bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kalorimetrische Untersuchungen zum Lösungsverhalten von Polyacrylsäure und Poly(natriumacrylat) in Wasser, Formamid und Ethylenglykol
Authors: Klein Joachim , Scholz Wilfried 
Published: April 2003

AbstractHeats of solution and heats of dilution of poly(acrylic acid) (PAAcH), poly(sodium acrylate) (PAAcNa), and poly(acrylamide‐co‐sodium acrylate) (1:1) (PAAm/PAAcNa) in water, formamide (FA), and ethylene glycol (EG) as measured at 25°C, are reported. While for PAAcH/H2O and PAAcH/EG only minor caloric effects are observed, the heats of solution for PAAcNa/H2O are strongly exothermic as a result of dissociation of the polysalt. Heats of dilution in this system are endothermic because of the hydrolysis reaction. PAAcH/FA shows large negative enthalpies on dissolution as well as on dilution. This is due to the dissoziation of the COOH‐groups which is much more pronounced in FA than in the aqueous system because formamide has a greater ionizing capability. Comparison between the behaviour of copolymer PAAm/PAAcNa and physical admixing of the homopolymers confirms the specific neighbouring group interaction of carboxylate and carbonamide groups along the same chain. Comparing the calorimetric results for PAAcH with those for the low‐molecular‐weight model compound propionic acid, it becomes evident that the differences are mostly due to the different state of order of the pure compounds, namely, due to the chain structure, the COOH‐groups in the polymers are not as flexible as in the monomers. Therefore, in the pure polymer less hydrogen bonds are formed than in the pure propionic acid. The calorimetric results are discussed in the light of previous work on viscosimetric dilute solution behaviour of these systems, showing the consistency of the different experimental findings.
Association of block copolymers in selective solvents, 1. Measurements on hydrogenated poly(styrene‐isoprene) in decane and in trans‐decalin
Authors: Mandema W. , Zeldenrust H. , Emeis C. A. 
Published: April 2003

AbstractThe dilute solution properties and association of hydrogenated poly(styrene‐isoprene) two‐block copolymers in decane and trans‐decalin have been studied by means of viscosity, diffusion and light‐scattering measurements. Data were obtained for two samples with molecular weights of 48 000 and 80 000, and both with a styrene content of 38%. In trans‐decalin the normal behaviour of a non‐associating polymer is found. Association occurs in decane with the formation of compact micelles, composed (at ambient temperatures) of about 80 molecules. In contrast to what is observed in other associating two‐block systems, the transition to the completely dissociated state at elevated temperatures causes a drop of the intrinsic viscosity. Moreover, and this is not evident from the viscometric results, the diffusion and light scattering studies reveal that in the intermediate region between association and dissociation another kind of structure with very large dimensions is formed that exists over an extended temperature range. A qualitative description of the observed phenomena is given.
Block copolymers of fluoral oligomer with urethanes: Preparation and thermal properties
Authors: Busfield W. Ken , Cowie Ian M. G. , Mondal M. A. Sattar 
Published: April 2003

AbstractTwo series of block copolymers have been synthesized comprising of soft polytrifluoroacetaldehyde (polyacetal) segments and of hard 4,4′‐methylenedi(phenyl isocyanate)/cis‐cyclohexane‐1,4‐diol polyurethane segments. The series‐A copolymers in which the soft segments were directly bound to the hard segments had significantly lower thermal stability than the series‐B copolymers in which the soft segments were linked to the hard segments by sebacic ester units. In both series the thermal stability decreased with increasing soft segment content. The series‐A copolymers exhibited two thermal transitions both characteristic of Tg's and separated by about 60 K. In contrast the series‐B copolymers exhibited two characteristic Tg's separated by 200–250 K, depending on composition, together with an additional endothermic transition at about ambient temperature. All transitions for both series decreased with increasing soft segment content. The observations have been compared with those of other polyether and polyester based polyurethanes.
Investigation of the topochemical solid‐state polymerization of a diacetylene by X‐ray methods and brillouin‐spectroscopy
Authors: Enkelmann V. , Leyrer R. J. , Wegner G. 
Published: April 2003

AbstractThe topochemical polymerization of the substituted diacetylene, 2,4‐hexadiynylene bis(p‐toluenesulfonate) (1), has been followed by X‐ray crystallography and by determination of the elastic constants of polymerizing crystals. For the first time the crystal structure of a polymerizable diacetylene monomer has been solved and the coordinates of all atoms prior and after the reaction have been determined. The length of the growing polymer chains and their distribution in the monomer matrix can be determined by the evaluation of the Brillouin spectra in terms of a model which considers the polymerizing crystal as a composite material of high‐modulus rod‐like macromolecules dispersed in the low‐modulus matrix of the residual monomer.
Zur stabilität der komplexen anionen bei der kationischen polymerisation
Authors: Heublein Günther , Spange Stefan , Hallpap Peter 
Published: April 2003

AbstractThe counterions appearing in the mechanism of the cationic polymerization are able to decay according to
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and so give rise to termination reactions. For the model systems (C6H5)3C⊕MtX⊖n+1(Mt = B, Al, Sn, P, As, Sb, In, Ti, Fe; X = F, Cl, Br) the decay has been investigated by spectroscopic and conductometric methods. The overall decay rate constant kz is hardly influenced by traces of water (cH2O<10−3mol.l−1) and by structure variations of the cation. On the other hand, kz increases by decreasing the concentration of the salt. When the structure is varied kz increases with decreasing donor strength of the ligands X; the sensitivity of the anion to changes in the ligand sphere increases corresponding to the ionization potential of the central atom Mt. Addition of tetracyanoethylene raises the stability of the anions.The results can be explained by the HSAB principle and fit well in a scheme of stabilization of anions by acceptors.
Mechanical denaturation of high polymers in solutions, 34. Nucleation and growth of poly(vinyl alcohol) crystals from flowing solution
Authors: Matsuzawa Shuji , Yamaura Kazuo , Umeda Yōichi , Inoue Yūji , Kitamura Hisako , Pak Sang‐Yong 
Published: April 2003

AbstractThe nucleation and growth of the crystals of poly(vinyl alcohol) (PVA) from its solution keeping in contact with air under steady‐state flow were investigated. The nucleation was considered to occur close to the solution surface because of the adsorption of PVA molecules to the solution surface. It was ascertained by the following results. The initial fibrillar crystal appeared under the solution surface after a few seconds of stirring. From the measurement of the surface tension of PVA solutions, PVA molecules were recognized to be adsorbed to the solution surface in a very short time. The random coil of PVA molecule cannot be extended and oriented in a solution stirred under steady‐state flow with a shear rate below 5.103 s−1 applied in this experiment. This was concluded from an evaluation of the chain extension in a velocity gradient in shearing flow using the dumbbell model. The propagation of the precipitate is accelerated by turbulent flow induced by the flow of the solution itself, foams and precipitates.
Coordination polymers of 1,2,5,8‐tetrahydroxyanthraquinone
Authors: Banerjie Vishwanath , Dey Arun K. 
Published: April 2003

AbstractFrom analytical studies, infrared and reflectance spectra, magnetic and thermogravimetric measurements of Cu(II), Ni(II), Co(II), Mn(II), Fe(II), and UO2(VI) complexes of 1,2,5,8‐tetrahydroxyanthraquinone, it was concluded that the complexes are polymeric coordination complexes with octahedral geometry. These were synthesized by refluxing an equimolar mixture of the ligand and hydrated metal acetates in N,N‐dimethylformamide at 140°C. Elemental analyses indicated a ligand: metal ratio of 1 : 1 and the association of water molecules with the central metal. The decreasing order of thermal stability of the complexes is: Mn(360°C)>Fe(340°C) ≈︁ Co(340°C)>Ni(320°C)>Cu(300°C).
Elimination and replacement of organometallic co‐catalysts during polymerization of propene with heterogeneous Ziegler‐Natta catalysts
Authors: Kohara Tadanao , Shinoyama Masayuki , Doi Yoshiharu , Keii Tominaga 
Published: April 2003

AbstractThe changes in the polymerization rates induced by the elimination or replacement of soluble organometallic co‐catalysts have been examined in the course of the polymerization of propene initiated with titanium trichloride and various types of organometallic co‐catalysts. The elimination of an organometallic co‐catalyst, A, in the liquid phase during the polymerization resulted in a slow deactivation of the catalysts by the attack of a propene monomer. In contrast, the replacement of an initial organometallic co‐catalyst, A, by a different co‐catalyst, B, during the polymerization caused a rapid change in the polymerization rate from the specific rate with TiCl3 and A to that with TiCl3 and B. These results have been interpreted in terms of the bimetallic mechanism that an organometallic co‐catalyst coordinates to a titanium ion, in an exchangeable form with the co‐catalysts in the liquid phase, and regulates the catalytic activity.
On structure and temperature transformations of nascent polyethylene, produced by polymerization of ethylene in presence of a modified Ziegler‐Natta catalyst
Authors: Mihailov Marin , Minkova Lili , Nedkov Emanuil , Kircheva Radka 
Published: April 2003

AbstractNascent polyethylene with high molecular mass (Mn ≈ 105, Mw ≈ 106) produced in hydrocarbon medium in presence of TiCl4/(C2H5)2AlCl/(C6H5)2Mg catalyst was studied by means of X‐ray diffraction, electron and light microscopy, and low‐angle light scattering. It consists of porous spherulite‐fibril aggregates indicating a not very high degree of crystallinity α(α≈). Data, concerning the dependence of spherulite dimensions, degree of crystallinity and other structure parameters of nascent polyethylene on polymerization time and temperature are discussed. Using the same structure‐analytical methods some samples of nascent polyethylene were studied after annealing them in nitrogen atmosphere at different temperatures between 110–250°C with successive cooling to room temperature. Furthermore both the endo‐ and exothermal transitions occurring in the nascent and annealed structures after heating to 250°C were studied by means of DTA and DSC. The experimental information leads to the conclusion that nascent polyethylene structures consist of crystalline folded chain lamellae with an increased amount of tie molecules between them as well as of extended chain crystals.
Crosslinking statistics, 3. Relation between relative reactivity and accessibility of cellulose hydroxyl groups
Authors: Luby P. , Kuniak Ľ. , Fanter C. 
Published: April 2003

AbstractFrom the results of a structural analysis of cellulose crosslinked by a bifunctional reagent conclusions can be drawn merely on the distribution of crosslinks among individual hydroxyl groups. No information is available to what extent this distribution is caused either by different relative reactivities of the hydroxyl groups or incomplete accessibility of glucose units. If each glucose unit had the same chance of reaction, at low levels of conversion only monosubstituted units should be present in the reaction product. If, however, some higher substituted units are present, this means that at a certain level of conversion there must have been a smaller number of units capable of reaction to which relatively more reagent had access. The relation between relative reactivity and accessibility of cellulose hydroxyl groups obeys certain statistical laws of random selection. A theory explaining these laws is developed in the present work and supported by good agreement with experimental results exemplified by microcrystalline cellulose crosslinked by epichlorohydrin (1‐chloro‐2,3‐epoxypropane). The relative reactivities of cellulose hydroxyls were found to increase in the order OH‐3, OH‐6, OH‐2 in the crosslinking reaction with epichlorohydrin.
On the dilute solution properties of styrene/methyl methacrylate copolymers
Authors: Chiantore Oscar , Casorati Ernesto , Costa Luigi , Guaita Marino 
Published: April 2003

AbstractThe solution properties of unfractionated styrene/methyl methacrylate copolymers were investigated over the entire range of copolymer composition. The Mark‐Houwink‐Sakurada constants Kη, and aη of the copolymers, as well as the constants KΘ and B′ from the Stockmayer‐Fixman procedure, related to the unperturbed chain dimensions and to the excluded volume, respectively, seem simply related to those of the parent homopolymers through some composition variables. In most cases, however, equations must be employed which have to be fitted to the experimental data, in order to evaluate parameters which are not otherwise predictable.
On the effect of solvent/nonsolvent combination in the column fractionation of polymers
Authors: Mencer Helena J. , Kunst Branko 
Published: April 2003

AbstractThe effect of some solvent/nonsolvent pairs on the efficiency of the column fractionation of polystyrene was investigated. Extensive cloud point titration experiments were shown to be needed for the correct assessment of thermodynamic qualities of a solvent/nonsolvent pair used in the column fractionation of polymers. Besides the thermodynamic suitability of solvent pairs their kinetic behavior was shown to differ. Possible reasons for the observed differences were discussed.
Exchange equilibria of anion resins, 1. Effect of physical structure of macroporous styrene‐divinylbenzene copolymers
Authors: Góźdź Antoni S. , Kolarz Bożena N. 
Published: April 2003

AbstractAnion exchange equilibria on benzyltrimethylammonium resins are studied on solvent‐modified copolymer matrices prepared from styrene‐divinylbenzene suspension copolymers obtained in the presence of a series of unbranched alkanes (C7  C16) and toluene. Equilibria involving the exchange of chloride anions for bromide, iodide and perchlorate in dilute 0,01 M aqueous solutions were determined by the limited batch technique. It is found that the structure of the copolymer depends strongly on the interaction of an inert solvent with the copolymer during its formation. This structure affects the hydration of the functional groups and counter‐ions in the gel phase and consequently brings about a variation of the selectivity of the resin.
Vinyl polymerization, 366. Polymerization of methyl methacrylate initiated with a hydrolyzed product of poly[bis(2‐chloroethyl) vinylphosphonate]
Authors: Imoto Minoru , Sakae Masatoshi , Ouchi Tatsuro 
Published: April 2003

AbstractPVPA, a simulated terpolymer from vinylphosphonic acid, 2‐hydroxyethyl hydrogen vinylphosphonic acid and 2‐chloroethyl hydrogen vinylphosphonic acid, was prepared by partial hydrolysis of poly[bis(2‐chloroethyl) vinylphosphonate] (2). In aqueous solution, PVPA was found to be able to polymerize methyl methacrylate (MMA) without any further initiator by a radical mechanism. The effects of the masses of water, PVPA and MMA on the polymerization were studied. The overall activation energy was found to be 77,7 kJ.mol−1. The Michaelis‐Menten equation could be applied for the relationship between the mass of MMA and the rate of polymerization (Rp). The plots of pH of aqueous solution against Rp gave a downward bell‐type curve. An initiation mechanism of the polymerization process is discussed.
Synthesis and conformational study of poly(ε‐N‐benzyloxycarbonyl‐L‐lysyl‐L‐valyl‐ε‐N‐benzyloxycarbonyl‐L‐lysine) in the solid state and in solution
Authors: Ciaschi Roberto , D'Alagni Maria 
Published: April 2003

AbstractPoly(ε‐N‐benzyloxycarbonyl‐L‐lysyl‐L‐valyl‐ε‐N‐benzyloxycarbonyl‐L‐lysine) (6) was synthesized via the p‐nitrophenyl active ester method. The dipeptide and the active ester of the tripeptide were obtained by using tert‐butoxycarbonyl‐N‐ε‐benzyloxycarbonyl‐L‐lysine succinimido ester and dicyclohexylcarbodiimide as condensing agents, respectively. Polymer 6 was investigated in the solid state by IR and X‐ray diffraction measurements and in trifluoroethanol solution by UV, CD, and IR spectroscopy. The results obtained in the solid state indicate the occurrence of the β‐conformation and some other unidentified conformation. No useful information was obtained from the study of the trifluoroethanol solution of 6. Once more it was found that the introduction of valyl residues in a chain, containing residues which are α‐helix formers, seems to favour the β‐structure.
Théorie des chaîcnes de markov et distribution moléculaire dans les copolycondensats linéaires, 1. Modèle mathématique et systèmes d'ordre I
Authors: Durand Dominique , Bruneau Claude‐Marcel 
Published: April 2003

AbstractMarkov chain theory combined with graph theory gives a mathematical model for the description, in linear elements, of the random evolution of polymerizing macromolecular systems. Applying this mathematical model to the study of molecular distribution in linear systems of order I, i.e. systems having identical functional groups (a link being able to occur between any two sites), allows one to obtain molecular distribution functions with a general form which can be applied to many different systems. The use of matrix calculus gives simple mathematical expressions which are well suited for computer programming.
Le tétrakis[(phényl‐1 vinyl)‐4 phenyl]plumbane sa synthèse et son utilisation dans la préparation de macromolécules‐modèle
Authors: Beinert Gérard , Herz Jean 
Published: April 2003

AbstractThe present paper describes the synthesis of tetrakis [4‐(1‐phenylvinyl)phenyl]plumbane (1). It was found that “living” mono‐ or difunctional carbanionic polystyrenes are able to react with compound 1 to form star‐shaped polymers or tetrafunctional crosslinked networks, resp., and it could also be shown that this polyfunctional lead compound can be used to prepare starshaped copolymers containing polystyrene and poly(methyl methacrylate) branches.
Hochmolekulare makrocyclische polycarbonate
Authors: Horbach Alfred , Vernaleken Hugo , Weirauch Kurt 
Published: April 2003

AbstractInterfacial condensation polymerization of bischloroformates of bisphenol A with bisphenol A results in the formation of cyclic aromatic polycarbonates of high molecular weight. Products made by this technique show a significant reduction (up to 95%) in their end group content. Also, in comparison to molecular weights determined by light scattering, these products show markedly lower molecular weights by solution viscocity measurements and by applying the Mark‐Houwink equation for linear polycarbonates. The existence of high molecular weight cyclic polycarbonates is confirmed by a controlled saponification reaction using piperidine as a basic compound. The saponification reaction causes nearly no change in the number average molecular weight of the polymer and causes an increase in the number of end groups of up to 2 end groups per molecule. The observed increase in the intrinsic viscosity data is similar to what would be expected from linear polycarbonates. It is shown that cyclic polycarbonates with molecular weights exceeding 100 000 are easily obtained.
On the interaction of styrene‐maleic anhydride copolymer with styrene
Authors: Bartoň Jaroslav , Vašková Viera 
Published: April 2003

AbstractThe interaction between alternating styrene/maleic anhydride copolymer as polymeric acceptor and styrene as low molecular weight donor in acetone and/or tetrahydrofuran was investigated by UV spectroscopy and polymerization technique. The equilibrium constant for the complex formation between styrene and the maleic anhydride structural unit of the styrene/maleic anhydride copolymer at 20°C was found to be 0,02 ± 0,001 dm3·mol−1 in acetone and 0,06 ± 0,003 dm3·mol−1 in tetrahydrofuran. The results of the thermally initiated polymerization of styrene in acetone in the presence of the alternating styrene/maleic anhydride copolymer indicate that the copolymer or the products of the interaction between the monomeric units of maleic anhydride in the copolymer and styrene do not initiate a radical polymerization of styrene.
Reaktionen bei der Bestrahlung von poly(N‐chloramid)en
Authors: Günster Engelbert J. , Schulz Rolf C. 
Published: April 2003

AbstractOn irradiating poly(N‐chloroamide)s in films or in solution in the range of 325–375 nm carboxamide groups are formed. The irradiated polymer contains chlorine which is linked to C‐atoms. This reaction can certainly not be explained with an intramolecular photorearrangement but with a sequence of photoreactions and dark reactions satisfactorily accounting for all observations.
Struktur und Eigenschaften segmentierter polyetherester, 3. Synthese definierter Oligomerer des polybutylenterephthalats
Authors: Hässlin Hans‐Walter , Dröscher Michael , Wegner Gerhard 
Published: April 2003

AbstractThe synthesis of some series of oligo(oxytetramethylene oxyterephthaloyl) [oligo(butylene terephthalate)s] with different but well‐defined end groups is described. The separation of artificial mixtures of the oligomers by high pressure liquid chromatography was studied under various elution and column conditions, and thus, the purity of the individual oligomers was demonstrated. The equilibrium melting point T = 236 ± 4°C and the corresponding heat of melting ΔH = 28,7 kJ·mol−1 of poly(butylene terephthalate) was determined from the analysis of the melting behaviour of the oligomers as depending on the degree of polymerization and the structure of the end groups.
Über enzymanalog gebaute Polymere, 11. Bindungsstellen im Polymer mit unterschiedlicher Zahl der Haftgruppen
Authors: Wulff Günter , Schulze Ilona , Zabrocki Karl , Vesper Wolfgang 
Published: April 2003

Abstract4‐Vinylphenylboronic esters 1 and 2 of L‐1,2‐propandiol (3a) resp. D‐mannitol (4a) were polymerized under different conditions to macroporous, crosslinked copolymers. Afterwards the alcohols 3a resp. 4a were split off. The alcohols have thus been used to form chiral microcavities within the polymer, of which those prepared from 1 contain 1 and those from 2 contain 3 binding groups B(OH)2. Binding sites with 2 binding groups have been investigated before. These polymers possessed capacity for the resolution of the racemate of the template used. The kinetics of the mass transfer within polymers with three binding groups per cavity is discussed in more detail. The chromatographic investigation of the binding ability at different pH‐values of polymers from 2 for D‐mannitol showed even in acidic media a pronounced binding through neutral esters 5, whereas in alcaline media a much stronger binding through basic esters 6 occurred.