bluuebunny/crossref_metadata_2025 huggingface dataset:
Relaxation and charge transport in mixtures of zwitterionic polymers and inorganic salts
Authors: Rozanski Stanislaw A. , Kremer Friedrich , Köberle Peter , Laschewsky André
Published: April 2003

Dielectric spectroscopy is employed to analyze the molecular dynamics and the charge transport in mixtures of zwitterionic polymers of the type poly{3 [N(ω‐methacryloyloxyalkyl)] N, [N‐dimethylammonio propanesulfonate] with sodium iodide in the frequency range of 102Hz–107 Hz and in the temperature range of 110 K‐400 K. The amount of inorganic salt added varies from 0–200 mol‐% relative to the number of zwitterionic groups present in the polymer, contributing strongly to the conductivity. One relaxation process is observed whose relaxation rate depends strongly on the length of the aliphatic spacer between the polymethacrylate main chain and the zwitterionic group. Exhibiting an Arrhenius‐like temperature depence with activation energy EA = 47 KJ/mol, this relaxation process is assigned to fluctuation of the quaternary ammonium groups in the side chains. At higher temperatures, the dielectric properties and the conductivity are primarily dominated by the mobile inorganic ions: conductivity strongly depends on the salt concentration, showing a pronounced electrode polarization effect. The frequency and salt concentration, dependences of the conductivity can be quantitatively described as hopping of charge carriers being subject to spatially randomly varying energy barriers. For the low‐frequency regime and for the critical frequency marking the onset of the conductivity's dispersion, the Barton‐Nakajima‐Namikawa (BNN) relationship is fulfilled.
“Compatibilizing effect” in interpenetrating polymer networks
Authors: Du Prez Filip , Goethals Eric J.
Published: April 2003

α,ω‐Acrylate terminated poly(1,3‐dioxolane) (polyDXL) was copolymerized with methyl acrylate and methyl methacrylate for the synthesis of block copolymer networks. It was shown by dynamic mechanical thermal analysis (DMTA) that the presence of covalent bonds between poly DXL and the polyacrylate leads to a high degree of compatibility. In contrast, the combination of the same two components in network form, leading to sequential interpenetrating polymer networks (IPN's), resulted in phase‐separated materials. When the above‐mentioned block copolymer structures, in which one of the blocks is chemically identical to the polyacrylate used in the second network, were applied in the first network of the IPN, an increase of miscibility between the two types of polymers was observed. DMTA analysis revealed that the morphology of these IPN's could be varied from phase‐separated to homogeneous materials by increasing the polyacrylate fraction in the first block copolymer network. The possibility to degrade the poly DXL segments in an acid environment allows the complete degradation and extraction of one network in the IPN's and hence provided an interesting approach to the study of domain characteristics by optical microscopy.
On the contribution of covalent and ionic species to the chain growth
Authors: Penczek Stanislaw , Szymanski Ryszard
Published: April 2003

The problem of computing of the covalent and ionic species contribution to the chain building in propagation is discussed, and it is shown that under certain conditions the reversibility of propagation does not influence the contribution of the given species.
A novel imaging system by dye‐sensitized photooxidation of oxazole groups attached to a polymer backbone, 4. Effect of oxazole content and spacer length
Authors: Ito Hiromitsu , Ichimura Kunihiro
Published: April 2003

Oxazole derivatives attached to a polymer backbone were transformed efficiently to the corresponding triacylamide compounds in a thin film by photooxidation using various dyes as photosensitizers. This photoinduced transformation proved to be applicable to a photoresist with positive tone and a holographic grating formation by development with an aqueous solution of amines to dissolve exposed areas of the film. In this system, the length of the methylene chain connecting the oxazole ring to the polymer backbone and the content of oxazole units in the polymer influence the efficiency of the image formation as well as development conditions.
Continuous fractionation of poly[(dimethylimino)decamethylene bromide] and molecular weight dependence of the glass transition
Authors: Schultes Klaus , Wolf B. A. , Meyer Wolfgang H. , Wegner Gerhard
Published: April 2003

30 g of the ionene poly[(dimethylimino)decamethylene bromide] were fractionated by a continuous counter‐current extraction method (CPF) using ethylene glycol monoethyl ether as the solvent and diisopropyl ether as the non‐solvent component. The efficiency of the separation was checked by viscometry and gel‐permeation chromatography (GPC) measurements. Eight fractions of different molar mass were prepared for differential scanning calorimetry (DSC) experiments. With bromide as counter‐ion, the glass transition temperature of the ionene increases from ca. 60 to 85°C as the intrinsic viscosity of this material (in 0,4 M aqueous solutions of KBr at 25°C) rises from ca. 14 to 22 mL/g. When bromide is replaced by tetrafluoroborate, the glass transition temperature remains almost constant at ca. 60°C, irrespective of the molar mass of the ionene.
Relative importance of side reactions in the RLi‐acrylonitrile — dimethylformamide system
Authors: Denisov Viktor M. , Yakimansky Alexander V. , Novoselova Anna V. , Erussalimsky Boris L.
Published: April 2003

The probability of interaction of anionically growing poly(acrylonitrile) chains with dimethyl‐formamide (DMF) in the acrylonitrile (AN)‐RLi‐DMF system was investigated by means of NMR data, poly(acrylonitrile) synthetized with various ROLi initiators does not contain traces of DMF fragments. Quantum chemical calculations were carried out taking CH3CH2CH(CN)Li as a model compound and simulating the anionic active site of AN. The results obtained show that the interaction of this compound with AN is highly preferred (by 100 kJ/mol) to that with DMF. Qualitatively similar results are related to the butyllithium(BuLi)‐AN and BuLi‐DMF systems. However, the reaction between BuLi and DMF is exothermic (in contrast to that between the active site of the model compound with DMF). This fact is in agreement with the effective addition of BuLi to DMF in the absence of any competing compound.
Formation and degradation of 1,4‐polybutadiene via metathesis: new results concerning cyclic oligomers
Authors: Thorn‐Csányi Emma , Hammer Jens , Pflug Kai P. , Zilles J. Ulrich
Published: April 2003

The ring‐opening metathesis polymerization (ROMP) of cyclic oligomers of butadiene (c,c‐1,5‐cyclooctadiene — COD —, t,t,t‐1,5,9‐cyclododecatriene — CDT —), the acyclic diene metathesis (ADMET) of 1,5‐hexadiene and the intramolecular metathesis degradation of 1,4‐polybutadiene (1,4‐BR) were studied using stable tungsten and molybdenum carbene complexes as well as conventional metathesis catalysts. The determination of cyclic oligomers up to rings containing eight butadiene units shows, compared to the literature, different results regarding the distribution, concentration and cis/trans ratio. Kinetic studies of the ROMP of COD and the intramolecular metathesis of 1,4‐BR allow to explain the discrepancy. The ROMP product spectrum for the cyclobutene system known and accepted until now in the literature as ring‐chain equilibrium is controlled kinetically and far apart from thermodynamic equilibrium according to our results.
Block copolymers with bipyridine containing segments: Synthesis and self‐organization by Cu(I) complexation
Authors: Eisenbach Claus D. , Göldel Andreas , Terskan‐Reinold Monika , Schubert Ulrich S.
Published: April 2003

The synthesis and properties of segmented ABA triblock and (AB)n multiblock copolymer systems with 6,6′‐disubstituted 2,2′‐bipyridine (bpy) building blocks B and poly(oxytetramethylene) soft segments A are described. The access to the disubstituted bipyridines in large scale quantities was achieved by modification of conventional synthetic routes. In the presence of copper(I) ions these polymers formed mononuclear [Cu(I)(bpy)2] complexes in solution through self‐assembly. The complexed copolymers were microphase separated systems in bulk with nano to mesoscopic superstructures consisting of copper‐bpy complex aggregates in a polyether matrix. The thermal, mechanical and elastomer properties of the block copolymers varied with composition.
New copolyamides based on adipic acid, aliphatic diamines and amino acids: Synthesis, characterization and biodegradability, 5
Authors: Arvanitoyannis Ioannis , Nikolaou Eleftherios , Yamamoto Noboru
Published: April 2003

Novel series of biodegradable copolyamides were synthesized via melt copolymerization. The statistical copolymides were produced by reaction of the salt of adipic acid (AA) and bis(para‐aminocyclohexyl)methane (PACM) or isophoronediamine (IPD)/α‐amino acids at 250°C. Elemental analyses, density, viscosity, differential thermal analysis (DTA) and gelpermeation chromatography (GPC) measurements and FT‐IR spectroscopy were employed for the characterization of these copolyamides. The semicrystalline (AA/PACM/α‐amino acids) or amorphous (AA/IPD/α‐amino acids) nature of these copolyamides was shown with DTA and wide angle X‐ray diffraction patterns. Several methods were used in order to investigate and assess their biodegradability such as alkaline hydrolysis (10% w/v NaOH, 80°C), burial in soil (microbial and bacterial attack) and enzymatic hydrolysis (α‐trypsin and α‐chymotrypsin). The degradation of the copolyamides was evaluated with the aid of GPC and DTA measurements and correlated to the α‐amino acid content. These copolyamides could eventually find applications in the field of food packaging and agriculture (disposable plastics) and medicine (sutures).
NMR investigations on a liquid‐crystalline side‐chain siloxane polymer with a wide biphasic region
Authors: Hempel Günter , Hänsge Heiko , Metzner Bernd , Krücke Bernd
Published: April 2003

A polysiloxane bearing two different kinds of side chains has been studied by nuclear magnetic resonance and relaxation investigations. Both side chains contain the same mesogenic core but differ in their connection to the main chain: one of them is bound directly to the backbone, the other is linked to it via a (CH2)3 spacer. In this sample, the isotropic and mesomorphic phases coexist over a relatively wide range of temperatures. We have tried to explain this phenomenon by microphase separation. For the sA –sB transition a similar biphasic behaviour could not be observed with our methods. The order parameter has been estimated selectively for carbons in different parts of the side chain (spacer, wing group, mesogenic core). The behaviour of the order parameter in the mesomorphic regions of the biphase was observed, and a possible explanation is given.
Characteristics of permeation and separation for aqueous ethanol solutions through methyl methacrylate‐dimethylsiloxane graft copolymer membranes
Authors: Miyata Takashi , Takagi Toru , Kadota Takeshi , Uragami Tadashi
Published: April 2003

Poly(methyl methacrylate) with oligodimethylsiloxane grafts (MMA‐g‐DMS) was prepared by copolymerization of a dimethylsiloxane (DMS) macromonomer with methyl methacrylate (MMA). Two glass transition temperatures (Tg) were observed at about 120°C and − 127°C and in all graft copolymer membranes. Transmission electron micrographs demonstrate that the MMA‐g‐DMS membranes show microphase separation. When an aqueous solution of 10 wt.‐% ethanol was applied to permeations through the MMA‐g‐DMS membranes by pervaporation, the ethanol concentration in the permeate and the permeation rate increased drastically with the DMS content in the copolymer. Especially, while at a DMS content of less than 40 mol‐% preferentially water permeates from an aqueous solution of 10 wt.‐% ethanol, the membranes with more than about 40 mol‐% of DMS show ethanol‐permselectivity. The relationship between the microphase‐separated structures and the permeation characteristics for an aqueous ethanol solution is discussed.
A new temperature‐ and pH‐responsive copolymer for possible use in protein conjugation
Authors: Chen Guohua , Hoffman Allan S.
Published: April 2003

The temperature‐ and pH‐sensitive copolymers of N‐isopropylacrylamide (NIPAAm) with 4‐pentenoic acid (PAc) were synthesized and the monomer reactivity ratios were estimated. The effects of polymer composition, pH and ionic strength of the aqueous solution on the lower critical solution temperature (LCST) of the copolymers were investigated. It was found that the LCSTs of these unusual copolymers can be either lowered or raised compared to the LCST of poly(N‐isopropylacrylamide) by changing the pH.
Relaxation of holographic gratings in liquid‐crystalline side chain polymers with azo chromophores
Authors: Bieringer Thomas , Wuttke Roland , Haarer Dietrich , Geßner Uwe , Rübner Joachim
Published: April 2003

The relaxation of holographic phase gratings was examined to obtain some information about the involved photochemically induced changes. The studies were performed with statistical liquid‐crystalline side group copolymers having different concentrations of the azobenzene dye. The formation of mesophases, which normally exist in the thermodynamic equilibrium, was prevented during the sample preparation by quenching the polymer films. Two relaxation processes were found in this glassy state of the polymers. The faster one could be described by a dispersive stretched exponential function and was attributed to relaxation processes which are related to the amorphous phase of the sample, while the slower one, corresponding to a single exponential process, correlates with the formation of light‐induced liquid‐crystalline microstructures. The latter are believed to be the main cause for the modulation of the refractive index.
On the anionic polymerization of dialkylaminoisoprenes, 3. A nuclear magnetic resonance study of the structure of oligo[5‐(N,N‐diisopropylamino)isoprenyllithium]
Authors: Petzhold Cesar , Kolshorn Heinz , Stadler Reimund
Published: April 2003

The structure of oligo[(5‐N,N‐diisopropylamino)isoprenyllithium] (number‐average degree of polymerization Pn = 1‐2) prepared by reaction of alkyllithium with 5‐(N,N‐diisopropylamino)‐isoprene

System. name: N,N‐diisopropyl‐2‐vinylallylamine.

in nonpolar (benzene) and polar (tetrahydrofuran) solvents has been studied by 1H and 13C NMR spectroscopy. In tetrahydrofuran, as expected, the negative charge at the terminal chain unit is more delocalized than in benzene and, consequently, the carbon‐lithium bond has a more ionic character. In both solvents the living chain end shows a cisoid‐4, 1‐structure. No cistrans isomerization could be detected. This independence of the carbanion structure of the solvent polarity is explained by the complexation of the Li+ counter ion to the amino group of the terminal monomer unit and by the bulkiness of the isopropyl side groups, which hinder isomerization and favour the cisoid conformation of the living chain end.
Regio‐ and stereospecificity in propene polymerization with MgCl2‐supported Ziegler‐Natta catalysts: effects of hydrogen and the external donor
Authors: Chadwick John C. , Van Kessel Gerard M. M. , Sudmeijer Olof
Published: April 2003

Investigation of the effects of hydrogen and different external donors on the stereoregularity and chain‐end distribution of polypropylene prepared using MgCl2/TiCl4/phthalate ester‐AlEt3‐alkoxysilane catalyst systems has not only confirmed the importance of regiospecificity in relation to hydrogen activation but has also indicated a significant effect of stereospecificity. Alkoxysilanes giving high isospecificity also give high molecular weight polypropylene. Polymer stereoregularity also increases with increasing hydrogen concentration in polymerization. These effects indicate that not only regioirregular but also stereoiregular insertion slows down chain propagation. In each case the probability of chain transfer with hydrogen is higher than that following a stereoregular insertion, and in each case chain transfer with hydrogen leads to the regeneration of isospecific propagation.
Continuous polymer fractionation of poly(methyl vinyl ether) and a new Kuhn‐Mark‐Houwink relation
Authors: Petri Hans‐Michael , Stammer Andreas , Wolf B. A.
Published: April 2003

Continuous polymer fractionation (CPF) — a new large‐scale method — was applied to the technical poly(methyl vinyl ether) (PVME) using toluence as solvent and petroleum ether as non‐solvent. Two different devices served as fractionation apparatus, namely a column packed with glass beads and a set of mixer‐settler extractors. Advantages and draw‐backs of these devices are discussed. The experiments yielded numerous PVME fractions, varying in molar mass from 22 to 87 kg/mol and in molecular non‐uniformity U = (M¯w/M̄n) – 1 from 0,25 to 0,41 according to gel‐permeation chromatography as compared with ca. U = 1,30 for the starting material. The following Kuhn‐Mark‐Houwink relation was established for PVME in ethyl methyl ketone at 30°C: [η]/(mL/g) = 2,6 . 10−3M̄0,86.
The effect of side groups on the dielectric relaxation of poly(methylhydrogensiloxane)
Authors: Goodwin Andy A. , Beevers Martin S.
Published: April 2003

The α‐relaxation of a linear poly(methylhydrogensiloxane) has been investigated as a function of temperature and frequency using dielectric relaxation spectroscopy. Replacement of the hydrogen with a hexyl group increased the temperature and broadness of the α‐process, and this is interpreted in terms of a slowing of the motions of the Si—O dipoles and plasticisation of the siloxane chain by the side groups. Replacement of the hydrogen with a mesogenic group produced a side‐chain liquid crystal which exhibited dielectric relaxation behaviour characteristic of the glass and liquid crystalline states.
2‐Perbromomethyl‐2‐oxazoline: a novel trifunctional initiator for the ring‐opening polymerization of 2‐methyl‐2‐oxazoline
Authors: Bera Tushar Kanti , Sivaram Swaminathan
Published: April 2003

Polymerization of 2‐methyl‐2‐oxazoline was carried out using a trifunctional initiator, 2‐perbromomethyl‐2‐oxazoline. The degree of polymerization (DP) of the resulting polymer was very close to the feed mole ratio of the monomer to initiator. The number‐average molecular weight M̄n increased linearly with conversion, indicating the living nature of the propagating chain end. 1H NMR and end‐group analyses results are consistent with the proposal that the polymer possesses a star‐shaped structure.
Data evaluation for unified multi‐detector size exclusion chromatography — molar mass, viscosity and radius of gyration distributions
Authors: Reed Wayne F.
Published: April 2003

The output of a size exclusion chromatography (SEC) system was connected to a single capillary viscometer, a multi‐angle laser light scattering detector (MALLS) and a refractive index detector (RI). This provides absolute distributions of molar mass, radius of gyration and reduced viscosity, which are valuable both for practical polymer characterization and as tests of physical polymer theories. The instrument interfacing is described, along with the method of data analysis. A quantitative investigation of systematic and random sources of error and their influence on polymer characterization is made. An experimental example using a biopolyelectrolyte (hyaluronate), including complete error analysis, is presented, along with other data. Although the emphasis here is on aqueous SEC, most of the principles should carry over to organic phase SEC. A simultaneous, in‐line comparison of a low‐angle laser light scattering (LALLS) detector and MALLS detectors was also made. The dangers of ‘universal calibration’ for hydrosoluble polymers are also illustrated.
A triple‐bonds‐containing poly(ether/ester): synthesis, characterization and cross‐polymerization
Authors: Denchev Zlatan , Dudevski Ivo , Petrova Jordanka , Fakirov Stoyko
Published: April 2003

A segmented poly(ether/ester) multiblock copolymer containing acetylene groups within the hard segment was synthesized starting from poly(ethylene glycol) with a number‐average molecular weight M̄n = 1000, 2‐butyne‐1, 4‐diol and terephthaloyl dichloride. Thermal and spectroscopic data suggest a blocky structure of the copolymer prepared. Nuclear magnetic resonance spectroscopy shows an average degree of polymerization of the hard segments of about 6. By heating in the presence or absence of a catalyst, the monoacetylene units in the hard segments are cross‐polymerized below and above their melting temperature. The crosspolymerized material reveals a maximum gel fraction of 93,5 wt.‐%, does not crystallize and shows reversible deformability in contrast to the starting polymer. In accordance with previous reports it is concluded that cross‐polymerization is possible only in a polymer distinguished by some degree of chain ordering.
Morphology, phase transitions and viscoelastic properties of poly(oxybisdimethylsilylene). A mesophase in a silicon analogue of a polyether
Authors: Pluta Miroslaw , Pakula Tadeusz , Kryszewski Marian , Kurjata Jan , Chojnowski Julian
Published: April 2003

Poly(oxybisdimethylsilylene) (POBDMS)

System. name: poly[oxy(tetramethyldisilane‐1,2‐diyl)].

has been studied by differential scanning calorimetry, polarizing microscopy, wide‐angle X‐ray scattering and dynamic mechanical measurements. The polymer shows a weakly marked glass transition near 154 K and three first‐order transitions: a crystal‐to‐crystal transition at 256 K, a crystal‐to‐mesophase transition at 294 K and a transition to the isotropic melt at 325 K. These transitions are correlated with the mechanical relaxations measured as a function of temperature. The rheological behaviour of the polymer in the isotropic liquid state and in the mesophase has been studied, as well. The properties of POBDMS are discussed in comparison with liquid‐crystalline polymers with mesogenic groups.
Micelle formation and polyisobutylene solubilization by polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐polystyrene block copolymers
Authors: Quintana José R. , Salazar Ramiro A. , Katime Issa
Published: April 2003

Thermodynamics of micellization and the structure of micelles formed by polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐polystyrene block copolymers were studied. A molar mass influence on the aggregation number of micelles was found. The lower the molar mass, the higher the micelle aggregation number. The solubilization of polyisobutylene by micelles of these copolymers in methyl isobutyl ketone was also examined. The saturation concentrations of polyisobutylene solubilized by different block copolymers in methyl isobutyl ketone were determined by laser light scattering. The solubility curves found were linear and dependent on the molar mass of the polyisobutylene solubilized and the copolymer. The logarithm of the maximum amount of polyisobutylene solubilized by mass unity of the triblock copolymer varies linearly with the logarithm of the molar mass of the polyisobutylene. This variation is hardly dependent on the copolymer molar mass and strongly dependent on the type of block copolymer.
Polymers containing formamidine groups, 4. Copolyformamidines prepared from triethyl orthoformate, benzidine and various diamines
Authors: Rillich Mailk , Jehnichen Dieter , Komber Hartmut , Böhme Frank
Published: April 2003

Fully aromatic and aromatic‐aliphatic polyformamidines were prepared by high‐temperature solution polycondensation of the appropriate diamines with triethyl orthoformate (TEOF). Copolyformamidines of benzidine (4,4′‐biphenyldiamine) with p‐phenylene and trans‐1,4‐cyclohexylene units, respectively, showed liquid‐crystalline behaviour. Both series of copolyformamidines differ distinctly in crystallinity. This has been discussed with respect to sequence distribution, which was determined by 13 C NMR spectroscopy.
Ring‐closing depolymerization of poly(ε‐caprolactone)
Authors: Nelißen Marion , Keul Helmut , Höcker Hartwig
Published: April 2003

Ring‐closing depolymerization of poly(ε‐caprolactone) in toluene solution with catalytic amounts of Bu2Sn(OMe)2 results in a mixture of cyclic oligomers, the equilibrium concentration of which corresponds to the concentration predicted according to the Jacobson‐Stockmayer theory. ε‐Caprolactone, however, is absent from this reaction mixture. When poly(ε‐caprolactone) is depolymerized in the melt at 260°C in the presence of a catalyst, beside ε‐caprolactone its cyclic dimer and trimer are distilled off. The composition is dependent on the catalyst used, e.g., Bu2Sn(OMe)2 produces 95,4 wt.‐% of ε‐caprolactone and 3,7 wt.‐% of its dimer while with Ti(OiPr)4 (iPr: isopropyl) 51,4 wt.‐% ε‐caprolactone and 49,6 wt.‐% of its dimer are obtained. Block copolymers containing poly(ε‐caprolactone) result in a similar product distribution, however, the second block may influence the rate of decomposition. The activation energy of the catalysed (0,5 mol‐% Bu2Sn(OMe)2) and uncatalysed ring‐closing depolymerization were determined to be 63 kJ/mol, and 87 kJ/mol, respectively.
Polymerization of phenylacetylene with WOCl4/tetraphenyltin catalyst in benzene/1,4‐dioxane. Synthesis of high‐molecular‐weight poly(phenylacetylene)
Authors: Sedláček Jan , Pacovská Marta , Vohlídal Jiří , Grubišić‐Gallot Zlatka , Žigon Majda
Published: April 2003

Phenylacetylene was polymerized with WOCl4/tetraphenyltin (mole ratio 1:2) catalyst in benzene and benzene/1,4‐dioxane mixtures. The resulting polymers were characterized by means of multidetector size‐exclusion chromatography and 1H NMR and IR spectroscopy. 1,4‐Dioxane used as a co‐solvent was found to increase both the content of cis units and the molecular weight of poly(phenylacetylene) (PPhA); a weight‐average molecular weight of M̄w = 1 · 106 was reached. In spite of the high mole ration monomer: catalyst (1260:1) used in the polymerizations high yields of PPhA were attained. No effect of an alteration in PPhA microstructure upon its degradation in tetrahydrofuran solution exposed to air has been observed.
Novel thermotropic behavior of (diphenyl/phenyl‐o‐tolyl)phosphazene random copolymer
Authors: Kojima Morio , Magill Joseph H. , Franz Uli , White Michael L. , Matyjaszewski Krysztof
Published: April 2003

[(Ph2PN)0,76(Ph(o‐tolyl)PN)0,24] random copolymer (Ph: phenyl) was synthesized by the reaction of Ph2POCH2CF3 and Ph(o‐tolyl)POCH2CF3 with trimethylsilyl azide. Differential scanning calorimetry (DSC) measurements showed that this copolymer has a single glass transition at ≈ 80°C and transforms into a mesophase at 162 ∼ 189°C depending upon the thermal history of the specimens. Lath shaped crystals with unit cell dimensions a = 1,30 nm, b = 1,13 nm and y = 87° (Form‐I) were obtained from mixed dilute monochlorobenzene and p‐xylene solution of the copolymer. Upon heating the specimens to 140°C, the “a” parameter of Form‐I changes to a = 2,21 nm and the “b”, “y” remain unaltered (Form‐II). When the specimens are cooled (10°C/min) from above T(1), the mesophase (δ‐form) is “frozen in” and the δ‐form specimens transform into Form‐II by heating to 140°C. Another structure change (Form‐III) occurs after the δ‐form specimens were heated to 180°C followed by cooling below the glass transition temperature Tg. However, upon cooling the specimens slowly (0,2°C/min) from above T(1), Form‐III results.
Intramolecular excimer formation in naphthalene‐containing polyesters. Bichromophoric model compounds derived from phthalic, succinic or malonic acid and 2‐hydroxynaphthalene or 2‐hydroxymethylnaphthalene
Authors: Pozuelo Javier , Mendicuti Francisco , Mattice Wayne L.
Published: April 2003

Steady state fluorescence measurements in dilute solutions are performed for bis(2‐naphthyl) phthalate, bis(2‐naphthylmethyl) phthalate, bis(2‐naphthyl) succinate, bis(2‐naphthylmethyl) succinate, bis(2‐naphthyl) malonate and bis(2‐naphthylmethyl) malonate, as models for polyesters containing naphthalene in their rigid units and flexible spacers that impose differences in the types of interactions between successive naphthalene units. The amount of intramolecular excimer in dilute solution depends on the type of flexible spacer, and also whether the compound is derived from 2‐naphthol or 2‐hydroxymethylnaphthalene. No excimer is detected from the compounds derived from 2‐naphthol, but all compounds derived from 2‐hydroxymethylnaphthalene showed excimer formation. These results are rationalized with a theoretical analysis of the conformations of the flexible spacers.
Thermotropic liquid‐crystalline aromatic polyester‐graft‐poly(2,6‐dimethyl‐1,4‐phenylene oxide) copolymers
Authors: Sato Moriyuki , Mangyo Takashi , Mukaida Ken‐ichi
Published: April 2003

Dicarboxy‐terminated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) macromonomers were prepared and subjected to the preparation of tailor‐made aromatic thermotropic liquid‐crystalline (LC) polyester‐graft‐PPO copolymers. The macromonomers were obtained by hydrolysis of dimethyl carboxylate‐terminated PPO macromonomers without cleavage of the PPO chains, which were derived from PPO oligomers with a terminal phenolic OH‐group and a bromo derivative of isophthalate. The tailor‐made aromatic thermotropic LC graft copolymers were prepared by direct polycondensation from the dicarboxy‐terminated macromonomers, p‐hydroxybenzoic acid, aromatic dicarboxylic acids and diphenols at definite mole ratios in pyridine in the presence of diphenyl chlorophosphate as a condensation reagent. The polyester‐graft‐PPO copolymers are thermally stable up to 280–300°C and show a thermotropic LC nematic phase in spite of introduction of PPO grafts on the polyester backbones.
Grafting on polybutadiene with macro or macromonomer initiators containing poly(ethylene glycol) units
Authors: Hazer Baki
Published: April 2003

Crosslinked poly(ethylene glycol)‐blockpolybutadience block copolymers were obtained by coupling reaction of polybutadiene (PBd) with macromonomer azo initiators (macroinimers) or polyazoesters (PAE) in moderate yield (22–75%). NMR and FT‐IR spectroscopy measurements were used to characterize and determine the poly(ethylene glycol) (PEG) contents (20–66%). The latter depends on the initial concentration of the azo compounds. Broad melting peaks appear in the DSC curves in a temperature range from about 65–130°C. The crosslinked polymers containing PEG‐1500 units showed sharp melting transitions and the second heating cycle showed that recrystallization rates are very high. Swelling ratios of the polymer networks were determined in water (1,22–2,96) and in CHCl3 (7,81–20,84). The morophology of the cold fractured area of the crosslinked polymers was analyzed by scanning electron microscopy (SEM).
Complex‐radical alternating terpolymerization of maleic anhydride, trans‐stilbene and N‐phenylmaleimide
Authors: Rzaev Zakir M. O. , Medyakova L. V. , Mamedova M. A. , Akovali Güneri
Published: April 2003

Radical terpolymerizations of maleci anhydride (MA), trans‐stilbene (Stb) and N‐phenylmale‐imide (PhMI) were carried out in methyl ethyl ketone (MEK) at 60–80°C in the presence of 2,2′‐azoisobutyronitrile (AIBN) as initiator. The terpolymerization was evaluated by using either the free monomer or complex participation models. The relative of MA toward poly(Stb) radical was found to be about 10,6 times lower than that of PhMl. The initial rate of copolymerization, the participation of the charge transfer complex (CTC) monomers and free monomers was quantitatively estimated. It was established that, even with a considerable change in the ratio of electron‐acceptor monomers (MA and PhMI) in the initial reaction mixture, terpolymers possessed always a composition ratio close to 1:2:1. Constants for copolymerization of MA…Stb (M1) and PhMI…Stb (M3) were determined by using the Kelen‐Tüdős equation, and r1 · K1/K3 = 0,03 and r2 · K3/1 =0,08, where K1 and K3 are complex‐formation constants of MA…Stb and PhMl…Stb complexes, respectively, were obtained. The result of kinetic studies of terpolymerization was interpreted as involving mainly alternating copolymerization of two complexomers with predominant participation in chain growth. Thermogravimetric analyses indicated the high thermal stabilities of terpolymers obtained.
Steric stabilization by grafting and copolymerization of water‐soluble oligomers and polymers
Authors: Brown Rebecca , Stützel Bernhard , Sauer Thomas
Published: April 2003

Different types of nonionic, water‐soluble polymers and macromonomers are investigated as emulsion stabilizers in the batch emulsion polymerization of styrene. A power law dependence of the rate of polymerization vs. stabilizer concentration is observed, in formal accordance to Smith‐Ewart kinetics. For water‐soluble polymers, exponents in the range of 0,6 are found which are close to that of the reference anionic surfactant (0,67). The differences are mainly attributed to the larger initial particle size which is accompanied by secondary agglomeration during polymerization. Several reasons for this agglomeration are discussed which have their origin in the solution and adsorption properties of the water‐soluble polymers. Compared to the non‐functional polymers some macromonomers show a similar kinetic behavior with exponents in the range of 0,4 to 0,5, while others give very small values. These differences strongly depend on the molecular structure of the macromonomers. They are in particular attributed to enhanced homopolymerization as well as solubility in monomer and polymer. No secondary agglomeration takes place when using macromonomers as emulsion stabilizers. This is due to the enhanced colloidal stability because of the defined bonding of the macromonomers to the latex particle surface as compared to the more random grafting of the non‐functional water‐soluble polymers.
Group‐transfer alternating copolymerization of 2‐phenyl‐1,3,2‐dioxaphosphorinane with trimethylsilyl 2‐(acryloyloxy)ethanesulfonate
Authors: Kobayashi Shiro , Kadokawa Jun‐ichi
Published: April 2003

This paper describes a new class of reaction, group‐transfer alternating copolymerization (GTAC), between 2‐phenyl‐1,3,2‐dioxaphosphorinane (1) and trimethylsilyl 2‐(acryloyloxy)ethanesulfonate (2). The copolymerization took place without any added catalyst and proceeded via quantitative trimethylsilyl group‐transfer process to give a 1:1 alternating copolymer 3a having a ketene silyl acetal group in the main chain. Results of spectroscopy as well as alkaline hydrolysis and bromination of the copolymer confirmed the structure.
Exchange reactions between covalent and carbocationic species in polymerization of vinyl ethers in the presence of lewis acids: dynamic NMR studies
Authors: Matyjaszewski Krzysztof , Teodorescu Mircea , Lin Chih‐Hwa
Published: April 2003

The ionization of 1‐chloro‐1‐isobutoxyethane (IBVCI) in the presence of BCI3 in CD2Cl2 and CD2Cl2/CDCl3 mixtures at variable temperatures was studied by 1H NMR spectroscopy. The presence of only one NMR signal for the methine proton in the intermediate stage of ionization indicated a fast exchange between covalent and cationic species. The dependence of its chemical shift on the [BCI3]0/[IBVCI]0 ratio was used to calculate the equilibrium constant of ionization at various temperatures, assuming only the ionization‐recombination process. The dependence of the calculate the equilibrium constant (Kapp) on the [BCI3]0/[IBVCI]0 ratio indicated the involvement of additional side equilibria, including the formation of oxonium ions by the reaction between the carbocation and the ether functionality, and the complexation of Lewis acid by the ether group. The width at half‐height of the methine proton signal was used to calculate the apparent rate constant of the recombination of the counterions in the ion pairs (K). It was found that K is larger in CDCI3/CD2CI2 mixtures than in CD2CI2. When BCI3 is present in excess, the calculated rate constants for ionization and recombination are higher than the reported rate constant of propagation for the cationic polymerization of isobutyl vinyl ether (IBVE). Attempts to use this finding in order to prepare well‐defined polymers were unsuccessful because of the consumption of BCI3 through the addition reaction to the double bond of the monomer.
Interpolymer complexes of (co)poly(vinyl ethers) of glycols and poly(carboxylic acids)
Authors: Kudaibergenov Sarkyt E. , Nurkeeva Zauresh S. , Mun Grigorii A. , Ermukhambetova Bayana B. , Akbauova Akzhan T.
Published: April 2003

The complex formation reaction of poly(vinyl ethers) of ethylene glycol (1), poly(vinyl ether) of diethylene glycol (2), copolymers of vinyl ether of ethylene glycol and vinyl butyl ether (3a–3c) with poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) was studied by conductimetric, viscometric and spectroturbidimetric methods in aqueous solution. It is shown that 1 and 2 do not form polycomplexes with PAA. While an introduction of hydrophobic vinyl butyl ether fragments into the structure of 1 enhances the complexation processes with respect to poly(carboxylic acids), the composition of the polycomplexes is independent of the mixing order of interacting components, temperature and composition of the copolymers. An addition of organic solvents to the aqueous solution of the polycomplexes leads to the cooperative destruction of polycomplex particles. An analysis of IR spectra of the polycomplex films shows the existence of COOH dimers, hydrogen bonds between hydroxyl groups and carboxylic groups as well as ester bonds.
Polymerizable dendrimers. Synthesis of a symmetrically branched methacryl derivative bearing eight ester groups
Authors: Draheim Georg , Ritter Helmut
Published: April 2003

The synthesis of chiral acryl and methacryl derivatives containing four ester groups, tetramethyl 5‐((meth)acryloylamino)isophthalamido‐di‐2L‐succinate (2a and 2b), was done by condensation of 5‐(N‐acryloylamino)isophthalic acid (1a) or 5‐(N‐methacrylamino)isophthalic acid (1b) with L‐aspartic acid dimethyl ester in a mole ratio of 1:2. In a similar way, a methacryl monomer bearing eight ester groups, octamethyl 5,5′‐[5‐(methacryloylamino)‐isophthalamido]bis(isophthalamido)tetra‐2L‐succinate (6b), was obtained using the Z‐protected intermediate tetramethyl 5‐(benzyloxycarbonylamino)isophthalamido‐di‐2L‐succinate (4). The monomers were homopolymerized radically with AIBN as initiator, yielding optically active polymers and oligomers (2a′, 2b′ and 6b′) with branched side groups and degree of polymerization Pn between 2 and 23, depending on the architecture of the monomers.
Orientational behavior of side‐chain liquid‐crystalline polysiloxanes deduced from measurements of second harmonic generation
Authors: Nemoto Nobukatsu , Nagase Yu , Abe Jiro , Matsushima Hiroshi , Shirai Yasuo , Takamiya Nobuo
Published: April 2003

Side‐chain functionalized polysiloxanes were prepared via polymer‐analogous esterification of poly[(3‐chloroformylpropyl)methylsiloxane] with 4‐(4‐hydroxyphenylazo)nitrobenzene (P1), 4‐[4‐(ω‐hydroxyalkyloxy)phenylazo]nitrobenzene (P2–P4), 4‐{4‐[N‐(2‐hydroxyethyl)‐N‐methyl]anilinoazo}nitrobenzene (P5), 4‐(4‐hydroxypiperidino)nitrobenzene (P6), or 4‐[4‐(2‐hydroxyethyl)piperidino]nitrobenzene (P7)., P1, P3, P4 and P5 exhibit liquid crystallinity, as deduced from differential scanning calorimetry, polarized microscopic observations and X‐ray diffraction measurements. The liquid‐crystalline phase of P1 and P5 is a nematic phase, and that of P3 and P4 is a smectic one. The second harmonic generation (SHG) measurement of a spin‐coated film of P1 was carried out by the Maker fringe method using a Q‐switched Nd:YAG laser (1064 nm). The SHG profile after the heat treatment of a spin‐coated film suggests a perpendicular orientation of the mesogenic molecules to the glass substrate. The SH light intensity of a corona‐poled film was 20‐fold higher than that of a film which was only heated, though no differences were observed in their UV‐vis absorption spectra. These findings suggest that the mesogenic‐molecular dipole moments are aligned to the same direction in the crystalline or liquid‐crystalline phase by a poling treatment.
Kinetic aspect of the emulsion polymerization of cyclothexyl methacrylate
Authors: Chu Hou‐Hsein , Gau Juen‐Hsien
Published: April 2003

The emulsion polymerization kinetics of cyclohexyl methacrylate (CHMA) at 50°C using a mixture of anionic and nonionic surfactants was investigated. The product of the propagation rate constant (Kp) and the number of radicals per particle (n̄) increased monotonously with the volume‐average particle diameter (Dv). The value of Kp was estimated to be 260 L/(mol · s). Changing the monomer mass fraction in the recipe (from 0,14 to 0,40), the value of n̄ remained constant and close to 0,5. On the other hand, increasing the initiator concentration ([I]), the value of n̄ increased rapidly and then leveled off.
Herstellung und Molmassencharakterisierung von poly[(dimethyliminio)ethylen(dimethyliminio)methylen‐1,4‐phenylenmethylen‐dichlorid]
Authors: Beyer Peter , Lechner M. Dieter , Nordmeier Eckhard , Mächtle Walter
Published: April 2003

The ionene poly[(dimethyliminio) ethylene(dimethyliminio) methylene‐1,4‐phenylenemethylene dichloride] was synthesized and characterized. Number‐, mass‐ and z‐average molar masses Mn, Mw and Mz, and molar mass distribution were determined using equilibrium ultracentrifugation. With detection by means of Schlieren, interference, and UV optics. Mw was additionally determined by static light scattering. All measurements yield within the experimental error the same value of Mw viz. Mw = 12,2 · 103 g/mol. This value agrees well with the value from an analysis of kinetical data, viz. Mw = 11,4 · 103 g/mol. Molar mass distribution w(M) was determined from the concentration profile extrapolated to concentration γ0 = 0; it is of a Wesslau‐type and relatively broad. The non‐uniformity U = Mw/Mn − 1 ≈ 3. According to the theory of polycondensation a Schulz‐Flory type of distribution should be obtained. A Schulz‐Flory distribution is not achieved because the monomers p‐xylylene dichloride and N,N,N′,N′‐tetramethylethylenediamine exhibit higher reactivity in the initiation reaction than the homologs during chain propagation which results in a broader molar mass distribution than a Schulz‐Flory distribution.
Molecular motions in a side‐chain liquid‐crystalline polymethacrylate. A thermally stimulated currents study of the dipolar relaxations in the vitreous and liquid‐crystalline phases and at the glass transition
Authors: Mano João F. , Correia Natália T. , Ramos Joaquim J. Moura , Coates David
Published: April 2003

In the present work we report the results of a Thermally Stimulated Discharge Currents (TSDC) study of a side‐chain liquid‐crystalline polymer. The different discharges observed in the TSDC spectrum have been analysed by the thermal sampling technique and have been attributed to specific relaxation mechanisms at the molecular level. A particular feature of the polymer studied in this work is that the mesogenic side group presents both longitudinal and transverse components of the dipole moment, and this seems to be at the origin of the presence of two separated relaxations in the liquid‐crystalline phase.
Poly[n]acene precursors via repetitive Diels‐Alder reactions with dehydrobenzenes
Authors: Horn Thomas , Wegener Stefan , Müllen Klaus
Published: April 2003

Due to their instability, higher [n]acenes are even poly[n]acenes are still elusive in solution. In the present paper the synthesis of new poly[n]acene precursors (7, 9) is described from which the fully aromatic structures should be available by pyrolysis in the solid state via cycloreversion. Polymer syntheses were carried out via repetitive Diels‐Alder reaction of a bicyclic bis‐diene precursor with dehydrobenzenes. Repetitive [4 + 2]cycloaddition was employed because of its potential for constructing defect‐free ladder‐type polymers. Arynes have only been used once before in the actual polymerization step of a polymer synthesis, but this case involved an AA‐type diazotated anthranilic acid. The present approach deals with AB‐type monomers containing dehydrobenzenes as active dienophilic species prepared from dibromobenzenes with butyllithium at low temperatures (−40°C). Aromatization of the precursor polymers 6 and 8 with tetrachloro‐p‐benzoquinone provides the aromatized polymers 7 and 9 interrupted only by the bicyclo[2.2.2]octadiene resp. ‐triene units.
Synthesis of N‐acryloyl‐N′‐4‐tolylurea copolymers and their grafting reaction with ceric ion
Authors: Qiu Kun Yuan , Li Zhao Yang , Zhao Tong
Published: April 2003

N‐Acryloyl‐N′‐4‐tolylurea (ATU) and N‐methacryloyl‐N′‐4‐tolylurea (MTU) were prepared via the reaction of 4‐tolyl isocyanate with acrylamide or methacrylamide. In conjunction with ceric ammonium nitrate (CAN), ATU and MTU promote the rate of acrylamide polymerization. Macromolecules having 4‐tolylureido pendant groups, such as poly(ATU‐co‐EA) and poly(MTU‐co‐EA), were synthesized by radical copolymerization of ATU and MTU with EA (ethyl acrylate), respectively. In the presence of CAN, a graft copolymerization of acrylamide onto the surface of these two copolymer films took place. The grafted copolymer was characterized by means of XPS and SEM and with respect to water absorption.
Small‐ and wide‐angle X‐ray scattering characterization of 1‐hexene linear low‐density polyethylene
Authors: Marigo Antonio , Cingano Gianmatteo , Marega Carla , Zannetti Roberto , Ferrara Giuseppe , Paganetto Guglielmo
Published: April 2003

Four ethylene‐1‐hexene copolymer samples were studied by small‐angle X‐ray scattering in order to investigate the correlation between the crystalline lamellar thickness and the comonomer content. The lamellar thickness was determined from the identity period of the one‐dimensional scattering function and from the analysis of the one‐dimensional correlation function. The crystallinity and the volume of the crystalline unit cell were determined by wide‐angle X‐ray scattering. Some considerations are reported on the effect of the side chains during the crystallization and on the polydispersity of the lamellar thickness.
Crystallization of a copolyester in microlayers and blends with polycarbonate
Authors: Haderski Denise , Nazarenko Sergey , Cheng Chih‐Min , Hiltner Anne , Baer Eric
Published: April 2003

The crystallization behavior of coextruded microlayered sheets comprised of 657 alternating layers of polycarbonate (PC) and a miscible copolyester of mainly 1,4‐cyclohexanedimethanol and terephthalic acid (KODAR) was investigated as a function of annealing time when the KODAR was crystallized isothermally from the glass at 195°C. Comparisons were made with crystallization of KODAR alone, and with crystallization of KODAR from melt blends with PC. The kinetics of crystallization and the morphology of the crystallized KODAR were characterized with differential scanning calorimetry, and by examination of thin sections microtomed from annealed specimens in the polarized light microscope and the transmission electron microscope. The growth rate of small, birefringent KODAR spherulites was non‐linear, and was strongly affected by diffusion of PC into the KODAR layers. Diffusion of amorphous PC into the KODAR layers retarded nucleation and spherulite growth and decreased spherulite density. The effect became more pronounced as the KODAR layer thickness was reduced. Spherulities nucleated randomly throughout the KODAR layers in the PC/KODAR 20/80 (w/w) microlayer and grew rapidly to form a continuous layer of impinged spherulites. In contrast, spherulites in the PC/KODAR 40/60 and 60/40 microlayers nucleated and grew along the center of the KODAR layers where the KODAR concentration was highest.