bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oligomer‐oligomer incompatibility, 3. End‐group effects
Authors: Wolf B. A. , Schuch W. 
Published: April 2003

AbstractIn order to investigate the influences of different end‐groups on oligomer miscibility with other substances, oligo(propylene glycol)s bearing OH groups (OPG‐OH) studied in the previous paper2, were acetylated at both ends (OPG‐AC). The limits of miscibility of OPG‐AC with oligo(dimethylsiloxane) (ODMS) were measured turbidimetrically. A simple and reliable method for the determination of the critical points from turbidity data is presented. The observed upper critical temperatures (Tc) increase with degree of oligomerization of ODMS (ranging from 1 to 5), whereas Tc shows a minimum when the degree of oligomerization of the OPG‐AC is raised (from 1 to 57,5). For lower mol. wt. oligoglycols, the Tc‐values of ODMS/OPG‐AC are lower by ca. 50 K as compared with those of ODMS/OPG‐OH. The different end‐groups play a minor role with respect to the pressure influences (up to 1 500 bar the miscibility increases in all cases). For OPG‐AC the chain length of optimum miscibility with a given ODMS is found at considerably lower values than for OPG‐OH. The theoretical evaluation of the experimental material on the basis of the lattice theory yields a reduction in the enthalpies of mixing up to 10% and an increase in the volumes of mixing (<0) up to 50% when OH is replaced by AC. For the treatment of end‐group effects, the solubility parameter theory, when combined with the concept of molar attraction constants, presents several advantages: In particular it is possible to describe the phase separation behaviour of the different oligomer mixtures simply by means of solubility parameters and molar volumes of the different segments and end‐groups and to forecast the presence or absence of a chain‐length of optimum miscibility.
Craze formation in highly stretched polyurethane elastomers
Authors: Caspary Rudolf , Schnecko Hans W. 
Published: April 2003

AbstractIn a microscopy investigation it was found that stress‐whitening of polyurethane elastomers in the highly stretched state is created by a typical craze formation. Additional tests indicated that strain‐induced crystallinity is a first stage of crazing, possibly a necessary one. Density measurements suggested a microporous structure of the crazed matter. A fibrillar texture of the drawn material is indicated. Since craze formation is an energy absorbing mechanism, changes of important mechanical properties should be ascribed to this process.
Studies on formaldehyde resins, 18. Kinetics of acid‐catalyzed hydrolysis of bis(hydroxymethyl)melamine
Authors: Sato Kenji , Maruyama Kazuhiro 
Published: April 2003

AbstractKinetics and mechanism of the acid‐catalyzed hydrolysis of N,N′‐bis(hydroxymethyl)melamine [6‐amino‐2,4‐bis(hydroxymethylamino)‐1,3,5‐triazine] (M2F) were studied in the pH region of 0,5 − 7,6 at 30°C, where 30 vol.‐% DMSO aqueous solution was used as a solvent. The main results are as follows. The hydrolysis of M2F was of ca. 1,5th order in [M2F]0 at constant pH of 2,7 − 7,6, and was of ca. 1st order in the strongly acidic region of pH 0,5 − 1,0. Moreover, the hydrolysis rate of M2F attained a maximum at pH 4,0 corresponding to [HCl]0/[M2F]0 = 0,5 and a minimum at pH 1,9. On the basis of these results and kinetic investigations, the main reaction of the hydrolysis of M2F is plausible to be a reaction of the conjugate acid of M2F with a M2F molecule in the acidic range of pH > 2,7.
Polymères thiocarboxyliques, 1. Synthèse et étude de la polymérisation radicalaire de monomères dithiocarboxyliques
Authors: Haraoubia Rachid , Bonnans‐Plaisance Chantal , Levesque Guy 
Published: April 2003

AbstractThe syntheses and free‐radical polymerizations of methyl and carboxymethyl 4‐vinyldithiobenzoates are described as well as various copolymers. Copolymerisation parameters were determined for the copolymerizations of the methyl dithioester with styrene and with methyl methacrylate.
Polymere Brenzcatechin‐Derivate, 3. Darstellung und Eigenschaften von 3,4‐Methylendioxybenzyl‐methacrylat und seinen polymeren Derivaten
Authors: Iwabuchi Susumu , Nakahira Takayuki , Ikebukuro Yasuhiro , Takada Tadayoshi , Kojima Kuniharu 
Published: April 2003

Abstract3,4‐Methylenedioxybenzyl methacrylate (3) was synthesized from 3,4‐methylenedioxybenzyl alcohol (2) and methacryloyl chloride. 3 was radically polymerized with tributylborane and copolymerized in cyclohexanone at room temperature under nitrogen. The following monomer reactivity ratios were determined M1 = 3: r1 = 0,68 and r2 = 0,40 for M2 = styrene, r1 = 0,78 and r2 = 0,16 for M2 = acrylonitril, and r1 = 0,28 and r2 = 1,47 for methyl methacrylate. Polymeric derivatives having 3,4‐dihydroxybenzyl units in the side chains were prepared from homo‐ and copolymers of 3. The thermal stability and redox behaviour of these polymers were investigated.
Lösungseigenschaften methyl‐ und chlorsubstituierter Bisphenol‐A‐Polycarbonate
Authors: Horbach Alfred , Müller Herbert , Bottenbruch Ludwig 
Published: April 2003

AbstractSolution properties of dilute polymer solutions are studied for polycarbonates from 3,3′,5,5′‐tetramethylbisphenol A, from 3,3′‐dimethylbisphenol A, from 3,5‐dimethylbisphenol A, and from 3,3′,5,5′‐tetrachlorobisphenol A in regard to the influences of the different methyl and chloro substitutions. The Mark‐Houwink relationships are established in dichloromethane at 25°C. The unperturbed dimensions, evaluated from viscosity data using the Burchard‐Stockmayer‐Fixman method, are compared with those for bisphenol A polycarbonate. The unperturbed end‐to‐end distances are increased by the methyl and chloro substituents. The flexibility factors, calculated on the basis of the unperturbed dimensions and the dimensions of the freely rotating chain, indicate a greater rigidity of the polymer chain of the methyl and chloro substituted polycarbonates.
Investigation of poly(arylenevinylene)s, 24. High‐resolution solid‐state 13C NMR spectroscopy of poly(1,4‐phenylenevinylene)s
Authors: Schröter Bernd , Hörhold Hans‐Heinrich , Raabe Dietrich 
Published: April 2003

AbstractHigh‐resolution 13C NMR spectra of solid poly(1,4‐phenylenevinylene), poly(1,4‐phenylene‐1,2‐diphenylvinylene) and of three related, substituted polymers (CN, OCH3, O) were obtained with a combined technique of heteronuclear decoupling, cross‐polarization and magic angle spinning. The reported chemical shifts were assigned by means of solid model compounds (trans‐stilbene, trans, trans‐1,4‐distyrylbenzene, tetraphenylethylene). Utilizing the high sensitivity of 13C NMR chemical shifts to chemical structure, this method is applied to structure confirmation, the determination of sp3‐defects in poly(phenylenevinylene)s PPV, and the determination of sterical and electronical effects of phenyl and phenylene groups.
Analysis of stress relaxation data for linear aromatic polyesters
Authors: Ng Tie Hwee , Leverne Williams H. 
Published: April 2003

AbstractThe stress relaxation of linear aromatic polyesters was measured at various temperatures for 1 h at a strain of less than about 0,7%. The polyesters of the terephthalate series had the highest relaxation moduli, E(t), when compared with the isophthalate and copolyester series of the same methylene sequence lengths at a fixed temperature and time. Within the individual series, the E(t) decreased with increasing methylene sequence length. Time‐temperature superposition was found to be applicable to the viscoelastic behaviours of only some of the semicrystalline polyesters under certain conditions. Subsequently, master curves for these polyesters were constructed. The data were studied by means of a generalized Maxwell model which fitted the corresponding master curves exactly. By the use of Andrews' second approximation, the relaxation time spectrum of these polyesters was obtained over a very wide time scale range. The resultant spectrum was fairly high and flat for the terephthalate and isophthalate series while that of the copolyester series resembled that of a typical amorphous polymer.
Über polyarylenalkenylene und polyheteroarylenalkenylene, 11. Synthesen von poly(1,4‐phenylenvinylen), poly(2,5‐thiophendiylvinylen) und poly(2,5‐furandiylvinylen) aus methylsubstituierten aldehyden
Authors: Koßmehl Gerhard , Yaridjanian Arshak 
Published: April 2003

AbstractBy means of the strong base sodium tert‐butoxide p‐tolylaldehyde (1a), 5‐methyl‐2‐thiophene carboxaldehyde (1b), and 5‐methyl‐2‐furancarboxaldehyde (1c) can be polycondensed in dimethylformamide to give poly(1,4‐phenylenevinylene) (2a), poly(2,5‐thiophenediylvinylene) (2b), and poly(2,5‐furandiylvinylene) (2c). 2a and 2b are also available from the Schiff's bases of 1a and 1b. The polymers are identical with polymers synthesized via the Wittig reaction. The vinylene units have the trans‐configuration.
Recherche de télomères à activité pharmacologique potentielle, 5. Réactions sur les télomères de l'acide acrylique
Authors: Bauduin G. , Bessière J.‐M. , Bondon D. , Martel J. , Piétrasanta Y. 
Published: April 2003

AbstractGrafting of alcohols and amines on the telomers of acrylic acid was investigated. Carboxylic functions were activated via acid chlorides, anhydrides, or p‐nitrophenyl esters. Activation rates and grafting yields were determined in each case.
Studies on carboxymethylated cellulose: Potentiometric titrations, 2
Authors: Trivedi Harikrishna C. , Patel Chiman K. , Patel Raman D. 
Published: April 2003

AbstractEffect of the sizes of counterions on the dissociation constant of carboxymethylated cellulose (CMC) is studied by potentiometry. Dissociation of protons from the CMC chains is suppressed with increasing size of the counterion. A good agreement is observed between the theory of Kagawa and Gregor and the experimental results accounting for the counterion size effect; a thermodynamic analysis of ΔpK supported this conclusion. Effects of concentration changes of the polyacid were also considered.
Characterization and morphology of thermoplastic interpenetrating polymer networks based on polystyrene and polystyrene‐polyisoprene three‐block copolymers
Authors: Widmaier Jean‐Michel , Hubert Jérôme , Meyer Guy 
Published: April 2003

AbstractSemi‐interpenetrating polymer networks based on polystyrene and polystyrene‐polyisoprene three‐block copolymers (SIS) were prepared by anionic polymerization. Factors affecting synthesis, such as composition, molecular weight of either the unattached SIS or the polystyrene between crosslinks, elastomer content, have been varied. Their effect on network formation was examined by extraction experiments and swelling measurements. Their morphology was investigated by means of electron microscopy.
Konjugierte polymere mit azobenzol‐einheiten
Authors: Koßmehl Gerhard , Wallis Jan 
Published: April 2003

AbstractBy means of a Wittig condensation polymerization starting from 4,4′‐azodibenzaldehyde (1) and bifunctional Wittig salts of the benzene and thiophene series (2a–c) poly(azo‐1, 4‐pheny‐leneivnylenearylene)s (3a–c) were synthesized. Analogously the model compounds 6a–c, 8a–d, and 10a–c were prepared. The structures of the intensive red to brown polymers and the orange to red model compounds were proved by elemental analyses, IR‐ and electronic spectra, respectively mass spectral data for the model compounds. The thermooxidative degradation of the polymers and the electrical conductivity of the polymers and model compounds were studied.
Polymerisation von fulvenen, 4. Anionische polymerisation von 6,6‐dimethylfulven
Authors: Kronig Peter , Slongo Mario , Neuenschwander Markus 
Published: April 2003

AbstractThe reaction of 6,6‐dimethylfulvene (1) with small amounts of sodium cyclopentadienide (Na‐CPD) gives a mixture of oligomeric products, from which 1‐cyclopentadienyl‐1,3,3,‐trimethyltetrahydropentalene (7) was isolated with 67% yield. The structure of the main product 7 was proved by combination of spectrosopic methods as well as by NMR spectroscopy of its dianion. A reasonable reaction mechanism is presented and supported by isolation of other dimers 9 and 12 and trimers 10 as well as of side products 11 and 13. The product distribution is severely influenced by increasing the amount of Na‐CPD (favouring oligomers of type 11 and 13) as well as by addition of crown ether.
Stabilization of block copolymer micelles by UV and fast electron radiation
Authors: Tuzar Zdeněk , Bednář Bohumil , Koňák Čestmír , Kubín Miroslav , Svobodová Štěpánka , Procházka Karel 
Published: April 2003

AbstractMicelles of a block copoymer poly(styrene/butadiene/styrene) with cores consisting of polybutadiene blocks were stabilized in dilute solutions by UV radiation in the presence of a photo‐initiator and also by fast electrons, and micelles of a block copolymer poly(styrene/ethene‐co‐1‐butene/styrene) with cores formed by the aliphatic blocks were stabilized by fast electrons, in dilute solutions. Stabilization of micelles, i. e., crosslinking of the chains in micellar cores as well as the properties of stabilized micelles were studied by conventional light scattering, by light scattering photon correlation spectroscopy and by gel permeation chromatography.
Wholly aromatic polyamides containing bridged biphenylylene groups, 1. Poly(3,8‐phenanthridinonediyl terephthalamide)
Authors: Kaneda Takaho , Ishikawa Seiji , Daimon Hiroshi , Katsura Toshio , Ueda Masahiro , Oda Kunio , Horio Masao 
Published: April 2003

AbstractAs a part of studies on wholly aromatic polyamides containing bridged biphenylylene groups, poly(3,8‐phenanthridinonediyl terephthalamide) (DAP‐T) was prepared from 3,8‐diaminophenanthridinone and terephthaloyl chloride. The solutions of DAP‐T samples in high concentration sulfuric acid exhibited optically different phases, depending on temperature and concentration, like those of poly(1,4‐phenylene terephthalamide) (PPD‐T). The phase diagram of the DAP‐T‐99,0% H2SO4 system was established and compared with that of the PPD‐T‐99,0% H2SO4 system. Both were essentially similar. The flow of high concentration dopes of DAP‐T and PPD‐T through spinneret holes showed non‐Newtonian characteristics. The liquid‐crystalline solutions of DAP‐T in 99,0% sulfuric acid were spun into fibers using water as a coagulant. The tensile strength and initial modulus increased with increasing degree of stretching between spinneret and collection roller. The annealing of fibers caused an increase in tenacity and modulus, and a tensile strength of 25 g/den and an initial modulus of 1 000 g/den could be reached. Both spun fibers and annealed fibers showed x‐ray diffraction patterns displaying distinct layer line streaks, from which the fiber period was estimated to be 17,2 Å. This agreed with the repeat distance in the direction of molecular axis calculated on the basis of extended chains with trans‐conformation.
Graft copolymerization of methyl methacrylate on chlorinated natural rubber, 3. Study of the interaction between chlorinated and organometallic compounds
Authors: Nogues P. , Dawans F. , Maréchal E. 
Published: April 2003

AbstractThe interaction of Ni[P(OR)3]4 (R = C2H5 or C6H5) with chlorinated rubber (CR) of CCl4 is studied. The results of the polymerization of methyl methacrylate (MMA) initiated by the system CR or CCl4Ni[P(OR)3]4 depend on the order in which the reagents are introduced. Trialkylphosphite, tetrakis(trialkylphosphite) nickel and the products resulting from the reaction of CCl4 or CR with Ni[P(OR)3]4 are characterized by 31P NMR. From this study, it appears that the initiation of polymerization by the system chlorinated compound‐nickel derivative does not involve the formation of free phosphite, which is at variance with previously reported assumption. 1H NMR study supports these results.
Effect of molecular weight on the crystallization kinetics of isotactic poly(1‐butene)
Authors: Cortazar Milagros , Guzman Gonzalo M. 
Published: April 2003

AbstractIsothermal crystallization of isotactic poly(1‐butene) fractions by calorimetry and microscopy was studied for a range of molecular weights from 96 000 to 964000. An Avrami exponent of 2 was found indicating a two‐dimensional growth rate of the crystal, following a predetermined nucleation mode, proving that such an exponent is independent of both temperature and molecular weight. The temperature and molecular weight dependence of the growth rate of spherulites and overall crystallization rates was analyzed by means of the theoretical expression given by Hoffman and Lauritzen. The product of the lateral and basal surface free energies of the crystallites, σ·σe, increases with molecular weight and approaches its limiting values when a certain molecular weight is attained.
Oxygen‐ascorbic acid‐Copper(II) initiating system. A kinetic study of the polymerisation of methyl acrylate in aqueous medium
Authors: Reddy G. Gangi , Nagabhushanam T. , Santappa M. , Rao K. Venkata 
Published: April 2003

AbstractPolymerisation of methyl acrylate (MA) initiated by O2‐ascorbic acid (AA)‐Cu2+ system was studied in aqueous medium at 40°C. The rate of polymerisation Rp, was found to increase, remain constant, and then decrease with increasing [Cu2+]. Rp was found to depend on [Cu2+]0,6, [AA]0, [O2]0,6, and [MA]1,3 in the increasing region, on [Cu2+]0, [AA]0, [O2]0,6, and [MA]1,6 in the constant region and on [Cu2+]−0,9, [AA]0, [O2]0,7, and [MA]2,0 in the decreasing region. Rate laws were derived assuming a plausible reaction mechanism for the different regions. Rp increased with ionic strength and decreased with [H2SO4,]. An initial increase, then steady state followed by a decrease in rate with temperature was noticed in the range 25 − 55°C. kp/kt1/2 values were calculated and compared with literature values. Chain lengths were determined viscometrically.
Nouvelle préparation de polychlorophosphazènes linéaires
Authors: Helioui Moncef , De Jaeger Roger , Puskaric Emile , Heubel Joseph 
Published: April 2003

AbstractPolychlorophosphazenes 2 can easily be obtained by thermal condensation of dichlorophosphinoyliminotrichlorophosphorane (1) under atmospheric pressure at 240–290°C, pure POCl3 being eliminated. The different stages of the reaction were studied by chemical analysis, 31P NMR, IR spectroscopy, and thin layer chromatography. The procedure enables one to obtain polymers of low and high molecular weights. The samples do not contain any cyclic or reticular polymers. Species of low molecular weights can be separated from those with high molecular weights by treatment with heptane. The total yield of phosphorus is 100% with regard to the starting material. Substitution products (Cl by OCH2CF3) are obtained which are identical with those obtained with the polychlorophosphazenes prepared via classical methods.
Studies on chitin, 8. Modification reaction of chitin in highly swollen state with aromatic cyclic carboxylic acid anhydrides
Authors: Kurita Keisuke , Ichikawa Hiroyuki , Ishizeki Shinichi , Fujisaki Hitoshi , Iwakura Yoshio 
Published: April 2003

AbstractReaction of partially deacetylated chitin with aromatic cyclic carboxylic acid anhydrides such as phthalic anhydride, trimellitic anhydride, and pyromellitic dianhydride was successfully carried out under almost homogeneous conditions in organic aprotic solvents using highly swollen precipitates of water‐soluble chitin with about 50% deacetylation. The resulting amic acid‐chitins were converted into the corresponding imide‐chitins by heating. In addition to imidization, this heat treatment also promotes removal of acid anhydrides reacted at the hydroxyl group giving rise to the formation of selectively N‐substituted derivatives. These novel chitin derivatives exhibit a much improved solubility in organic solvents and aqueous alkaline solutions. As anticipated, the imide‐chitins, derived from trimellitic anhydride and pyromellitic dianhydride, showed reactivity toward amine under heterogeneous conditions, and the reaction capacities toward p‐chloroaniline were determined to be 4,2 · 10−4 and 4,6 · 10−4 mol · g−1, respectively.
Effects of substituents in aromatic amine N‐oxide and amine modifiers on ziegler‐type propylene polymerization catalyst performance
Authors: Karayannis Nicholas M. , Lee Sam S. 
Published: April 2003

AbstractStudies of the effects of ring substituents in aromatic amine N‐oxide or amine modifiers on Ziegler‐type propylene polymerization catalyst performance are reported. Among sterically hindered amines or N‐oxides, the o,o‐dimethyl substituted derivatives provide the best stereospecificity with little loss in activity. On the other hand, m‐ or p‐substituted derivatives with electron‐withdrawing substituents were found to activate the catalyst, producing higher yields relative to the unmodified (TiCl3‐Al alkyl) catalyst system. The inductive and steric effects introduced by the modifiers in the catalyst system are discussed. Aromatic amine N‐oxides generally produce less active catalyst systems relative to their parent amines, owing presumably to a redox reaction between the N—O function and Ti3+.
Formaldehyde polymers, 30. Preparation of 5‐hydroxy‐4‐chromanones and 8‐hydroxy‐1‐tetralon and their properties as UV‐absorbers
Authors: Ninagawa Akira , Nakamura Masashi , Matsuda Haruo 
Published: April 2003

Abstract5‐Hydroxy‐6,8‐dimethyl‐4‐chromanone (4a) and 8‐hydroxy‐5,7‐dimethyl‐1‐tetralon (4b) were synthesized from 6,8‐dimethyl‐4 chromanone (1a) and 5,7‐dimethyl‐1‐tetralon (1b), respectively. 5‐Hydroxy‐7‐methody‐2,2‐dimethyl‐4‐chromanone (6) was prepared from 5,7‐dihydroxy‐2,2‐dimethyl‐4‐chromanone (5). Cyclohexane solutions of 1a, 1b, 4a, 4b, 6, 5‐hydroxymethyl‐6,8‐dimethyl‐4‐chromanone (7), 3‐hydroxy‐2,6‐dimethyl‐4‐chromanone (8), and 2‐hydroxy‐4‐octyloxybenzonphenone (9) were irradiated. The photostability of these compounds was found to decrease in the following order: 4b > 4a, 6 > 9 > 1a, 1b. 7, 8. Poly(venyl chloride) films containing 5, 0 wt.‐% of 4a, 4b, or 6 were found to be stable against photooxidation.
Hydrogen bonding in monodisperse and polydisperse oligo(ethylene glycol)s
Authors: Teo Hoon H. , Marshall Alan , Booth Colin 
Published: April 2003

AbstractInfrared spectra of monodisperse (DP ≤ 35) and polydisperse (average DP ≤ 45) oligo(ethylene glycol)s are recorded for melts and for solids over a temperature range (+70°C to ‐80°C). Spectra in the hydroxyl stretching region show that the solid monodisperse oligomers with DP ≤ 25 at temperatures well below the melting point have highly ordered lamella end surfaces with hydroxyl groups from adjacent lamellae hydrogen bonded in long chains, whereas the solid polydisperse oligomers of comparable chain length have disordered lamella end surfaces with hydroxyl‐ether as well as hydroxyl‐hydroxyl hydrogen bonding.
Synthèse et transformations chimiques des télomères de l'undécène‐10 oate de méthyle, 1
Authors: Belbachir Mohamed , Boutevin Bernard , Piétrasanta Yves , Rigal Gérard 
Published: April 2003

AbstractRedox of radical telomerizations of methyl 10‐undecenoate (1) with different telogens such as CCl4, CCl3Br, CCl3CF3, HPO (OEt)P2 or different adducts of CCI4, on vinylidene chloride and chlorotrifluoroethylene, were studied. Chemical transformation of the end of the chains led to the corresponding difunctional compounds. Starting with these last compounds, polycondensation reactions were carried out.