bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laser light scattering studies of soluble high performance fluorine‐containing polyimides, 1. Polyimide synthesized from 2,2′‐bis(3,4‐dicarboxyphenyl)‐hexafluoropropane dianhydride and 2,2′‐(trifluoromethyl)‐4,4′‐biphenyldiamine
Authors: Kwan Simon Chi Man , Wu Chi , Li Fuming , Savitski Edward P. , Harris Frank W. , Cheng Stephen Z. D. 
Published: April 2003

AbstractFive fractions of a polyimide synthesized from 2,2′‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2′‐(trifluoromethyl)‐4,4′‐biphenyldiamine (PFMB) (6FDA/PFMB) in tetrahydrofuran (THF) at 30°C were investigated by a combination of static and dynamic laser light scattering (LLS). The relations of 〈Rh〉 (nm) = 2.38 x 10−2 Mw0.560 and A2 (mol · cm−3 · g−2) = 2.1 × 10−1 Mw−0.43 were established, where Mw, 〈Rh〉 and A2 are weight‐average molecular weight, average hydrodynamic radius and second virial coefficient, respectively. A combination of Mw and the translational diffusion coefficient distribution G(D) leads to a relation of D(cm2/s) = 2.41 × 10−4 M0.564. With this relation, we successfully convert each G(D) into a corresponding molecular weight distribution (MWD). On the basis of the Benoit‐Doty theory, we found that the persistence length and the Flory characteristic ratio C∞ of the 6FDA‐PFMB chain are ∼3.3 nm and ∼40, respectively, indicating that the 6FDA‐PFMB chain is more extended than typical random‐coil chains. On the other hand, the ratio of the radius of gyration to the hydrodynamic radius, i.e., 〈Rg〉/〈Rh〉 ∼ 1.8, together with the values of the exponents (∼0.56) indicate that the 6FDA‐PFMB chain has a coil chain conformation. Therefore, the 6FDA‐PFMB chain has an extended coil conformation in THF at 30°C.
High‐pressure free‐radical copolymerization of ethene and methyl acrylate
Authors: Buback Michael , Dröge Thomas 
Published: April 2003

AbstractThe free‐radical copolymerization of ethene (E) and methyl acrylate (MA) is studied between 220 and 290°C at 2000 bar. The reactions which have been induced thermally are carried out in a continuously operated device at total monomer conversions mostly below 1%. Monomer concentrations are obtained from measured mass fluxes. Copolymer composition is determined via elemental analysis. Reactivity ratio data, rE and rMA, are derived from non‐linear least squares fitting of the monomer mixture and copolymer compositions. rE and rMA, e.g., at 220°C and 2000 bar, are found to be 0,045 ± 0,002 and 5,3 ± 0,2, respectively. The rE and rMA values slightly, but significantly, differ from corresponding data for ethene‐butyl acrylate (BA) and ethene‐2‐ethylhexyl acrylate (EHA) copolymerizations. Toward higher temperature rE increases and the acrylate (MA, BA, EHA) reactivity ratio rA decreases. The temperature dependences of rE and rA can not be distinguished for the three ethene‐acrylate systems. From an experiment at two levels of polymerization pressure, 1500 and 2000 bar, the pressure dependence of rE has been estimated. The available data for rE and rA allow to model monomer concentration vs. polymer composition behavior of free‐radical ethene‐acrylate copolymerizations at technically relevant temperatures and pressures.
Miscibility behavior of syndiotactic and atactic polystyrene
Authors: Ermer Hubert , Thomann Ralf , Kressler Jörg , Brenn Rüdiger , Wünsch Josef 
Published: April 2003

AbstractBlends of atactic and syndiotactic polystyrene have a single composition dependent glass transition temperature. This does not confirm the miscibility of both polymers, however, unambiguously because there is only a small difference of 10°C in the glass transition temperatures of both neat polymers. Diffusion measurements of syndiotactic polystyrene and deuterated atactic polystyrene using the nuclear reaction D(3He,α)p confirm at least partial miscibility of both components. The average diffusion coefficient at 190°C is 2.3 ± 0.2 × 10−15 cm2/s.
Synthesis and characterization of polymers containing 4‐cyanobiphenyl‐based side groups for nonlinear optical applications, 4. Poly[(4,4‐dimethyl‐2‐vinyl‐5‐oxazolone)‐co‐(methyl methacrylate)]s
Authors: Guichard Bertrand , Noël Claudine , Reyx Danièle , Chevalier Samy , Senet Jean‐Pierre , Kajzar François 
Published: April 2003

AbstractThis paper describes the synthesis, characterization and nonlinear optical properties of a series of side chain copolymers prepared by chemical modification of poly[(4,4‐dimethyl‐2‐vinyl‐5‐oxazolone)‐co‐(methyl methacrylate)]s (P(VDM‐co‐MMA)s) with 4,4′‐disubstituted biphenyl. First, a poly(4,4‐dimethyl‐2‐vinyl‐5‐oxazolone) (PVDM) and four P(VDM‐co‐MMA)s were prepared by free‐radical polymerization. Chemical transformation reactions were then performed on these polymer backbones with 4‐cyano‐4′‐(β‐aminoethoxy)biphenyl. This amine was synthesized according to a novel procedure. The functionalized polymers are isotropic and show glass transition temperatures up to 132°C. They can easily be processed by spin‐coating into thin films of optical quality. These films were oriented by a corona discharge process, and ultraviolet spectroscopic measurements were performed to study the axial ordering kinetics as a function of poling conditions. Second‐order nonlinear optical coefficients (d33 and d31) were measured at a fundamental wavelength of 1064 nm. The ratio d33/d31 was found to be close to 3, as expected for amorphous isotropic polymers. No significant relaxation was observed at ambient conditions in 2 months. Hydrogen bonding between CO‐NH groups of neighboring side chains are felt to contribute to the stability of the second‐order nonlinear optical properties in these PVDM systems.
Rigid maleimide‐alt‐vinylpyridine copolymers with pendant chromophores. Synthesis, characterization and monolayer formation
Authors: Noordegraaf Marina A. , Kuiper Gert Jan , Marcelis Antonius T. M. , Sudhölter Ernst J. R. 
Published: April 2003

AbstractA new series of rigid polymers was synthesized via radical copolymerization of N‐phenylmaleimides, bearing pendant chromophores, with 4‐vinylpyridine or styrene. Structural characterization was achieved by 1H NMR and 13C NMR spectroscopy, gel permeation chromatography (GPC), elemental analysis and differential scanning calorimetry (DSC). The thermal properties as well as the morphology of the investigated polymers at the air‐water interface appear to be related to their rigidity. In spite of the presence of excellent mesogenic units, the polymers do not exhibit liquid crystalline behaviour. The 4‐vinylpyridine copolymers form stable monolayers at the air‐water interface. The attached chromophores electronically behave as monomers, as shown with in situ UVVIS absorption spectroscopy. Brewster angle microscopy shows a spontaneous aggregation of these polymers into domains on a neutral subphase, whereas on an acidic subphase a more homogeneous monolayer is formed. The monolayers give Z‐type transfer onto hydrophilic quartz. However, the chromophores seem to be oriented randomly at the substrate surface. The styrene copolymers do not form stable monolayers as a result of crystallization at the air‐water interface.
Syntheses and radical polymerizations of methacrylamides derived from optically active amino alcohols
Authors: Koyama Emiko , Sanda Fumio , Endo Takeshi 
Published: April 2003

AbstractSyntheses and radical polymerizations of methacrylamides derived from optically active amino alcohols were carried out. The monomers were prepared by condensation of optically active amino alcohols and methacrylic acid using 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride (EDC · HCl). Radical polymerizations of the monomers were carried out in the presence of 2,2‐azoisobutyronitrile (AIBN) (3 mol‐%) in methanol and N,N‐dimethylformamide (DMF) as solvents, resulting with good yields in polymers with Mn's in the range 17 800–81 000. The monomer reactivity ratios of N‐(1‐hydroxy‐4‐methyl‐2‐pentyl)methacrylamide (MA‐Lol) and methyl methacrylate (MMA) in the copolymerization were estimated to be 0.50 and 2.38, respectively. The lower reactivity of MA‐Lol in comparison with MMA is similar to common methacrylamide derivatives. The hydrophilicity of the polymers was evaluated by the heat of fusion of water using differential scanning calorimetry (DSC). The determined order poly(MA‐Aol) > poly(MA‐Lol) > poly(MA‐Fol) reflects the bulkiness of the side chains.
Triblock copolymer based thermoplastic elastomeric gels of a large service temperature range: preparation and characterization
Authors: Yu Jian M. , Jérôme Robert , Overbergh Noel , Hammond Phil 
Published: April 2003

AbstractPoly(methyl methacrylate)‐block‐polybutadiene‐block‐poly(methyl methacrylate) (MBM) triblock copolymers and their hydrogenated counterparts with poly(ethylene‐co‐1,2‐butylene) midblock (MEBM) were swollen by an aliphatic oil of high boiling point which is a selective solvent for the central block. Thermoreversible gels are accordingly formed by both MBM and MEBM copolymers above a critical polymer content (Cr), which depends on the nature of the midblock and not on the copolymer molecular weight, at least in the investigated range. Cr has been found to be 5 wt.‐% for an MBM block copolymer and 2 wt.‐% for MEBM copolymers of various molecular weights. Gels of MEBM triblock copolymers exhibit interesting mechanical properties, such as high elongation at break (up to 870%) and high tensile strength (32 kPa). The most interesting feature of the MEBM gels is an upper service temperature as high as 170°C, thus more than 100°C higher than the value (47°C) reported for gels of an SEBS copolymer (S = polystyrene) of comparable molecular weight (100000) and composition (ca. 30 wt.‐% hard block). The morphology of MEBM gels was studied by scanning electron microscopy (SEM) and found to be cocontinuous in case of a gel containing 20 wt.‐% copolymer.
Multinuclear NMR investigation of methylaluminoxane
Authors: Babushkin Dmitrii E. , Semikolenova Nina V. , Panchenko Valentina N. , Sobolev Anatolii P. , Zakharov Vladimir A. , Talsi Evgenii P. 
Published: April 2003

AbstractBy means of 27Al, 1H, 17O and 13C NMR spectroscopy the structure of the methylaluminoxane (MAO) cocatalyst of Kaminsky‐Sinn catalysts was investigated. We have found that the 27Al NMR resonance line of MAO is extremely broad at room temperature (δ ≈ 60, Δω1/2 50 ± 10 kHz). At elevated temperatures (40–120°C) MAO exhibits an 27Al resonance at δ 110 ± 10, Δω1/2 15–10 kHz, that is, within the range reported for the aluminoxane clusters [(t‐Bu)Al(μ3‐O)]6 and [(t‐Bu)Al(μ3‐O)]9 with cage structures. The 27Al resonance at δ 149–153, usually attributed to MAO, belongs to AlMe3 present in MAO samples. The 17O NMR resonance of MAO at 50°C (δ 67, Δω1/2 1.7 kHz) is within the range typical for three‐coordinate oxo ligands, but it can be attributed only to a minor part of MAO oligomers. It was shown that the intensity of 27Al and 17O NMR resonances of MAO increases with increasing temperature, whereas the width of both resonances is almost constant. The results obtained lead to the conclusion that at ambient conditions MAO forms oligomers (MeAlO)n with cage structure and MeAlO3 environment. Upon increasing the temperature these oligomers reversibly break into smaller MAO units. Based on the 27Al NMR data the average radius (R) of MAO oligomers is approximately 5.1 ± 0.3 Å at 120°C. This radius corresponds to (MeAlO)n species with 9 < n < 14. At ambient conditions the predominant part of MAO forms oligomers with R = 7 ± 0.5 Å and 20 < n < 30.
Polymer complexes of dimethylbenzylalkylammonium chlorides
Authors: Anufrieva Elizaveta V. , Panarin Eugenij F. , Pautov Vladimir D. , Kirpach Andrej B. , Krakovyak Mark G. , Luschik Vanda B. , Solovskij Michael V. 
Published: April 2003

AbstractThe interaction of cationic surfactants from the series of dimethylbenzylalkylammonium chlorides (DMBAAC, alk. = CnH2n+1 (n = 10, 12, 14)) with water‐soluble copolymers of N‐vinyl‐2‐pyrrolidones (VP) with methacrylic, acrylic, and crotonic acids in aqueous and aqueous‐salt solutions was investigated by polarized luminescence. It was established that the main factors determining the stability of water‐soluble DMBAAC complexes with carboxyl‐containing VP copolymers include the composition and structure of the copolymer, the length of the alkyl group of DMBAAC, the ratio of the interacting components, the pH, and the ionic strength of the solution. The equilibrium dissociation constants of these complexes in aqueous solution were determined. Potentiometric titration, turbidimetry, and viscometry showed that the complexation features manifested by the interaction of individual DMBAAC's with carboxyl‐containing VP copolymers are also characteristic of complexation processes occurring with participation of industrial DMBAAC, which is a mixture of individual DMBAAC's.
Synthesis and characterization of ABA‐triblock copolymers with polystyrene and main‐chain liquid crystalline polyester segments
Authors: Reichelt Norbert , Schulze Uwe , Schmidt Hans‐Werner 
Published: April 2003

AbstractThis paper reports on the synthesis and characterization of polystyrene‐block‐poly(2,2′‐dimethyl‐4,4′‐biphenylene phenylterephthalate)‐block‐polystyrene. The ABA‐triblock copolymers were synthesized by condensation reactions of telechelic poly(2,2′‐dimethyl‐4,4′‐biphenylene phenylterephthalate) with anionically prepared ω‐hydroxy polystyrenes. Three different lengths of the liquid‐crystalline polyester (M̄n = 2650, 5 500, 10 100 g/mol) were used as central block B. The number‐average molecular weight M̄n of the polystyrene segments was varied in the range of 690 to 10 000 g/mol. The liquid crystalline behavior and the transition temperatures are discussed with respect to the molecular weight of the polystyrene segments and the block copolymer composition. A comparison with the corresponding polymer blends is given and first results on the morphology of the block copolymers are presented.
Study of the long‐period changes in samples of isotactic poly(propylene) obtained by quenching from the melt and subsequent annealing at different temperatures
Authors: Gerardi Francesco , Piccarolo Stefano , Martorana Antonio , Sapoundjieva Diana 
Published: April 2003

AbstractThe structural modifications induced in samples of isotactic poly(propylene) obtained by quenching from the melt at 100°C/s and subsequently annealed at 40, 60 and 80°C for different annealing times have been studied using simultaneous wide‐angle and small‐angle X‐ray scattering at the synchrotron radiation source of DESY. The occurrance of two different long‐period values is demonstrated. These values are related to the mesomorphic phase, existing in the starting quenched material, and to the α‐monoclinic one, which settles during the annealing process, respectively.
Polymerization of acrylates by atom transfer radical polymerization. Homopolymerization of glycidyl acrylate
Authors: Matyjaszewski Krzysztof , Coca Simion , Jasieczek Christina B. 
Published: April 2003

AbstractAtom transfer radical polymerization (ATRP) was applied to the homopolymerization of glycidyl acrylate (GA). This functionalized monomer can be polymerized to high conversions and high molecular weights using halogenated initiators and CuBr/4,4′‐bis(5‐nonyl)‐2,2′‐bipyridine (dNbipy) as the catalyst. The polymerizations exhibit first order kinetics and molecular weights increase linearly with conversion. The M̄n of the products is controlled by the ratio Δ[M]0/[I]0. The polymers obtained showed narrow molecular weight distributions, M̄w/M̄n = 1.25.
Synthesis and characterization of metal containing polychloranilamides
Authors: Allmendinger Thomas 
Published: April 2003

Abstract2,5‐Diamino‐3,6‐dichloro‐1,4‐benzoquinone (chloranilamide) condensates, under generation of HCl, above 300°C to form polychloranilamide. The reaction was studied by thermovolumetric measurements, especially in the presence of different metal salts (cobalt, iron and manganese). The composition of the brittle black polymers is as expected, and the IR spectra resemble to those of the corresponding model compounds based on 5,8‐dihydroxyquinoxaline. Their electrical conductivity is 10−8 – 10−5 S · cm−1. Metal contents of up to 25 wt.‐% were achieved corresponding to 80% of the theoretical value. The metal complexes are not stable against acids, and the compounds are not very resistant in a strongly alkaline milieu. Nevertheless, they could be promising, e.g., as ion exchangers, as precursors for organic materials with high metal contents such as catalysts, or as model compounds for similar polymers.
Catalytic behavior of a silica‐supported polystannazane‐copper complex for the oxidation of methanol to formaldehyde at mild reaction conditions
Authors: Tang Li‐Ming , He Qiang , Huang Mei‐Yu , Jiang Ying‐Yang 
Published: April 2003

AbstractA very cheap catalyst, a silica‐supported polystannazane‐copper complex (abbreviated as SiO2SnNCu) was prepared by the reaction of the silica‐supported polystannazane ligand with CuCl2 in ethanol. The results showed that SiO2SnNCu can catalyze the oxidation of methanol to formaldehyde in high yield at mild conditions, i.e. at 40°C and 1 atm of oxygen. The catalyst could be recovered and could catalyze the reaction repeatedly.
Synthesis and properties of polyurethanes containing phosphatidylcholine analogues in the polymer backbone
Authors: Yamada Mitsuaki , Li Yujun , Nakaya Tadao 
Published: April 2003

AbstractNew polyurethanes (4a, 4b) and a segmented polyurethane (4c) bearing phosphatidylcholine moieties in the main chain were synthesized. They are thermally stable up to 300°C and show the viscosity behaviour of common polyelectrolytes. Preliminary studies suggest that these polyurethanes are interesting new biomaterials.
On the difference of reactivities of various aggregated forms of aluminium triisopropoxide in initiating ring‐opening polymerizations
Authors: Duda Andrzej , Penczek Stanislaw 
Published: April 2003

AbstractThe polymerization of ε‐caprolactone (εCL) initiated with aluminium triisopropoxide (Al(OiPr)3) trimer (A3) and/or tetramer (A4) was studied. The rate of A3 ⇔︁ A4 interconversions in the diluted (≤0,1 mol · L‐1) C6D6, C6D6/εCL, and THF/εCL solutions were found to be slow, when compared with the rate of propagation. Comparison of the 1H NMR spectra of the initiators with those of the polymerization mixtures revealed that A3 is much more reactive than A4 in their reactions with εCL. From the initiator reacted with εCL all threeOiPr groups from Al(OiPr)3 are transferred into the poly(εCL) as end groups. Kinetic studies of polymerization confirmed the large reactivity difference between A3 and A4.
Structural correlation between the columnar mesophase and the melt in poly(di‐n‐alkylsiloxane)s
Authors: Out Gerardus J. J. , Turetskii Alexei A. , Möller Martin 
Published: April 2003

AbstractPhase transitions of poly(dialkylsiloxane)s substituted with propyl and butyl groups are reported based on X‐ray diffractometry. The structure in the mesophase and in the melt of polymers with 2 to 10 carbon atoms in each side chain is compared. Both phases display a linear dependence of the molecular cross‐section on the length of the alkyl group demonstrating their structural similarity. By means of differential scanning calorimetry it is shown that the temperature range of the mesophase remains practically unchanged in width as well as in absolute temperature for dibutyl up to dihexyl substituted polysiloxanes.
Copolymerization of ethylene and 1‐butene with highly active TI/MG bimetallic catalysts. Effect of partial activation by Alet2Cl
Authors: Kim Jae Ha , Han Taek Kyu , Choi Hong Ki , Kim Il , Woo Seong Ihl 
Published: April 2003

AbstractCopolymerization of ethylene and 1‐butene were performed using the catalyst system TiCl3 · 1/3 AlCl3/MgCl2/THF with or without partial activation by AlEt2Cl. The catalyst and the copolymers were characterized by IR spectroscopy. The experimental results reveal that partial activation strongly affects the catalytic sensitivity toward 1‐butene and obviously leads to a two‐step polymerization rate profile.
Fourier‐transform infrared study of the switching process in a ferroelectric liquid crystalline polymer
Authors: Shilov Sergej V. , Okretic Stefano , Siesler Heinz W. , Zentel Rudolf , Öge Tanja 
Published: April 2003

AbstractThe implementation of the step‐scan technique on our FT‐IR spectrometer enabled us to follow the electric‐field induced reorientation dynamics of different molecular segments of a ferroelectric liquid crystalline polymer on a sub‐millisecond time scale. It was detected that not only the mesogen but also the spacer and at least part of the backbone take part in the reorientation process.
Selective salt transport through a crosslinked poly(L‐glutamic acid) membrane for KCl/LiCl mixed systems
Authors: Huh Yang‐Il , Satoh Mitsuru , Komiyama Jiro 
Published: April 2003

AbstractSelective salt transport of KCl over LiCl has been studied for a crosslinked poly(L‐glutamic acid) membrane immersed in 80 vol.‐% ethanol. The permeabilities (Ps) and solubilities were measured for various mixing ratios of the salts. The highest permselectivity (Ps (KCl)/Ps (LiCl) = 4,3) has been obtained at a LiCl mole fraction of 0,2. It is similar to that obtained in single salt systems.
Semi‐rigid thermotropic liquid‐crystalline copolycarbonates comprising main‐chain hexafluoropentane segments
Authors: Sato Moriyuki , Tada Yuji , Goto Yusuke , Mukaida Ken‐ichi 
Published: April 2003

AbstractNovel semi‐rigid fluorocarbon‐containing coplycarbonates composed of biphenyl moiety and rigid rod‐like hexafluoropentane chain were prepared by melt polycondensation of 6,6′‐(biphenyl‐4,4′‐diyldioxy)dihexanol (1) and 2,2,3,3,4,4‐hexafluoro‐1,5‐pentanediol (2) with alkylene diphenyl dicarbonates 3 of various aliphatic lengths (m = 6, 8, 10 and 12). The structures of the copolymers 4 were confirmed by FT‐IR, 1H and 13C NMR spectra and elemental analyses. The thermal and liquid‐crystalline (LC) properties were examined by differential scanning calorimetry (DSC), polarizing microscopy and temperature‐changeable X‐ray analyses. These measurements indicated that the copolymers show well‐defined thermotropic nematic textures and have block‐like sequences. It is suggested that the introduction of the hexafluoropentane chain into the main chain gives more stable LC phases.
Structure of chain‐ends in polybutadiene produced with the CoBr2(PPh3)2/MgCl2/SiPh2(OCH3)2‐Al(CH3)3 catalyst system
Authors: Takeuchi Masaki , Shiono Takeshi , Soga Kazuo 
Published: April 2003

AbstractPolymerization of 1,3‐butadiene with the CoBr2(PPh3)2/MgCl2/SiPh2(OCH3)2‐Al(CH3)3 catalyst system was conducted in the presence of ethylene. It was found that addition of ethylene causes a marked decrease in the molecular weight of polybutadiene although ethylene is not incorporated at the chain‐end. The structure of chain‐ends was analyzed using very low molecular‐weight polybutadiene produced in the presence of ethylene, which led to the conclusion that 1,2 and 2,1 insertion reactions predominate at the initiation and propagation steps, respectively.
Anionic polymerization of β‐lactones initiated with potassium hydride. A convenient route to polyester macromonomers
Authors: Kurcok Piotr , Matuszowicz Andrzej , Jedliński Zbigniew 
Published: April 2003

AbstractThe anionic polymerization of 2‐oxetanone and 4‐methyl‐2‐oxetanone initiated with the potassium hydride/18‐crown‐6 complex was investigated. The α‐proton abstraction of the monomer was found to proceed at the initiation step of this polymerization. The salt of the unsaturated carboxylic acid formed initiates further propagation, leading to functionalized polyesters with unsaturated, dead end‐groups.