bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis, structure‐property relations and lyotropic behavior of perfluoroalkyl‐substituted para‐linked aromatic polyamides
Authors: Hatke Wilfried , Schmidt Hans‐Werner
Published: April 2003

A series of perfluoroalkyl‐containing para‐linked aromatic polyamides based on trifluoromethyl‐p‐phenylenediamine and a mixture of trifluoromethyl‐ and pentafluoroethyl‐substituted terephthalic acid have been synthesized. The polyamides were prepared by a low temperature solution polycondensation of aromatic diacyl chlorides with N,N′‐bis(trimethylsilyl)‐substituted aromatic diamines. The influence of these perfluoroalkyl substituents on thermal properties, solubility and lyotropic behavior is discussed. 19F NMR spectroscopy was utilized for molecular weight determination and for further examination of the polymer structure.
Synthesis and dielectric characterization of poly[acrylonitrile‐co‐acrylamide‐co‐(acrylic acid)] terpolymer gels
Authors: Hu David Shiaw‐Guang , Lin Yow‐Shi
Published: April 2003

The acidic hydrolysis of polyacrylonitrile, stabilization and thermal gelation in mixed solvents were sequentially carried out to yield a variety of terpolymer gels made up of 58,5 to 89,4 mol‐% units of acrylonitrile, 10,2 to 39,2 mol‐% acrylamide and 0,4 to 2,3 mol‐% acrylic acid. The posthydrolysis stabilization at temperature below 0°C was shown to induce chemical conversion from acrylonitrile to acrylamide, that is more pronounced for a certain range of initial acrylamide contents than others as evidenced by the kinetic analysis using 1H NMR and base titration. The dielectric relaxation measurements on swollen gels show three relaxation transitions, α, β and γ in decreasing order of temperature, over −150 to 0°C. The β‐transition, due to the segmental motion of the polymer, is the least distinct of the three. The β‐ and γ‐transitions in decreasing order of temperature are associated with the cooperative motion of polar groups with water and glass transition of water, respectively, as judged from the activation energy and temperature of relaxation. The β‐relaxation was shown to be strongly influenced by the type of swelling solvent in the gel, water contents and chemical composition of the gel. Furthermore, the Cole‐Cole plots in the region of the β‐relaxation were constructed to demonstrate the role of morphology in the dielectric behaviour of hydrogels.
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

The 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

3,4‐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

The 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

Various 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

The 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

Room temperature recast Nafion

General 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

Novel 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

The 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

In 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

The 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

The 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

A 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

The 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

The 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

A 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

N‐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

A 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

A 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

Enthalpies 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

Polymerization 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

Well 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.
Sequence distribution of poly(ether‐sulfone)/poly(ether‐ketone) copolymers by mass spectrometry and 13C NMR
Authors: Montaudo Giorgio , Montaudo Maurizio S. , Puglisi Concetto , Samperi Filippo
Published: April 2003

The sequence distributions of four poly(ether‐sulfone)/poly(ether‐ketone) (PES/PEK) copolymer samples were determined by means of fast atom bombardment mass spectrometry (FAB‐MS) and by 13C NMR spectroscopy. The controlled partial degradation of the copolymer chains to produce oligomers suitable of FAB‐MS analysis was performed with sodium methoxide in dimethyl sulfoxide solution at 130°C, and the experimental conditions were optimized. The sequential arrangements of ether‐sulfone/ether‐ketone units present in these materials were estimated by a best‐fit minimization method using the MACO4 computer program which compares the experimental FAB‐MS spectral intensities with theoretical intensities. Random PES/PEK copolymer samples showed quite the same sequence arrangements as expected from monomer feed‐ratios used in the syntheses. Instead, a PES/PEK copolymer sample expected to be exactly alternating (from the synthesis procedure) showed 44% of random sequences owing to the transetherification reaction which occurred in the synthesis. The results of sequential analysis obtained from 13C NMR data compare well with the data obtained by the FAB‐MS analysis.
Initiation of polymerization with substituted ethanes, 13. Free radical polymerization of methyl methacrylate and styrene with substituted succinonitriles
Authors: Braun Dietrich , Skrzek Thomas , Steinhauer‐Beißer Susanne , Tretner Hartmut , Lindner Hans Jörg
Published: April 2003

Tetraarylsuccinonitriles 2 were synthesized via oxidative dimerization of diarylacetonitriles 1 in basic media. The thermal decomposition of 2 results in two identical diarylcyanomethyl semi‐radicals 3. The dissociation energy (Ea) measured using the thiophenol radical scavenging technique was found to amount to 94,3 ± 9,2 kJ/mol in the case of tetraphenylsuccinonitrile 2a. Tetraarylsuccinonitriles 2 show an atypical “stepwise” initiation mechanism in free‐radical polymerization, particularly in the case of methyl methacrylate (MMA) as monomer. In the initial phase of the polymerization reaction a very high concentration of diarylcyanomethyl primary radicals 3 leads to the formation of short‐chain telechelics with both end groups originating from the initiator. In the further course of the polymerization these MMA telechelics are able to re‐form radicals by the scission of thermolabile carbon‐carbon bonds and by the release of initiator end groups, and so the MMA telechelics ‘re‐initiate’ the free‐radical polymerization (“resuscitable free‐radical polymerization”). In styrene polymerization, tetraarylsuccinonitriles 2 indeed cause a pronounced primary radical termination effect, but the styrene telechelics formed in contrast to MMA telechelics are thermostable, and therefore no “re‐initiation” effect occurs. The X‐ray structure determination of the styrene telechelic 2,2,3,5,5‐pentaphenyladiponitrile 4a exhibits a bond length of the thermolabile carbon‐carbon bond of 158,7 pm as compared to 162,8 pm of the corresponding MMA telechelic 2,2,5,5‐tetraphenyl‐3‐methoxycarbonyl‐3‐methyladiponitrile and emphasizes the higher thermal stability of 4.
Polymerizable tautomers, 11. Tautomerism and polymerization of p‐vinylbenzoylacetone
Authors: Masuda Seizo , Tomida Tahei , Tanaka Masami , Asahi Yutaka
Published: April 2003

Solvent effects on tautomerism and polymerization of p‐vinylbenzoylacetone (1) were studied. 1 exhibits the coexistence of the ketonic and enolic forms (the latter is pedominant), and the tautomeric equilibria shift with the solvents. Multiparametric regression analysis of the tautomeric constants reveals that the equilibria depend on polarity and hydrogen bond donor acidity of the solvents. On the other hand, the polymerization of 1 is not affected by the solvents. The polymerization of 1 conforms to the conventional model (rule of square root). Monomer reactivity ratios r1 = 2,56 and r2 = 0,32 were obtained in the copolymerization of 1 (M1) and styrene (M2) in benzene.
Characterization and kinetics of mesophase transition for naphthalene‐based thermotropic polyesters with polymethylene spacers
Authors: Liu Shur‐Fen , Lee Yu‐Der
Published: April 2003

Main‐chain thermotropic polyesters containing naphthalene rings and flexible spacers with 2 ≤ n ≤ 10 methylene groups were prepared in this study. Their thermotropic properties were investigated by means of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The nematic mesophase dominates the anisotropy of the prepared polymers except for the polymers with n = 7 and n = 9. Moreover, the nematic domain size depends upon the number n. On the other hand, the naphthalene ring in the mesogen has a strong effect on the mesomorphic properties of the prepared polyesters. The polymers with n = 7 and n = 9 exhibit cooling rate‐dependent anisotropic behavior of nematic and smectic phases. The crystallization for the investigated polymers is strongly influenced by the anisotropic behavior. The kinetics of crystallization at higher temperatures does not satisfy the Ozawa theory, while it does at lower temperatures. Nucleation begins to occur in the nematic shreads and the crystal growth proceeds toward liquid‐crystalline domains from the observation by POM. Thus, the Avrami exponent a is dependent upon the polymethylene spacer with n being even or odd and high or low. In addition, the parameters of crystallization obtained from DSC and X‐ray diffraction were consistent with the results of non‐isothermal crystallization kinetics and the observation by POM.
Synthesis and properties of liquid‐crystalline AB‐block copolymers poly[6‐(4′‐methoxy‐4‐biphenylyloxy)hexyl methacrylate]‐block‐polystyrene
Authors: Van de Velde Kathleen , Van Beylen Marcel , Ottenburgs Raoul , Samyn Celest
Published: April 2003

Liquid‐crystalline AB‐block copolymers poly[6‐(4′‐methoxy‐4‐biphenylyoxy)hexyl methacrylate]‐block‐polystyrene were synthesized by direct coupling of the homopolymers with functional end groups. Like the liquid‐crystalline homopolymer with mesogenic units in the side chain, all block copolymers show a nematic mesophase. The transition temperatures are hardly affected by the composition and molecular weight of the block copolymers.
Synthesis and characterization of alternating copolyimides containing two different diimide units
Authors: Rhee Suh Bong , Park Ji‐Woong , Moon Bong Seok , Lee Myong‐Hoon , Chang Ji Young
Published: April 2003

Soluble and stable precursors of aromatic imidodiamines were prepared and employed in polymerization reactions with aromatic dianhydrides to yield poly(amic acid ester)s. Thermal imidization of the polymers produced strictly aromatic copolyimides. The reaction of pyromellitic dianhydride (PMDA, 1c), 3,3′,4,4′‐ biphenylteracarboxylic dianhydride (BPDA, 1a), or 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA, 1b) with isopropyl alcohol produced a mixture of isomeric esters. These isomer mixtures were employed in amidation reactions without further separation. Direct amidation with ethyl chloroformate was employed. The acids were reacted with ethyl chloroformate in tetrahydrofuran and the resulting solutions were added slowly to solution of excess 1,4‐ or 1,3‐phenylendediamine in tetrahydrofuran. The reaction of diamines 5a–f with dianhydrides yielded poly(amic acid ester)s. The poly(amic acid ester)s were more stable against depolymerization during storage in solution compared with the corresponding poly(amic acid)s. Alternating copolyimides 6–11 had two different diimide units derived from PMDA (1c), BPDA (1a), or BTDA (1b). In differential scanning calorimetry (DSC) analyses, alternating copolyimides 7,9 and 11 containing 1,3‐phenylenediamine units exhibited distinct and reproducible glass transition temperatures, which were a little lower than the average values of corresponding homopolyimides and those of random copolyimides. But alternating copolyimides 6, 8, and 10, which contain 1,4‐phenylenediamine units, showed very weak glass transitions.
Influence of branch length on the dynamic fatigue properties of short‐chain branched polyethylenes
Authors: Yeh Jen‐taut , Hong Huei‐song
Published: April 2003

An investigation of the influence of the short‐chain branch length on the dynamic fatigue behavior of short‐chain branched polyethylenes (SBPE) is reported. The number of fatigue failure cycles (Nf) increases significantly with increasing branch length at temperatures above the β‐transition of SBPE polymers. In addition, an examination of the fracture surfaces of these specimens indicates a transition to a more ductile‐type behavior when specimens are associated with larger branch lengths. Detailed characterization shows that these SBPEs have approximately the same molecular weight, molecular weight distribution, branch frequency, crystallinity or microstructure but different branch length. The difference in branch length is suggested to be responsible of the dramatic change in Nf and in the morphology of the fracture surface at temperatures above the β‐transition of SBPEs. In contrast, no significant change in Nf and in the morphology of the fracture surface were found with increasing branch length at temperatures near or below the β‐transition. This dramatic change in the effect of short‐chain branches on Nf and on the morphology of the fracture surface are attributed to the change in the molecular relaxation motion at temperatures near the β‐transition of SBPE polymers.
Sequence ordered copoly(arylester‐carbonate)s: synthesis and characterization
Authors: Shaikh Abbas‐Alli G. , Sivaram Swaminathan
Published: April 2003

A new class of ester‐carbonate monomers was prepared by reaction of monomethylcarbonate of bisphenol‐A with tere/isophthaloyl chloride. Self polycondensation of these monomers in presence of titanium tetraisopropoxide as catalyst resulted in the formation of copoly(arylester‐carbonate)s having an ester to carbonate ratio of 2: 1. Copoly(arylester‐carbonate)s rich in either carbonate groups were also prepared by copolymerization of ester‐carbonate monomer with dimethyl terephthalate and the bismethylcarbonate of bisphenol‐A. The polymer structure was established by 1 H NMR and IR spectroscopy. The ordered sequence of estercarbonate groups in the polymer was established by 13C NMR spectroscopy.
Miscibility and morphology of AB/C‐type blends composed of block copolymer and homopolymer or random copolymer, 1. Polyisoprene‐block‐poly(methyl methacrylate)/modified polystyrene blends
Authors: Jiang Ming , Huang Tianzi , Xie Jingwei
Published: April 2003

The miscibility and morphology of AB/C‐type blends composed of polyisoprene‐block‐poly(methyl methacrylate) [PI‐b‐PMMA] and a modified polystyrene with hydroxyl‐containing units [PS(OH)] has been studied by transmission electron microscopy (TEM). In the blends the density of hydrogen bonding between C and B block is adjustable. The miscibility and morphology of the blends cast from toluene, which is inert to hydrogen bonding, are found to depend on the hydroxyl content in PS(OH). Immiscibility between PMMA blocks and PS(OH) alters to miscibility when the hydroxyl content in PS(OH) reaches 1,6 mol‐%. Little effect of the relative molecular weight of PS(OH) to that of the PMMA block is found, which is different from that for AB/A‐type blends. An apparent effect of the casting solvent on the miscibility and morphology is observed. Being a proton‐acceptor solvent, tetrahydrofuran (THF) considerably decreases the miscibility, and a homogeneous microphase structure appears only when the hydroxyl content reaches 10 mol‐%. This implies that the main driving force for the miscibility between PS(OH) and PMMA blocks is hydrogen bonding between hydroxyl groups of PS(OH) and carbonyl groups of PMMA.
Miscibility and morphology of AB/C‐type blends composed of block copolymer and homopolymer or random coploymer, 2. Blends with random copolymer effect
Authors: Jiang Ming , Huang Tianzi , Xie Jingwei
Published: April 2003

This work is an extension of the concept of miscibility window in homopolymer/random copolymer blends to blends containing block copolymers. The miscibility and morphology of THF‐cast blends composed of the block copolymer polyisoprene‐block‐poly(methyl methacrylate) (Pl‐b‐PMMA) and the random copolymer poly(styrene‐ran‐acrylonitrile) (SAN) (22 wt.‐% AN) has been studied by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). Most blends show miscibility between PMMA blocks and SAN, presenting a homogeneous microdomain structure. Coupling of macrophase separation occurs only when the ratio of molecular weights of SAN to the PMMA bock is very large and SAN becomes the dominant component. The excellent miscibility in the block copolymer/random copolymer blends can be understood by considering that the monomer unit composition of SAN is within the miscibility window in PMMA/SAN blends. The main driving force for the miscibility is repulsion between S and AN units rather than hydrogen bonding between SAN and PMMA, since a proton‐acceptor type solvent does not show any effect on the miscibility in the blends. Apparent broadening of the glass transition of the ‘hard phase’ is observed and explained with the aid of the segment density gradient model.
Rheo‐optical FT‐Raman study of uniaxially stretched poly(vinylidene fluoride)
Authors: Rodríguez‐Cabello José Carlos , Merino Juan Carlos , Pastor José María , Hoffmann Uwe , Okretic Stephano , Siesler Heinz Wilhelm
Published: April 2003

A Fourier‐transform Raman‐sepectroscopy‐based rheo‐optical system was used to study the process of uniaxial stretching of poly(vinylidene fluoride) (PVF2). This rheo‐optical system made possible to reduce the rate of stretching and favoured the acquisition of a higher number of spectra in different mechanical stages during the stretching process. Those can be the eleastic zone or the formation of the neck. Thus, it has been possible to establish that the stretching‐induced phase transition in PVF2 takes place in the beginning of the neck formation. Shortly after the neck development that transition has reached its maximum extent. The performance of the transition was highly temperature dependent. As the temperature of stretching increases, the extent of the transition decreases. Along with this permanent modification of the sample structure, other transient modifications were found. High resolution spectra of the phase β of loaded PVF2 showed a wavenumber shift of specific absorption bands. These band shift have been interpreted as a deformation of the geometry of the bonds reflected by the absorption band. This bands with high contribution of skeletal CC bonds suffered the highest band shift, suggesting that these bonds were most sensible to the applied load. This band shift and, consequently, bond deformation immediately vanished after removal of the load.
Anisotropy in electrical conduction of polypyrrole/polyethylene composite films by drawing
Authors: Kurachi Kouichirou , Kise Hideo
Published: April 2003

Polypyrrole/polyethylene composite films were prepared by vapor phase polymerization of pyrrole on porous polyethylene films using iron(III) chloride as an oxidant. By drawing the films before or after the polymerization of pyrrole, anisotropy in electrical conduction was observed parallel and perpendicular to the drawing direction. The effects of drawing on the conductivity and the mechanism of conduction are discussed in terms of the temperature dependence of the conductivity.
Mass spectrometric characterization of a 2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]propane‐aniline addition polymer and its telechelic prepolymers
Authors: Klee Joachim E. , Hägele Klaus , Przybylski Michael
Published: April 2003

Fast‐atom bombardment (FAB) and plasma desorption mass spectrometry of high molecular weight addition polymers of 2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]propane (DGEBA) and aniline show protonated molecular ions of the intact polymer and oligomer molecules. The oligomeric products consist mainly of cyclooligomers. Their formation can be observed during the polymerization reaction. Telechelic prepolymers having epoxide end groups as well as telechelics containing amino end groups were found with lower degree of polymerization in the mass spectra. Side reactions such as ether formation or epoxide polymerization were not observed. Telechelic DGEBA‐aniline prepolymers are shown to consist of a series of oligomers as shown by highpressure liquid chromatography (HPLC) analyses. Consequently, the FAB mass spectra of the prepolymers show molecular ions of the different oligomers. Furthermore, under the conditions of the FAB mass spectrometric analysis fragmentation of the prepolymers to iminium fragment ions was observed.
Ring‐opening metathesis polymerization of 7‐phenylnorbornadiene and benzonorbornadiene
Authors: Hamilton James G. , Rooney John J. , Snowden David G.
Published: April 2003

Ring‐opened metathesis polymers of 7‐phenylnorbornadiene and benzonorbornadiene have been prepared using a variety of catalysts based on Ru, Os, Ir, W and Mo chloride salts and complexes. Detailed 13C and 1H NMR spectra of these materials and their corresponding hydrogenated derivatives have been obtained and analysed for information concerning tacticities and fractions of cis double bonds (σc). The behaviour of 7‐phenylnorbornadiene is similar to that of 7‐methylnorbornadiene in that a strong preference for the anti over the syn mode of monomer insertion is observed in contrast to 7‐tert‐butoxynorbornadiene which shows little or no regioselectivity. Pronounced effect on σc are also observed using the OsCl3 catalyst as expected from previous experience of ring‐opening metathesis polymerization (ROMP) systems containing chelating dienes and this catalyst. Weaker effects of this type due to complexation of monomer as a spectator ligand are also indicated for the polymerization of benzonorbornadiene; these are also compared to the effects of using Michael acceptor additives in metathesis systems.
Tensions superficielles de copolymères méthacryliques perfluoroalkylés
Authors: Guery‐Rubio Claudine , Viguier Michel , Commeyras Auguste
Published: April 2003

The surface properties of methacrylic copolymers with a random distribution of perfluoroalkyl pendent groups were studied by a tensiometric method and were found to depend on the concentration of fluorinated units (2‐hydroxy‐4,4,5,5,6,6,7,7,8,8,9,9,9‐tridecafluorononyl methacrylate (1)), and the nature of the non‐fluorinated methacrylic ester (methyl, butyl, stearyl). The surface tensions estimated by various approaches (critical surface tension, geometric and harmonic mean approximations) are very low (11 mN · m−1 < y < 12 mN · m−1). The surface tension of the copolymers drops drastically when a few percent of fluorinated units are incorporated into the polymeric chain. The wetting hysteresis, observed particularly in the case of water, could be due to the mobility of macromolecular chains at the interface, leading to a reorganization of fluorinated groups in order to minimize the interfacial energy.
Ordering of liquid crystalline solutions of rigid‐rod aramids using mechanical shearing and electric‐field poling
Authors: Weder Christoph , Glomm Bernhard H. , Neuenschwander Peter , Suter Ulrich W.
Published: April 2003

2′,5′‐Diamino‐4‐(dimethylamino)‐4′‐nitrostilbene was polymerized with terephthaloyl dichloride and 2,6‐difluoroterephthaloyl dichloride in a low‐temperature solution polycondensation to give two novel, fully aromatic rigid‐rod polyamides. Nematic solutions of these polymers were processed into fibers and films that were characterized by wide‐angle X‐ray diffraction measurements. A post‐spin annealing process was employed to enhance the chain orientation in the fibers. The dominating crystal structure was found to be similar to “modification II” of the fibers from poly(p‐phenyleneterephthalamide), but the fibers do not suffer a comparable structural transformation upon heat treatment. A corona‐discharge poling process gave rise to a remarkable gain in average chain orientation in the films. Again the crystal structure was found to be similar to “modification II”. The aramids investigated in this work represent a new approach to the design of liquid‐crystalline rigid‐rod polymers, where different mechanisms of orientation can be combined. In the nematic phase, the rigid‐rod molecules form highly oriented domains that can be oriented using mechanical processes such as shearing. In addition the stilbene units that are fixed in the polymer backbone with their dipole moments oriented transverse to the main chain can be oriented in an electric field. The combination of both orientation mechanisms seems to cause a synergistic effect, probably since each affects different levels of the polymer microstructure in the solid.
Radical ions of poly(phenylsilyne) and poly(phenylgermyne)
Authors: Watanabe Akira , Komatsubara Tadaharu , Matsuda Minoru , Yoshida Yoichi , Tagawa Seiichi
Published: April 2003

Poly(phenylsilyne) and poly(phenylgermyne), which have a network Si‐ and Ge‐skeleton, were synthesized by electrochemical reduction of trichlorophenylsilane and trichlorophenylgermane, respectively. The poly(phenylsilyne) showed broad absorption and emission bands that are characteristic of silicon network polymers. Similarly broad absorption and emission bands were observed for the poly(phenylgermyne). Radical anions and radical cations of poly(phenylsilyne) and poly(phenylgermyne) were produced by pulse radiolysis. The radical ions of these network polymers showed broad transient absorption bands from the UV to the IR region. Within 200 ns after pulse radiolysis, the absorption band of the radical cation in the UV region decreased, whereas the band in the IR region increased. The time‐dependent spectral change of the radical cation suggests the formation of a change resonance band of the delocalized positive charge on the σ‐conjugated polymer chain. In contrast to the radical cation, the radical anion of the network polymers did not show a spectral change.
Concentration quenching of photoluminescent Ru(bpy) dispersed in a polysiloxane film containing 2,2′‐bipyridine pendant groups in dependence of molecular distribution
Authors: Nagai Keiji , Ueno Yukihiko , Takamiya Nobuo , Kaneko Masao
Published: April 2003

The photoluminescent Ru(bpy) complex was dispersed in a polysiloxane film containing 2,2′‐bipyridine (bpy) pendant groups. The unusually long photoluminescence lifetime of the Ru(bpy) (1,94 μs at 25°C) and the blue‐shifted photoluminescent wavelength suggest a rigid polymer matrix. The fluorescence yield becomes lower with higher probe concentration, indicating concentration quenching. According to the analysis based on Stern‐Volmer plots, the quenching obeys a mechanism composed of both static and dynamic processes. A statistical intermolecular distance distribution between the probes was used to interpret the results in terms of static and dynamic quenching. It is shown that in the present system the dispersed complexes diffuse slightly during the excited state.