bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthetische wasserlösliche polymere—stand und ausblick
Authors: Spoor Herbert 
Published: April 2003

AbstractEs wird ein Überblick über Synthese, Eigenschaften, Anwendung und Charakterisierung synthetischer wasserlöslicher Polymerer gegeben. Auf einen kurzen Abriß über die Synthese modifizierter Naturpolymerer folgt eine Darstellung der Herstellverfahren für vollsynthetische wasserlösliche Polymere. An die ausführliche Übersicht über die wirtschaftlich bedeutenden Einsatzgebiete wasserlöslicher Polymerer schließt sich eine knappe Darstellung neuerer physikalisch‐chemischer Charakterisierungs‐methoden an. Das Referat endet mit einer Zusammenfassung der Trends auf dem Gebiet der wasserlöslichen Polymeren.
Das verhalten von polyvinylalkohol in wäßriger lösung
Authors: Lechner M. D. , Mattern R. 
Published: April 2003

AbstractPolyvinylalkohol wurde in wäßriger Lösung mit Hilfe der inelastischen und der elastischen Lichtstreuung sowie durch Viskositätsmessungen untersucht. Um bei höheren Temperaturen und Drücken bis 4000 bar arbeiten zu können, wurde eine Hochdruckapparatur entwickelt, der ein Photon‐Korrelations‐Spektrometer der Firma Malvern zugrunde liegt. Es zeigte sich, daß der Diffusionskoeffizient D von Polyvinylalkohol in Wasser mit steigendem Druck bei niedrigen Temperaturen einen geringen Anstieg zeigt und bei höheren Temperaturen einen relativ starken Abfall. Die inelastische und die elastische Lichtstreuung deuten auf eine sehr hohe Molmasse des Systems hin. Viskositätsmessungen und Lichtstreuungsmessungen and reacetyliertem Polyvinylalkohol ergeben dagegen eine sehr viel geringere Molmasse. Dies kann durch Wasserstoffbrücken‐Bindungen der Polymermoleküle erklärt werden.
The physical chemistry of polyelectrolyte solutions
Authors: Mandel Michel 
Published: April 2003

AbstractSome physical properties of aqueous solutions containing linear, flexible, polyelectrolytes are reviewed in order to emphasize the role of charge interactions in these systems which strongly depend on the charge of the macromolecular chain and the concentration of low molar mass electrolyte in solution. Particular emphasis is put on polyelectrolyte solutions containing an excess of added salt, which from a theoretical point of view are easier to understand. Both the dilute and the semi‐dilute case will be discussed. In the former the problem of the electrostatic potential around the macromolecular chain is briefly reviewed as well as the use of a wormlike chain model to derive average dimensions of polyelectrolytes in solutions. In the latter the scaling approach to concentration effects in polyelectrolyte solutions is briefly discussed. The pecularities of the semi‐dilute regime in polyelectrolyte solutions is illustrated with the help of results obtained with dynamic light scattering and the time dependent decay of electric birefringence.
Molecular weight distributions and solution properties of poly(2‐trimethylammoniumethyl methacrylate chloride)
Authors: Stickler Manfred 
Published: April 2003

AbstractSolution properties of the cationic polyelectrolyte poly(2‐trimethylammoniumethyl methacrylate chloride), PTMAC, in aqueous sodium chloride solutions of varying ionic strength were investigated with unfractionated samples in the molecular weight range 7, 7 × 103 ≤ M̄W ≤ 1, 1 × 107 by light scattering, viscometry, and sedimentation velocity analysis. Molecular weight distributions were determined by size exclusion chromatography and sedimentation velocity experiments. The influence of polydispersity on static and dynamic solution properties was eliminated by appropriate correction procedures.The results show that solutions of PTMAC in 1 n NaCl can be essentially treated like those of uncharged polymers in organic solvents with classical theories.
Synthese und eigenschaften von polymeren hydrogelen
Authors: Heitz W. , Krappitz W. , Stützel‐Bilbao C. , Neumann B. 
Published: April 2003

AbstractPolymere Hydrogele sind aus physikalisch oder chemisch vernetzten, wasserlöslichen Polymeren aufgebaut. Eine physikalische Vernetzung ist durch eine Blockstruktur mit hydrophilen und hydrophoben Segmenten möglich. Die chemische Vernetzung ist durch Vernetzung wasserlöslicher Polymerer oder durch vernetzende Copolymerisation durchzuführen. Die für viele Anwendungen optimale Kugelgestalt der Polymerteilchen wird durch Suspensionspolymerisation erzeugt. Da hydrophile Polymere in der Regel wasserlösliche Monomere als Basis haben, müssen spezielle Techniken der Suspensionspolymerisation eingesetzt werden. Die Anwendung hydrophiler Gele als beliebig dimensionierbares wasserresevoir, als stationäre Phase in der Gel‐ und Affinitätschromatographie, als Träger für Enzyme oder als Wirkstoffdepot erfordert die Variation der Porenstruktur in einem weiten Bereich. Während bei kleinen Poren eine Regelung der Größe über den Vernetzergehalt möglich ist, werden große Poren durch eine heterogene Verteilung der Vernetzungsdichte gebildet. Der Einfluß von Art und Menge des Vernetzers sowie der Inertkomponente werden diskutiert. Die Ursache der Bildung von Hydrogelen mit dichter Hüllstruktur wird an mehreren Beispielen erläutert.
Structure and liquid crystalline phases of amphiphilic side chain polymers in aqueous solution
Authors: Lühmann Bernd , Finkelmann Heino , Rehage Günther 
Published: April 2003

AbstractFunctional amphiphilic molecules which form liquid crystalline (l.c.) phases in aqueous solutions, can be polymerized to amphiphilic side chain polymers. Depending on the formation of the polymer backbone via the hydrophobic (type A) or hydrophilic part (type B) of the monomer, it can be differentiated between two polymers. For both types of polymers a model is proposed which explains their micellar association in solution. In aqueous solutions polymers of type A should form normal spherical, rodlike and disc‐like micelles, while polymers of type B should form the corresponding reversed micelles.The phase behavior in aqueous solutions is investigated with two model systems of monomer/side chain polymer of type A. It is shown that the polymers exhibit l.c. phases, which are stable within a broader concentration range, as well as to higher temperatures compared to the corresponding monomers. The structures of the l.c. phases are in accordance with the model considerations.
Herstellung und charakterisierung von hydrogelen als kontaktlinsenmaterialien
Authors: KoßMehl Gerhard , Klaus Norbert , Schäfer Horst 
Published: April 2003

Abstractß‐Hydroxyethylmethacrylat = HEMA wird mit verschiedenen Vernetzern copolymerisiert und in isotonischer NaCl‐Lösung zu Hydrogelen gequollen. Es wird gefunden, daß die Vernetzung von der Länge des Vernetzermoleküls stärker abhängt als von seiner Hydrophilie. Der Wassergehalt von Hydrogelen läßt sich geringfügig steigern, wenn dem Polymerisationsansatz Ethylenglykol oder Glycerin zugesetzt wird. Hydrogele mit bis zu 70% Wasser werden aus HEMA und Dimethylaminoethylmethacrylat = DMAEMA und solche mit bis zu 90% Wasser aus HEMA und Methacrylsäure = MA erhalten. Hydrogele aus HEMA, DMAEMA und MA, die einen Wassergehalt von bis zu 70% besitzen, zeichnen sich durch einen vernachlässigbaren Schrumpf beim Wechsel von NaCl‐ in CaCl2‐Lösung sowie eine sehr gute Sauerstoff‐Permeation aus.
Kinetics of particle nucleation and growth in the emulsion polymerization of acrylic monomers
Authors: Fitch Robert M. , Palmgren Tor H. , Aoyagi Tatsuhiro , Zuikov Aleksander 
Published: April 2003

AbstractThe rates of particle formation and growth during the earliest stages of the emulsion polymerization of several acrylic monomers have been studied as a function of surfactant concentration by means of the time‐dependence of light scattering from the reaction mixtures. Investigated were methyl methacrylate, and methyl, ethyl and butyl acrylates at concentrations of SDS surfactant from 0 to several times the CMC. Under continuous photoinitiation the Rayleigh scattering intensities rose rapidly with slopes that increased with decreasing SDS concentration. The more water‐soluble the monomer, the more slowly was the rate of increase in scattering intensity.Computer modeling, using HUFT theory, could be used to obtain values for the various parameters involved for MMA. The Fuchs stability factor, W, was found to be 1 for [SDS] = 0 and infinity for [SDS] = CMC or grester. The partition coefficient for J‐mer oligomers between the aqueous and organic phases must rise exponentially with J. Electrostatic effects on radical capture by particles are considered to be negligible, but very important as they affect coagulation kinetics.
Neue aspekte der industriellen emulsionspolymerisation
Authors: Markert Gerhard 
Published: April 2003

AbstractDie Emuisionspolymerisation ist vor allem unter dem Aspekt der anwendungsorientierten Produktoptimierung zu sehen. Die Basis dafür wird von den spezifischen Eigenschaften des Verfahrens und der breiten Variation der stofflichen Zusammensetzung geboten. Anhand einiger Beispiele wird verdeutlicht, wie eng die Kopplung mit den Systemeigenschaften gebrauchsnaher Endprodukte ist, obwohl diese überwiegend aus anderen Materialien bestehen. Diese ganzheitlichen Aspekte können in Zukunft noch an Bedeutung gewinnen.
Kinetik der dispersionspolymerisation von acrylamid
Authors: Reichert Karl‐Heinz , Baade Wolfgang 
Published: April 2003

AbstractUntersucht wurde die Kinetik der Polymerisation von Acrylamid in Dispersion, bestehend aus Wasser‐in‐Isoparaffin Emulsionen mit Sorbitanmonooleat als Emulgator. Als Initiatoren wurden sowohl öl‐ als auch wasserlösliche Azoverbindungen verwendet. Im untersuchten Konzentrationsbereich wurden für die maximale Reaktionsgeschwindigkeit folgende Zeitgesetze ermittelt:rmax = k cI cM cE‐0,2 für öllösliche Initiatoren mit k = f (Temperatur und Phasengrenzfläche) rmax = k' cI0,5 cM für wasserlösliche Initiatoren mit k' = f (Temperature) Unter vergleichbaren Reaktionsbedingungen resultieren mit öllöslichen Initiatoren Polymere mit wesentlich größeren Molmassen. Aufgrund der Kinetischen Befunde wird für das System auf Basis öllöslicher Initiatoren in Paraffinen ein Reaktionsmodell vorgeschlagen, wonach die Polymerisation in den dispergierten Wassertröpfchen abläuft und der geschwindigkeitsbestimmende Teilschritt der Stoffübergang von Primärradikalen aus der öl‐ in die Wasserphase ist. Micellare Strukturen konnten in Paraffinen nicht nachgewiesen werden. Im Gegensatz zu Polymerisationen in Systemen mit Aromaten als organischer Phase sollte man die Reaktion in diesem System nicht als inverse Emulsionspolymerisation bezeichnen.
Divinylidene compounds and their role as key compounds for the synthesis of blockcopolymers
Authors: Bastelberger Thomas , Höcker Hartwig 
Published: April 2003

AbstractDivinylidene compounds with isolated double bonds of the type
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are quantitatively transformed into soluble dilithio organic compounds with sBuLi and may be used as bifunctional initiators for the anionic polymerization of butadiene (B) and subsequently styrene (S). Beside the expected SBS block copolymers also SB block copolymers are obtained because of partial termination of the dilithio compounds.By means of GPC analysis of the reaction compounds, i.e., of the homopolybutadiene, the blockcopolymers and the homopolystyrene after oxidative degradation using dual detection it is proved that the bifunctional species because of intramolecular association adds the monomer with significantly lower rate than the monofunctially growing species. Choosing suitable conditions the rate differences may be minimized.
N‐alkyl‐p‐aminosalicylic acid‐formaldehyde polymers, 3
Authors: Patel H. S. 
Published: April 2003

AbstractSeveral N‐alkylsubstituted derivatives of p‐aminosalicylic acid (PAS) have been prepared and polycondensed with formaldehyde in the presence of acid. The polymer samples have been characterized by elemental analysis, IR spectra, viscosity measurements, molecular weight determination, and thermogravimetry. They were also screened for their antifungal activity. Base catalyzed polycondensation of N‐alkyl PAS with formaldehyde was associated with decarboxylation.
Porous structure of highly crosslinked styrene‐divinylbenzene copolymers
Authors: Wieczorek Piotr P. , Kolarz Bożena N. , Galina Henryk 
Published: April 2003

AbstractPorous structure of two series of styrene (S)‐divinylbenzene (DVB) copolymers has been studied. The copolymers were prepared by suspension copolymerization of the monomers (50 wt.‐% of DVB) in the presence of heptane‐toluene mixtures as inert diluents. The fraction of diluents in the polymerization system or heptane: toluene ratio was changed.Both the pore volume and specific surface area increase as does dilution or the fraction of heptane in diluents, but the measured values change depending on sample pretreatment.A mechanism of structure built up is discussed and the porosity changes explained in terms of a microsyneresis of inhomogeneous S‐DVB copolymer gel.
The effect of several surface modified sepiolites on the transition temperatures and crystallinity of filled polypropylene
Authors: Acosta Jose Luis , Rocha Carlos Marco , Ojeda M. Carmen , Linares Amelia , Arroyo Miguel 
Published: April 2003

AbstractIn order to study the influence of several surface modified sepiolites on the filler/polypropylene interphase, thermal and dynamic measurements have been carried out. The results obtained make clear the existence of ordered structures of a different nature in the interphase as a function of the surface treatment.
Mechanochemisch eingeleitete Polymerisationsreaktionen. 7. Einfluß der Radikalinitiatoren und ‐akzeptoren auf die durch Schwingmahlung des Styrols mechanochemisch eingeleitete Polymerisation
Authors: Oprea Cleopatra Vasiliu , Weiner Felicia 
Published: April 2003

AbstractIn der vorliegenden Arbeit wurde der Einfluß von Agenzien, die freie Radikale bilden, auf die durch Schwingmahlung mechanochemisch eingeleitete Polymerisation von Styrol untersucht.Die synthetisierten Polymeren wurden durch Elementaranalyse, IR‐Spektroskopie, ESR‐Spektren, Mössbauerspektren und Differential‐Thermo‐Analyse (DTA) charakterisiert.Aufgrund der erhaltenen Resultate wurde auf den Mechanismus der mechanochemischen Polymerisation dieses Monomeren geschlossen.
Grafting of vinyl monomers onto natural rubber, II. Graft copolymerization of methyl methacrylate onto natural rubber using tetravalent ceric ions
Authors: Lenka Subasini , Nayak Padma L. , Das Anil P. , Mohanty Indu B. 
Published: April 2003

AbstractThe use of tetravalent ceric ions to initiate graft‐copolymerization of methyl methacrylate onto natural rubber (NR) has been investigated. The rate of grafting has been determined by varying the concentration of monomer and cerium(IV), the temperature and the solvents. The graft yield increases with increasing monomer concentration up to 1.877 M, with further increase of the monomer, the graft yield decreases. The percentage of grafting increases with increasing cerium(IV) concentration up to 0.035 M, thereafter it decreases. With increasing temperature the graft yield increases. The effect of CuSO4 on the rate of grafting has also been investigated. A plausible mechanism has been suggested and the kinetic rate expressions have been derived.
Structure of rigid domains and viscoelastic properties of ion‐containing polyurethane semicarbazides
Authors: Vilensky V. A. , Kercha Y. Y. , Lipatov Y. S. , Shtompel V. I. , Yakovenko A. G. , Grekov A. P. 
Published: April 2003

AbstractBy using small‐angle X‐ray scattering, thermo‐mechanical analysis, stress relaxations under constant deformation, etc. the effect of different quaternizing agents on the structure formation in cation‐active segmented polyurethanes was investigated.The results obtained have been used for developing a model of a rigid domain, according to which the domain is a complex particle consisting of hard block microassociates. The hard block microassociates result from dipole‐dipole, dipole‐ion, and ion‐ion interactions.The optimum viscoelastic and thermomechanical characteristics of polyurethane ionomers of the given chemical structure are realized when a part of tertiary nitrogen atoms remains unquaternized.
Some aspects on interpolymer complex formation between polycarboxylic acids and nonionic polymers
Authors: Chatterjee S. K. , Malhotra A. 
Published: April 2003

AbstractThe configurational environment of a polymer molecule has been found to influence the mode of formation and stoichiometry of an interpolymer complex between polycarboxylic acid and a nonionic polymer. It could be shown through several experimental techniques, e.g. viscometry, potentiometry and conductometry that a distinct stepwise complex formation takes place between the component polymers. Probable structures of the complexes have been proposed.
Chain transfer reactions for styrene free radical polymerization in presence of mixed ethylbenzene and EPDM rubber
Authors: Severini Febo , Quattroni Giuseppe , Gallo Raffaele 
Published: April 2003

AbstractInvestigations were made on the radical polymerization of styrene in presence of ethylene propylene diene terpolymers and ethylbenzene. The results obtained allowed to calculate the transfer constants of polystyryl radical to terpolymer and ethylbenzene in a mixed system. Meanwhile the same results showed a lower radical reactivity of the elastomer in presence of the aromatic transfer agent.
DSC studies on polyester‐polyamide biconstituent fibers
Authors: Savov M. , Bechev C. , Georgiev Y. , Dimov K. 
Published: April 2003

AbstractThe melting and crystallization behaviour of undrawn poly(ethylene terephthalate)‐nylon 6 biconstituent fibers (BCF) have been investigated by DSC measurements. A decrease of the internal ΔT between the temperature of the glass transition and the temperature of the cold crystallization has been found. Changes of the temperature of the melt crystallization of the two components depending on the blend ratios (e.g. the phase morphology) have been also observed. These effects have been explained by an interface physical interaction which changes the degree of order of the molecules inside the phases. A relation between the decrease in ΔT of the PETP component and the maximum draw ratio λmax of the BCF has been established. It is supposed that the change in ΔT causes the occurrence of local tensions and the initial formation of microcracks in the PETP phase which lead to a decrease of λmax.
Emulsion xanthation of cotton and bagasse celluloses in presence of sodium and potassium hydroxides
Authors: Abou‐State M. Amine , El‐Megeid Fouad F. Abd , Michael Michael G. 
Published: April 2003

AbstractSodium hydroxide swelled cotton and bagasse celluloses to a greater extent than potassium hydroxide. Higher alkali concentration during xanthation favoured the dissolution of cellulose and the formation of the main sulphur byproducts. Compared to sodium hydroxide, potassium hydroxide resulted in lower dissolution of cellulose, higher degree of xanthation (γ‐number) of dissolved xanthate and greater formation of sulphur byproducts. The xanthation of the more open and accessible bagasse cellulose resulted in higher solubility, lower γ‐number of dissolved xanthate, and higher amounts of sulphide and thiocarbonate than in case of the more compact and less accessible cotton cellulose. Reducing the carbon disulphide ratio reduced the γ‐number of dissolved xanthate and the amounts of the main sulphur byproducts as well as the dissolution of cellulose. In case of xanthating cotton cellulose at the lower carbon disulphide ratio potassium hydroxide resulted in a lower γ‐number of dissolved xanthate than sodium hydroxide.
Investigation of lignins from soda and sulphate cooking of rice straw and corn stalks
Authors: Nagieb Zenat A. , Shukry Nadia 
Published: April 2003

AbstractSoda lignins separated from soda cooks of rice straw and corn stalks were found to be completely soluble in most organic solvents, while thiolignins separated from kraft cooks consist of two fractions, a soluble (A) and an insoluble (B) fraction. The carbon content of both types of lignin decreases in the order soluble > soda > insoluble, while the content of methoxy groups decreases in the order soda > soluble > insoluble.The soluble lignins isolated from kraft cooks have higher contents of phenolic OH/C9‐functions than soda lignins. The ratio of phenolic OH:OCH3 is also higher for kraft lignins than for soda lignins of both rice straw and corn stalks.The calculated value for MeO/C9 from nitrobenzene oxidation on the basis of molar proportion of aldehydes is higher than that determined by chemical analysis due to the presence of condensed units.1H‐NMR spectra show the percentage of condensed units in lignins from soda cooks to be much lower than from kraft cooks of both rice straw and corn stalks.
Polyacrylamide as a filler retention aid for bagasse paper pulp
Authors: Ibrahem A. A. , Nada A. M. A. , El‐Saied H. , El‐Ashmawy A. E. 
Published: April 2003

AbstractThe polyacrylamide (PAM) produced as a homopolymer byproduct during the grafting of cellulose by acrylamide was partially hydrolysed for 2 and 4 hours. The three prepared polymers besides Accostrength® 86, which is mainly a dry strength resin and also improves retention of fillers and fines, were used as filler retention aids for bleached bagasse. Three fillers were used, namely titanium dioxide, silica and kaolin. The results obtained showed that the PAM hydrolysed for 2 hours gave the best results for both filler retention and improvement of strength properties. The values obtained for this polymer were comparable with those obtained for the commercial polymer.
Investigation on the crystalline morphologies of polyphenylene sulfide and interfacial effect in its fibre composites
Authors: Zeng Hanmin , Ho Guoren 
Published: April 2003

AbstractUncured polyphenylene sulfide (PPS) may form a perfect spherulite structure with a diameter of the spherulites larger than 100 μm. On the free surfaces of uncured PPS samples after isothermal crystallization a variety of spherulite patterns can be observed by means of scanning electron microscopy (SEM). However, the crystalline morphologies of PPS are greatly affected by the curing conditions. Graphite fibres, carbon fibres, and glass fibres possess the ability for inducing the transcrystallization of PPS to a different degree. The corrosive resistance of the PPS resin is not only related to its chemical structure, but also to its aggregation structure, and furthermore to the interfacial effect of carbon fibres in the composites.
Tubular interpolymer ion exchange membranes 1. Cation exchange membranes based on polyethylene modified with styrene‐divinylbenzene copolymers
Authors: Poźniak Gryzelda , Trochimczuk Witold 
Published: April 2003

AbstractTubular cation exchange membranes were prepared from the system polyethylene/poly(styrene‐co‐divinylbenzene) [PE/poly(St‐co‐DVB)] by extruding tubes followed by their sulfonation with a solution of chlorosulfonic acid in 1,2‐dichloroethane. The content of DVB in the system PE/poly(St‐co‐DVB) as well as the parameters of extrusion and sulfonation were varied. The best properties for the use in the Donnan dialysis had membrane tubes containing 4 wt.‐% of DVB in the aromatic component of the polymer system, sulfonated with a 20 vol.‐% solution of chlorosulfonic acid for 6 h.
Stark basische ionenaustauscher auf guanidiniumsalz‐formaldehyd‐aceton‐basis
Authors: Okay Oguz , Schindlbauer Hellmuth 
Published: April 2003

AbstractEine alkalische Vorkondensation von Formaldehyd mit Aceton vor der Vernetzungsreaktion vermindert deutlich die Wasserlöslichkeit der Guanidiniumsalz‐Formaldehyd‐Harze, wobei mit steigendem Aceton: Formaldehyd‐Molverhältnis die Wasserlöslichkeit abnimmt, die durch Zusatz von Melamin weiter herabgesetzt wird. Die gute Austauschkapazität der Chlorid‐Form sinkt jedoch dadurch gegenüber Phosphat‐ bzw. Aniontensid‐Ionen beträchtlich ab, steigt aber bei Hydroxyl‐Ionen an.