,4‐oxadiazole‐2,5‐diyl residue is better than the 1,4‐phenylene unit.
Kinetische und morphologische Untersuchungen zur polymerisation von oxacyclischen Monomeren im festen Zustand, 1. Zur Morphologie der bei der Polymerisation von 1,3,5,7‐Tetroxocan mittels chemischer Katalysatoren entstehenden Polyoxymethylene
Authors: Muñoz‐Escalona Antonio 
Published: April 2003

AbstractIn order to elucidate the reaction mechanism of the chemically induced solid‐state polymerization of 1,3,5,7‐tetroxocane, the nascent morphology of poly(oxymethylene), (POM) crystals was investigated. The results show that POM has a lamellar morphology consisting of folded polymer chains. This morphology is different from that of the fibrous morphology obtained by radiation induced solid‐state polymerization of 1,3,5,7‐tetroxocane. Based on this the reaction takes place according to a crystallization succeeding polymerization mechanism, where the monomer passes through the gasphase to reach the reaction center.