bluuebunny/crossref_metadata_2025 huggingface dataset:
Infrared spectroscopic studies on polyethylene, 7. The use of the methyl deformation band for branch characterisation
Authors: Maddams William F. , Parker Stewart F.
Published: April 2003

The factors relating to measuring the position of the methyl deformation mode at about 1378 cm−1 with sufficient precision to permit its use for the identification of the different branches present in the various types of “linear” low density polyethylene(as manufactured by the copolymerization of ethylene and a 1‐alkene) have been examined systematically. With a data density of eight points per wavenumber, and the well established subtraction procedure with polymethylene or with a near‐linear polyethylene to remove the overlapping methylene deformation band, it is possible to achieve a precision of ±0,15 cm−1. This is ample to distinguish between methyl, ethyl, and butyl or hexyl branches, but not to characterise uniquely these last two. The use of Fourier self‐deconvolution to separate the methyl band has also proved very effective. The precision obtainable when these methods are applied to spectra measured with one data point per wavenumber is somewhat lower, but is still adequate for characterisational purposes. The results for a series of polymers containing ethyl branches at various concentrations suggest a small difference for the peak position for branches present in crystalline and amorphous regions.
Terpolymérisation acrylonitrile‐styrène‐acrylate de méthyle, 4. Copolymérisation en emulsion styrène‐acrylate de méthyle en réacteur fermé (batch) en présence de persulfate de potassium
Authors: Ramirez‐Marquez Walter , Guillot Jean
Published: April 2003

To improve the knowledge of emulsion copolymerization of monomers both swelling their copolymers, but which are of quite different polarity (water solubility), a series of styrene (S)/methyl acrylate (MeA) copolymerizations was carried out in batch at 50°C with potassium persulfate as initiator. The overall rates of copolymerization increase with the amount of MeA in the monomer feed. Copolymer composition follows the usual copolymerization equation if bulk/solution reactivity ratios (rij) and monomer partition between aqueous and organic phase are taken into account (simulation). However, accurate kinetic data at low conversion (gas chromatography) put in evidence an enhanced polymerization of the more hydrophilic monomer (MeA), which can be attributed to polymerization in the water phase. Particle sizes increase with conversion and tend to a limiting value, the higher the MeA content is. Particle number (Np), which is practically constant with conversion of S homopolymerization, tends to increase with MeA content as polymerization proceeds. This trend is enhanced if the emulsifier (sodium dodecanesulfonate, SDS) concentration is increased. Overall propagation rate constants were estimated as function of the experimental conditions and monomer concentration within the particles. From kinetic data (rate of polymerization) and Np, it was found that the average number of radicals per particle, ñ, remains close to 0,5. It was then possible considering S(kp = 125 1 · mol−1 · s−1) as a standard monomer, to estimate the polymerization rate constant for MeA (335 1 · mol−1 · s−1). Since adsorption of emulsifier was shown to be closely related to particle surface composition, the specific area As of SDS was measured on latices at various conversions and initial monomer feeds. As conversions increases, the particle surface appears to be richer and richer in MeA, which corresponds to a particle structuration. Strong and weak acid group titration is also in quite good agreement with the colloidal behaviour.
Terpolymérisation acrylonitrile‐styrène‐acrylate de méthyle, 5. Copolymérisation en emulsion styrène‐acrylate de méthyle en réacteur fermé en présence du styrène amorceur redox persulfate the potassium/hydrogénodisulfite de sodium
Authors: Ramirez‐Marquez Walter , Guillot Jean
Published: April 2003

A series of emulsion copolymerizations of styrene (S) with methyl acrylate (MeA) initiated by the redox system potassium persulfate (KPS)/sodium hydrogen disulfite (SBS) was carried out at 50°C. The monomer feed composition and the monomer/water (M/W) ratios were widely varied. The polymerization rate was found to be higher than in the case when only KPS was applied. Initial (influence of polymerization in water phase) and final copolymer molecules (accumulation of MeA in the feed due to a lower reactivity) are richer in the more hydrophilic monomer (MeA). It could be shown that a high water solubility makes the emulsion reactivity ratios to be “apparent” kinetic parameters, which result in a higher number of azeotropic compositions, compared to bulk or solution, according to the M/W ratio. Particle sizes are smaller and the size distribution is larger than in polymerizations in the presence of KPS alone. Particle number (Np) tends to increase with conversion for monomer mixtures rich in MeA, contrary to S homopolymerizations in which Np remains constant. Comparison of Np and kinetic data suggests that only part of the particles in actually active in polymerization (N). N can be estimated assuming that the average number of radical per particle, ñ remains close to 0,5 – as found in a previous study – which gives also an estimate of very tiny particles generated at low conversion and undetectable by the usual QELS and MET techniques. The experimental data, to some extent, allow to quantify the competition between micellar and homogeneous nucleation mechanisms.
Liquid crystals from side‐chain mesogenic poly(vinyl ether‐alt‐maleic anhydride)
Authors: Frère Yves , Yang Fang , Gramain Philippe , Guillon Daniel , Skoulios Antoine
Published: April 2003

Alternating copolymers of maleic anhydride with vinyl ethers, bearing a 4′‐methoxy‐4‐biphenylyl mesogenic group via an oligo(ethylene oxide) spacer, were synthesized and structurally characterized. From X‐ray diffraction observations, a smectic E phase was observed. Smectic layers are single layers of ribbon‐like polymer chains, with all pendant groups arranged in a single row and pending on the same side of the backbone. Mesogenic groups are oriented up and down at random, and polymer chains are aligned along the [110] direction of the rectangular lattice describing the packing of the pendant groups.
Group transfer polymerization of methyl methacrylate in acetonitrile, 1. Initiation by [(1‐methoxy‐2‐methyl)‐1‐propenyloxy]‐trimethylsilane
Authors: Sitz Hans‐Dieter , Speikamp Hans‐Dieter , Bandermann Friedhelm
Published: April 2003

The group transfer polymerization (GTP) of methyl methacrylate in acetonitrile with [(1‐methoxy‐2‐methyl)‐1‐propenyloxy]trimethylsilane as initiator and tetraethylammonium cyanide as catalyst is accompanied by a severe termination reaction of both the initiator and the active chains with the solvent leading to trimethylsilylacetonitrile and methyl isobutyrate or inactive polymer. Therefore, in order to work under reaction conditions characteristic for a living system acetonitrile as solvent has to be avoided.
Thermal and photoinitiated copolymerization of the cyclic disulfide lipoamide with styrene
Authors: Nambu Yoko , Acar Metin H. , Suzuki Tatsuki , Endo Takeshi
Published: April 2003

Thermal and photoinitiated copolymerizations of lipamide (1), a cyclic disulfide, with styrene in the absence of initiators were investigated. The thermal copolymerization is initiated via styrene radicals producing a copolymer with sulfide and disulfide linkages in the main chain and with amide and phenyl side groups. In the photopolymerization, the diradical formed by ringopening of 1 through homolytic fission of its strained disulfide bond is the main initiating species, attacking styrene to produce a copolymer with a high content of monomeric units of 1.
Enzymatisch katalysierte peptidknüpfung von alanin an phenylalaninhaltige methacrylpolymere mittels α‐chymotrypsin
Authors: Rehse Henning , Ritter Helmut
Published: April 2003

The α‐chymotrypsin catalyzed peptide‐bond formation was demonstrated by coupling the monomer N‐methacryloylaminoundecanoylphenylalanine (3 c) with alanine‐tert‐butylester in a water/chloroform system yielding N‐methacryloylaminoundecanoylphenylalanylalanyl‐tert‐butylester (7). The kinetics of the corresponding α‐chymotrypsin catalyzed coupling of alanine‐tert‐butylester with methacrylic polymers containing aminohexanoylphenylalanine and aminoundecanoylphenylalanine as spacergroups was correlated with the Huggins coefficient of the polymer by viscosity measurements.
Vertically‐oriented charge mosaic microdomains by means of epitaxial growth
Authors: Ishizu Koji , Hayashi Takeo , Fukutomi Takashi
Published: April 2003

Vinyl alcohol (VA)/4‐vinylpyridine (4VP) graft copolymers were prepared by the macromonomer method. After domain fixing of the PVA matrix of this graft copolymer, the water/1‐propanol mixed solution of poly(sodium p‐styrenesulfonate) (PSSS)/P4VP polymer blends was cast on the microheterophase surface of VA/4VP graft copolymer which served as a support membrane. The surface characterization of this composite membrane was carried out by means of transmission electron microscopy (TEM) and Electron Spectroscopy for Chemical Analysis (ESCA). The TEM observation indicated that charge mosaic microdomains formed by means of epitaxial growth are oriented perpendicularly to the film surface. The ESCA results clearly indicated that the two‐phase composition of the surface (in sampling depths of ≈ 1 and ≈ 5 nm) is proportional to the overall bulk composition of the polymer blends.
Oscillation of electrical current in water‐swollen polyelectrolyte gels
Authors: Osada Yoshihito , Umezawa Kayo , Yamauchi Aizo
Published: April 2003

An artificial oscillating system consisting of water‐swollen polyelectrolyte gels, to which a constant electric potential was applied, is described. It was found that repetitive oscillations occurred in three‐dimensional crosslinked gels made of synthetic polyelectrolytes, proteins and of polysaccharides. The repetitive oscillations were rather stable regardless of the “stimulating” current density, and the frequency was of the order 0,01 to 0,2 Hz which gradually decreased with time. Power spectra and Lorentz plots were obtained and a semi‐quantitative analysis of the oscillation was carried out.
Influence of chemical structure on glass transition temperatures of poly(propylene terephthalate) and poly(propylene isophthalate)
Authors: Pérez Crisantos , Guzmán Julio , Riande Evaristo , De la Campa José G. , de Abajo Javier
Published: April 2003

Poly(propylene terephthalate)

Systematic IUPAC name: poly(oxypropyleneoxyterephthaloyl).

(PPTP) and poly(propylene isophthalate)

Systematic IUPAC name: poly(oxypropyleneoxyisophthaloyl).

(PPIP) were prepared by melt polycondensation. Different fractions with number‐average molar masses in the range 5 000 − 20 000 g·mol−1 were obtained and their respective glass transition temperatures (Tg) determined by calorimetry. The solubility parameters of the polymers were obtained by viscosity measurements in different solvents and were found to be 9,4 and 9,5 cal1/2·cm−3/2 (19,2·103 and 19,4·103 J1/2·m−3/2) for PPIP and PPTP, respectively. The glass transition temperatures were compared with those reported for analogous polyesters and it was shown that intramolecular interactions highly influence the Tg of these polyesters, whereas the effect of intermolecular interactions seems to be less important.
Contribution to the study of acrylamide polymerization, 1. Polymerization in the presence of an inhibitor
Authors: Vašková Viera , Oremusová Daniela , Bartoň Jaroslav
Published: April 2003

The average rate of initiation, Ri, is determined for the polymerization of acrylamide (AAM) in water in the presence of the water‐soluble initiator ammonium peroxodisulfate (APS) and the inhibitor 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (HTPO). The inhibitor and products from its interaction with the initiator to some extent participate also in other reactions: some lead to partial regeneration of inhibitor and some may be considered to be transfer reactions to the inhibitor. The determined ratio of the rate constant of termination and the square of the rate constant of propagation kt/k2p which does not significantly differ from the value listed for the AAM polymerization in water without admixtures, shows that participation of HTPO in propagation and termination reactions is not important.
Contribution to the study of acrylamide polymerization, 2. Polymerization in water/aliphatic alcohol mixtures
Authors: Vašková Viera , Oremusová Daniela , Bartoň Jaroslav
Published: April 2003

The polymerization of acrylamide is studied in mixtures of water and the aliphatic alcohols methanol, ethanol, 1‐propanol, and 2‐propanol in the presence and in the absence of the inhibitor 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (HTPO). The aliphatic alcohols reduce both the rate of polymerization and the molecular weight proportionally to their concentration in the mixtures with water and to the length and character of the aliphatic chain. Transfer constants to the individual aliphatic alcohols used are determined. The presence of the inhibitor HTPO leads to a further decrease of the molecular weight of the poly(acrylamide) formed.
Synthesis of soluble poly(divinylbenzene‐co‐styrene) and poly(divinylbenzene‐co‐vinylpyridine) by lithium amide‐initiated anionic copolymerization
Authors: Nagasaki Yukio , Taniuchi Masahiro , Tsuruta Teiji
Published: April 2003

Polymerization of 1,4‐(or 1,3‐)divinylbenzene (DVB) in the presence of styrene initiated with lithium diisopropylamide was found to give soluble poly(DVB‐co‐styrene) having reactive vinyl group as pendant group of the polymer chain. The reactivity of 1,4‐DVB is higher than that of 1,3‐DVB in the copolymerization reaction with styrene as comonomer. It was found also that 1,4‐DVB can be copolymerized with 2‐vinylpyridine to form a soluble copolymer which consists primarily of 2‐vinylpyridine units.
Cationic transannular polymerization of 1,5‐cyclooctadiene
Authors: Yuan Cuiming , Yan Deyue , Xu Xiangming , Wang Fosong , Gong Zhi
Published: April 2003

The cationic transannular oligomerization of cis‐cis‐1,5‐cyclooctadiene (1), initiated by AlEtCl2 and Al2Et3Cl3, was studied. Several cationic catalysts were examined, and the order of activities of these catalysts was found to be the following one: BF3 · OEt2 < AlCl3 < AlEtCl2 < Al2Et3Cl3. The number‐average molecular weights of the resultant polymers are ≈ 1000 – 2000, and the softening temperature ranges 130 – 160°C. By means of NMR, IR and PC‐MS spectral analyses, the structure of poly(1,5‐cyclooctadiene), proposed earlier by Marvel et al., could be corroborated.
Synthesis and polymerization of a macromonomer derived from phosphatidylcholine
Authors: Ohkatsu Yasukazu , Yokota Masao , Kusano Toru
Published: April 2003

A lecithin‐type macromonomer 1 was synthesized from natural egg phosphatidylcholine (lecithin). The macromonomer has an olefinic polymerizable group at the hydrophilic site, and is characterized by its chemical structure resembling lecithin. It could be polymerized in a liposome system by UV irradiation, giving polymers with a maximum molecular weight of 98 000. Polymers with molecular weights above 48 000 form thin and flexible membranes with a few 10 μm in thickness. The polymers can also be redispersed in water and the liposomes can be reconstituted.
Poly(vinylsaccharide)s, 4. Synthesis and polymerization of 6‐o‐methylallylgalactose derivatives
Authors: Klein Joachim , Blumenberg Klaus
Published: April 2003

Methylallyl ethers of 1,2:3,4‐di‐O‐isopropylidene‐D‐galactopyranose and 1,2:3,4‐di‐O‐cyclohexylidene‐D‐galactopyranose were synthesized as new monomers containing saccharide moieties and copolymerized with maleic anhydride. The hitherto unknown 6‐O‐(2‐alkoxycarbonylallyl)‐1,2:3,4‐di‐O‐isopropylidene‐D‐galactopyranoses (8a and 8b; alkyl: methyl and ethyl, respectively) were prepared and polymerized under free radical conditions. The substances were characterized by 13C NMR, elemental analyses and molecular weight determinations. Water solubility of these polymers was obtained by removing the isopropylidene protecting groups. The inherent viscosities of these polymers, measured in 0,1 M Na2SO4 aqueous solution, were of the same order of magnitude as those of polyacrylamides of the corresponding degrees of polymerization.
Ring‐chain competition in kinetically‐controlled condensation polymerization
Authors: Yuan Xue‐Feng , Masters Andrew J. , Nicholas Christian V. , Booth Colin
Published: April 2003

Gordon and Temple's scheme of rate equations for ring‐chain competition reactions in condensation polymerization has been solved analytically (for very small rates of ring formation) and numerically over a wide range of conditions. The numerical method was computationally efficient. Except in extreme cases, the distribution of ring sizes was found to be practically the same as that predicted for equilibrium conditions by Jacobson and Stockmayer, viz. that the number concentration of rings with a degree of polymerization i is proportional to i−5/2 at the end of the reaction.
Radikalische hochdruckpolymerisation von ethylen im zweiphasensystem
Authors: Luft Gerhard , Fischer Norbert
Published: April 2003

In order to modify the properties of low density polyethylene (LDPE), the radically initiated polymerization of ethylene can be performed at pressures below 1200 bar and moderately high temperatures. Under such conditions the reaction mixture separates into a less dense phase, rich in monomer, and a dense phase, rich in polymer. The polymerization proceeds mainly in the monomer‐rich phase. When the polymer concentration exceeds the solubility limit, polymer precipitates from the monomer‐rich phase and moves into the polymer‐rich phase. By polymerization under two‐phase conditions, polyethylene resins with a narrow molecular weight distribution can be obtained.
Properties of poly(dimethylsiloxane) chains and gels in toluene and in toluene/ methanol mixtures
Authors: Aven Michael R. , Cohen Claude
Published: April 2003

Four different samples of α‐dimethylvinylsilyl‐ω‐vinylpoly(oxydimethylsilanediyl) (α,ω‐divinylPDMS) chains of different molar masses have been endlinked in the absence of solvent to form “model” polymer networks. These networks have been subjected to swelling experiments at 30°C in toluene and toluene/methanol mixtures. The volume fraction of polymer in the gel at equilibrium swelling v3 is determined gravimetrically. The preferential sorption coefficient λ is found using interferometry. Large preferential sorption effects prevent the solvent mixtures from being treated as pseudo‐one‐component solvents. The variation of swelling and preferential sorption with network and solvent composition is discussed. The thermodynamic properties of α,ω‐divinylPDMS chains in dilute solution with toluene, toluene/methanol mixtures, and tetrahydrofuran are determined at 30°C using intrinsic viscosity measurements. Polymer‐solvent interaction parameters and Mark‐Houwink constants as well as unperturbed dimensions are determined in both the pure solvents and solvent mixtures.
Electro‐optical properties and molecular flexibility of polyelectrolytes in dilute solutions
Authors: Oppermann Wilhelm
Published: April 2003

Measurements of the electric birefringence of aqueous polyelectrolyte solutions in the very dilute regime ( ≈ 10−5 g · mL−1) reveal that the macroions are fully extended. However, this rod‐like conformation is easily altered towards a more coiled conformation when a strong static electric field is applied, particularly in the case of very high molar‐mass polymers. With the application of rectangular dc pulses, as ordinarily used in Kerr‐effect measurements, the change of molecular shape interferes with the transient rise and decay of the birefringence signal, because the rotational mobility as well as the optical anisotropy of the macroions become time‐dependent. As a result, the mean relaxation time for the rise curve is considerably smaller than that of the field‐free decay, and the steady‐state birefringence is much lower than expected for the unperturbed macroions. The change of the molecular shape can be avoided if the orientation of the macroions is induced by high‐frequency ac pulses. This experimental technique is therefore suitable to obtain the unperturbed shape and size of the macroions. A molecular interpretation for the dependence of the birefringence function on the pattern of the electric field is proposed.
Magnetic species present in styrene/methacrylic acid copolymers neutralized with cu(II)
Authors: Yamauchi Jun , Yano Shinichi
Published: April 2003

Electron spin resonance (ESR) spectra of styrene/methacrylic acid copolymers neutralized with Cu(II) were observed at room temperature. Three magnetic species were detected; isolated Cu2+, Cu2+‐Cu2+ pairs of Cu(II) acetate monohydrate type and anhydrous Cu(II) formate type. One of the absorption patterns due to the Cu2+‐Cu2+ pair is the same as that of Cu(II) acetate monohydrate except linewidth. ESR data from the other species are summarized. ESR parameter, effect of the acid and Cu(II) contents, and spectral changes depending on sample preparation procedures or temperatures are discussed.
Influence of the far order effect on the reactivity of functional end groups of macromolecules in non‐equilibrium polycondensation
Authors: Ignatov Vladimir N. , Vasnev Valerii A. , Vinogradova Svetlana V. , Korshak Vasilii V. , Tseitlin Henrich M.
Published: April 2003

The influence of the number of oxyethylene repeating units in the oligomeric derivatives of ethylene bis(4‐chlorocarbonylbenzoate) (1, n = 3, 6,4, 13, 22,3, 45 and 68) on the reactivity of the chlorocarbonyl end groups in the acceptor‐catalytic esterification was determined by means of thermodynamic and kinetic investigations in diluted solutions. The violation of the principle of equal reactivity was found to be caused by the far‐order effect, when with increasing chain length the effective local concentration of oxyethylene repeating units increases in the environment of the end group whose reactivity is determined by the ratio between the “solvating ability” of the repeating units and the solvent. The far‐order effect influences not only the kinetics, but also the reaction mechanism.
Chain branching of poly(dimethylsiloxane): A competitive side reaction of the hydrosilylation reaction
Authors: He Xiongwei , Lapp Alain , Herz Jean
Published: April 2003

Poly(dimethylsiloxane) (PDMS) fitted at both chain ends with dimethylsilyl functions was heated at 90 and 110°C in the presence of chloroplatinic acid. A chain‐branching reaction was observed yielding very‐high‐molecular‐weight species. The phenomenon, which occurs as well in solution as in the bulk, is temperature dependent. This reaction can exist as a side reaction of the hydrosilylation reaction between PDMS (1) and 1,4‐bis(dimethylvinylsilyl)benzene (2) or tetraallyloxyethane (5) when dimethylsilyl functions are in excess. However, it does not take place in hydrosilylations in which mole ratios 1/2 equal to unity or higher are applied.
Nuclear magnetic resonance studies on bacterial copolyesters of 3‐hydroxybutyric acid and 3‐hydroxyvaleric acid
Authors: Doi Yoshiharu , Kunioka Masao , Tamaki Akira , Nakamura Yoshiyuki , Soga Kazuo
Published: April 2003

Copolyesters of 3‐hydroxybutyric acid (HB) and 3‐hydroxyvaleric acid (HV), P(HB‐co‐HV), were isolated from Alcaligenes eutrophus and characterized by solution NMR, solid‐state 13C CP/MAS NMR, and differential scanning calorimetry. The 13C CP/MAS NMR analysis was compatible with that of a random copolyester of oxy‐(1‐methyl‐3‐oxotrimethylene) (B) and oxy‐(1‐ethyl‐3‐oxotrimethylene) (V) units which adopts a regular conformation of a 21 ‐helix in the solid state throughout a wide range of compositions varying from 0 to 90 mol‐% V units. The chain dynamics of P(HB‐co‐HV) in chloroform was studied by analysis of the 13C and 1H NMR spectra. The carbon‐13 spin‐lattice relaxation times (T1) and nuclear Overhauser enhancements (NOE) indicated that the copolyester molecules in chloroform are not rigid but rather flexible. The conformational preferences of the copolyester molecules were determined by analysis of the 1H NMR spectra.
Polymers of 1‐azabicyclo[4.2.0]octane, 1. Structure of monomer and homopolymer
Authors: Mühlbach Klaus , Schulz Rolf C.
Published: April 2003

The structure of 1‐azabicyclo[4.2.0]octane (1) was evaluated by NMR spectroscopy. It was found that the six‐membered ring has a chair conformation with the four membered ring in the N‐axial and C‐6‐equatorial position, and as a consequence, the monomer allows neither a ring inversion nor a nitrogen inversion. It possesses two centers of chirality, one at the nitrogen atom and one at C‐6. Homopolymerization was carried out in methanol at 60°C with N‐alkyl ammonium salts of 1 affording the polymer in high yield within a few hours. Its NMR spectra reveal that the polymer chain is preferably arranged in the biequatorial position of the six‐membered ring. As a polybase the polymer can be titrated quantitatively with acids. Its glass transition temperature is 8°C, the decomposition starts at 320°C.
Synthesis and rheological study of some maleic and fumaric acid stereoregular polyesters, 2. Polyesters derived from 1,4‐dibromobutane or 1,8‐dibromooctane
Authors: Jaćović Mihailo S. , Djonlagić Jasna , Sepulchre Maurice , Sepulchre Marie‐Odile , Leborgne Alain , Spassky Nicolas
Published: April 2003

Configurationally pure, high‐molecular‐weight poly(butylene maleate)s, poly(butylene fumarate)s, poly(octamethylene maleate)s, and poly(octamethylene fumarate)s were synthesized by reaction of the corresponding potassium dicarboxylates and dibromoalkanes in 1‐methyl‐2‐pyrrolidone at 95 to 114°C. The polyfumarates show about ten times higher dynamic viscosities at 150°C than the polymaleates of the same limiting viscosity numbers, which might be attributed to the more extended conformations of the former.
The backbone conformation of liquid‐crystalline side‐chain polymers in the mesophases and in the isotropic phase determined by scattering methods
Authors: Ohm Hubertus G. , Kirste Rudolf G. , Oberthür Radulf C.
Published: April 2003

Light scattering, neutron scattering and viscosity measurements on a nematic and a smectic polymethacrylate demonstrate the presence of molecularly disperse coils in solution. For the nematic polymer, toluene is a theta solvent, the behaviour familiar from conventional polymers (unperturbed coil conformation) being exhibited at the theta point. The isotropic melts likewise contain unperturbed coils; in the case of the nematic polymers, however, the coils in the melt have a radius of gyration which is about 30% smaller than that in solution at the theta point. In the liquid‐crystalline phase, the mean radii of gyration in both cases are identical to the corresponding parameters in the isotropic melt. In the nematic material, however, the coils can be shown to have a substantial anisotropy, the radius of gyration parallel to the director being about 20% smaller than that at right angles to this direction. On the basis of a theoretical chain simulation, a model for the main‐chain conformation has been developed which takes into account both short‐range interactions along the main chains and three‐dimensional interactions by the oriented side groups. This model indicates the degree of orientation from which a change in the mean radius of gyration can be expected. Wide‐angle neutron scattering experiments on smectic polymer provide information about the main‐chain distribution in the smectic phase. The main chains are present in a substantially higher concentration between the smectic layers, but there are hints that they do not have a true two‐dimensional arrangement.
Polymerization of 1‐alkynes initiated by μ‐alkylidene complexes of tungsten, 3. Kinetics and mechanism of the propagation reaction
Authors: Meziane Driss , Soum Alain , Fontanille Michel
Published: April 2003

A comprehensive study of the propagation step of 1‐heptyne polymerization initiated by a dinuclear μ‐alkylidene complex of tungsten, was carried out. Kinetic orders, apparent rate constants and thermodynamic parameters were determined. The structure of the active species and that of the organic side‐products appearing during this step, were analyzed by NMR and mass spectroscopy. According to the experimental data, a mechanism of the propagation reaction is proposed: the propagating species could derive from inactive metalated oligomers by loss of a carbonyl ligand; the monomer then coordinates at the free site of the transition metal of the μ‐alkylidene active species and inserts into the CW bond. In competition with the normal insertion of the monomer molecule, termination and transfer reactions occur (including or not the monomer and/or the polymeric chain).
Electroinitiated cationic polymerization by anodic dissolution
Authors: Pierre Gérard , Limosin Danièle , Cheradame Hervé
Published: April 2003

The polymerization of several monomers, such as styrene, α‐methylstyrene, lactones, isobutyl vinyl ether, and hexamethylcyclotrisiloxane, was carried out in H‐shaped cells equipped with sacrificial anodes. The solvents, dichloromethane or nitromethane, contained tetrabutylammonium perchlorate playing the role of supporting electrolyte. Among the different metals tested (Cu, Ag, Hg, Al, Pb, Sn), only mercury and aluminium anodes gave initiation. The conditions of the electrolysis, the nature of the monomers, and the results of special experiments carried out in the presence of a hindered pyridine demonstrate that the polymerization involves the electrophilic addition of the active species to the monomer followed by cationic chain growth.
Influence of internal and external donors on activity and stereospecificity of ziegler‐natta catalysts
Authors: Soga Kazuo , Shiono Takeshi , Doi Yoshiharu
Published: April 2003

Three kinds of MgCl2‐supported TiCl4 catalysts (ester‐free, ethyl benzoate (EB, monoester) and dibutyl phthalate (DNBP, diester) as internal donors) were prepared. Polymerization of propylene was carried out using these catalysts with and without phenyltriethoxysilane (PTES) as an external donor. Significant differences were observed in the kinetic behavior of polymerization among ester‐free, monoester, and diester systems. Addition of PTES, however, did not change the kinetic behavior. The polymers produced were separated into three fractions by extraction with boiling heptane and octane, and the molar mass distribution (MMD) curves were measured for these three fractions. The heptane‐insoluble, isotactic polymer obtained in the absence of PTES was found to consist of two fractions, octane‐soluble and ‐insoluble. The octane‐soluble polymer having lower molar mass contained appreciable amounts of syndiotactic stereoblocks in the chains, whereas the octane‐insoluble polymer did not contain such stereoblocks. Addition of PTES drastically increased the octane‐insoluble fraction without changing the average molar mass. On the other hand, the MMD curve for the heptane‐soluble, atactic polymer gradually shifted to the lower molar mass range with an increase in the concentration of PTES. From these results, the effects of internal and external donors on catalyst activity and stereospecificity were discussed putting emphasis on the differences between monoesters and diesters.
Thermodynamic properties in the liquid state of high melting polymers containing phenylene and naphthylene groups
Authors: Cheng Stephen Z. D. , Pan Robert , Bu Hai Shan , Cao Miao‐ Yong , Wunderlich Bernhard
Published: April 2003

High melting polymers of three different types of crystallization behavior were analyzed as to their thermal properties. The heat capacity at constant pressure of liquid poly(butylene terephthalate) (PBT) from 490 to 540 K was measured by scanning calorimetry. Combining with prior measured liquid heat capacity data of poly(oxy‐1,4‐phenylene) (PO) (358 – 620 K), poly‐(thio‐1,4‐phenylene) (PPS) (540 – 600 K), poly(ethylene 2,6‐naphthalenedicarboxylate) (PEN) (400 – 450 K, 530 – 600 K), an addition scheme for liquid heat capacities was constructed. In addition, the thermodynamic functions H and S have been calculated for those five polymers. The absolute, molar, residual entropy for the glassy state at zero kelvin is estimated to be 6,6,15,2, 7,48, 5,70, and 19,9 J/(K · mol) for PPS, PEN, PPO, PO, and PBT, respectively. Another two polymers with similar structure, poly(1,4‐oxybenzoic acid) (POB) and poly(2,6‐oxynaphthoic acid) (PON), were also studied in their high temperature mesophase states. A test of the addition scheme has been made to predict their heat capacities.
Cross polarization/magic angle spinning 13C solid state nuclear magnetic resonance of model compounds related to supported ziegler‐natta catalysts
Authors: Abis Luigi , Albizzati Enrico , Giannini Umberto , Giunchi Giovanni , Santoro Ettore , Noristi Luciano
Published: April 2003

Cross polarization/magic angle spinning 13C NMR has been applied to the investigation of some solid organometallic compounds of the general formulae TiCl4 · n RCOOR′, MgCl2 · n RCOOR′ (RCOOR′ = p‐CH3C6H4COOCH3 and C6H5COOC2H5, n = 1; 2; and 0,15). Compounds with n = 1 and 2 show narrow resonance lines indicative of crystalline regular structures while for MgCl2 · 0,15 RCOOR′ a disordered structure is found with the organic ligands strongly bonded to the surface of MgCl2 crystallites. For n = 2 splitting into a doublet is found for some resonances due to the spatial non‐equivalence of the two ligands induced by crystalline packing. A shift has been found for some resonances in going from Mg to Ti complexes which reflects the different Lewis acidity of the two metal atoms.
Influence of shear on the demixing of polymer solutions, 2. Stored energy and theoretical calculations
Authors: Krämer‐Lucas Helga , Schenck Heiko , Wolf B. A.
Published: April 2003

Phase diagrams were calculated for flowing solutions of polystyrene in trans‐decahydronaphthalene assuming that the energy (Es) stored in the sheared state has to be added to the Gibbs energy of mixing; Es is computed from viscometric data (flow curves). The resulting phase diagrams exhibit two maxima in most of the cases instead of only one for the stagnant solutions. A comparison with experimental data (Part 1) shows that the calculated demixing behaviour agrees well for moderate shear rates and concentrations of the polymer. Deviations in the semidilute region, particularly for higher values, are a consequence of the fact that so far no reliable theoretical relation has been given for these conditions to calculate Es from viscometric data. In all cases, however, the present attempt describes the characteristics of the phase diagrams very well, namely the eulytic points and the inversion of shear dissolution into shear demixing.
The glass transition temperatures of homogeneous blends of polystyrene, poly(methyl methacrylate), and copolymers of styrene and methyl methacrylate
Authors: Braun Dietrich , Kohl Paul R. , Hellmann Goetz P.
Published: April 2003

The glass transition temperatures Tg of homogeneous binary blends of the homo‐ and the statistical copolymers of the system poly(styrene‐co‐methyl methacrylate) were studied. Some of the blends, which are in the equilibrium phase separated, were forced into homogeneity. Tg (ϕ) of the homopolymer blends (PS/PMMA)ϕ follows the Fox equation, while Tg (x) of the pure copolymers P(SxMMA1 − x) exhibits a minimum. This minimum can be effectively removed by blending the copolymers with small fractions (ϕ ≈ 0,2) of one of the two homopolymers or a differently composed copolymer P(SyMMA1 − y).
Experimental verification of a model describing the occupied volume by polymers in solution
Authors: Dondos Anastasios , Pierri Evgenia , Skartsis Labros , Economou Christos
Published: April 2003

A relation is proposed which yields the occupied volume by macromolecular chains in solution. The experimental verification of the model is carried out by a viscometric study of the ternary system polymer A/polymer B/solvent. More precisely the viscometric study permits the determination of the critical concentration c** corresponding to the incipient overlap of spherical coils.
Electrochemical preparation of poly(di(2‐thienyl)benzene)s and poly(4,4′‐di(2‐thienyl)biphenyl)
Authors: Mitsuhara Toshio , Tanaka Susumu , Kaeriyama Kyoji
Published: April 2003

1,3‐Di(2‐thienyl)benzene (T13B), 4,4′‐di(2‐thienyl)biphenyl (TBP), and 3,5‐di(2‐thienyl)‐pyridine (T35P) were prepared. Films were deposited on the electrode in the anodic oxidative polymerization of T13B, 1,4‐di(2‐thienyl)benzene (T14B) and TBP, but the oxidation product of T35P did not cover the entire surface of the electrode. The infrared spectra of the films indicated oxidative coupling to occur at the 5 and 5′ positions of the thiophene rings. While the cyclic voltammograms of poly‐T14B were well‐defined, those of poly‐T13B and poly‐TBP had complex shapes with two or three anodic peaks. When the absorption spectra were measured during electrochemical oxidation, new peaks appeared at 2,0 and 1,9 eV for poly‐T13B and poly‐TBP, respectively. The films looked green in the oxidized state and faintly yellow in the neutral state. The green colour was retained without applied voltage in the cell and in the dry state. It was concluded that conjugation along the main chain is insufficient in these polymers.
Combined liquid‐crystalline polymers with chiral phases, 2. Lateral substituents
Authors: Kapitza Heinrich , Zentel Rudolf
Published: April 2003

Chiral combined liquid‐crystalline polymers (i. e. polymers with the mesogenic groups in the main chain as well as in the side groups) with dipole moments perpendicular to the mesogenic groups were synthesized and characterized. These dipole moments were introduced by lateral substituents, which were located at different parts of the mesogen or directly at the chiral centre. The polymers, thus prepared, show crystalline or glassy phases at room temperature and smectic A, chiral smectic C* or cholesteric phases at higher temperatures. Since the lateral substituents decrease the melting temperature more strongly than the clearing temperature, the liquid‐crystalline phases are broadened compared to the unsubstituted polymers. Often glassy liquid‐crystalline phases are obtained. The dipole moments perpendicular to the mesogenic groups or at the chiral centre may help to obtain a high spontaneous polarisation in the chiral smectic C* phase (ferroelectricity).
Computer simulation of the steady state in reversible polymer‐analogous reactions, 3. Flows and statistics in detailed balance
Authors: Krieger Dorit , Klesper Ernst
Published: April 2003

The steady state of reversible polymer‐analogous reactions was simulated by Monte Carlo calculations. The length of the simulated copolymer chains was chosen large enough to yield data with an acceptable degree of statistical fluctuation. Two types of sets of relative rate constants K were investigated, first K1 = K2 = K3, and second K1 ≠ K2, K1 ≠ K3, K2 ≠ K3, with K1 · K3 = K22. The relative rate constants K are defined as K1 = k(AAA)/k(ABA), K2 = k(AAB+)/k(ABB+), and K3 = k(BAB)/k(BBB), where k is the ordinary rate constant pertaining to the reaction of the central monomeric unit in the triad given in parentheses, with two different types of monomeric units A and B in the binary copolymer. For both types of sets of relative rate constants the simulation showed a detailed balance to prevail for the kinetics in the steady state. It was also shown that the same kinetics and statistics were obtained in the steady state when starting the simulation first from a homopolymer consisting of A‐monomeric units, and then from a homopolymer of B‐monomeric units. Based on the finding of a detailed balance and on the definition of K, it could be shown by analysis that the first type of the sets of K leads to a Bernoullian statistics of the copolymers in the steady state, while the second type leads to a first‐order Markov statistics. Correspondingly, equations are given which allow to calculate the relative rate constants from statistics and vice versa. The equations have also been confirmed by Monte Carlo simulation. In addition, the equations for the interrelations between the standard Gibbs free energies of the individual reactions for the central units in the triads are given.
Analysis of hydrodynamic data on linear poly(dimethylsiloxane) under theta‐conditions in terms of the bead‐chain and the continuous worm‐like cylinder models
Authors: Bohdanecký Miloslav , Petrus Vladimír , Horská Jitka , Edwards Christopher J. C. , Stepto Robert F. T.
Published: April 2003

Hydrodynamic data for linear poly(dimethylsiloxane)s (103 ≦ molecular weight ≦ 106) under theta‐conditions (intrinsic viscosity [η]Θ, intrinsic translational friction coefficient [f]Θ) are compiled and discussed in terms of theories developed for the bead‐chain model and the continuous worm‐like cylinder. While the former as applied fits the [f]Θ data only, the latter is found to describe consistently the molecular‐weight dependences of both [η]Θ and [f]Θ. Parameters of the worm‐like cylinder are estimated. The Kuhn statistical length, AK, agrees well with the theoretical value of the rotational isomeric state model. The effective diameter, 1,1 cm ≦ d · 108 ≦ 1,6 cm, is very low as compared with the diameter of the cross‐sectional area obtained from crystallographic data or the partial specific volume. Factors which may account for this discrepancy and the shortcomings of the interpretations using the bead‐chain model are discussed.
Mechanism of stereoselective polymerization of propylene oxide with [{MeOCH2CH(Me)OZnOCH(Me)CH2OMe}2 · {EtZnOCH(Me)CH2OMe}2] as initiator
Authors: Hasebe Yoshihiro , Tsuruta Teiji
Published: April 2003

A series of studies on molecular level elucidation of stereospecific polymerizations of propylene oxide (PO) were carried out with a well‐defined organozinc complex of ‘chair’ type structure, [{CH3OCH2CH(Me)OZnOCH(Me)CH2OCH3}2 · {EtZnOCH(Me)CH2OCH3}2] ([Zn‐MP]2,2), which contains two four‐coordinated Zn and two six‐coordinated Zn atoms, the latter being surrounded, respectively, by three types (endo‐coordinated, exo‐coordinated and non‐coordinated) of D‐ and L‐methoxypropoxy groups. An experiment using a partly deuterated [Zn‐MP]2,2 and PO‐α‐d showed the initiation reaction to be caused by an attack of the non‐coordinated methoxypropoxy (MP) group on a monomer molecule. Another experiment using (L)‐PO as monomer showed that the (D)‐MP group was preferentially transferred to (L)‐monomer to break its OCH2 bond. A molecular model study of [Zn‐MP]2,2 complex suggested that there may be chiral holes which can accomodate only one sense of enantiomeric PO molecule. The chiral structure of the hole around the six‐coordinated zinc atom is presumably determined by the chair type ZnO framework together with the coordinated MP groups.
Lineare und sternförmige hybrid‐polymere, 4 Ein neuer weg zur synthese von cellulose und amylose enthaltenden blockcopolymeren
Authors: Pfannemüller Beate , Dengler Thomas
Published: April 2003

(A‐B)n‐Block copolymers containing oligosaccharide blocks (A) and synthetic polymer blocks (B) coupled by amide linkages were synthesized. As starting material fully substituted cellulose and amylose derivatives with protecting groups of variable stability were used: triacetates, tricarbanilates and trimethyl ethers. The reaction steps were as follows: (i) trisubstituted oligosaccharides in the range of 2 < P̄n < 20 with OH endgroups at C‐1 and C‐4 were obtained by acidolysis or alcoholysis of the polysaccharide derivatives. (ii) By reaction of the OH endgroups with isocyanatoacetic ethyl or methyl ester, ester endgroups were introduced. (iii) Condensation with diamines [dodecamethylenediamine, NH2‐terminated poly(oxyethylene)] could be achieved by direct amidation of the ester endgroups in the case of the tricarbanilates and trimethyl ethers. As an alternative route, saponification of the ester endgroups and conversion into the more reactive p‐nitrophenyl ester was investigated. While condensation of the p‐nitrophenyl ester with diamines proceeds under mild conditions, difficulties arise in the quantitative p‐nitrophenylation of the COOH groups. In the case of the triacetates acetyl and ester endgroups were cleaved simultaneously by saponification, leading to unsubstituted oligosaccharides with COOH or lactone groups at both ends, a building block suitable for various reactions.
Syntheses of thermotropic copolyesters and their minimum needed fraction of mesogenic units
Authors: Zhang Hongzhi , Ning Xin , Wang Pingping , Zhang Zhibin , Guan Zhibin
Published: April 2003

Several series of thermotropic copolyesters with different spacers, containing the moieties of 1,4‐butanediol (4a or 4b), 1,6‐hexanediol (6a or 6b), bisphenol‐A (10a), bisphenol‐S (10b) or a telechelic polysulfone (12a or 12b) were synthesized. The mesomorphic properties of the resulting copolyesters were examined by visual observation of stir‐opalescence and birefringence under a polarizing microscope. Copolyesters 4a, 4b, 6a or 6b with mole fractions of mesogenic units over a broad extent (≥0,2) being thermotropic within wide mesomorphic temperature ranges, regardless of the spacers based on 1,4‐butanediol or 1,6‐hexanediol, have microstructures of block sequence distribution and do not retain liquid‐crystallinity if the mean lenghts of mesogenic segments are shorter than that of the triad with three phenyl rings. For the thermotropic copolyesters 10a, 10b, 12a or 12b the minimum mole fraction of mesogenic units needed is not higher than 0,10, despite of the different varieties and lengths of rigid spacers.
Synthesis of difunctional poly(dimethylsiloxane)s: Application to macromonomer synthesis
Authors: Gnanou Yves , Rempp Paul
Published: April 2003

Difunctional poly(dimethylsiloxane) (PDMS) macromonomers were synthesized. Emphasis was put on the synthesis of short PDMS chains exhibiting a narrow molecular weight distribution. This was achieved by the selection of an efficient initiator and under polymerization conditions such as to minimize reshuffling reactions. The macromonomers were subsequently obtained by deactivation of the living sites with an electrophilic unsaturation. Accurate characterization of the macromonomers (GPC, end‐group analysis) was performed.
Polymeric chiral crown ethers, 3 Synthesis of polymers incorporating D‐mannitol moieties via cyclopolymerization, and chiral recognition towards α‐amino acids
Authors: Kakuchi Toyoji , Takaoka Tohru , Yokota Kazuaki
Published: April 2003

A novel approach to the production of chiral, polymeric crown ethers incorporating D‐mannitol moieties was developed. Three optically active divinyl ethers (3, 6 and 9), derived from 1,3 : 4,6‐di‐O‐benzylidene‐, 1,2 : 5,6‐diisopropylidene‐ and 1,4 : 3,6‐dianhydro‐D‐mannitol (2, 5 and 8) were polymerized with cationic catalysts. The cyclopolymerization led to the chiral polymeric crown ethers 4, 7 and 10 consisting of only cyclic constitutional units. Both monomer 9 and polymer 10, containing 1,4 : 3,6‐dianhydro‐D‐mannitol moieties are amphiphilic compounds. Polymer 4 with 1,3 : 4,6‐di‐O‐benzylidene‐D‐mannitol moieties was found to exhibit chiral recognition in favour of the (S)‐isomer of racemic ester salts of phenylglycine, phenylalanine, valine and methionine. The ability of chiral recognition, which was estimated as enantiomer distribution constants (EDC), is comparable to that of polymeric crown ethers with (R)‐2,2′‐binaphthyl moieties.