bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the chirality of polyvinyl compounds, 16. Optical activity of copolymers consisting of distyryl diads alternating with substituted maleimide or maleic anhydride units
Authors: Wulff G. , Krieger Stephan 
Published: April 2003

AbstractThe copolymerization of 3,4‐O‐cyclohexylidene‐D‐mannitol 1,2 : 5,6‐bis‐O‐[(4‐vinylphenyl)‐boronate] (M1) with different N‐substituted maleimides and with maleic anhydride has been studied. These monomers copolymerize in 1 : 1 proportion, yielding after removal of the template (3,4‐O‐cyclohexylidene‐D‐mannitol) copolymers with bis(4‐vinylphenylboronic acid) diads alternating with the other comonomeric unit. By deboronation these diads can be transformed to distyryl diads. These diads possess predominantly (S,S)‐configuration; thus optically active polymers with main‐chain chirality were produced. The chiroptical properties (optical rotation circular dichroism) of the copolymers were studied. Corresponding copolymers with maleic pride units can easily be transformed by polymer analogous reaction with nucleophiles, as exemplified by alcoholysis with fatty alcohols.
On the chirality of polyvinyl compounds, part 17. Investigations on main‐chain chiral copolymers with alternating structure
Authors: Wulff Günter , Krieger Stephan 
Published: April 2003

Abstract3,4‐O‐Cyclohexylidene‐D‐mannitol 1,2:5,6‐bis‐O‐[(4‐vinylphenyl)boronate] (M 1) was copolymerized with methyl methacrylate (MMA) in presence of AlEt1,5 or SnCl4. The expected alternating bis(4‐vinylphenylboronic acid)‐MMA triad structures were only formed to a lesser extent. Instead, predominantly alternating 4‐vinylphenylboronic acid‐MMA structures were obtained. Since no crosslinking was observed, a cyclocopolymerization must have occurred. In this case an MMA unit is inserted between the two styrene residues of M 1, thus forming a 21‐membered ring system. Copolymerization forming alternating 4‐vinylphenylboronic acid‐MMA diads is apparently even faster than the direct copolymerization forming distyryl diads. After removal of the template (3,4‐O‐cyclohexylidene‐D‐mannitol), these copolymers still show pronounced optical activity and circular dichroism with a negative Cotton effect at 233 nm. After deboronation of the copolymers, optically active, predominantly alternating styrene‐MMA copolymers are obtained.
Distribution of cyclized units present in isoprene oligomers synthesized by cationic oligomerization
Authors: Audisio Guido , Priola Aldo , Gozzelino Giuseppe , Mendichi Rainiero , Rubino Federico M. 
Published: April 2003

AbstractThe structure of isoprene oligomers synthesized by cationic oligomerization in the presence of the BF3 · H2O complex as an initiator in a hexane solution at 40°C was investigated. These oligomer fractions obtained with the degree of polymerization (DP) in the range 5‐12, and the completely hydrogenated oligomers were examined using the direct inlet system‐mass spectrometry (DIS‐MS) technique. The distribution of the cyclic and linear structures in the oligomers was obtained by integrating the selected ion current of the different hydrogenated products. The results obtained were interpreted by means of a statistical simulation based on a step‐by‐step competition between cyclization and monomer addition reaction. The value of the probability of cyclization was found to be very high for low‐molecular‐weight oligomers and to decrease with increasing molecular weight of the oligomers.
Poly(ether‐sulfone)s with indan structure elements
Authors: Maier Gerhard , Yang Dazhong , Nuyken Oskar 
Published: April 2003

AbstractVarious poly(ether‐sulfone)s with 1,1,3‐trimethylindan units along the main chain were synthesized from different diphenols and activated dihalogen monomers containing the 1,1,3‐trimethylindan moiety. The indan‐containing monomers were derived from 1,1,3‐trimethyl‐3‐phenylindan by sulfonylation with 4‐halobenzenesulfonyl chloride in the presence of the Friedel‐Crafts catalysts. The polymers are amorphous with glass transition temperatures between 206 and 247°C, and decomposition temperatures above 460°C in air. Due to their solubility in common organic solvents such as tetrahydrofuran and chloroform, the polymers could be fully characterized by gel‐permeation chromatography as well as 1H‐ and 13C NMR spectroscopy.
The influence of the catalyst preparation on the homo‐ and copolymerization of butadiene and isoprene
Authors: Oehme Annekatrin , Gebauer Ulrich , Gehrke Klaus , Beyer Peter , Hartmann Brigitte , Lechner M. Dieter 
Published: April 2003

AbstractThe catalyst system Nd(octanoate)3/Al2Et3Cl3/Al(iBu)3 (Et: ethyl, iBu: isobutyl) in heptane for the polymerization of butadiene and isoprene was examined. The concentration of Al2Et3Cl3, Al(iBu)3 and the order of addition of the components were varied. The results of the determination of conversion, microstructure, molar mass and molar mass distribution are illustrated. The optimum component concentration ratio (Nd(octanoate)3/Al2Et3Cl3/Al(iBu)3 = 1 : 1,5 : 25) at a catalyst concentration of 1,0 mmol Nd/L was fixed and used for the copolymerization of butadiene and isoprene. Copolymers obtained under various monomer feed ratios were characterized by 1H, 13C NMR spectroscopy, gel‐permeation chromatography (GPC), and differential scanning calorimetry (DSC) investigations.
Characterization of recast Nafion films by small‐ and wide‐angle X‐ray scattering
Authors: Halim John , Scherer Günther G. , Stamm Manfred 
Published: April 2003

AbstractRoom temperature recast NafionGeneral formula:
films, prepared under different humidities in the curing atmosphere, were characterized by small‐ and wide‐angle X‐ray scattering (SAXS and WAXS). SAXS reveals that the humidity influences the size of the ionic clusters in these polymer films. It was found that the number and size of ionic clusters increases with increasing relative humidity. WAXS indicates the presence of locally ordered regions of the backbone polymer. These results allow a qualitative understanding of the electrochemical behaviour of Nafion recast films cured at different humidities, as described in the literature.
Synthesis of novel chitin derivatives having poly(2‐alkyl‐2‐oxazoline) side chains
Authors: Aoi Keigo , Takasu Akinori , Okada Masahiko 
Published: April 2003

AbstractNovel chitin derivatives having poly(2‐alkyl‐2‐oxazoline) side chains, i.e., chitin‐graft‐poly(2‐methyl‐2‐oxazoline) (4a) and chitin‐graft‐poly(2‐ethyl‐2‐oxazoline) (4b), were synthesized by means of the reaction of ca. 50% deacetylated chitin (3) with living poly(2‐methyl‐2‐oxazoline) (2a) and poly(2‐ethyl‐2‐oxazoline) (2b), respectively. The reaction between amino groups of 3 and the oxazolinium active species of 2 was examined by changing molar ratios of the feed ([2]0/[D‐glucosamine units of 3]0, ranging from 1,0 to 9,9) under mild conditions (at 27°C in dimethyl sulfoxide (DMSO)). 4a having monodisperse poly(2‐methyl‐2‐oxazoline) side chains on almost every D‐glucosamine unit of the main chain was obtained in 35% yield. The number of poly(2‐alkyl‐2‐oxazoline) side chains was roughly controlled by the molar feed ratio of 2 and 3. 4 is soluble in water, N,N‐dimethylformamide, and DMSO, and partially soluble in methanol, acetonitrile, and chloroform. 4 shows improved solubilities in organic solvents, compared with 3 or chitin. The molecular motion of 4b in aqueous solution was discussed by employing 1H NMR analytical data measured with changing temperature and solvent. In D2O and, especially, in DMSO, it is suggested that motion of the chitin backbone is restricted, compared with that of the poly(2‐ethyl‐2‐oxazoline) side chain. The content of the side chain in 4 was calculated from the 1H NMR spectra recorded in D2O/CD3CO2D (vol. ratio 95:5) above 60°C.
Effect of ethoxy‐ and methoxysilane donors in propene/1‐hexene copolymerization with high‐yield supported Ziegler‐Natta catalysts
Authors: Fan Zhi‐Qiang , Forlini Fabrizio , Tritto Incoronata , Locatelli Paolo , Sacchi Maria Carmela 
Published: April 2003

AbstractThe effects of two alkoxysilane donors, triethoxyphenylsilane (PTES) and dimethoxydi‐tert‐butylsilane (DTBDMS), on the propene/1‐hexene copolymerization with MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) are compared. Two series of copolymers of different compositions were produced and the copolymers with the lowest hexene content, were fractionated. An analogous series, produced with the same catalyst without the use of an external donor, is the point of reference. All the fractions were characterized by 13C NMR. The data reported show that there is a noticeable difference in the behaviour of ethoxy‐and methoxysilanes in the copolymerization. The copolymers prepared with ethoxysilanes can be separated into fractions characterized by increasing isotacticity and decreasing comonomer content as long as the fractionation temperature increases. The copolymer obtained with DTBDMS is nearly completely isospecific while the comonomer content distribution is even wider than with ethoxysilanes. The sum of these data provides a deeper insight into the alkoxysilane activation mechanism.
Reaction of polystyryllithium and 2‐polystyryl‐1,1‐diphenyl‐ethyllithium with methyl acetate, methyl benzoate and the corresponding acyl chlorides
Authors: Zgonnik Vladimir , Melenevskaya Elena , Kever Jenö , Litvinova Larisa , Khachaturov Alexander , Terentieva Irina 
Published: April 2003

AbstractIn the course of the reaction of polystyryllithium (PSL) and 2‐polystyryl‐1,1‐diphenylethyl‐lithium (PSDPEL) with methyl acetate (MA), methyl benzoate (MB) and acetyl (ACI) and benzoyl (BCI) chlorides as coupling agents (CA), the quantity of the product of combination P2Y, where P2 corresponds to double molecular weight (MW) of the initial PS or PSDPE and the CA residue is referred to as Y, strongly depends on the nature of CA, and to a lower degree on the CA/PSL (PSDPEL) ratio and the nature of the solvent (benzene or THF). The maximum yield of P2Y from the reaction of MA and PSL did not exceed 80%, and 12% for MA and PSDPEL. It was shown using CD3COOCH3 and 500 MHz NMR that this incomplete conversion is due to a side reaction of PSL or PSDPEL with the D(H) atoms of the methyl group of MA, proceeding simultaneously with the main reaction and yielding PSD(H) or PSDPED(H). Using a special approach, the polymeric ketone corresponding to the first stage of this reaction can be obtained; its yield was in the case of PSL and MA higher than 50%. For the PSDPEL‐MA system, the product of the reaction, based on NMR data, consists of approximately equal portions of the polymeric ketone and the product resulting from the side reaction, i.e., PSDPE‐H. In the latter case the sterically hindered polymeric ketone did not react with excess PSL or PSDPEL. Products of the reaction of PSL or PSDPEL with MB dit not contain PSH or PSDPEH, respectively.
The influence of thermal history on water associated with polyelectrolytes and cellulose
Authors: Hofmann Klaus , Hatakeyama Hyoe 
Published: April 2003

AbstractThe formation of freezing water as a function of temperature and time has been studied in polyelectrolytes and in cellulose. In such systems, a portion of the sorbed water is not crystallizable under normal conditions. However, it was observed that in rapidly cooled systems the ratio between freezing and non‐freezing water is variable and depends on the annealing temperature. The difference between the saturated concentration of freezable water and the concentration of freezing water which is formed immediately after the rise of the sample's temperature is dependent on the materials geometry. It is assumed that the rise of the annealing temperature above room temperature increases the amount of mobile water which can crystallize. By comparing the measured concentration of freezing water with desorption analysis, the average distance of transportation of mobile water for sodium carboxymethylcellulose was calculated as 8–10 μm.
Polymer‐bound porphyrins and their precursors, 11. Syntheses and polymerization of methacryloyloxy and 2,4‐hexadienoyloxy derivatives of porphyrins and phthalocyanines
Authors: Eichhorn Holger , Sturm Michael , Wöhrle Dieter 
Published: April 2003

AbstractThe syntheses of tetraphenylporphyrins 1b, d, e containing four methacryloyloxy or 2,4‐hexadienoyloxy substituents and phthalocyanines 2b, d containing four methacryloyloxy substituents are described. Copolymerizations with styrene in solution were investigated in detail, and the compositions and molecular weights of the copolymers were determined. In addition, homopolymerizations in solution were carried out. After coating on quartz or KBr plates, the thermal and photochemically induced homopolymerizations were investigated fundamentally.
Photopolymers for non‐linear optics: Design and synthesis of a polymer containing styrene‐terminated tolane chromophores and its stabilization in an oriented configuration by photocrosslinking
Authors: Godt Adelheid , Fréchet Jean M. J. , Beecher Jody E. , Willand Craig S. 
Published: April 2003

AbstractA new photocrosslinkable polymer designed for application in second harmonic generation has been prepared and tested for frequency doubling of IR lasers. The polymer is based on a colorless polyurethane with pendant tolane nonlinear optical chromophores that carry a polymerizable styrene moiety at their extremities. Photocrosslinking is achieved by irradiation of films containing a small amount of a bleachable radical photoinitiator. The effect of photoinduced radical crosslinking on the mobility of the chromophores has been studied by recording the intensity of the frequency doubled light, generated by a poled sample, with increasing temperature. As expected, photocrosslinking leads to NLO materials with highly stable chromophore orientation.
Polysilanes fonctionnels, 4. Duplication réductrice de chlorosilanes par le lithium pour la synthèse d'α,ω‐bis(triméthylsilyl) oligo(méthylphénylsilane)s. Réactions parasites de silylation des noyaux phényle
Authors: Reyx Danièle , Martins José Manuel Natário , Campistron Irène , Noireaux Patrick 
Published: April 2003

AbstractThe coupling of dichloromethylphenylsilane (1) with chlorotrimethylsilane (2) by lithium is considered for the synthesis of low‐molecular‐weight organosilane polymers 3 and for the preparation of heptamethylphenyl‐2‐trisilane (3a) and octamethyldiphenyl‐2,3‐tetrasilane (3b). Size‐exclusion chromatography, ultraviolet and infrared spectroscopies and nuclear magnetic resonance (1H, 13C and 29Si NMR) analyses of the crude product 3 were performed and compared with those of 3a and 3b. According to the spectroscopic characteristics of heptamethyltetrakis(trimethylsilyl)‐3,4,5,6‐cyclohex‐1‐enyl‐2‐trisilane (4), and the observed silylation of the trisilane 3a when it is submitted to the action of a (CH3)3SiCl/Li/tetrahydrofuran system, the silylation of the phenyl ring during the reductive condensation of the chlorosilanes is supported by NMR identification of 4‐like structures.
Synthesis and characterization of liquid crystalline polysiloxanes with “two‐chain” diol units in the side chain
Authors: Schellhorn Matthias , Lattermann Günter 
Published: April 2003

AbstractThe synthesis and the thermal behaviour of different polysiloxanes containing cis,cis‐(3,5‐dihydroxycyclohexyl) 3,4‐bis(alkoxy)benzoate mesogens (“two‐chain” diol unit) in the side chain are described. Aggregation via intermolecular hydrogen bonding between different “two‐chain” diol units leads to the formation of mesomorphic supramolecular structures. The phase behaviour changes drastically by variation of the dimethylsiloxane content of the backbone. Thus, the homopolysiloxane is the first example of a polymer with a thermotropic cubic mesophase, being observed below a hexagonal columnar one. However, the copolymers exclusively form the hexagonal columnar mesophase. The thermal transitions of all polymers, investigated by means of differential scanning calorimetry (DSC) as well as by polarizing microscopy, are discussed. The mesophase structures have been determined by X‐ray measurements in combination with miscibility studies.
Poly(α‐butyl β‐L‐aspartate): A second alkoxycarbonyl nylon‐3 derivative in helical conformation
Authors: López‐Carrasquero Francisco , Alemán Carlos , García‐Alvarez Montserrat , de Ilarduya Antxon Martínez , Muñoz‐Guerra Sebastián 
Published: April 2003

AbstractA structural study was carried out on poly(α‐butyl β‐L‐aspartate), which is a stereoregular nylon‐3 derivative with an alkoxycarbonyl group attached to the β‐carbon of the main‐chain repeating unit. Two crystal forms, namely hexagonal and tetragonal, made of 13/4 and 4/1 helices, respectively, and bearing a structural resemblance to the polypeptide α‐helix, were characterized by X‐ray diffraction. Though these forms are basically identical to those previously reported for poly(α‐isobutyl β‐L‐aspartate), the crystal transition from hexagonal to tetragonal known to take place in this polymer by effect of heating, was not observed in the present case. Modeling calculations revealed that although similar conformations are favoured for the two polymers in both crystal forms, the relative stability of the 13/4 helix to the 4/1 helix was found to be significantly reduced in the case of the butyl derivative. The presence of helical conformation in solution has been evidenced by both 1H NMR and circular dichroism and the helix‐coil transition promoted by acids was investigated by means of these techniques.
Copolymers of N‐vinyl‐2‐pyrrolidone and 2‐(dimethylamino)ethyl methacrylate, 2. Quaternization with octyl bromide — kinetic studies
Authors: Deboudt Karine , Delporte Michèle , Loucheux Claude 
Published: April 2003

AbstractN‐Vinyl‐2‐pyrrolidone — 2‐(dimethylamino)ethyl methacrylate copolymers were quaternized with octyl bromide in tetramethylene sulfone. The quaternization kinetics was studied, varying the concentrations of reagents and the composition of copolymers. The initial rate constant is not disturbed by the concentration of reagents, but it is by the initial copolymer composition: the higher the initial octyl bromide concentration, the higher the maximal conversion rate. These kinetic results were interpreted, observing the influence of the steric effect, the electrostatic effect and the effect of solvation. The kinetic models proposed in the literature were applied to our data and discussed. None of them describes perfectly the behaviour of our system.
Nonlinear optically active polymethacrylates with high glass transition temperatures
Authors: Eckl Martin , Müller Harry , Strohriegl Peter , Beckmann Stefan , Etzbach Karl‐Heinz , Eich Manfred , Vydra Jan 
Published: April 2003

AbstractA number of novel nonlinear optically (NLO) active polymethacrylates were prepared from the NLO active methacrylates 2a–d with azobenzene side groups and the bulky comonomer 1‐adamantyl methacrylate. The polymers exhibit unusually high glass transition temperatures between 160°C and 190°C. The copolymerization parameters of the monomer pair 1‐adamantyl methacrylate (1)/Disperse red methacrylate 2b (r1 = 1,1 ± 0,2, r2 = 0,8 ± 0,2) show that the two monomers are incorporated almost statistically into the polymer chain. Polymers 3a–d are soluble in common organic solvents and excellent films can be obtained by spin coating. After poling in an electric field of 120 V/μm polymer 3b shows a large electrooptic (EO) coefficient (r33) of 25 pm/V at 633 nm. Within two weeks, only a negligible decay of 7% of the EO coefficient was observed at room temperature. On‐line monitoring of the second harmonic generation (SHG) at 100°C showed a fast initial drop (10%) of the SHG signal and subsequently a slow decay of 20% within 10 h. Afterwards, the signal remained almost constant for further 5 h at 100°C. The novel polymers can thus be considered as easy processible NLO materials with a high thermal stability of the chromophore orientation obtained by poling.
Linear cyclodextrin‐containing polyelectrolytes, 1. Synthesis of poly(1‐vinylimidazole)‐supported β‐cyclodextrin. Effect of pH and ionic strength on the solution behaviour
Authors: Deratani André , Pöpping Barbara , Muller Guy 
Published: April 2003

AbstractA series of linear weak polyelectrolytes containing β‐cyclodextrin pendant groups was synthesized by chemical modification of poly(1‐vinylimidazole). Studies on their solution behaviour as a functon of pH and the nature and ionic strength of added salts showed original features which are explained in terms of competitive residue‐residue and residue‐solvent interactions and anion binding to cyclodextrin moieties.
Enthalpies of dilution of the system lignin‐dimethyl sulfoxide at 298,15 K
Authors: Bogolitsyn Konstantin G. , Volkova Natalia N. 
Published: April 2003

AbstractEnthalpies of dilution of two samples of Björkman's lignin in dimethyl sulfoxide (DMSO) were determined calorimetrically at the temperature 298,15 K. Enthalpies were derived for infinitely dilute solutions.
Diene polymerization by mixed sodium‐ and lithiumalkyl initiators in hydrocarbon medium
Authors: Pakuro Natalia I. , Zolotareva Irina V. , Kitayner Alla G. , Rogozhkina Elena D. , Izyumnikov Anatoliy L. , Arest‐Yakubovich Alexander A. 
Published: April 2003

AbstractPolymerization of butadiene and isoprene initiated by the hydrocarbon‐soluble mixture 2‐ethylhexyllithium/2‐ethylhexylsodium in toluene was studied. The components of the initiator when taken separately give rise to polymers greatly different in both their molecular weight and microstructure: living polydienes with high 1,4‐unit content are formed when alkyllithium is used while organosodium initiators produce polymers of high 1,2(3,4)‐structure and of low molecular weight due to strong chain transfer to toluene. Polymers obtained with mixed initiators were found to have the same structure as the “sodium” ones, while their molecular weights are either the same as those of the polymers obtained with alkyllithium alone (in the case of butadiene) or decrease gradually with increase of sodium content in the initiator (in the case of isoprene). The calculations performed show that the simple scheme assuming chain propagation through individual lithium and sodium active centres and fast exchange of counter‐ions between them cannot explain the results obtained. It is suggested that the true active centres in mixed systems are bimetallic complexes containing both sodium and lithium atoms simultaneously.
Synthesis of poly(N‐vinylcarbazole)‐graft‐polyisoprene
Authors: Ishikawa Satoshi 
Published: April 2003

AbstractWell defined poly(N‐vinylcarbazole)‐graft‐polyisoprenes were synthesized by reaction between the chloromethyl group of chloromethylated poly(N‐vinylcarbazole) and living polyisoprene (PIP) anions. The obtained graft copolymers were characterized by gel‐permeation chromatography, NMR, and IR spectra. The reaction was not complete (unreacted chloromethyl groups were found) because of hindrance effects of the polyisoprene chain.