bluuebunny/crossref_metadata_2025 huggingface dataset:
Racemic resolution of mandelic acid on polymers with chiral cavities, 4. A kinetic study
Authors: Sarhan Ali
Published: April 2003

L‐Mandelic acid‐1,2‐O‐(4‐vinylphenyl)boronate (2) was copolymerized with divinylbenzene to yield a highly crosslinked macroporous polymer. 59% of incorporated L‐mandelic acid (used as template) could be split‐off on hydrolysis. The resulting polymer, with phenylboronic acid groups in the chiral cavities of type P1, was equilibrated in a batch process with D,L‐mandelic acid in acetonitrile. The change of covering percentage, and that of the efficiency for racemic resolution, with time were followed by acidimetric titration and measurement of the optical rotation. A reasonable mechanism for the polymer‐substrate interaction could de deduced. The selectivity terms for each of the forward and reverse reaction could be separately evaluated. Diffusional limitations significantly affect the observed efficiency of racemic resolution. Thermodynamically controlled separation, attainable by a suggested exchange reaction, required much more time than the considerably less effective kinetically controlled separation.
Copolymerizations of styrene with magnesium, calcium, strontium and barium acrylates in dimethyl sulfoxide
Authors: Gronowski Adam , Wojtczak Zbigniew
Published: April 2003

Radical copolymerizations of styrene with acrylates of magnesium, calcium, strontium and barium were carried out in dimethyl sulfoxide. The monomer reactivity ratios were determined by the Yezrielev‐Brokhina‐Roskin and the Kelen‐Tüdős methods. In all cases the monomer reactivity ratio for styrene exceeded one and those for the salts were less than one. The Q‐values of the Alfrey‐Price scheme for the metal acrylates were within the range 0,1 − 0,2. For the values of the polarity parameter e the following sequence was found: eMgA2 < eCaA2 < eSrA2 < eBaA2 and the tendency for alternation in copolymerizations increased in the same order. The results indicate that the course of copolymerizations under study is predominantly affected by polarization of the vinyl groups in the salts.
Polymeric chiral crown ethers, 4. Substituent effects of methyl and phenyl groups in the 3,3′‐positions on chiral recognition of poly(crown ether)s synthesized by cyclopolymerization of divinyl ethers derived from 1,1′‐bi‐2‐naphthol
Authors: Kakuchi Toyoji , Hasegawa Toshiyuki , Sasaki Hiroshi , Ohmori Hiroshi , Yamaguchi Kazumi , Yokota Kazuaki
Published: April 2003

Chiral poly(crown ether)s were synthesized by cationic cyclopolymerization of (S)‐2,2′‐bis(2‐vinyloxyethoxy)‐3,3′‐dimethyl‐1,1′‐binaphthyl [(S)‐1b] and (R)‐2,2′‐bis[2‐(2‐vinyloxyethoxy)‐ethoxy]‐3,3′‐dimethyl (or 3,3′‐diphenyl)‐1,1′‐binaphthyl [(R)‐3b or (R)‐3c]. The substituents in the 3,3′‐positions of binaphthyl moiety disturb the intramolecular cyclization in the polymerization of monomer (S)‐1b, but have no influence on the cyclopolymerization tendency of monomers (R)‐3b and (R)‐3c. The polymers from (R)‐3b and (R)‐3c [(R)‐4b and (R)‐4c] have a higher ability of chiral recognition towards a‐amino acids, such as phenylglycine, phenylalanine, valine, and methionine, than the polymer from (R)‐3a [(R)‐4a], which has no substituent in 3,3′‐positions. The methyl and the phenyl substituents in the 3,3′‐positions undoubtedly act as additional barrier causing an increase in the ability of chiral recognition, though the effect is less than expected from the result of model crown ethers.
Preparation of poly(amide‐imide)s by means of triphenyl phosphite, 1. Aliphatic‐aromatic poly(amide‐imide)s based on trimellitimide
Authors: Yang Chin‐Ping , Hsiao Sheng‐Huei
Published: April 2003

Aliphatic‐aromatic poly(amide‐imide)s with high molecular weight (ηinh up to 2,91 dl/g in DMAc/5% LiCl) were synthesized by direct polycondensation reaction of imide‐containing dicarboxylic acids and aromatic diamines using triphenyl phosphite in N‐methyl‐2‐pyrrolidone (NMP)/pyridine solution in the presence of metal salts. The factors affecting the reaction of N‐(trimellitoyl)glycine and 4,4′‐oxydianiline were investigated. The molecular weight of the polymer varied with the amount of metal salts, showing a maximum at a concentration of about 1 wt.‐% CaCl2 or about 2 wt.‐% LiCl in the reaction mixture. A monomer concentration of about 0,2 mol/l gave the most favorable result. Among the solvents tested, NMP was most effective. Similarly, polycondensations of several combinations of three imide‐diacids with various aromatic diamines were carried out. Solubility, thermal properties, and tensile properties of the polymers are discussed.
Terpolymerization of sulfur dioxide with maleic anhydride and vinyl monomers
Authors: Florjańczyk Zbigniew , Raducha Dorota , Zygadło Ewa
Published: April 2003

The free radical polymerization in ternary systems comprising sulfur dioxide, maleic anhydride and vinyl monomers, such as ethylene, propene, 2‐methylpropene, 1‐hexene, 1,3‐butadiene, styrene, α‐methylstyrene, vinyl chloride and methyl acrylate, was studied. In systems with α‐methylstyrene only a copolymer of this monomer with maleic anhydride was obtained. In systems with methyl acrylate a terpolymer containing mainly methyl acrylate monomeric units was produced, whereas in all the other systems terpolymers containing ca. 50 mol‐% of vinyl monomeric units were formed. In terpolymerizations carried out at low temperatures, SO2 is a more reactive monomer than maleic anhydride. With increasing temperature the content of SO2 monomeric units decreases in the products obtained. This is connected with an enhancement of the depropagation rate of this monomer. On the basis of the results obtained some aspects of the propagation and depropagation mechanisms in the systems studied are discussed.
Group transfer polymerization of methyl acrylate in acetonitrile
Authors: Schubert Walter , Bandermann Friedhelm
Published: April 2003

Results of group transfer polymerization (GTP) of methyl acrylate (MA) in acetonitrile with 1‐methoxy‐1‐propenyloxytrimethylsilane (MTP) as initiator and tris(dimethylamino)sulfonium difluorotrimethylsilicate, tris(piperidino)sulfonium difluorotrimethylsilicate, tris(dimethylamino)sulfonium bifluoride, tris(piperidine)sulfonium bifluoride, tetrabutylammonium fluoride trihydrate and tetraethylammonium cyanide as catalysts are presented. Difluorotrimethylsilicate‐and bifluoride‐derived catalysts are more active in GTP of MA than fluoride‐ and cyanide‐derived ones, and lead to higher but in no case complete conversion. Polymers with number‐average molecular weights up to 10000 and dispersion indices as low as Mw/Mn = 1,3 can be prepared. Molecular weight control is poor and not possible without calibration of reaction conditions, since all catalysts activate side reactions of MA (to low‐molecular‐weight compounds and oligomers), of MTP, and (as is assumed) also of growing chains with the solvent acetonitrile under termination. Furthermore, catalysts containing fluoride and cyanide anions initiate an anionic polymerization of MA, accompanying GTP to an appreciable extent.
Structural characterization of vinylidene fluoride/vinyl fluoride copolymers
Authors: Guerra Gaetano , Di Dino Gabriele , Centore Roberto , Petraccone Vittorio , Obrzut Jan , Karasz Frank E. , MacKnight William J.
Published: April 2003

The crystalline structure and the melting behavior of vinylidene fluoride/vinyl fluoride (VF) copolymers are reexamined. For copolymers containing even a small mole fraction of VF units (≈︁ 12%) a structure similar to the β‐form of poly(vinylidene fluoride) and to the crystalline structure of poly(vinyl fluoride) is stabilized. Combined wide‐angle X‐ray scattering, differential scanning calorimetry and dielectric measurements show that in contrast to other vinylidene fluoride copolymers, no crystal‐crystal transition below the melting region is present.
Active transport of linear polyions in oppositely charged swollen polyelectrolyte networks
Authors: Kabanov Victor A. , Zezin Alexander B. , Rogacheva Valentina B. , Prevish Victoria A.
Published: April 2003

The interaction between oppositely charged linear and crosslinked polyelectrolytes and the molecular mechanism of the transport of linear polyelectrolytes into oppositely charged gels were studied. The mechanism represents a “relay‐race” transfer of polyion segments from one fragment of the polyelectrolyte network to the other via interpolyelectrolyte exchange reaction. Thus, the whole layer of the formed interpolyelectrolyte complex serves as an active zone. The driving force for the transport is produced by interpolyelectrolyte addition reaction on the solution/gel interface.
In‐situ photopolymerization of oriented liquid‐crystalline acrylates, 3. Oriented polymer networks from a mesogenic diacrylate
Authors: Broer Dirk J. , Boven Jan , Mol Grietje N. , Challa Ger
Published: April 2003

Synthesis, mesomorphism, orientation and photo‐initiated chain crosslinking of the liquid‐crystalline diacrylate 1,4‐phenylene bis{4‐[6‐(acryloyloxy)hexyloxy]benzoate} (1) are studied. Monomer 1 exhibits a broad nematic phase between 108 and 155°C and a monotropic smectic phase below 88°C. The monomer is uniaxially oriented in its nematic phase at a substrate which has been coated with polyimide and unidirectionally rubbed with tissue. At the transition temperature to the smectic phase the order parameter is measured to be 0,7. During polymerization, the ordering of the mesogens is frozen‐in, yielding a uniaxially crosslinked network. The clear films of oriented poly(1) exhibit a birefringence Δn between 0,12 and 0,15, depending on the polymerization temperature. In the highest oriented state of 1 a small reduction of the degree of order is observed during the crosslinking reaction, whereas at higher temperatures and lower ordering of 1, the uniaxially orientation increases upon reaction. A special feature of the oriented networks is that the ordering is maintained while heating at high temperatures. The polymerization of the acrylate groups in the mesomorphic phases proceeds fast and to high conversion. Below 90°C the polymerization behaviour is similar to that of conventional isotropic diacrylates. Above 90°C the polymerization reaction of the liquid‐crystalline diacrylate proceeds faster than that of an isotropic diacrylate.
Spacer effect on the asymmetric addition of butyllithium to aldehydes with chiral polymers containing (+)‐bornane moieties as catalysts
Authors: Liu Jui‐Hsiang , Wang Jenn‐Hwa , Kuo Jue‐Cheng
Published: April 2003

Three types of chiral polymer containing dimethylaminobornane moieties were synthesized. The asymmetric addition of butyllithium to various aldehydes in the presence of chiral polymers as catalysts were carried out at different reaction temperatures. The highest enantiomeric excess (54,7%) was achieved with the chiral homopolymer with a spacer inserted between the polymer chain and the dimethylaminobornane moiety. The chiral polymers can be easily separated from the reaction mixture and re‐used.
Fixation d'amines pharmacologiquement actives sur les polyphosphonates, 1. Etude sur molécule modèle
Authors: Brosse Jean‐Claude , Fontaine Laurent , Derouet Daniel , Chairatanathavorn Supachat
Published: April 2003

Chemical modification of poly(alkylene phosphonate)s via the Atherton‐Todd reaction was investigated with diethyl phosphonate (3) as a model molecule. The study of the reaction showed that in the presence of a sufficiently basic tertiary amine, the reaction with carbon tetrachloride leads to an intermediate chlorophosphate. The variation in phosphorylation yields with the pKa of the primary amine highlights the role played by the basicity of the reaction medium.
Fixation of pharmacologically active amines on polyphosphonates, 2. Application to benzocaïne and phenethylamine
Authors: Brosse Jean‐Claude , Derouet Daniel , Fontaine Laurent , Chairatanathavorn Supachat
Published: April 2003

The Atherton‐Todd reaction was used for the preparation of a new class of hydrophilic drug carriers with an organic polyphosphate main chain. Chemical modification of poly(propy1ene phosphonate) (3) and poly(3,6,9‐trioxaundecamethylene phosphonate) (4) with benzocaine (ethyl 4‐aminobenzoate) (1) and phenethylamine (2) led in one step to polyphosphoramidates 7a, b and 8a, b bearing pharmacologically active amines in the side chain with modification yields of 60 to 75%.
Synthèse de molécules fonctionnelles deutérées sélectivement
Authors: Pichon Hervé , Laguerre Albert , Durand Dominique , Rabadeux Jean‐Claude
Published: April 2003

For the study of the orientational order in strained polyurethane elastomers, selectively deuterated molecular probes were synthetized. End‐deuterated poly(propylene oxide)s were obtained using deuterated methanol as initiator. Coupling of theses prepolymers with hexamethylene diisocyanate led to products deuterated at both ends. To obtain derivatives deuterated in the centre of the chain, various deuterated hexamethylene diisocyanates were synthetized and coupled with poly(propylene oxide) containing one hydroxyl end group.
Ring‐opening polymerization of norbornene initiated by tungsten alkylidene complexes. Activation by AlCl3
Authors: Leymet Isabelle , Siove Alain , Parlier Andrée , Rudler Henri , Fontanille Michel
Published: April 2003

Addition of aluminium compounds to the stable metal‐carbene complex tetracarbonyl[4–5‐η‐1‐methoxy‐4‐pentenylidene]tungsten (1), showing an intramolecular coordination of double bond to the transition metal, leads to highly active catalytic systems in the polymerization of norbornene. It is shown that, in optimal conditions, AlCl3 is more efficient than AlEt3 for cyclo‐olefin polymerization. From spectroscopic studies (UV‐visible, 1H and 13C NMR) of the activated system 1‐AlCl3, a mechanism of activation by AlCl3 is proposed involving a modification of the nature of carbene 1 by the Lewis acid.
Synthesis of telechelic polysiloxanes, 3. Synthesis of aliphatic diamines and diimides
Authors: Boutevin Bernard , Guida‐Pietrasanta Francine , Robin Jean‐Jacques
Published: April 2003

Telechelic oligo(dimethylsiloxane)s 6 and 7 with chloro‐, cyano‐ or aminopropyl end groups were synthesized from the corresponding chlorodimethylsilanes 2a–c and α‐hydro‐ω‐hydroxyoligo(dimethylsiloxane)s 4 and 5. The ω‐cyano derivatives 6b and 7b were reduced to the 4‐aminobutyl derivatives 8a and 8b with LiAlH4. 8a was subsequently transformed into 1,7‐bis(4‐maleimidobutyl)‐1,1,3,3,5,5,7,7‐octamethyltetrasiloxane (10) by reaction with maleic anhydride, via the intermediate dimaleamic acid 9. The products were characterized by IR, 1H, 29Si, and 13C NMR spectroscopy.
New monofunctional derivatives of poly(ethylene glycol)s via monotrityl intermediates
Authors: Pozzo Alma Dal , Vigo Angelo , Donzelli Giovanni
Published: April 2003

Four new monofunctional poly(ethylene glycol)s (PEGs) and one new monofunctional poly(propylene glycol) (PPG) were prepared and characterized. Monosubstitution of the dihydroxyfunctional PEGs was achieved through an intermediate PEG protected at one end‐function with a trityl group. These polymers are proposed as pro‐moieties for the synthesis of pro‐drugs.
Fourier transform infra‐red spectroscopy of atactic polystyrene in the glass transition region
Authors: Magonov Sergei N. , Shen Deyuan , Qian Renyuan
Published: April 2003

Fourier transform infra‐red (IR) studies on samples of atactic polystyrene with different thermal history, i.e. quenched from the melt (QM), quenched from the rubbery state (QR), slowly cooled (SC), and sub‐glass‐transition (sub‐Tg) annealed (AN), were carried out in the absorption region from 500 to 600 cm−1 with gradually increasing temperatures through the glass transition region at 100°C. The heights of the positive peak (532 cm−1) and the negative peak (566 cm−1) appearing in the temperature difference spectra, T‐60°C, are considered to be a measure of the amount of frequency shifts for the 540 cm−1 and 557 cm−1 bands in the conformationally sensitive spectral range of atactic polystyrene. These bands show a continuously increasing low‐frequency shift with increasing temperature, except for sample QM, the 557 cm−1 band of which shows an inappreciable frequency shift in the range 60 < T/°C < 100. The different temperature behaviour of these shifts for samples QM, QR, SC and AN is due to changes in their intermolecular interactions. Sub‐Tg annealing of the sample QM is shown to shift the frozen high‐temperature state of the quenched sample to the temperature‐defined equilibrium. For all samples of different thermal history the difference in their IR spectra vanish at temperatures above Tg.
Stereospecific polymerization of higher α‐olefins with the solvay type catalyst TiCl3/Cp2Ti(CH3)2
Authors: Soga Kazuo , Lee Dong Hee , Shiono Takeshi , Kashiwa Norio
Published: April 2003

Polymerizations of higher α‐olefins (C10–C20) were carried out at 40°C in heptane, using the following three catalysts which differ in the isospecificity for propene polymerization: Solvay type TiCl3/Cp2TiMe2((A) highly isospecific), Solvay type TiCl3/AlEt3((B) isospecific) and TiCl3.3Py/MgCl2/AlEt3((C) aspecific). The isospecificity of the catalysts was found to decrease in the following order: (A) ≫ (B) ≫ (C), which agrees well with the results obtained in propene polymerization. The crystallinity of these polymers is discussed in brief.
Group transfer polymerization of methyl acrylate in tetrahydrofuran with tetrabutylammonium fluoride trihydrate and tetrabutylammonium cyanide as catalysts
Authors: Schubert Walter , Bandermann Friedhelm
Published: April 2003

Group transfer polymerization (GTP) of methyl acrylate (MA) with 1‐methoxy‐1‐propenyloxytrimethylsilane (MTP) as initiator and tetrabutylammonium fluoride trihydrate and tetrabutylammonium cyanide as catalysts in tetrahydrofuran was investigated. Tetrabutylammonium fluoride trihydrate turned out to be absolutely unsuited as GTP catalyst, since its crystal water destroys the initiator and the active centres. Furthermore, in side reactions between the initiator and the catalyst, the concentrations of both are diminished. Tetrabutylammonium cyanide is a powerful catalyst of GTP of MA, leading to complete conversion of the monomer, but initiates an anionic polymerization of MA too, which, however, is of minor importance in the main part of the reaction. Reaction rates may easily be controlled by the catalyst concentration. Number‐average molecular weights are dependent on initiator concentration. They are lower as well as higher than those expected for a really living system, pointing to a rather complicated overall reaction.
Synthèse de polystyrènes chlorométhylés renfermant des radicaux tétrathiafulvalène carbonyloxyméthyles
Authors: Fabre Jean‐Marc , Giral Louis , Montginoul Claude , Mungroo Aumduth , Sagnes René , Schué François
Published: April 2003

In order to solve the problem of polymer swelling, which limits the resolution for negative resists, new resists were developed which show no swelling. The undesirable swelling can be suppressed by converting nonpolar crosslinked polymers into polar ones, which are soluble after irradiation. This aim was attained by mixing a polystyrene bearing tetrathiafulvalenyl (TTF) groups with 1,2‐dibromo‐1,1,2,2‐tetrachloroethane. For our study, we applied resists including poly(4‐chloromethylstyrene)s containing tetrathiafulvalenecarbonyloxymethyl groups (1 and 2). Poly(4‐chloromethylstyrene)s (4) or poly[styrene‐co‐(4‐chloromethyl)styrene]s (5) with a variety of controlled molecular weights and molecular weight distributions were prepared by radical chain polymerization. The reaction of cesium tetrathiafulvalenecarboxylate (3) with 4 or 5 was carried out and the resultant substituted polymers 1 and 2 were characterized.
Crystallization of the γ‐form of isotactic poly(propylene)
Authors: Marigo Antonio , Marega Carla , Zannetti Roberto , Paganetto Guglielmo , Canossa Enrica , Coletta Flaviano , Gottardi Francesca
Published: April 2003

The pure γ‐form of isotactic poly(propylene) can be obtained by melt‐crystallization starting from a fraction of a random ethylene‐propene copolymer (ethylene content 4 wt.‐%) soluble in p‐xylene at 28°C. Some structural models previously reported are tested by comparing calculated wide‐angle X‐ray diffraction patterns with the experimental ones. A method for the quantitative determination of the γ‐form crystallinity by X‐ray line profiles is proposed. The original copolymer and its fractions are characterized by differential scanning calorimetry and 13C NMR techniques.
Molecular weight and temperature dependence of the cold‐drawing behavior of ethylene‐tetrafluoroethylene copolymer
Authors: Gundert Friedhelm , Smith Paul
Published: April 2003

The temperature dependence of the cold‐drawing behavior of melt‐crystallized films of ethylene‐tetrafluoroethylene copolymer (E/TFE) was investigated by tensile deformation from medium to ultrahigh molecular weight (UHMW), with the draw ratio at break λ as the crucial quantity. From meltrheological measurements at T = 300°C, the weight‐average of molecular weight (M̄w) is calculated to be in the range of 100 to 17000 kg/mol (zero‐shear viscocity η0 = 104–1010 Pa. s). The results of tensile experiments are discussed in comparison to polyethylene (PE) within the scope of a model of entanglement kinetics for tensile deformation presented by Termonia and Smith recently. In contrast to PE, the values of the maximum draw ratio at break λmax are low and increase with M̄w(λmax = 4,5–6,5; for PE λmax = 30–10 for M̄w = 125–1500 kg/mol). Also different to PE is the lack of correlation of Tmax (T at λmax) with melting point Tm in the case of UHMW‐E/TFE (Tmax ≈ 180°C < Tm = 280°C; for PE Tmax ≡ Tm). These findings are explained by the transition from orthorhombic crystal phase to hexagonal mesophase in E/TFE, which was reported to occur at Tα ≈ 100°C by Tanigami et al. On the molecular scale the onset of this order‐disorder transition is described as a drastic increase of chain slippage in the crystallites during deformation and cannot be compensated by entanglements in amorphous regions, which act as transient crosslinks.
Liquid‐crystalline elastomers with cholesteric and chiral smectic C* phases
Authors: Zentel Rudolf , Reckert Gertrude , Bualek Sauvarop , Kapitza Heinrich
Published: April 2003

A series of 9 new chiral and crosslinkable liquid‐crystalline copolymers were synthesized and transformed into liquid‐crystalline elastomers by crosslinking using a hydrosilylation reaction. Both the soluble copolymers and the elastomers show cholesteric, smectic A and chiral smectic C* phases, which are not affected by the crosslinking procedure. First measurements show that the helical superstructure of elastomers with cholesteric and chiral smectic C* phases can be reversibly untwisted by stretching. Thereby a cholesteric structure can be transformed into a nematic structure and a chiral smectic C* structure into a smectic C one.
Photooxidation of poly(diacetylene) single crystals
Authors: Poole Nicholas J. , Day Richard J. , Smith Brian J. E. , Batchelder David N. , Bloor David
Published: April 2003

Single crystals of poly(diacetylene) 1a with p‐tosyloxymethyl side groups undergo photooxidation when irradiated with visible light of wavelength 520 nm or less. The presence of molecular oxygen adsorbed on the surface of the crystals and its subsequent photochemical reaction with the polymer were monitored using resonance Raman spectroscopy and the formation of holographic gratings. Reaction products which were identified include hydroperoxy groups, p‐toluenesulfonic acid and poly(diacetylene) oligomers. The photooxidation reaction appears to proceed by the “ene” mechanism; the polymer reacts with singlet oxygen produced by energy transfer with the photoexcited poly(diacetylene) backbone.
Vergleichende berechnungen an stereoisomeren modellverbindungen des polyacrylnitrils und polyvinylchlorids
Authors: Röttger Jutta , Pittel Bernd , Michels Gisbert , Korte Siegfried , Süling Carlhans
Published: April 2003

Zusammenfassend läßt sich sagen, daß sich die Modelle für die Diastereomere des PAN in ihren Stabilitäten und Reaktivitäten noch weniger unterscheiden als die entsprechenden PVC‐Modelle. Daraus läßt sich der Schluß ziehen, daß eine Beeinflussung der Stereoregularität des PAN allein durch Erniedrigung der Polymerisationstemperatur nicht zu erreichen ist.
New polymer syntheses, 40. Syntheses of substituted polybenzodioxazoles from aryloxyterephthalic acids
Authors: Kricheldorf Hans R. , Engelhardt Jürgen
Published: April 2003

Substituted polybenzodioxazoles were synthesized from silylated 2,5‐diaminohydroquinone (5) and various aryloxyterephthaloyl dichlorides (6). Either a “one‐pot procedure” or a two step procedure was used. In the latter case the silylated monomer was condensed with a terephthaloyl dichloride at −15°C in 1‐methyl‐2‐pyrrolidone and the isolated polymer 8 was cyclized at 350°C in an inert reaction medium. The optimum reaction conditions were determined for a low‐molecular‐weight model and the reaction products were characterized. The substituted polybenzodioxazoles are soluble in dichloromethane/trifluoroacetic acid mixtures, yet, they do not form a mobile melt up to 600°C.
Synthesis and properties of model oligomers of poly(naphthylenevinylene)s
Authors: Stenger‐Smith J. D. , Lenz Robert W. , Enkelmann Volker , Wegner Gerhard
Published: April 2003

Model compounds for poly(1,4‐naphthylenevinylene) (1) and poly(2,6‐naphthylenevinylene) (2) were synthesized by the Wittig synthesis and studied by UV/VIS spectroscopy and cyclic voltammetry. The values of 2,0 eV for the band gap edge and 0,7 V vs. the saturated calomel electrode for the oxidation potential, which were estimated by an extrapolation of the band gap edge and oxidation potential of model dimer and trimer of 1, are in excellent agreement with the literature values for the polymer. A value of 2,3 eV for the band gap edge of 2 was found by extrapolating the band gap edge of a model dimer and trimer, but the oxidation potential of polymer 2 could not be estimated, because the model trimer was not sufficiently soluble in solvents used. The stoichiometries of the radical cation salts of the model compounds, which were prepared by electrocrystallization, were evaluated from elemental analysis. A single crystal, radical cation salt was obtained for the model dimer of polymer 2.
Thermotropic polyesters, 5. Liquid‐crystalline segmented polyesters containing non‐rigid mesogenic units with variable geometry
Authors: Bilibin Alexander Yu. , Tenkovtsev Andrey V. , Piraner Olga N.
Published: April 2003

Thermotropic liquid‐crystalline polyesters, containing the 3,3′‐biphenylylene unit as part of a conformationally mobile mesogenic group, were synthesized. Preliminary investigation of polymers as to their ability for manifesting liquid‐crystalline properties was carried out by polarizing microscopy and DSC.
Hydrogen peroxide formation by using redox resins containing nitroxyl radical groups
Authors: Dulog Lothar , Valet Andreas
Published: April 2003

Crosslinked copolymers from styrene, divinylbenzene and maleic anhydride were reacted with 4‐amio‐2,2,6,6‐tetramethylpiperidine to form imides, then oxidized to form polynitroxyles, and reduced to polyhydroxylamines. These resins form hydrogen peroxide when oxygen is blown through an aqueous slurry. The highest yield was found at 80°C.
Thermal degradation of polybutadiene, 1. Reactions at temperatures lower than 250°C
Authors: Chiantore Oscar , di Cortemiglia Maria Paola Luda , Guaita Marino , Rendina Gabriele
Published: April 2003

The thermal degradation of polybutadiene (PB) samples having different initial contents of cis‐1,4‐, trans‐1,4‐ and 1,2‐units were investigated at temperatures lower than 250°C, where cyclization, cross‐linking and cis‐trans isomerization occur without depolymerization. Changes of the cis‐trans content and decrease of double bonds in the polymers were measured at different temperatures. The rates of double bond loss were found to follow the order: trans‐1,4 > 1,2 > cis‐1,4, whereas the opposite occurred for the isomerization process. The reactions responsible for the structural changes of PB at temperatures lower than 250°C are reviewed and discussed.
Transition temperatures of thermotropic liquid‐crystalline copolyesters
Authors: Zhang Hongzhi , Zhang Zhibin
Published: April 2003

A series of thermotropic copolyesters with glass transition temperatures (Tg) ranging from 70°C up to 180°C based on terephthaloyl chloride (1), chlorohydroquinone (2a) or hydroquinone (2b), 4,4′‐isopropylidenediphenol (bisphenol‐A) (3) and ethylene glycol (4) was synthesized. The mesomorphic properties of the copolyesters were examined by visual observation of stiropalescence and birefringence under a polarizing microscope. The Tg values of the copolyesters depend mainly on the composition of non‐mesogenic or spacer segments and are practically independent of the content of mesogenic units. The structure of mesogenic units also shows a relatively small influence on the Tg behaviour.
13C NMR spectroscopical sequence analysis of poly(ethylene terephthalate‐co‐oxybenzoate)s
Authors: Jancke Harald , Böhme Frank , Graßhoff Karin , Rätzsch Manfred , Rafler Gerald
Published: April 2003

The sequence distribution of liquid‐crystalline poly(ethylene terephthalate‐co‐oxybenzoate)s was determined by 13C NMR spectroscopical investigations of samples with different compositions. All possible oxybenzoate‐ and terephthalate‐centered triads could be identified and assigned. The analysis of NMR substituent effects confirms the assignment. The comparison of the calculated statistical with the experimentally determined triad distribution shows a tendency for the formation of oxybenzoate blocks in the polymer chain.
In‐situ photopolymerization of oriented liquid‐crystalline acrylates, 4. Influence of a lateral methyl substituent on monomer and oriented polymer network properties of a mesogenic diacrylate
Authors: Broer Dirk J. , Hikmet Rifat A. M. , Challa Ger
Published: April 2003

Mesomorphism and the molecular orientation of 1,4‐phenylene bis{4‐(6‐(acryloyloxy)hexyloxy)benzoate} (1) and its derivative with a methyl‐substituent in the central phenylene group (2) are studied. The methyl group affects the transition temperatures and the thermodynamic parameters, but not the order parameter of the monomers. The photoinitiated polymerization of the diacrylate monomers in their uniaxially oriented state leads to highly oriented and densely crosslinked polymer networks. The order parameter of these networks depends on the polymerization temperature, but becomes nearly temperature‐independent after polymerization. The presence of the methyl group leads to a significant lower degree of order in the polymeric state. In addition, data are presented on the monomeric viscosity of 2 and on the tensile moduli, glass transitions and refractive indices of the oriented polymer networks. In order to extend the mesomorphous temperature range, mixtures of 1 and 2 are also investigated.
Living cationic polymerization of isobutyl vinyl ether, 1. Initiation by hydrogen iodide/tetraalkylammonium salts
Authors: Nuyken Oskar , Kröner Hubertus
Published: April 2003

Addition of hydrogen iodide to isobutyl vinyl ether (1) yields 1‐(1‐iodoethoxy)‐2‐methylpropane (2). The cationic polymerization of 1 initiated by 2/tetraalkylammonium salts (R4N+A−) shows the characterstics of a living polymerization. Different tetraalkylammonium salts were investigated. The coinitiator R4N+A− has no effect on the molar mass and the molar mass distribution of the resulting polymers. However, the rate of polymerization depends heavily on the nature and concentration of the coinitiator. The effect of the coinitiator is discussed on the basis of a special salt effect.
Studies in ring‐opening polymerisation, 10. Pyridine‐initiated polymerisation of cyclic anhydrocarboxylates of α‐mercapto acids
Authors: Ali M. Mobarak , Ammas Allan J. , Tighe Brain J.
Published: April 2003

The kinetics of the pyridine‐initiated polymerisation of simple 1,3‐oxathiolan‐2,5‐diones (3a–c) in nitrobenzene was studied at various temperatures. Results show that, although the substituents in 4‐position have a marked effect on rate of polymerisation, the polymerisation of the three monomers studied is linked by a common mechanism. Thus, the pyridine, nucleophile attacks the carbonyl in 5‐position and forms a charge transfer complex which decomposes to form a highly reactive α‐thiolactone intermediate 8 together with carbon dioxide and pyridine. Chain addition continues by the direct attack on the thiolactone by the terminal‐SH group of traces of parent acid. The reaction of each of the three monomers with pyridine was found to show first order kinetic dependence on both monomer and pyridine, although the initiator (i.e. pyridine) is not consumed. The resultant polymers (molecular weight typically around 20000) are highly crystalline and relatively insoluble in common organic solvents.
Synthesis and characterization of substituted aromatic polyesters derived from phenoxy‐ and tert‐butylhydroquinone
Authors: Heitz Walter , Nießner Norbert
Published: April 2003

Aromatic polyesters 5 and 6 were synthesized from tert‐butyl‐ and phenoxyhydroquinone (4a and 4b) and terephthalic acids 3a–e. The introduction of substituents reduces the phase transition temperature and increases the solubility of the corresponding polyesters in common solvents. As a result, soluble, amorphous and liquid‐crystalline aromatic polyesters were obtained. Unexpectedly, the phenoxyhydroquinone moiety suppresses the formation of a mesophase in some polyesters.
Miscibility behavior in blends of poly(2,6‐dimethylphenylene oxide) and random or block copolymers of styrene with methyl methacrylate
Authors: Kressler Jörg , Kammer Hans‐Werner , Morgenstern Ute , Litauszki Beata , Berger Werner , Karasz Frank E.
Published: April 2003

The Miscibility in blends of poly(2,6‐dimethylphenylene oxide)

Systematic IUPAC name: poly[oxy(2,6‐dimethyl‐1,4‐phenylene)].

(PPO) with random or block copolymers of styrene and methyl methacrylate (MMA) was studied by light microscopy and glass transition temperature measurements. Blends of PPO and the random copolymers were found to be miscible up to a copolymer content of 18 wt.‐% MMA. The transition from miscibility to immiscibility in these blends in independent of temperature in the range 100 to 350°C. From these data, the segmental interaction parameter between units of the homopolymer and MMA, χPPO/PMMA is estimated to be about 0,5. Blends of PPO and the block copolymers of styrene and MMA used behave essentially as the corresponding homopolymers in terms of miscibility.
Synthesis and permeation behavior of membranes from segmented multiblock copolymers containing poly(ethylene oxide) and poly(β‐benzyl L‐aspartate) blocks
Authors: Yokoyama Masayuki , Anazawa Hayato , Takahashi Akeo , Inoue Shohei , Kataoka Kazunori , Yui Nobuhiko , Sakurai Yasuhisa
Published: April 2003

Novel segmented multiblock copolymers (7) were synthesized by linking poly(ethylene oxide) (PEO) blocks with poly(β‐benzyl L‐aspartate)(PBLA) blocks via urethane and urea bonds, which were formed by the reaction of 4,4′‐methylenediphenyl isocyanate (5) with the terminal hydroxyl groups of α‐hydro‐ω‐hydroxypoly(oxyethylene) (4) and the terminal amino groups of poly(β‐benzyl L‐aspartate)‐block‐iminohexamethyleneimino‐block‐poly(β‐benzyl L‐aspartate) (3) [prepared from 1,6‐hexanediamine (1) and β‐benzyl L‐aspartate N‐carboxy anhydride (2)], respectively. Membranes with various water contents were obtained from these copolymers by changing the lengths of the PEO and PBLA segments. The study of the permeation of 1‐phenyl‐1,2‐ethanediol, vitamin B12 and myoglobin through the membranes showed a high dependency of the permeability on the molecular weight of the solutes.
Electrochemical copolymerization of 3‐dodecylthiophene and 3‐methylthiophene
Authors: Sato Masa‐aki , Shimizu Toshimi , Yamauchi Aizo
Published: April 2003

3‐Dodecylthiophene (1a) and 3‐methylthiophene (1b) were copolymerized electrochemically. The visible and IR spectra of the neutral copolymers prove the copolymers to be of random structure, which can be denoted as that of poly(3‐alkyl‐2,5‐thienylene)s. 1b polymerizes with preference over 1a. With increasing fraction of monomeric units of 1b in the copolymers, the conductivity increases and the solubility of the neutral copolymers decreases. The copolymer containing 58 mol‐% monomeric units of 1b has a high conductivity of 220 S/cm and a good solubility of 75 wt.‐% in chloroform. 1H NMR spectra of poly(3‐dodecylthienylene) and copolymers show two chemical shifts for the α(1)‐methylene protons of the monomeric units of 1a as well as of the methyl protons of the monomeric units of 1b. This fact may be explained by the presence of head‐to‐head and other constitutions.
Kinetic studies on the Menschutkin reaction of dimethylamino‐terminated poly(oxytetramethylene) with halides
Authors: Kohjiya Shinzo , Ohtsuki Tohru , Yamashita Shinzo
Published: April 2003

The kinetics of the Menschutkin reaction between dimethylamino‐terminated poly(oxytetramethylene) [AT‐PT (1), molecular weight 1160] and dihalides was followed by means of 1H NMR spectroscopy of NCH3 protons. For comparison, low‐molecular‐weight monoamines were subjected to similar experiments. No difference was found between the second‐order rate constants of AT‐PT and those of monoamines. But the rate constants depend on the kind of halide, i.e., the bromides [1,4‐bis(bromomethyl)benzene, 1,4‐dibromo‐2‐butene, benzyl bromide, allyl bromide] are much more reactive than the corresponding chlorides. Different from the usual nucleophilic reactions, the rate in a polar solvent (methanol) is smaller than that in the non‐polar chloroform. According to the activation parameters, this anomaly is due to hydrogen bonding, which has to be broken for the reaction to occur in a polar protic solvent.
Conformational properties and complex formation ability of poly(methacrylic acid)‐block‐poly(1‐methyl‐4‐vinylpyridinium chloride) in aqueous solution
Authors: Bekturov Esen A. , Frolova Vera A. , Kudaibergenov Sarkyt E. , Schulz Rolf C. , Zöller Joachim
Published: April 2003

It is shown that the block‐like structure of the polyampholyte poly(methacrylic acid)‐block‐poly(1‐methyl‐4‐vinylpyridinium chloride) considerably influences its conformational behaviour. This specific behaviour is explained by the formation of intra‐macromolecular polyelectrolyte complexes stabilized by cooperative ionic contacts between acidic and basic units near the isoelectric point (i. e. p.). The structure of the block‐polyampholyte at the i. e. p. is suggested to be close to the structure of non‐stoichiometric polyelectrolyte complexes. The complex formation ability of the block‐polyampholyte with respect to anionic, cationic, and nonionic polymers is also studied. By means of potentiometric, conductometric, and viscometric methods the composition of interpolymer complexes is determined and the degree of conversion in complex formation reactions is calculated. The water solubility (or insolubility) of interpolymer complexes is determined by the length of acid or basic blocks. It is proposed that a dissociation of interpolymer complexes into their individual components takes place at the i. e. p. of the block‐polyampholyte.
Synthetic and thermodynamic investigations in the polymerization of ethylene carbonate
Authors: Vogdanis Lazaros , Martens Barbara , Uchtmann Hermann , Hensel Friedrich , Heitz Walter
Published: April 2003

The polymerization of ethylene carbonate using different metal alkoxides results in poly(oxy‐ethylene‐alt‐ethylene carbonate). Polymers containing low amounts of CO2 or pure poly(oxy‐ethylene) are formed with anionic and cationic initiators. Poly(ethylene carbonate) is not accessible from ethylene carbonate by variation of temperatures and concentration. The reason is not the low ceiling temperature, but the positive enthalpy of polymerization. A ΔHp‐value of 125,6 kJ/mol was obtained from calorimetric investigations.
Stereo block copolymers of L‐ and D‐lactides
Authors: Yui Nobuhiko , Dijkstra Pieter J. , Feijen Jan
Published: April 2003

Sequential diblock copolymers composed of L‐ and D‐lactic acid residues were synthesized through a living ring‐opening polymerization of L‐ and D‐lactide initiated by aluminium tris(2‐propanolate). The composition of the block copolymers was varied by changing the reaction conditions and monomer over initiator ratio and confirmed by 1H NMR analysis, molecular weight determination and optical rotation measurements. Molecular weights ranged from 1,3 to 2,0 · 104 with 1,2 < M̄w/M̄n < 1,4. Stereocomplex formation in all block copolymers was determined using differential scanning calorimetry showing melting temperatures of about 205°C.
Effect of Pt(II) coordination on the thermotropic liquid‐crystalline behavior of poly(acrylic ester)s containing 4′‐cyano‐4‐biphenylyloxy mesogenic groups
Authors: Hanabusa Kenji , Suzuki Takashi , Koyama Toshiki , Shirai Hirofusa , Hojo Nobumasa , Kurose Akio
Published: April 2003

Poly(acrylic ester)s 3a–f and 4a–g, containing 4′‐cyano‐4‐biphenylyloxy mesogenic groups coordinating to Pt(II) ions with various contents, were synthesized by ligand exchange reaction of poly(acrylic ester)s 1 and 2 with dichlorobis(benzonitrile)platinum (II). The effect of Pt(II) coordination of the mesogen on the thermotropic liquid‐crystalline behavior was examined by DSC, X‐ray diffraction, and polarizing microscopy. For polymers 1, 3a–c with a content x of 4′‐cyano‐4‐biphenylyloxy mesogen coordinating to the Pt(II) ion less than 24 mol‐%, a nematic mesophase was observed between Tg and Tc. For polymers 2, 4a–e with x < 20 mol‐%, a smectic mesophase was found between Tg and Tc. On the other hand, polymers 3d–f and 4 f and g with a high amount of mesogenic groups coordinating to the Pt(II) ion do not form mesophases due to the cross‐linked structure resulting from the coordination of the mesogen to the Pt(II) ion.
Macromolecular prodrugs of 5‐aminosalicylic acid, 1. Azo‐conjugates
Authors: Callant Dominique , Schacht Etienne
Published: April 2003

Polymeric prodrugs of 5‐aminosalicylic acid, a drug used for the treatment of inflammatory bowel diseases such as ulcerative colitis and Crohn's disease, were synthesized and characterized. The active drug 5‐aminosalicylic acid was first coupled to a spacer group via an azo bond. All spacer‐pharmacon systems prepared have a terminal primary amino function, which by nucleophilic reaction was coupled under mild conditions to poly(methyl vinyl ether‐co‐maleic anhydride) (5) and poly(1‐vinyl‐2‐pyrrolidon‐co‐maleic anhydride) (6), without crosslinking. The polymeric prodrugs were characterized by UV and NMR. All polymer derivatives are insoluble in water at acidic pH‐range, but dissolve slowly in neutral or slight alkaline medium.
Haloaldehyde polymers, 40. Stereostructure of chloral oligomers prepared with lithium tert‐butoxide: Helical conformation of the linear isotactic oligomers in crystal and in solution
Authors: Ute Koichi , Nishimura Tohru , Hatada Koichi , Xi Fu , Vass Frantisek , Vogl Otto
Published: April 2003

The stereostructures of linear chloral oligomers were determined by X‐ray single crystal analysis. The chloral oligomers from dimer to pentamer were isolated by distillation and by GPC fractionation from the oligomer mixture prepared with t‐BuOLi initiation and acetate endcapping. The dimer fraction was a diastereomeric mixture of the racemo (1) and meso (2) isomers, while the trimer, tetramer and pentamer fractions each contained a single diastereomer (3, 4 and 5). The single crystals of 2, 3, 4 and 5 grown from methanol solutions belong to the space groups P1−, P21/n, P21/a and Pca21, respectively. X‐ray analyses showed that the acetal backbones of 2, 3 and 4 consist exclusively of meso dyads. The backbone arrangements of 2, 3 and 4, are essentially identical and approximate the repeat gauche(+)‐skew(−) sequences from the t‐BuO group to the acetyl terminal group (for S‐configurations). The conformation of (S,S,S,S)‐4 is very similar to a unit sequence of a 4/1‐helical structure of isotactic polychloral with left‐handed helicity. The axis of the helix is parallel to the c‐axis of the crystal, and the repeat distance is 4,81 Å. The conformations of the acetal backbones of 4 and 5 in solution were also investigated by NMR spectroscopy, on the basis of dihedral angle dependence of 3JCOCH coupling constants.
13C NMR spectroscopic studies on polyanion‐polycation complexes and their component polyelectrolytes
Authors: Kötz Joachim , Ebert Andreas , Kunze Jürgen , Philipp Burkart , Lindberg Johan , Soljamo Kari
Published: April 2003

Position and intensities of the 13C NMR signals and relaxation times T1 of several anionic and cationic polyelectrolytes in the solid state were compared with those of the appropriate polyanion‐polycation complexes. At a high charge density of the components, the most significant changes of the parameters in question due to complex formation are observed for the C atoms adjacent to the charge centers, indicating a strong Coulombic interaction. At lower charge density, conformational changes of the polymer chains have also to be taken into consideration.
Large scale fractionation of polyethylene by means of the continuous polymer fractionation (CPF) method
Authors: Geerißen Heinz , Schützeichel Peter , Wolf B. A.
Published: April 2003

The countercurrent extraction method recently developed for the continuous polymer fractionation (CPF) was applied to linear polyethylene (M̄w = 55 kg/mol; M̄n = 16,7 kg/mol). At temperatures higher than 130°C, moderately concentrated solution of polyethylene were extracted to remove the low‐molecular‐weight components. Discontinuous fractionation experiments served to detect the best suited solvents. Diphenyl ether was chosen to demonstrate that the present extraction can be performed even with the same single solvent used to prepare the feed. For very high‐molecular‐weight polymers, mixed solvents are, however, normally better than single ones, since they allow an easier tailoring of thermodynamic conditions, and yield much less viscous solutions. Mixtures of tetralin and triethylene glycol turned out to be best suited for polyethylene. By means of four successive CPF runs with the single solvent, polyethylene fractions with non‐uniformities U = (M̄w/M̄n) − 1 of approx. 0,3 to 0,4 were obtained on a 100 g scale. The rule of thumb that U can be halved in each CPF step without extensive optimization of the method was corroborated.
High‐molecular‐weight poly(alkylene phosphonate)s by condensation of dialkylphosphonates with diols
Authors: Pretula Julia , Penczek Stanislaw
Published: April 2003

The conditions of polycondensation of dimethyl phosphonate (1) with different diols were elaborated, leading to polymers with molecular weights up to 3,3 · 104. The novelty of the method is based on a two stage process. In the first stage an excess of 1 was used and short chains with methyl ester end groups were produced. These further react with elimination of 1 from the chain ends. In this way the coupling of macromolecules provides high‐molecular‐weight material and side reactions, due to the presence of the diols in the system (e.g. dehydration), are virtually suppressed.
Synthesis and structural studies of new copolyimides
Authors: Orzeszko Andrzej , Mirowski Krzysztof
Published: April 2003

A series of copolyimides, deriving from pyromellitic anhydride, was synthesized. Copolymers were prepared by condensation of N,N‐bis(chloroformylmethyl)pyromellitimide (1) with polydiols 2. The resulting copolymers show good solubility and thermoplastic properties. The effect of molecular weight of the polyglycol units on crystallinity and melting point of the copolyimides was studied by X‐ray diffractometry and differential scanning calorimetry. The increase of the number‐average molecular weight of the polyglycol units (M̄n) causes an increase of the crystallinity of the copolyimides. The differences between the degree of the crystallinity and the weight fraction of the polyglycol units in the copolyimides prove that only some part of polyglycol in the copolyimides can be retained within the crystalline structure.