bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermolysin‐catalyzed peptide synthesis in aqueous polymer two‐phase systems
Authors: Kitano Hiromi , Maeda Yasushi , Yamamoto Masayo , Izumida Rie 
Published: April 2003

AbstractA proteolytic enzyme, thermolysin, was covalently immobilized to dextran which has a small number of carboxyl groups. Enzymatic synthesis of aspartame derivative (Boc‐Asp‐Phe‐OMe) using the dextran‐conjugated thermolysin was carried out in an aqueous polymer two‐phase system, where poly(ethylene glycol) (PEG) and dextran dissolved in water make a phase separation. The yield of the peptide catalyzed by the dextran‐conjugated thermolysin was higher than that using a native enzyme in the aqueous polymer two‐phase system partly due to the effect of the microenvironment around the modified enzyme and partly due to the “mass‐law” effect (the preferential dissolution of the peptide product into the PEG phase). The aqueous polymer two‐phase system would be very useful to carry out enzymatic organic syntheses in high yields.
Copolymerization of styrene and 1‐butene with a novel MgCl2‐supported Ti catalyst
Authors: Gao Feng , Lin Shangan 
Published: April 2003

AbstractCopolymerization of styrene and 1‐butene was first conducted at 50°C with a novel Ti catalyst by using Al(iBu)3 (iBu = isobutyl) as cocatalyst. The Ti catalyst is composed of MgCl2/TiCl4/PhCOOEt/Ph2SiCl2/SiCl4/NdClx(OR)y/Al(iBu)3 (assigned as SN‐1 catalyst), which gave mixtures of poly(1‐butene), polystyrene, and a copolymer of both monomers. The catalytic efficiency is 1 200 ‐ 4 000 gp/(gTi · h). The monomer reactivity ratios were estimated to be rs = 0.47 and rb = 29.1. The polymers produced were fractionated successively, and a styrene‐1‐butene copolymer was obtained which was characterized in detail.
Photoresponse of polymethacrylamides bearing 1,3‐diphenyl‐2‐propen‐1‐one (chalcone) functions in the side chains
Authors: Goretzki Christian , Ritter Helmut 
Published: April 2003

AbstractSynthesis and free radical polymerization of 1‐(4‐methacryloylaminophenyl)‐3‐phenyl‐2‐propen‐1‐one (2), 1‐[4‐(6‐methacryloylaminohexanoylamino)phenyl]‐3‐phenyl‐2‐propen‐1‐one (7) and 1‐[4‐(11‐methacryloylaminoundecanoylamino)phenyl]‐2‐propen‐1‐one (8) are described. The monomers and a model compound (1) were characterized by NMR and IR spectroscopy. The corresponding homopolymers (9–11) and a copolymer with methyl methacrylate (12) were characterized by DSC, GPC and TG analysis and also spectroscopically. Furthermore, the kinetics of E/Z‐isomerisations and [2 + 2] cycloadditions of chalcone functions in the polymers and the model compound were examined.
X‐ray investigation on melt‐crystallized bacterial poly(3‐hydroxybutyrate)
Authors: Gazzano Massimo , Tomasi Gianpaolo , Scandola Mariastella 
Published: April 2003

AbstractFilms of bacterial poly(3‐hydroxybutyrate), obtained by crystallization from the melt at different temperatures up to 120°C, were investigated by powder X‐ray diffraction analysis and optical microscopy. With increasing crystallization temperature (Tc) the diffraction patterns differed more and more from that of the “as received” powder in both relative intensity of the reflections and peak width. The relative peak intensities also varied in response to temperature changes of the melt from which the polymer was quenched to a selected Tc. The differences in the X‐ray diffraction patterns were correlated with changes of average spherulite size (0.1 mm to 2 mm) in films with limited thickness. When the spherulites were large the lamellar crystals were strongly oriented parallel to the film plane. Full profile Rietveld analyses allowed to quantify the preferred orientation effect and to extract additional morphological and structural informations.
Aggregation behavior and interaction with human serum albumin of 2‐oxazoline block copolymers in aqueous solutions
Authors: Naka Kensuke , Nakamura Tohru , Ohki Akira , Maeda Shigeru 
Published: April 2003

AbstractThe structure of the aggregates of block copolymers containing poly[(N‐acetylimino)ethylene] as hydrophilic block and poly[(N‐acylimino)ethylene]s as hydrophobic block was studied by size exclusion chromatography, dynamic light scattering, and transmission electron microscopy. The morphology of the aggregates, consisting of spherical and rod‐like micelles, depends on the chemical structure of the block copolymers. The adsorption behavior of human serum albumin (HSA) onto each polymer aggregate was studied by size exclusion chromatography. The maximum amount of HSA bound onto the polymer aggregates depends on the morphology of the polymer aggregates. Adsorption isotherms of HSA for each polymer aggregate are in good agreement with a Langmuir adsorption isotherm. The amount of HSA adsorbed onto the aggregates is not influenced by the fatty acid content in HSA. The electrophoretic mobility of the aggregates without HSA is close to zero, and the negative mobility increases when HSA is incorporated into the aggregates. The experimental results suggest that adsorption of HSA to the aggregates occurs mainly at the surface or at the hydrophilic shell of the polymer aggregates, not at the hydrophobic core of the polymer micelles.
Synthesis of new polymers involving deltahedral carborane units
Authors: Vohlídal Jiří , Vangani Veena H. , Plešek Jaromír , Rajabi Farzaneh H. , Blechta Vratislav , Němec Ivan 
Published: April 2003

AbstractAminocarboranes nido‐7‐NH3+‐(7‐CB10H12)− and closo‐1‐NH3+‐(CB11H11)− were copolymerized with α,ω‐dihalogenoalkanes to high‐molecular‐weight alternating copolymers. The nido‐compound copolymer was crosslinked by means of sandwiching two open cages with CoIII ion yielding bis(monocarbollide)‐cobaltate(III) units as the new type knot points. Metallacarboranes, 1,1′‐diaminobis(monocarbollide)nickelate(IV) and two bridged bis(dicarbollide)cobaltates(III) (8,8′‐μ‐imino‐ and 8,8′‐μ‐oxyimino‐), have provided hemipolymers of molecular weight up to a few thousands in the same type of copolymerization. A new methacrylic‐type monomer was prepared by reaction of glycidyl methacrylate with 8,8′‐(μ‐imino)‐(1,2‐C2B9H10)‐3‐CoIII and copolymerized with methyl methacrylate to high‐molecular‐weight statistical copolymers.
Physical ageing phenomena in poly(tert‐butylacetylene): influence of the microstructure
Authors: Costa Giovanna , Chikhaoui Saida , Turturro Antonio , Carpaneto Luca 
Published: April 2003

AbstractAgeing phenomena in cast films of poly(tert‐butylacetylene) (PTBA) of different tacticity were studied by dilatometric and calorimetric techniques and by morphological observations. Films of different density (p) obtained by varying solvent evaporation times, both from cis/trans or 100% cis PTBA, show during the first dilatometric run the presence of a temperature Tp at which a packing effect occurs. Therefore, first dilatometric curves show two linear tracts, the latter representing the sum of thermal dilation and simultaneous packing induced by molecular motions leading to a better packing. Following measurements show a linear increase of the specific volume. The packing process is also revealed by differential scanning calorimetry as a broad endotherm. Δρ is the more pronounced the lower the initial density of the sample for mixed cis/trans PTBA, but, quite surprisingly, in 100% cis PTBA the trend is opposite and, in this case, denser samples undergo a more relevant packing. A tentative explanation is inferred on the basis of a conformational model recently proposed. An improvement of the chain packing is responsible of the fast ageing process of this polymer, as suggested by a preliminary X‐ray diffraction analysis.
ω‐Chloro‐α‐olefins as co‐ and termonomers for the synthesis of functional polyolefins
Authors: Bruzaud Stéphane , Cramail Henri , Duvignac Laurent , Deffieux Alain 
Published: April 2003

AbstractThis paper deals with the use of ω‐chloro‐α‐olefins as monomers for the synthesis of chloro‐functional homo‐, co‐ and terpolyolefins in the presence of (IVb) metallocene/MAO catalytic systems. Two ω‐chloro‐α‐olefins, 11‐chloroundec‐1‐ene and 5‐chloropent‐1‐ene, were tested. It was found that only the functional olefin containing the longer aliphatic spacer between the alkene function and the halide polymerizes readily in the presence of the rac‐Et(Ind)2ZrCl2/MAO catalyst. The drastic influence of the reaction solvent on the chloro‐olefin reactivity and (co)polymerization behavior is examined and discussed. Finally, the terpolymerization of 11‐chloroundec‐1‐ene with ethylene and propene is investigated. In a second part, the quantitative preparation, by derivatization of 11‐chloroundec‐1‐ene units, of functional polyolefins bearing benzoate, hydroxy or azido functions as side groups is described. The corresponding functional polymers are characterized by IR and 1H NMR spectroscopy.
Ni‐catalyzed dehalogenation polycondensation of dihaloaromatic compounds with NaH
Authors: Yamamoto Takakazu , Hayashida Naoki , Maruyama Tsukasa 
Published: April 2003

AbstractNi‐catalyzed dehalogenation polycondensation of p‐dichlorobenzene, 2,5‐dichloropyridine, and 1,4‐dialkoxy‐2,5‐dichlorobenzene in the presence of NaH affords corresponding π‐conjugated poly(arylene)s in high yields. In this polymerization system, Ni(II)‐compounds used as the catalyst are considered to be reduced to Ni(0)‐complexes by NaH, and the Ni(0)‐complexes are regarded to be responsible for the polycondensation. The π‐conjugated poly(arylene)s obtained have well‐defined linkages between the monomer units as revealed by NMR spectroscopy. Poly(2,5‐diethoxybenzene‐1,4‐diyl) (PEOP) and poly(2,5‐dibutoxybenzene‐1,4‐diyl) (PBOP) have number‐average molecular weights (Mn) of 4300 and 11 000 as determined by GPC (vs. polystyrene), respectively. The chemical and electrochemical properties of resulting polymers are discussed in comparison with those of corresponding poly(arylene)s reported previously.
Influence of branching on melting behavior and isothermal crystallization of poly(butylene terephthalate)
Authors: Righetti Maria Cristina , Munari Andrea 
Published: April 2003

AbstractThe melting behavior and the isothermal crystallization kinetics of linear and randomly branched poly(butylene terephthalate)System. name: poly(tetramethylene terephthalate).
(PBT) samples were investigated by differential scanning calorimetry. The multiple endotherms typical of linear PBT were observed also in branched samples and were found to be influenced both by temperature and degree of branching. The isothermal crystallization kinetic constants, obtained applying Avrami's treatment, were analysed on the basis of Hoffman's secondary nucleation theory. A decrease in the crystallization rate was observed as the content of branching units increased. This result was correlated to surface effects: the product of the surface free energies σσe was found to increase with the ramification content. As far as the nucleation process is concerned, the induction time was determined for all the samples at different crystallization temperatures, and the results suggested that in the presence of branching points the nucleation process is favoured.
Synthesis and characterization of poly[(2,6‐dimethyl‐1,4‐phenylene oxide)‐block‐isoprene] diblock copolymers
Authors: Servens Emmanuelle , Löwik Dennis , Bosman Anton , Nelissen Laurent , Lemstra Piet J. 
Published: April 2003

AbstractAs a first stage in the synthesis of a new class of thermoplastic elastomers, a suitable synthetic route for elastomeric tailor‐made diblock copolymers based on poly(2,6‐dimethyl‐1,4‐phenylene oxide), PPE, as the thermoplastic block and on 1,4‐polyisoprene, PIP, as the elastomeric block, is outlined. The 2,6‐dimethyl‐1,4‐phenylene oxide‐block‐isoprene diblock copolymers were synthesized via an amidation coupling route between the ammonium salt of PPE and the monocarboxylic acid of PIP in the presence of dicyclohexylcarbodiimide, DCC. Preliminary studies were focused on the synthesis of a welldefined low molar mass diblock copolymer (Mn = 10000) in order to facilitate the quantitative characterization by proton NMR spectroscopy. The developed amidation coupling route was successively applied to the synthesis of a similar diblock copolymer with a number‐average molar mass of 40000 in order to obtain optimum overall properties.
Partially fluorinated maleimide copolymers for Langmuir films of improved stability, 1. Synthesis, copolymerisation behaviour and bulk properties
Authors: El‐Guweri Moheddin , Hendlinger Peter , Laschewsky André 
Published: April 2003

AbstractVarious new partially fluorinated polymers on the basis of substituted N‐phenylmaleimides are prepared by radical copolymerisation. Nearly alternating copolymers are produced with vinyl ethers and styrene derivatives. The copolymers show high stability against thermal degradation in comparison to conventional vinyl and vinylidene polymers, and high glass transition temperatures. Highest thermal stability is found for copolymers in which the classical hydrophilic and hydrophobic fragments are reduced to a minimum.
Cationic coating polymerization of cyclopentadiene onto silica particles
Authors: Spange Stefan , Langhammer Elke 
Published: April 2003

AbstractThe cationic polymerization of cyclopentadiene (CPD) initiated by different initiators (triphenylmethyl chloride, triphenylmethyl bromide, methyl triflate, and trifluoroacetic acid) onto silica particles yields polycyclopentadiene (PCPD)‐silica composites in high yield beside small amounts of soluble polymers. The novel PCPD‐silica particles are characterized by UV/VIS reflectance spectra and IR spectra. The percentage of coating (PG) is determined by combustion analysis and depends on the reaction temperature and the technical procedure of the polymerization. The influence of the initiator used and initiator/monomer ratio on the PG of the silica particles are investigated, too. It can be shown that the total amount of coating strongly depends on the initiator used. In case of trifluoroacetic acid initiation, particle aggregation takes place if the carbon content of the PCPD particles exceeds 15% carbon weight due to crosslinking between the PCPD layers of the coated silica particles, as evidenced by electron scanning microscopy.
Influence of polymer/solvent acid‐base interactions on the aggregation of stereoregular PMMA
Authors: Bistac Sophie , Schultz Jacques 
Published: April 2003

AbstractStereoregular poly(methyl methacrylate) (PMMA) is able to form aggregates in solution. This aggregates formation depends strongly on the nature of the solvent, and occurs only with complexing solvents. The influence of the solvent type on the aggregate formation is not yet clarified. Apparently, there is no obvious relationship between the solvent polarity and the ability to induce aggregation of PMMA chains. In the present work, based on bibliographic studies, we tend to prove that the formation of aggregates depends, among other parameters, on the development of acid‐base interactions between PMMA chains and the solvent molecules. As a matter of fact, the PMMA is considered as a basic polymer, and exchanges strong acid‐base interactions with acidic solvents, like chloroform, which is a non‐complexing solvent. Such acid‐base links prevent PMMA macromolecular chains to aggregate. On the contrary, complexing solvents exhibit a basic character, like PMMA. Therefore, the probability to develop PMMA/solvent acid‐base interactions is strongly reduced. As a consequence, aggregation of PMMA chains is then favoured.
Crosslinked polyimide foams derived from poly(imidepropylene oxide) copolymers
Authors: Hedrick J. L. , Carter K. , Sanchez M. , Di Pietro R. , Swanson S. , Jayaraman S. , McGrath J. G. 
Published: April 2003

AbstractA new route for the synthesis of high glass transition temperature, thermally stable polymer foams has been developed, using compositionally asymmetric microphase‐separated block copolymers where the minor component (poly(propylene oxide)) is thermally labile and the major component (polyimide) is thermally stable. The minor component decomposes to low molecular weight species upon heating, and the decomposition products diffuse out of the film, leaving behind pores embedded in a matrix of the thermally stable component. In this study, the polyimide block was crosslinked with ethynyl functionalities to obtain a stable porous structure. The decomposition of the propylene oxide in the block copolymer was studied by thermogravimetric, dynamic mechanical and thermomechanical analyses. Mild conditions were required to avoid rapid depolymerization of the propylene oxide and plasticization of the polyimide matrix. The foams showed pore sizes with diameters up to a micrometer in size as well as the expected reduction in the mass density.
Structure and properties of high‐speed spun fibers of nylon 6
Authors: Murase Shigemitsu , Kashima Masaru , Kudo Kazushige , Hirami Matsuo 
Published: April 2003

AbstractStructure and properties of high‐speed spun fibers of nylon 6 were studied in the range of take‐up speeds from 5 to 12 km/min. With increasing take‐up speed, Young's modulus increased uniformly, while tenacity passed through a maximum at 8 km/min. WAXD data demonstrated the increase in the perfectness of the crystalline state with increasing take‐up speed. First, the γ‐form crystal structure predominated up to 9 km/min along with increase in its crystal size; second, in the range of 9 to 12 km/min, the a‐form crystal structure appeared and developed as reflected by the increase in its crystal perfection. The structure‐properties relationships are discussed, and it is indicated that the increasing tendency of Young's modulus over 9 km/min can be attributed to the development of the a‐form crystals.
Crosslinkable epichlorohydrin terpolymers with aromatic pendent groups
Authors: Reina José Antonio , Cádiz Virginia , Serra Angels 
Published: April 2003

AbstractPoly(epichlorohydrin) (PECH) and poly[epichlorohydrin‐co‐(ethylene oxide)] (PECH‐PEO) were modified with several aromatic carboxylates (benzoate, 4‐(allyloxy)benzoate, 4‐(5‐hexenyloxy)benzoate, 3‐(allyloxy)‐2‐naphthoate, 3‐(5‐hexenyloxy)‐2‐naphthoate and 2‐(allylthio)nicotinate) under solid‐liquid phase transfer conditions to obtain crosslinkable terpolymers with well‐separated double bonds and a low chlorine content. Simultaneously to the substitution reaction, cleavage and crosslinking reactions take place. Most of these polymers were crosslinked by treating a mixture of them with 10 wt.‐% dicumyl peroxide (bis(‐1‐methyl‐1‐phenylethyl) peroxide). In some cases it was more suitable to use 10 wt.‐% 2,2′‐azoisobutyronitrile as initiator, although it always gave low degrees of crosslinking. Arrhenius kinetic parameters could only be determined for crosslinking processes promoted by dicumyl peroxide.
Preparation and characterization of fluorine‐containing aromatic condensation polymers, 5. Aromatic polybenzimidazoles from 4,4′‐(hexafluoroisopropylidene)dibenzoic acid and aromatic tetramine tetrahydrochlorides
Authors: Saegusa Yasuo , Horikiri Masahiro , Nakamura Shigeo 
Published: April 2003

AbstractTwo novel fluorine‐containing aromatic polybenzimidazoles were synthesized by direct polycondensation of 4,4′‐(hexafluoroisopropylidene)dibenzoic acid with 3,3′‐diaminobenzidine tetrahydrochloride and 1,2,4,5‐benzenetetramine tetrahydrochloride. The effect of introduction of fluorine on the synthesis and properties of these polymers is discussed. The new polybenzimidazoles show good solubility in organic solvents, excellent mechanical properties and high thermal stability.
Synthesis and ion‐coupling reactions of telechelic polystyrene having cyclic onium salt groups
Authors: Tezuka Yasuyuki , Imai Hiroshi , Shiomi Tomoo 
Published: April 2003

AbstractA series of mono‐ and bifunctional polystyrenes (1 c and 1′c) having 1‐methylpyrrolidinium salt end groups were prepared through sequential derivatization, i.e., tosylation and quaternization reactions, of prepolymers having 3‐hydroxypropyl groups (1 a and 1′a) produced by end‐capping reactions of the relevant living polymers. The 1‐methylpyrrolidinium salt end group was found to undergo a selective ring‐opening reaction at 100°C by nucleophilic attack of a benzoate counter anion introduced by ion‐exchange reaction. The ion‐coupling reaction of 1 c and 1′c with poly(styrene‐co‐acrylate salt) was found to take place upon coprecipitation of an equimolar mixture into methanol to afford ionically linked pseudo‐graft and network products, respectively. The subsequent heat treatment, converting the ionic bond into a covalent one, results in branched and crosslinked polystyrene with predetermined structural parameters.
Synthesis and characterization of new polyquinolines having terdendate N‐N‐N or N‐C‐N binding sites in the main backbone
Authors: Mamo Antonino , Stefio Ivan 
Published: April 2003

AbstractBy reacting the monomer 4,4′‐diamino‐3,3′‐bis(p‐methoxybenzoyl)diphenyl sulfide with 4,4′‐diacetyldiphenyl sulfide and alternatively, with 2,6‐diacetylpyridine or 1,3‐diacetylbenzene in a m‐cresol/di‐m‐cresyl phosphate medium, six new polyquinolines having terdendate N‐N‐N or N‐C‐N binding sites in the main backbone were obtained. The lower is the number of binding sites present in the main backbone the higher is the degree of rigidity of the resulting polymers. 1H nuclear magnetic resonance (NMR) and infrared (IR) spectral data support the structure of the synthesized polymers. Thermal analysis data confirm the good thermal stability of this class of polymers. Two examples of macromolecular complexes with Os++ are also reported.
Synthesis and characterization of polyphosphazene homopolymers and copolymers
Authors: White Michael L. , Matyjaszewski Krzysztof 
Published: April 2003

AbstractThe preparation of polyphosphazene random and block copolymers bearing trifluoroethoxy and alkoxyalkoxy groups by the anionically initiated polymerization of phosphoranimines and poly(diarylphosphazene)s from phosphine azide intermediates is discussed. The properties of these materials were studied by differential scanning calorimetry, wide‐ and small‐angle X‐ray scattering, thermogravimetric analysis, dynamic mechanical analysis, dielectric relaxation spectroscopy, single crystal X‐ray and electron diffraction, density measurements and optical microscopy, and were correlated with molecular architecture, molecular weight, composition and side groups structure.
Synthesis of C60‐capped vinyl ether oligomers by living cationic polymerization technique
Authors: Okamura Haruyuki , Minoda Masahiko , Komatsu Koichi , Miyamoto Takeaki 
Published: April 2003

AbstractThis study concerns the synthesis of C60‐capped vinyl ether (VE) oligomers with well‐defined structure by living cationic polymerization technique. The VE oligomers bearing C60 at the chain end were prepared by addition reaction between monoocynylfulleride anions and living cationic VE oligomers. Living oligo(isobutyl vinyl ether) (IBVE) and oligo(methyl vinyl ether) (MVE) were synthesized using CH3CH(OiBu)Cl/ZnI2 as initiating system. The C60‐capped VE oligomers were obtained as dark brown gummy solid in 28% for IBVE and 34% for MVE. The UV/VIS and 13C NMR spectra indicated the formation of C60‐capped oligomers via 1,2‐addition reaction. It was also found that the films of blends of C60‐capped oligomers with poly(IBVE) and polystyrene (5 wt.‐% C60) are homogeneous on a micron scale and transparent, resulting from a good dispersion of C60 in the polymer matrix.