bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on polyamide 3 — synthesis, characterization and properties
Authors: Morgenstern Ute , Berger Werner
Published: April 2003

The synthesis of polyamide 3 (PA 3) by hydrogen transfer polymerization is described. The reaction proceeds homogeneously in N,N‐dimethylacetamide/LiCl in contrast to the heterogeneous reaction in 1,4‐dioxane and pyridine. By IR, NMR, differential scanning calorimetry and extraction experiments it was shown that the reaction product is nearly pure PA 3.
Polymers of carbonic acid, 8. Linear polybiurets
Authors: Kricheldorf Hans R. , Meier‐Haack Jochen
Published: April 2003

Linear polybiurets can be synthesized by polycondensation of chloroformyl isocyanate and N,N′‐bis(trimethylsilyl)‐α,ω‐diaminoalkanes or silylated aromatic diamines. The polybiurets were characterized by elemental analyses, inherent viscosity measurements, IR spectroscopy, 1H, 13C, 15N NMR spectroscopy in solution, differential scanning calorimetry (DSC) measurements, wide‐angle X‐ray scattering (WAXS) and thermogravimetric analyses. All polybiurets are semicrystalline materials with a low rate of crystallization and unexpectedly low melting points. 13C and 15N NMR cross‐polarization/magic angle spinning (CP/MAS) spectra of the solid polybiurets indicate different conformations for the amorphous and crystalline phase. All polybiurets gradually decompose upon heating above 200°C. Synthetic methods and properties of linear biurets were also checked by synthesis and characterization of N,N′‐dioctylbiuret.
Synthesis and polymerization of epoxymethacrylates, 1. Catalysis and kinetics of the addition reaction of methacrylic acid and 2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]propane
Authors: Sandner Barbara , Schreiber Ramona
Published: April 2003

The kinetics of the addition reaction of methacrylic acid (1) and 2,2‐bis[4‐(2,3‐epoxypropoxy)‐phenyl]propane catalyzed by tertiary aliphatic amines, aromatic N‐heterocycles and quaternary ammonium salts, respectively, was studied in bulk with equimolar amounts of functional groups from room temperature to 120°C. A reaction order of 1,5 with regard to the conversion of epoxy as well as carboxylic groups was observed. This can be explained assuming the formation of an ammonium alkoxide ion pair by the equilibrium reaction of an epoxy group with ammonium carboxylate and the irreversible consecutive reaction of the ion pair with (1) under formation of 2‐hydroxyester groups and regeneration of ammonium carboxylate. The reaction rate constants increase linearly with the concentration of the catalyst and increase with increasing basicity of alkylpyridines. The advantage of the aromatic N‐heterocyclic catalysts consists in their stability to peroxides which are ingredients of preparations together with the epoxy methacrylate Bis‐GMA, e. g. in dental composites and adhesives.
Local mobility and liquid‐crystalline state in side‐chain polymers with mesogenic groups directly bonded to the main chain
Authors: Nikonorova Natalia A. , Stepanova Tamara P. , Malinovskaja Vera P. , Burstein Lija L. , Borisova Tamara I. , Korshun Alexander M. , Skorochodov Sergei S.
Published: April 2003

The intramolecular mobility of copolymers 4 was investigated by means of dielectrospectroscopy. The copolymers exhibit a convenient model for the study of local mobility in side‐chain thermotropic polymers without spacer. The dependencies of the dielectric losses on frequency and temperature point to the presence of relaxation processes related to the intramolecular mobility of fragments of the mesogenic group. For the formation of the liquid‐crystalline state two factors are important: different forms of local mobility inside the mesogenic groups and a flexible connection between side chain and main chain.
Emulsion polymerization of styrene using phospholipids with polymerizable chain as an emulsifier
Authors: Watanabe Shinji , Ozaki Hiroyuki , Mitsuhashi Ken‐ichi , Nakahama Seiichi , Yamaguchi Kazuo
Published: April 2003

Emulsion polymerizations of styrene with various phospholipids as emulsifiers were carried out to obtain latices bearing the lipids. Using 1‐palmitoyl‐2‐(4‐vinylbenzoyl)‐sn‐glycero‐3‐phospho‐choline (2a) and 1‐[5‐(4‐vinylphenyl)pentanoyl]‐sn‐glycero‐3‐phosphocholine (3) as emulsifiers, latices of narrow size distributions were produced in high yields with a water‐soluble initiator, K2S2O8. The lipids were found to be quantitatively immobilized onto the latex surface. With a hydrophobic initiator, 1‐palmitoyl‐2‐[5‐(4‐vinylphenyl)pentanoyl]‐sn‐glycero‐3‐phosphocholine (2c) were bound densely on the latex surface, although the yields were not high. Phospholipase C was found to hydrolyze 2b and 2c attached to the surface.
On the kinetics of polymerization and copolymerization of poly(oxyethylene) macromonomers and styrene
Authors: Capek Ignac , Riza Medyan , Akashi Mitsuru
Published: April 2003

The homogeneous and the dispersion polymerzation and copolymerization of methacryloyl‐terminated poly(oxyethylene) (MMA‐PEG) and of p‐vinylbenzyl‐terminated poly(oxyethylene) (St‐PEG) macromonomers and styrene, initiated by a radical initiator, was investigated using conventional gravimetric and NMR methods at 60°C. The batch polymerizations in N,N‐di‐methylformamide and in ethanol/water were conducted to either low or high conversion. The fractional conversion rates of the solution polymerization and copolymerization indicate that the homopolymerizations of macromonomers involve steady‐state conditions, whereas copolymerizations proceed under non‐stationary conditions. The ratios of the rate constants for propagation and termination (kp/k) for polymerization and copolymerization of MMA‐PEG and St‐PEG are by one order of magnitude higher than that for styrene. The increase in kp/k is more pronounced in dispersion polymerization, which is ascribed to the decrease of both kp and kt. The rates of dispersion polymerization are proportional to the particle concentration. The number of particles increses up to 50% conversion. The particle growth is suggested to proceed via association of partcles and by propagation within polymer particles. The decrese of the number of radicals per particles as conversion proceeds is ascribed to the decrese of the growing radical activity and to the transfer of monomeric radicals to the continuous phase. The molecular weights correlate inversely with the particle size.
Synthesis of new polymers via Diels‐Alder reaction, 2. Soluble polymers via copolymerization
Authors: Kuhrau Martin , Stadler Reimund
Published: April 2003

A series of copolymers are synthesized by repetitive Diels‐Alder polyaddition reaction of bifunctional cyclohepta‐1,3,5‐trienes with bifunctional 1,2,4‐triazoline‐3,5‐diones. The copolymers of different bistriazolinediones with a bisdiene, or of different biscycloheptatrienes with a dienophile, have good solubility in CH2Cl2 and CHCl3, while the homopolymers are poorly soluble. The copolymers were characterized by standard analytical techniques to test the structural regularity of these systems. Due to the kinetic control, it is possible to apply copolymerization statistics to these systems. Based on a model study, it is concluded that alipatic and aromatic bistriazolinediones have the same reactivity towards ditropyl. Nonstoichiometric polyaddition with a slight excess of bistriazolinedones provides a possibility to prepare telechelics with highly reactive triazolinedione end‐groups. The end‐group concentration can be checked by UV spectroscopy. These telechelics are efficient bulky blocks to prepare two‐component networks with a variety of polydienes.
Preparation of 4‐nitrophenyl carbonate esters of poly‐ [5N‐(2‐hydroxyethyl)‐L‐glutamine] and coupling with bioactive agents
Authors: Marre Anne De , Schact Etienne
Published: April 2003

Poly[N‐(2‐hydroxyethyl)‐L‐glutamine] (PHEG) is a suitable carrier for the design of macromolecular prodrugs. A method is described for partial conversion of hydroxyl side groups into reactive carbonate esters. Activation is achieved through the reaction with 4‐nitrophenyl chloroformate. It is shown that during the course of the activation no intra‐ or intermolecular carbonate esters are formed. The content of reactive carbonates can, for a given set of reaction conditions, be controlled by the amount of chloroformate added. The activated polymer easily reacts with numerous amines. Reaction with a melphalan prodrug and amino‐terminated glycosides demonstrated the feasibility of the presently described activation method to prepare macromolecular prodrugs.
Cationic polymerization of bis(1‐alkylvinyl)benzenes and related monomers, 6. Improved synthesis of polyindanes
Authors: Maier Gerhard , Leitner Michael B. , Nuyken Oskar
Published: April 2003

Reaction conditions have been found which allow the synthesis of polyindanes with improved molar mass. The properties of four different polyindanes are described and compared with those of polyindanes with low molar mass from former investigations. The range of glass transition temperatures which can be achieved with polyindanes has been extended from − 10°C to 293°C. In addition, one of the newly snythesized polyindanes exhibits crystallinity with a melting point of 253°C. This is in sharp contrast to all other polyindanes investigated up to now, which were completely amorphous.
Iodine‐poly(vinyl alcohol) interactions, 5. Releasing mechanism of I− and I2 in the decomposition process of the blue complex
Authors: Yokota Toshio , Kimura Yoshiharu
Published: April 2003

By treating a blue‐colored solution of poly(vinyl alcohol) (PVA), iodine and boric acid with an anion exchange resin, a solution consisting only of the polyiodide ion bound to the PVA matrix was obtained. In order to re‐establish the equilibrium between polyidodide, I2 and I−, the bound polyiodide ions decomposed to I− and I2. When this happend at temperatures below 10°C, only I− was released from the PVA matrix with I2 remaining in it, and a new equilibrium state was reestablished. However, above 20°C all polyiodide ions were decomposed without recovering the equilibrium of the reaction. In this case both I2 and I− were released from the PVA matrix. Based on these findings a new mechanism for the formation and decomposition of polyiodide ions was deduced. From the initial and equilibrium concentrations of the polyiodide ions at 5 and 10°C, approximate dissociation constants to I− (free) and I2 (bound) were estimated.
Enhanced crystallization by annealing of poly(phenylene sulfide) in presence of CO2 and N2O
Authors: Schultz Joachim Dirk , Böhning Martin , Springer Jürgen
Published: April 2003

Crystallization of amorphous poly(phenylene sulfide) was carried out upon annealing in the presence of sorbed CO2 and N2O at pressures of 50 bar. Thermal crystallization at the same pressure allows the comparison of crystallization rates. From the results of IR‐spectroscopy, wide angle X‐ray diffraction, differential scanning calorimetry and density measurements, it is seen that in the presence of sorbed gas molecules crystallization occurs even at temperatures below the glass transition measured at atmospheric conditions. At a given temperature, gas sorption yields accelerated crystallization. The results, show the considerable plasticizing influence of sorbed gas molecules. From the crystallization rate at sorbed gas conditions the plasticizing ability of the gas may be estimated. That of N2O exceeds that of CO2 by a factor of three. Assuming a simple two‐phase model for the crystalline polymer the comparison of heat of melting and density values for t → ∞ allows the conclusion that parts of the noncrystalline volume fraction become less dense by annealing in the presence of sorbed gas molecules. An increased free volume fraction which may be formed in the non‐crystalline regions is discussed. It is possible that the remaining lower density results from a hindered relaxation of chain molecules from the dilated state they take due to gas sorption. In this context the influence of decreased mobility of non‐crystalline chains is discussed in terms of the “rigid amorphous phase” concept.
Esterification and amidation of polymeric acyl chlorides. A new route to polymethacrylates and polymethacrylamides with a variety of different side groups
Authors: Strohriegl Peter
Published: April 2003

This paper describes the synthesis of a number of polyacrylates, polymethacrylates and polymethacrylamides by polymer analogous esterification or amidation of polymeric acyl chlorides. The reactive prepolymers are accessible by free‐radical polymerization of acryloyl or methacryloyl chloride. Prepolymers with a reduced amount of reactive groups were prepared by copolymerization of methacryloyl chloride and methyl methacrylate. Polymer analogous esterification of the prepolymers leads to polyacrylates and polymethacrylates with azobenzene, carbazole and azosulfonate side groups. The synthesis of some polymethacrylates with NLO‐active side groups including photocrosslinkable materials is also described.
Structural variations as a function of temperature and dynamic‐mechanical relaxations for ethylene‐tetrafluoroethylene and ethylene‐chlorotrifluoroethylene alternating copolymers
Authors: Guerra Gaetano , De Rosa Claudio , Iuliano Mauro , Petraccone Vittorio , Corradini Paolo , Ajroldi Giuseppe
Published: April 2003

The X‐ray diffraction patterns at different temperatures of alternating ethylene‐tetrafluoroethylene (ETFE) and of alternating ethylene‐chlorotrifluoroethylene (ECTFE) copolymer samples are compared. For ECTFE, a reversible variation with temperature of the half‐width of the diffraction peaks, analogous to but much smaller than that one which corresponds to the topotactic crystal‐to‐crystal transition of ETFE, was found. A comparison of the dynamic mechanical spectra of the two copolymers seems to confirm the different nature of the two high‐temperature relaxation peaks. In particular, the so called α and β relaxations of ECTFE occur in the amorphous phase while the so called α and α′ relaxations of ETFE occur in the amorphous and crystalline phase, respectively.
Structure and behaviour of SiO2/MgCl2 bisupported Ziegler‐Natta catalysts for olefin polymerization
Authors: Lu Honglan , Xiao Shijing
Published: April 2003

Bisupported catalysts for olefin polymerization were prepared by mixing a butyl alcoholate solution of MgCI2 with pretreated SiO2 in heptane, and further treating with TiCI4 solution. The silica pretreating conditions and their effects on the composition of the catalysts were studied. The interaction mechanism of the two supports, MgCI2 and SiO2, is discussed. The effect of the composition and the structure of the catalyst on the behaviour of ethylene and propylene polymerization is described. The calcination temperature of SiO2 has a significant effect on composition, structure and properties of the catalysts. There exist both chemical bonding and physical absorption between SiO2 and MgCI2 supports. The activities for propylene polymerization remarkably increase with increasing mole ratio Mg/Ti of the catalysts, while for ethylene polymerization, the activities mainly depend on the Ti content of the catalysts and the calcination temperature of SiO2 used.
Liquid crystalline polyacrylates containing biphenyl and chiral terminal groups in the side chain, 2. Influence of the nature of the chiral group
Authors: Tabrizian Maryam , Bunel Claude , Vairon Jean‐Pierre , Friedrich Claude , Noël Claudine
Published: April 2003

Acrylate monomers with a chiral group have been synthesized bearing a propyl, isopropyl or benzyl substituent on the asymmetric carbon. All of the monomers are crystalline. Above their melting point, they give a clear, isotropic melt. The corresponding polymers have been prepared by free radical polymerization. They were examined by differential scanning calorimetry, optical microscopy and X‐ray diffraction. They were found to show a reproducible liquid‐crystal behavior. On cooling from the isotropic state, SA, S (or S) and crystal‐like (probably SH or SH′) phases become evident. Our results do not preclude the existence of a S phase between the SA and S phases. It is noteworthy that polyacrylates of the same series but with side chains terminated by a chiral group bearing a methyl substituent exhibit SA, SB and crystal‐like (probably SE) phases.
Composition and microstructure of a copolyester formed in the melt‐mixing of poly(ethylene terephthalate) and poly(ethylene truxillate)
Authors: Montaudo Giorgio , Montaudo Maurizio S. , Scamporrino Emilio , Vitalini Daniele
Published: April 2003

This study shows that is possible to determine the composition and microstructure of the copolyester formed in the melt‐mixing process of poly(ethylene truxillate)

System. name of truxillic acid: 2,4‐diphenylcyclobutane‐1,3‐dicarboxylic acid.

(PETx) and poly(ethylene terephthalate) (PET), by applying a novel method of statistical modeling of mass spectra of copolymers. The peak intensities of molecular ions appearing in the fast atom bombardment mass spectrum of the melt‐mixed equimolar mixture of PETx and PET were found to reflect the relative amounts of oligomers present in the sample and to be directly related to the microstructure of the copolymer formed. The statistical analysis of copolymers allows one to generate a number of different theoretical mass spectra that can be fitted with the experimental mass spectrum data, thus determining the most likely copolymer composition.
Stereospecific polymerization of methylthiirane in homogeneous phase, 4. Solvent effect on stereospecificity and enantioasymmetry
Authors: Boucard Valérie , Dumas Philippe , Sigwalt Pierre , Rucar Delphine , Guérin Philippe
Published: April 2003

The living stereospecific polymerization of methylthiirane initiated by a chiral cadmium compound was run in different solvents. The general features of the mechanism of stereoregulation are the same as in bulk. In heptane and in heptane/propylene carbonate mixtures, the stereospecificity of the reaction does not depend on monomer concentration and on the dielectric constant ε of the medium. This independence of stereospecificity is in agreement with the absence of a variation of the complexation constant between a model cadmium derivative and the monomer with the variation of ε in a large range. The enantioasymmetric process depends on the molecular weight of the chain bearing the active sites. A change from diastereoisomeric to enantiomeric forms of active sites occurs for molecular weights around 50000. The enantioasymmetric constant depends on the nature of the medium and we observed a Born law for the dependence of the enantioasymmetric constant versus reciprocal dielectric constant: log kR ∝ 1/ε. This effect can be explained by a variation of the reactivities of the two types of active sites and occurs without a change in their relative amounts.
Water‐soluble polymers bearing biologically active residues, 1. Synthesis and characterization of poly(ether‐ester)s bearing hydroxyl side groups and their derivatization with 1‐naphthylacetic acid
Authors: Sepulchre Maurice , Kraba Nadjat Wafia , Sepulchre Marie‐Odile , Spassky Nicolas , Manolova Nevena , Ignatova Milena , Rashkov Iliya
Published: April 2003

The synthesis of low‐molecular‐weight poly(ether‐ester)s bearing hydroxyl side groups by poly‐condensation, in 1‐methyl‐2‐pyrrolidone at 105–110°C, of the potassium salts of racemic malic and (R,R)‐tartaric acids and α‐(2‐bromoethyl)‐ω‐bromopoly(oxyethylene)s of different molecular weights is described. The polymers were characterized by GPC and 1H and 13C NMR. The fixation of 1‐naphthylacetic acid, a plant growth regulating agent, was successfully achieved in the case of poly(ether‐ester)s deriving from tartaric acid, by carrying out the esterification reaction at room temperature in the presence of N,N′‐dicyclohexylcarbodiimide and 4‐dimethylaminopyridine.
Synthesis and electrical and optical properties of poly‐(2‐methoxy‐1,4‐phenylenevinylene) and copolymers
Authors: Shim Hong‐Ku , Hwang Do‐Hoon , Lee Kwang‐Sup
Published: April 2003

Poly(2‐methoxy‐1,4‐phenylenevinylene) (PMVP) and copolymers containing both unsubstituted (1,4‐phenylenevinylene, PV) and 2‐methoxy‐1,4‐phenylenevinylene (MPV) units were prepared in thin films from their water‐soluble sulfonium salt precursor polymers. Drawn films (L/L0 = 6) of the PMPV homopolymer could be doped with I2 vapor and FeCl3 to give conductivities of 3,2 and 4,0 ċ cm−1, respectively. The conductivity of FeCl3‐doped copolymer films ranged from 100 to ca. 102 ċ cm−1 depending on the composition. The third‐order nonlinear susceptibility, χ(3), for the PMPV film was investigated by degenerate four‐wave mixing technique using 400 femtosecond pulses at 602 nm. A relatively large χ(3) value (7,9 ċ 10−10 esu) with a subpicosecond response was observed.
Conducting polymers from anodic coupling of some N,N′‐bridged 2,2′‐bipyrrolyl monomers
Authors: Berlin Anna , Pagani Giorgio , Zotti Gianni , Schiavon Gilberto
Published: April 2003

Anodic coupling in CH3CN + 0,1 M tetraethylammonium perchlorate of some 2,2′‐bipyrrolyl monomers bridged by X groups at the N,N′‐positions (X = CHCH (1), o‐C6H4 (2) CH2 (3), (CH2)2 (4) and (CH2)3 (5)) produces conducting, α‐coupled polypyrroles (from IR spectroscopy), containing 0,25–0,30 counteranions per pyrrole ring (from elemental analysis). The in‐situ conductivity spans from values commonly found for N‐substituted polypyrroles (4 ċ 10−3 S/cm for 5) to unusually high values (2,5 S/cm for 4). A linear correlation between redox potentials and log of conductivities of the polymers evidences the influence of the polymer electronic properties of charge transport.
Synthesis of membranes for the dehydration of water/acetic acid mixtures by pervaporation, 2. Poly(vinyl alcohol) membranes containing covalently bonded carboxylic groups
Authors: Nguyen Trong Q. , Essamri Azzonz , Schaetzel Pierre , Néel Jean
Published: April 2003

Poly(vinyl alcohol) (PVA) membranes containing small amounts of fixed carboxylate groups were prepared by two methods: reaction with chloroacetic acid in alkaline medium, and polymerization of acrylic acid on radical sites issued from Ce4+ ‐oxidation of PVA membranes. In the first method, when the reaction was carried out on the dissolved PVA, the crystallinity was greatly reduced, leading to a large increase in permeation flux, a slight decrease in selectivity and a significant increase in the overall performance. The activation energy of permeation was slightly decreased after the reaction. Clear qualitative correlations between different properties were obtained. In the second method, grafting was carried out on the solid membrance and the crystallinity degree was not significantly altered, yet enough to yield membranes with slightly lower selectivity and higher permeability. The Arrhenius plots of permeation rates for some membranes in acetic acid/water mixtures of different compositions showed a transition temperature which is reminiscent of a glass transition temperature the value of which is decreased by the presence of solvent molecules.
Porous copolymers of trimethylolpropane triacrylate and acrylonitrile
Authors: Kolarz Bozena N. , Wojaczyńska Maria , Trochimczuk Andrzej W.
Published: April 2003

The homopolymer of trimethylolpropane triacrylate (TMPA) was synthesized by suspension polymerization using a thermodynamically good solvent (toluene) as a porogen (vol. ratio 1:1). This polymer possesses a high specific surface area (437 m2 · g−1) and porosity (50%). It was found by sorption of benzene and cyclohexane that the majority of the pores are in the range of 1–5 nm. Sorption of phenol, a standard sorbate, from a water solution is proportional to the specific surface area of the mesopores. This sorption is higher than that of nonspecific sorbents (like styrene/divinylbenzene copolymers) and smaller than the sorption of specific ones (like acrylonitrile/divinylbenzene copolymers).

Two sets of reactive copolymers were obtained. In the first set, TMPA (20–40 vol.‐%) was polymerized with acrylonitrile (AN) in the presence of a constant amount of toluene as an inert diluent (vol. ratio 1:1). In the second set of copolymers the cross‐linking degree was kept constant (30 or 40 vol.‐% of TMPA) but various solvent mixtures were used, namely: toluene/tetradecane or hexadecane, toluene/2‐ethylhexanol, cyclohexanol/tetradecane or hexadecane, cyclohexanol/2‐ethylhexanol (vol. ratio 9:1). It was found that all the copolymers are macroporous (volume of pores approx. 1,0 cm3 · g−1) but those obtained in the presence of good solvents display a higher specific surface area and hence better sorption properties towards phenol than those obtained in the presence of poor solvents. The swelling of AN/TMPA copolymers is smaller than that of the TMPA homopolymer due to the presence of additional physical crosslinks formed by the strongly polar nitrile groups.
On the structure of the mesomorphic form of syndiotactic polystyrene
Authors: Petraccone Vittorio , Auriemma Finizia , Poggetto Francesco Dal , De Rosa Claudio , Guerra Gaetano , Corradini Paolo
Published: April 2003

In this contribution, the X‐ray diffraction (XRD) pattern of a highly oriented sample of syndiotactic polystyrene in the mesomorphic form, collected by an automatic diffractometer, is presented, thus providing quantitative and more complete information relative to the diffracted intensity. The structural changes induced by annealing procedures in mesomorphic samples are shown through the analysis of the XRD patterns: both unoriented and oriented mesomorphic samples are transformed gradually into α‐form crystals. On the basis of these evidences and of preliminary comparisons between the calculated Fourier transform of simplified models and the experimental diffraction intensity, it is suggested that the local organization in triplets of trans‐planar chains, typical of the different modifications of the α‐form, would be largely present also in the disordered chain agglomerates of the mesomorphic form.
The applicability of copolymer composition and sequence distribution data to the mechanistic study of the alternating copolymerisation of maleic anhydride with substituted styrene derivatives
Authors: Brown Paul G. , Fujimori Kiyohisa , Brown Anthony S. , Tucker David J.
Published: April 2003

The composition and sequence distribution of copolymers of maleic anhydride (MA) with p‐methoxystyrene (p‐MST) and p‐chlorostyrene (p‐CST) prepared in ethyl methyl ketone at 50 ± 0,1°C were analysed using 13C DEPT NMR techniques, in order to compare the applicability of composition and sequence distribution data to the study of the mechanism of copolymerisation using the terminal, penultimate and complex‐participation models. In the case of the strongly alternating copolymerisation of p‐MST with MA, the comparison of models on the basis of sequence distribution data was found to be better at separating each model in terms of its applicability, with the complex‐participation model providing the best fit to the data. In the case of the less strongly alternating copolymerisation of p‐CST with MA, neither method of comparison could clearly distinguish between the penultimate and complex‐participation models.
Electron microscopy on highly branched polystyrene starshaped polymers
Authors: Buchholz Udo , Lutz Pierre , Kunz Martin , Burchard Walther
Published: April 2003

The technique of transmission electron microscopy (TEM) in combination with electron spectroscopic imaging and digitized image processing was used for determination of particle size and size distribution of a starshaped polystyrene sample. The results were compared with measurements of the translational diffusion coefficient Dz from dynamic light‐scattering method. The particle diameter dEM achieved by TEM‐measurements is in good agreement with the effective hydrodynamic radius Rh from the Stokes‐Einstein relationship.
Pressure and solvent influences on the shear thinning behavior of moderately concentrated solutions of poly(butyl methacrylate)
Authors: Horst Roland , Mertsch Rüdiger , Wolf B. A.
Published: April 2003

The viscosities of moderately concentrated solutions of poly(butyl methacrylate)—M̄w = 1820 kg/mol–in the thermodynamically good solvent toluene and in the theta solvent 2‐propanol were measured up to pressures of 2000 bar as a function of shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} in the temperature interval from 40 to 70°C. Both systems obey Graessley's equation so that it is possible to obtain the following rheological parameters in addition to the zero‐shear viscosity η0 from the dependences \documentclass{article}\pagestyle{empty}\begin{document}$ \eta (\dot \gamma ) $\end{document}. η can be split into an entanglement part ηent plus a frictional contribution ηfric, and the characteristic viscometric relaxation time τ0 becomes accessible. The present results demonstrate that the application of pressure raises the above parameters much less for good than for bad solvents. In contrast to ηfric (which can react differently to the application of pressure due to special circumstances) η0 and τ0 are always influenced to the same degree as T or p are changed. This result implies that the steady state shear compliance (τ0/η0) is independent of the variables of state irrespective of the thermodynamic quality of the solvent. For the good solvent the effects of temperature can be described by the Arrhenius equation, whereas the WLF equation has to be used for the bad one.
Microstructure of styrene‐methacrylic acid and styrene‐acrylic acid copolymers, 6. Relation of the glass transition temperature to the microstructure of (meth)acrylic acid‐styrene copolymers
Authors: S̀witala‐Żeliazkow Maria
Published: April 2003

The glass transition in acrylic acid‐styrene and methacrylic acid‐styrene copolymers prepared in benzene solution and in emulsion were investigated. A dependence of the glass transition temperature of the copolymer on the diad sequence distribution was found. There are two possible explanations of such a dependence: the microstructure determines the amount of intermolecular hydrogen bonds, and/or the microstructure of the copolymer, i.e. the diad sequence distribution, determines the intramolecular flexibility of the copolymer.
Polymerization of propene with zirconocene‐containing supported catalysts activated by common trialkylaluminiums
Authors: Soga Kazuo , Kaminaka Manabu
Published: April 2003

This paper reports on propene polymerization conducted with modified Kaminsky‐type catalysts activated by common alkylaluminiums. Several kinds of heterogeneous catalysts containing zirconocene were prepared by supporting Et[IndH4]2ZrCl2, iPr(Flu)(Cp)ZrCl2 and Cp2ZrCl2 on A12O3, SiO2, MgO, MgCl2, MgF2, CaF2 and AlF2 using an impregnation method. When Al2O3, MgCl2, MgF2, CaF2 and AlF3 were used as carriers, the resulting catalysts were easily activated by common trialkylaluminiums to give isotactic, syndiotactic and atactic polypropene in fairly good yields, whereas the other supported catalysts, combined with common trialkylaluminiums, did not show any polymerization activity. However, highly active catalysts were obtained by supporting the zirconocene compound on SiO2 that had been reacted with a small amount of methylaluminoxane. The use of C1‐containing alkylaluminiums always killed the catalyst activity.
Surface tension of liquid polysiloxanes having fluorinated alkyl side‐chains
Authors: Kobayashi Hideki , Owen Michael J.
Published: April 2003

The surface tension of viscous polymer liquids, viz. polysiloxanes having fluorinated alkyl sidechains, was evaluated based on the pendant‐drop method. The polysiloxane fluids studied are poly‐(3,3,3‐trifluoropropylmethylsiloxane), poly(3,3,4,4,5,5,6,6,6‐nonafluorohexylmethylsiloxane) (PNFHMS), poly(3,3,4,4,5,5,6,6,7,7,8,8‐tridecafluorooctylmethylsiloxane) (PTDFOMS) and poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10‐heptadecafluorodecylmethylsiloxane) (PHDFDMS). The surface tension of liquid poly(dimethylsiloxane)s was also examined as standard silicone fluids. The surface tensions of liquid PNFHMS, PTDFOMS and PHDFDMS were very low, as low as the value previously reported for poly(oxyhexafluoropropylene) fluids. Low‐ and hightemperature properties of these highly fluorinated polysiloxanes were also evaluated.
Studies on free radicals in popcorn and in normal polychloroprene
Authors: Fawcett Allan H. , Flockhart Brian D. , Poon Lai W. , Harrod Sydney
Published: April 2003

The electron paramagnetic resonance (EPR) spectrum from the radicals responsible for the growth of chloroprene popcorn has been observed as a broad singlet. During proliferous growth at 20°C the first‐order growth constant is 5,1 · 10−2 h−1, and the activation energy for the process is 38 kJ · mol−1. The rate of growth is reduced by exposure of the material to oxygen. Pure oxygen and air cause the EPR signal to diminish in intensity, as also do nitric oxide and nitrogen dioxide. The latter substance also reacts with the residues of chloroprene in popcorn and in normal bulk polychloroprene to form a nitroxide radical at a site that is a crosslink between two chains. The signal from this radical is an anisotropic triplet, characteristic of its restricted motion. On standing it becomes converted by protonation to a more complex pattern, and that signal diminshes in intensity in a reversible manner, probably because NO combines with the radical.
Solution behaviour of a liquid‐crystalline side‐group polymer
Authors: Fritz Lydia , Springer Jürgen
Published: April 2003

Dilute and semidilute solutions of fractions of a liquid‐crystalline side‐group polymer were investigated by means of size‐exclusion chromatography (SEC), static light scattering (LS), density and viscosity measurements. The mass‐average molar mass ranged from M̄w = 1 · 105 g · mol−1 to 1,5 · 106 g · mol−1. Large discrepancies were found between the molar mass determined through SEC and through LS. Strong interactions between the mesogenic groups can be assumed by the results of density and LS measurements. Due to the determined characteristic ratio of C∞ = 19,5 a similar chain stiffness as a poly(alkyl methacrylate) of equal length of the side chain is observed. In semidilute solutions an excess low‐angle scattering (ExLAS) occurs which increases at higher concentrations. The dependence of the reduced osmotic modulus [M̄w/(RT)](∂π/∂c)T on the parameter x = A2 · M̄W · c was studied.
Photodégradabilité de copolymères styrèniques comportant des motifs de chaîne α‐phényl et β‐phénylcétone. Polycétones issues de I'hydrolyse de polyméres et copolymères d'acétoxyphénylbutadiéne et de phényl(triméthylsiloxy)butadiènes
Authors: Guemra Kaddour , Casals Pierre‐François , Oulmidi Abdelkader , Mansri Ali , Reyx Danièle
Published: April 2003

The present work reports on the photodegradation of macromolecules (poly(styrene‐co‐carbon oxide)) having α‐phenyl and β‐phenylcarbonyl groups along the main chain. The photochemical behavior of polyketones containing β‐phenylcarbonyl groups and their comparison with the behaviour of a polyketone containing α‐phenylcarbonyl are expected to give useful informations. With this purpose polyketones constituted of 3‐oxo‐1‐phenylbutane‐1,4‐diyl units (i) regularly head‐to‐tail linked (I), (ii) included in polystyrene (II) or (iii) in poly(1‐phenylbutadiene) (III) and polyketone constituted of 3‐oxo‐2‐phenylbutane‐1,4‐diyl units (IV) have been considered. The synthesis of I by hydrolysis of polymers of 3‐acetoxy‐1‐phenyl‐1,3‐butadiene (2a) and of 1‐phenyl‐3‐(trimethylsiloxy)‐1,3‐butadiene (2b) have been tested: the polyketones I are proved to be more easily accessible from 2b and its polymer (3b) than from 2a and its polymer (3a). The polyketones II, III and IV have then been synthesized from the copolymer (4) of 2b with styrene, the copolymer (5) of 2b with 1‐phenyl‐1,3‐butadiene, and the polymer (8) of 2‐phenyl‐3‐(trimethylsiloxy)‐1,3‐butadiene (7), respectively. The photochemical behavior of these polyketones and copolyketones is in accordance with the previously observed regiospecific α‐phenyl‐side towards the β‐phenyl‐side fragmentation and shows that the expected photosensibilisation of the β‐phenyl‐side fragmentation by increasing phenyl to carbonyl ratio is not observed.
Ion‐conduction of lithium fluoroalkylsulfonates in oligo(oxyethylene)‐branched poly(phosphazene)
Authors: Tada Yuji , Sato Moriyuki , Takeno Noboru , Nakacho Yoshifumi , Shigehara Kiyotaka
Published: April 2003

Novel organic‐soluble lithium salts, lithium 1,1,2‐trifluoro‐4‐methoxy‐1‐butanesulfonate (I) and lithium 3‐(2‐methoxyethoxy)‐1‐propanesulfonate (II), were synthesized. Their ionic conductivities were examined in a solid polymer matrix of endo‐methoxy oligo(oxyethylene)‐branched poly(phosphazene) (III) and compared with the ordinary hybrids of LiCIO4/III or LiSO3CF3/III. The ionic conductivity of I/III hybrid was as high as 2,2.10−5 S. cm−1 at 25°C, which is comparable to that of LiCIO4/III or LiSO3CF3/III hybrids. Although anions are the major carrier ions in the LiCIO4/III or LiSO3CF3/III hybrids, the lithium transport number of I/III hybrid was about 0.5 due to the larger size of the counter anion.
New polymer syntheses, 65. New terephthalic acids with aromatic substituents and thermotropic polyesters derived from them
Authors: Kricheldorf Hans R. , Bürger Rolf
Published: April 2003

New terephthalic acids with aromatic substituents were prepared in two different ways. A first attempt was made by nucleophilic substitution of dimethyl nitroterephthalate with phenoxide ions. The formation of phenyl methyl ethers is a significant side reaction in this procedure. The second method consists in the arylation of dimethyl 2‐(4′‐hydroxyphenylthio) terephthalate with activated fluoroaromatics. Insufficient electrophilicity of the fluoro compound is here the limiting factor. Thermotropic polyesters were prepared from 4,4′‐biphenyldiol and various arylthioterephthalic acids. It was found that increasing length of the aromatic side chain improve both solubility and meltability. All polyesters form a nematic phase above their melting point (Tm).
Water‐soluble polymers bearing biologically active residues, 2. Complexes of poly(ether‐ester)s with polyacrylic and polymethacrylic acids
Authors: Ignatova Milena , Manolova Nevena , Rashkov Iliya , Sepulchre Maurice , Spassky Nicolas
Published: April 2003

The complex formation between poly(acrylic acid) (PAA) or poly(methacrylic acid) (PMA) with poly(ether‐ester)s such as poly[oxymaloyloxypoly(oxyethylene)]s (PMEGs) and poly[oxytartaroyloxypoly(oxyethylene)]s (PTEGs) as well as with their derivatives with the synthetic plant‐growth regulator 1‐naphthylacetic acid (NNA) was studied. Complex formation with PAA occurs below a critical polyether chain length for polymer‐polymer complexation. This peculiarity is discussed in view of the stabilizing effect of hydrophobization resulting from intramolecular hydrogen bonding. The hydrophobic 1‐naphthylacetyl groups of PMEG and PTEG esters are found to stabilize the polycomplexes even more. Derivatives with NAA as well as their complexes with PAA and PMA exhibit auxin activity.
Equilibria and kinetics of the cationic ring‐opening polymerization of permethylated 1,4‐dioxa‐2,3,5,6‐tetrasilacyclohexane. Comparison with cyclosiloxanes
Authors: Kurjata Jan , Chojnowski Julian
Published: April 2003

Equilibrium constants were determined for the formation of cyclic oligomers of the general formula \documentclass{article}\pagestyle{empty}\begin{document}$ {\hbox{-\hskip-5pt-\hskip-5pt-}[({\rm CH}_3})_2 {\rm Si \hbox{---} Si(CH_3})_2\hbox{---} {\rm O\hbox{-\hskip-6.5pt-}]}_n , n = 2 - 6$\end{document}, in the polymerization of the n = 2 homologue, octamethyl‐1,4‐dioxa‐2,3,5,6‐tetrasilacyclohexane (1). The formation of a linear polymer is thermodynamically favoured in bulk and in concentrated solutions. The equilibrium concentration of cyclics is little dependent on temperature. The six‐membered ring, n = 2, used here as a monomer, is the most abundant cyclic in the equilibrium mixture. Kinetics of the conversion of 1 during the polymerization initiated with CF3SO3H, CH3SO3H and CF3COOH was studied in methylene dichloride solution. In its first stage, the reaction follows first order, but it slows down at higher monomer conversion. The order of the reaction with respect to the acid is two. Some kinetic features of the polymerization initated with CF3SO3H were similar to those exhibited by the polymerization of octamethylcyclotetrasiloxane (D4). In particular small amounts of additional water have rather small effect on the rate, but change to a considerable extent the entropy and enthalpy of activation. The concentration of cyclic oligohomologues passes through a maximum during monomer conversion, which indicates the kinetic enhancement of the cyclisation process. This observation is somewhat similar to those in the polymerization of hexamethylcyclotrisiloxane (D3). However, in contrast to the polymerization of D3 and similarly to the polymerization of D4, the excessive formation of oligomers being multiples of the monomer is not observed.
Sequential assignments of polymers by 2D NMR techniques: application to stereochemical configuration assignment of poly(acrylic acid)
Authors: Beshah Kebede
Published: April 2003

Two‐dimensional heteronuclear single quantum coherence — total correlation spectroscopy (2D HSQC‐TOCSY) was used to make end‐to‐end sequential assignments and determine stereochemical configuration at the triad, tetrad and pentad levels of poly(acrylic acid). The pseudo three‐dimensional experiment allows heteronuclear (13C‐1H) as well as homonuclear (1H‐1H) corelations in a single 2D NMR experiment. The stereochemical configuration assignment is based on sequential identification of neighboring species. For example, a mmr tetrad resonance (methylene‐13C) is determined by its correlations to the mm and mr triad resonances (methine) that constitute it. Hence, it is independent of chemical shift and peak intensity estimates that are requisites of the conventional method. This self‐consistent technique enables absolute assignments of all magnetically unique tetrads and some of the pentad resonances. In addition, some resonances in the methylene and methine regions that have been difficult to characterize by conventional techniques were unequivocally assigned to endgroup resonances and other polymerization by‐products of the low‐molecular‐weight poly(acrylic acid).
A posteriori error estimation for convection dominated problems on anisotropic meshes
Authors: Kunert Gerd
Published: April 2003

A singularly perturbed convection–diffusion problem in two and three space dimensions is discretized using the streamline upwind Petrov Galerkin (SUPG) variant of the finite element method. The dominant convection frequently gives rise to solutions with layers; hence anisotropic finite elements can be applied advantageously.

The main focus is on a posteriori energy norm error estimation that is robust in the perturbation parameter and with respect to the mesh anisotropy. A residual error estimator and a local problem error estimator are proposed and investigated.

The analysis reveals that the upper error bound depends on the alignment of the anisotropies of the mesh and of the solution. Hence reliable error estimation is possible for suitable anisotropic meshes. The lower error bound depends on the problem data via a local mesh Peclet number. Thus efficient error estimation is achieved for small mesh Peclet numbers.

Altogether, error estimation approaches for isotropic meshes are successfully extended to anisotropic elements. Several numerical experiments support the analysis. Copyright © 2003 John Wiley & Sons, Ltd.
Interaction of elementary waves for scalar conservation laws on a bounded domain
Authors: Liu Hongxia , Pan Tao
Published: April 2003

This paper is concerned with the interaction of elementary waves on a bounded domain for scalar conservation laws. The structure and large time asymptotic behaviours of weak entropy solution in the sense of Bardos et al. (Comm. Partial Differential Equations 1979; 4: 1017) are clarified to the initial–boundary problem for scalar conservation laws ut+ƒ(u)x=0 on (0,1) × (0,∞), with the initial data u(x,0)=u0(x):=um and the boundary data u(0,t)=u‐,u(1,t)=u+, where u±,um are constants, which are not equivalent, and ƒ∈C2 satisfies ƒ′′>0, ƒ(0)=f′(0)=0. We also give some global estimates on derivatives of the weak entropy solution. These estimates play important roles in studying the rate of convergence for various approximation methods to scalar conservation laws. Copyright © 2003 John Wiley & Sons, Ltd.
Presence and developmental regulation of serotonin N‐acetyltransferase transcripts in oocytes and early quail embryos (Coturnix coturnix japonica)
Authors: Oblap Ruslan , Olszańska Bożenna
Published: April 2003

By RT‐PCR two transcripts for arylalkylamine N‐acetyltransferase (AA‐NAT; serotonin N‐acetyltransferase; EC 2.3.1.87), the key enzyme in melatonin synthesis, were found, for the first time, in the oocytes and blastoderms from freshly laid eggs (323‐ and 238‐bp RT‐PCR products), and one (238‐bp product) in the pineal gland of Japanese quail (Coturnix coturnix japonica). The two products differed by an intron of 85‐bp present in the 323‐bp band and absent from the 238‐bp band. The identity of the products was confirmed by restriction analysis and sequencing. The ratio of the 323:238‐bp bands changed during oogenesis from ∼17:1 in small 3‐mm oocytes to ∼4:1 in immature vitellogenic oocytes and ∼1:1 in mature, preovulatory oocytes; it was reversed to ∼0.2:1 in blastoderms from fertile freshly laid eggs, corresponding to embryo of ∼40,000 cells. It is proposed that the longer 323‐bp product, containing an intron, represents a translationally inactive form of the transcript, stored in maternal RNA. The shorter 238‐bp product lacking an intron may represent the mature active AA‐NAT mRNA found in the pineal gland and in early embryos, and—to a lower proportion—in older oocytes. These data constitute the first direct proof of an intron sequence in maternal RNA of avian oocyte. It is possible that differential processing of the immature mRNA is part of a transcriptional regulation mechanism of AA‐NAT activity. A possible role of extrapineal melatonin in early avian development is discussed. Mol. Reprod. Dev. 65: 132–140, 2003. © 2003 Wiley‐Liss, Inc.
γ‐Ray exposure accelerates spermatogenesis of medaka fish, Oryzias latipes
Authors: Kuwahara Yoshikazu , Shimada Atsuko , Mitani Hiroshi , Shima Akihiro
Published: April 2003

To examine the spermatogenesis (and spermiogenesis) cell population kinetics after γ‐irradiation, the frequency and fate of BrdU‐labeled pre‐meiotic spermatogenic cells (spermatogonia and pre‐leptotene spermatocytes) and spermatogonial stem cells (SSCs) of the medaka fish (Oryzias latipes) were examined immunohistochemically and by BrdU‐labeling. After 4.75 Gy of γ‐irradiation, a statistically significant decrease in the frequency of BrdU‐labeled cells was detected in the SSCs, but not in pre‐meiotic spermatogenic cells. The time necessary for differentiation of surviving pre‐meiotic spermatogenic cells without delay of germ cell development was shortened. More than 90% of surviving pre‐meiotic spermatogenic cells differentiated into haploid cells within 5 days after irradiation, followed by a temporal spermatozoa exhaust in the testis. Next, spermatogenesis began in the surviving SSCs. However, the outcome was abnormal spermatozoa, indicating that accelerated maturation process led to morphological abnormalities. Moreover, 35% of the morphologically normal spermatozoa were dead at day 6. Based on these results, we suggest a reset system; after irradiation most surviving spermatogenic cells, except for the SSCs, are prematurely eliminated from the testis by spermatogenesis (and spermiogenesis) acceleration, and subsequent spermatogenesis begins with the surviving SSCs, a possible safeguard against male germ cell mutagenesis. Mol. Reprod. Dev. 65: 204–211, 2003. © 2003 Wiley‐Liss, Inc.