bluuebunny/crossref_metadata_2025_split huggingface dataset:
A carbonyl‐olefin exchange reaction. New route to conjugated polymers, 3. Influence of the reaction conditions
Authors: Schopov Ivan , Mladenova Lyudmila , Kovachev Georgi 
Published: April 2003

AbstractThe reaction conditions influencing the carbonyl‐olefin exchange reaction were studied. It could be established that highest yields and molecular weights are obtained for a mole ratio catalyst/monomer of 1 : 1, the former being introduced in several portions. The observed slowdown of the reaction is explained by deactivation of WCI6, due to complex formation with the resulting polymer. Increase of solvent polarity, temperature and duration also leads to higher yields and molecular weights.
Cyclopolymerization, 14. Influence of temperature on free‐radical cyclopolymerization of N‐allylmethacrylamide and N‐allylacrylamide
Authors: Kodaira Toshiyuki , Sakaki Shuzo 
Published: April 2003

AbstractCyclopolymerizations of N‐allylmethacrylamide (1a) and N‐allylacrylamide (1b) are conducted over the temperature range below and above the ceiling temperature (Tc) of N‐propylmethacrylamide (2a), one of the monofunctional counterparts of 1a. Increasing the polymerization temperature extensively enhances the cyclopolymerizability of 1a at temperatures in the vicinity of the Tc of 2a, while the cyclopolymerizability of 1b increases slightly with temperature. The polymerization tendency of N‐propylacrylamide (2b), one of the monofunctional counterparts of 1b, is lying high above the temperature range investigated and both monoallyl counterparts of 1a and 1b showed similar polymerizabilities. The differences between the cyclopolymerizabilities of 1a and 1b are interpreted by applying the hypothesis that the lower the polymerizability of the corresponding monofunctional counterparts of the unconjugated dienes, the higher their cyclopolymerizabilities. Another point focused on the reversibility of intramolecular cyclization, because polymerization of 1a was carried out in the vicinity of the Tc of 2a. It appears that the cyclic structure of poly(1a) consists exclusively of a 5‐membered ring whereas poly(1b) contains 5‐ and 6‐membered rings. The polymerization temperature does not affect the proportion of these two cyclic structures for both polymers. These results suggest that reversibility of intramolecular cyclization need not be taken into consideration to explain the cyclopolymerization behavior of 1a and 1b.
Stereochemical configuration of polyfumarates as studied by 13C nuclear magnetic resonance spectroscopy
Authors: Wang Xiaogong , Komoto Tadashi , Ando Isao , Otsu Takayuki 
Published: April 2003

AbstractThe 125 MHz 13C NMR spectra of some poly(dialkyl fumarates) (PDAF) and poly(dicycloalkyl fumarates) (PDCF) prepared by radical polymerization are measured in CDCl3 solution at 60°C. The multiplet resonances of the main‐chain carbon atoms and the ester carbonyl carbon atoms are assigned to stereochemical triad and pentad sequences, respectively, using model compounds as well as computer simulation. From these results it is found that PDAF and PDCF exhibit essentially atactic structures with meso addition favoured over racemic addition, and that the ratio of meso to racemic content varies with different kinds of alkyl and cycloalkyl groups. The tactic sequence proportions of the polymers cannot be explained by one‐parameter Bernoullian statistics, but can be successfully explained by modified Bernoullian trial.
Characterization of the surface morphology in carboxylated methyl methacrylate‐butyl acrylate emulsion copolymers
Authors: Emelie Brigitte , Pichot Christian , Guillot Jean 
Published: April 2003

AbstractA series of carboxylated methyl methacrylate (MMA)‐butyl acrylate (BuA) (weight ratio 1 : 1) copolymer latexes were prepared by emulsion polymerization with varying the nature of carboxylic acid (acrylic (AA), or methacrylic acid (MAA)), the type of emulsifier (sodium dodecyl sulfate (SDS) or nonylphenyl polyoxyethylene ether (HV25®) surfactants), or the polymerization method (batch or shot process). Results of surface characterization and rheological behavior of the latexes were found to provide information on the carboxylic acid location and the interfacial layer thickness, respectively. Stability studies against different types of electrolyte and temperature showed that the surface morphology is strongly dependent upon the nature of oligomers formed during the synthesis, especially the presence of sequences rich of poly‐(carboxylic acid)s, and how they are anchored onto the particle. According to the type of emulsifier and polymerization process, stability is predominantly determined either by electrostatic or steric forces. In some cases, when surfactant HV25® is used, enhanced steric stabilization prevails.
The mechanism of copolymerization of maleic anhydride with methyl methacrylate and with methyl acrylate
Authors: Brown Anthony Stuart , Fujimori Kiyohisa , Craven Ian 
Published: April 2003

AbstractComposition diagrams for the copolymerization of maleic anhydride with methyl methacrylate and with methyl acrylate in ethyl methyl ketone at 50°C were determined using a non‐aqueous potentiometric direct titration method. The data were analysed using non‐linear least squares minimization procedures to test the applicability of terminal, penultimate and complex models for both systems. In both systems, the penultimate model was an improvement over the terminal model, though the penultimate effect was more pronounced in the methyl methacrylate system. No evidence could be found for complex participation in either system.
Molecular structure of 2,6‐bis[2‐(heptamethylcyclotetrasiloxan‐2‐yl)ethyl]hexamethylcyclotetrasiloxane as a model of poly(hexamethylcyclotetrasiloxane‐2,6‐diylethylene)
Authors: Ovchinnikov Yu. E. , Shklover V. E. , Struchkov Yu. T. , Astapova T. V. , Zhdanov A. A. 
Published: April 2003

AbstractThe molecular and crystal structure of 2,6‐bis[2‐(heptamethylcyclotetrasiloxan‐2‐yl)ethyl]hexamethylcyclotetrasiloxane (1) representing a three‐unit oligomer (“trimer”) of the corresponding poly(hexamethylcyclotetrasiloxane‐2,6‐diylethylene) (3) was determined. A similarity of the crystal packings of 1 and the earlier studied “dimer” 2 allows to establish the parameters of the “subcell” of polymer 3, which are in a good agreement with the data of its wide‐angle X‐ray study.
The molecular structure of 4‐(dimethylmaleimido)phenyl methacrylate
Authors: Puranik Vedavati G. , Tavale Sudam S. , Row Tayur N. Guru , Sehra Jagdish C. 
Published: April 2003

AbstractThe molecular structure of 4‐(dimethylmaleimido)phenyl methacrylate was determined by means of X‐ray diffraction. Crystals are orthorhombic, space group F2dd, a = 3,993(1) Å, b = 36,650(6) Å, c = 39,460(8) Å and Z = 16; dcalc = 1,360 g · cm−3, V = 5774,7 Å3, M = 285,3, λ = 0,7107 Å, μ (MoKα) = 1,06 cm−1, F(000) = 2400. The structure was solved by direct methods and refined to R = 0,062 for 304 observed reflections. The molecule has a synperiplanar conformation as to the CC and CO double bonds about C(7)C(8) and also as to the CO and CO bonds about C(7)O(1).
Small angle X‐ray scattering investigations on cold‐drawn nylon 6
Authors: Ferracini Elena , Ferrero Adele 
Published: April 2003

AbstractSmall angle X‐ray scattering (SAXS) on cold‐stretched nylon 6 supports the model of fully extended chains as a consequence of mechanical deformation. There is no evidence for the persistence of lamellar fragments. The ordered zones present before cold‐stretching exhibit a dimension of 4,7 nm and those formed after cold‐stretching and annealing one of 6,3 nm in fibre direction. The long period of the as‐extruded samples is 11,5 nm, and that of the coldstretched and annealed samples is 8,3 nm. The reduction of the long period and the increase of particle dimensions in the annealed samples support the hypothesis that a new lamellar system is formed.
Morphologie der segmentierten polyetheresteramide auf der basis von polyamid 12 und oligotetrahydrofuran
Authors: Lohmar Jörg , Meyer Kurt , Goldbach Günther 
Published: April 2003

AbstractPolyetheresteramides (PEEA) on the basis of polyamide 12 and oligotetrahydrofuran (OTHF) may be referred to as intrinsically plasticized and intrinsically impact strength toughened thermoplastic elastomers. This is due to their special 4‐phase morphology consisting of two pure crystalline and two mixed amorphous phases, which was completely analysed by various TEM preparation techniques. PEEA containing more than 50% PA 12 hard segments exhibit a space filling dendritic superstructure of lamellar crystallized hard segments. In the range of 50 – 30% PA 12, the dendrites become more and more isolated, and below 30% PA 12 only single lamellae can be observed. The matrix in all PEEA is an amorphous, PA 12‐rich mixed phase (“OTHF‐plasticized PA 12”) located between the hard segment lamellae. An amorphous OTHF‐rich mixed phase is very finely dispersed in PEEA and acts as an intrinsically impact strength toughening modifier. Lamellar crystallized soft segments could be imaged by TEM in this dispersed phase, but only in PEEA products with a higher molecular OTHF and at sufficient low temperatures.
An easy calculation of the expected n‐ad sequence proportions in polymers obeying first‐order markov statistics and being prepared by ring‐opening polymerization of chiral heterocyclic monomers
Authors: Sepulchre Maurice 
Published: April 2003

AbstractAn easy and fast calculation method of the normalized n‐ad sequence proportions in optically active polymers which derive from heterocyclic monomers and which obey first‐order Markov statistics is developed. The proposed method does not require any computer calculation and provides very accurate values up to high conversions in polymer. It can be applied over a wide range of enantiomeric excess of the initial monomer, and of copolymerization reactivity ratios. This is useful for testing whether a polymer fits the first‐order Markov propagation model.
Molecular design of block and graft copolymers by vinyl‐substituted xanthates
Authors: Niwa Masazo , Higashi Nobuyuki , Shimizu Motoyuki , Matsumoto Takahiro 
Published: April 2003

AbstractThe selective polymerization behavior of O‐ethyl S‐4‐vinylbenzyl xanthate (1) was investigated on the basis of polymerization kinetics in the dark and in the presence of UV‐light. S‐Benzyl O‐ethyl xanthate (2) was used as a non‐polymerizable model compound of 1 to evaluate chain transfer constants. In the homopolymerization and the copolymerization of 1 initiated with AIBN in the dark, styryl groups selectively take part in the polymerization, and xanthate groups are not responsible for it. The monomer reactivity ratios (r1 = 0,51 and rMMA = 0,41) of 1 with methyl methacrylate (MMA) are very close to those of styrene with MMA. The photolysis of 2 was investigated by 1H NMR. It was found that photodecomposition of 2 takes place at CH2S (a) and SC( = S) bonds (b) with the ratio: a/b = 1/5. The polymerization of MMA was carried out with 1 upon photoirradiation. Number‐average degrees of polymerization of the polymers obtained increase linearly with conversion. Block and graft copolymers were prepared by using these macrophotoinitiators.
New polymer syntheses, 27. Syntheses of aromatic polyethers from 2,6‐difluoropyridine and silylated aromatic diols
Authors: Kricheldorf Hans R. , Schwarz Gert , Erxleben Jörg 
Published: April 2003

AbstractAromatic polyethers were prepared by bulk condensation of 2,6‐difluoropyridine (1) with various silyalated diphenols and benzelnediols at temperatures between 140 and 240°C. Colorless products were obtained with inherent viscosities in the range of 0,4–1,4 dl/g. DSC measurements revealed that the polyethers derived from bisphenol‐A, phenolphthalein, 4,4′‐oxydiphenol and phenylhydroquinone are amorphous with glass‐transition temperatures in the range of 90–190°C. Polyethers derived from hydroquinone or 4,4′‐biphenyldiol are crystalline with melting points in the range of 200–270°C. Thermogravimetry in air indicates thermostabilities up to 450°C (at 5% loss of weight). Poly(pyridinediylether‐co‐ketoether)s (4) and poly(pyridinediylether‐co‐arylsulfoether)s (5) were obtained by cocondensation of 1 with 4,4′‐difluorobenzophenone or 4,4′‐difluorodiphenyl sulfone and various silylated aromatic diols. For these copolyethers inherent viscosities in the range of 0,6–1,0 dl/g were found, and tough films could be cast from solution. Incorporation of the pyridinediyl units was found to significantly lower the glass‐transition temperatures. The copolyethers obtained from 1, 4,4′‐difluorobenzophenone and hydroquinone or 4,4′‐biphenyldiol are crystalline. Thermodynamical analyses indicate high heat‐distortion temperatures (>200°C) for annealed samples of these crystalline polyethers. Thermogravimetry conducted at a heating rate of 10°C/min in air only indicates a moderate thermostability.
Greffage de monomères acryliques induit par un plasma froid sur un polypropylène
Authors: Epaillard Fabienne , Brosse Jean‐Claude , Legeay Gilbert 
Published: April 2003

AbstractCold plasma can be applied to polymer chemistry especially when grafting is to be achieved. Multifunctional acrylate monomers could be grafted onto polypropylene after its surface was activated. Grafting, the final stage of this plasma‐induced polymerization, is the consequence of a reaction of a macroradical, which has diffused to the surface of the substrate, with a reactive species created on the polypropylene surface. The rate of grafting was found to be smaller than the rate of monomer disappearance. The rate increases with the power, but no relation could be established between both.
Poly(oxyethylene) terminated with tertiary amino or quaternary ammonium groups
Authors: Masař Bohumil , Janout Václav , Čefelín Pavel 
Published: April 2003

Abstractα‐(3‐Dimethylaminopropyl)‐ω‐dimethylaminomethylpoly(oxyethylene)s (2a–e) were prepared from α‐(3‐aminopropyl)‐ω‐aminomethylpoly(oxyethylene)s (1a–e) (M̄n = 430–2300 g·mol−1), by the Wallach‐Leuckart reaction, with a degree of transformation of NH2 into N(CH3)2 groups of 70–98%. The samples were characterized by means of IR spectrometry and Siggia's acylation method, adjusted for microdetermination. The polymers terminated with 3‐dimethylaminopropoxy groups were transformed into the corresponding derivatives bearing quaternary ammonium end groups, and characterized both as dihydroxides and dichlorides. The content of the quaternary ammonium groups was found to differ considerably for the individual samples in the range of 19–97%. The reason for this variability was found not to be a low efficiency of the quaternization reaction, but the Hofmann‐degradation giving rise to terminal vinyl groups of the polyether chain.
Solution properties of ultrahigh‐molecular‐weight polymers, 16. Unperturbed dimensions of poly(isobutyl methacrylate)
Authors: Simionescu Cristofor I. , Ioan Silvia , Flondor Aurelia , Simionescu Bogadan C. 
Published: April 2003

AbstractThree techniques, i. e., the Lenka extrapolation method, the Stockmayer‐Fixman method, and the extrapolation of the Mark‐Houwink constants to a = 0,5 were applied to determine the unperturbed dimensions of ultrahigh‐molecular‐weight poly(isobutyl methacrylate). A correction term, depending on the exponent a of the Mark‐Houwink relation, is suggested to be introduced into the Stockmayer‐Fixman‐Burchard equation.
Correlation of viscoelastic properties with the molar mass distribution for aqueous polyacrylamide solutions
Authors: Müller Rolf‐Joachim , Klein Joachim 
Published: April 2003

AbstractThe dependence of viscous and elastic rheological functions on molar mass and molar mass distribution was investigated under shear flow conditions using concentrated solutions of polyacrylamides and polyacrylamide mixtures. The zero‐shear viscosity η0 correlates with the weight‐average molar mass M̄w; with increasing shear rate the corresponding controlling molar mass average tends to change to the number‐average molar mass M̄n. It is shown that the analysis of the shape of the whole flow curve is a simple way to obtain qualitative information about molar mass distribution. Elastic forces are influenced mainly by the high‐molar‐mass tail of a molar mass distribution. The zero normal stress coefficient ψ0 depends on a molar mass average between M̄w and z‐average molar mass M̄z·ψ0 increases with the 7,4th power of the molar mass for the polyacrylamides (not for the mixtures). The steady‐state compliance Je(0) is, for the investigated system, independent of the absolute molar mass, but increases with the 5,5th power of the ratio M̄z/M̄w. The elasticity modulus G0(A) can be correlated with M̄n of the polyacrylamide samples and their mixtures. These investigations show that the analysis of various rheological functions can lead to a wealth of information about the molar mass distribution of a polymer.
Interaction effects on linear dimensions of polymer chains in polymer mixtures
Authors: Sariban Alla , Binder Kurt 
Published: April 2003

AbstractMonte Carlo simulations are presented for binary (AB) symmetric polymer mixtures (chain lengths NANBN) for the case that an attractive interaction ϵ exists between monomers of the same kind, and the limiting case that one species (B) is very diluted. It is shown that with increasing interaction strength ϵ/(kB · T), T being the absolute temperature, the minority chains collapse to a very dense configuration, while the majority chains stay nearly Gaussian. Both chain radii, structure factors and numbers of nearest neighbour contacts are discussed.
Dioxygen sensitivity of a photoexcited thin film of phthalocyanine dispersed in poly(N‐vinylcarbazole)
Authors: Kaneko Masao , Wöhrle Dieter , Schlettwein Derck , Schmidt Volker 
Published: April 2003

AbstractThin films (thickness 0,3 μm) of a mixture of phthalocyaninatozinc(II) (1) and poly(1‐vinylcarbazole) (2) are prepared by coating from a solution on ITO glass. The blue coloured films are investigated in an electrochemical cell under irradiation with visible light. In the presence of dioxygen from air the films exhibit an intensive cathodic photocurrent. The action spectrum of the photocurrent corresponds to the absorption spectrum of the phthalocyanine. The results show a device which can be switched by air and visible light.
Effect of secondary structure on salt permeability of poly(γ‐methyl‐L‐glutamate) membranes
Authors: Minoura Norihiko 
Published: April 2003

AbstractPoly(γ‐methyl‐L‐glutamate) membranes with α‐helix structure and with ß‐sheet structure were prepared by casting. The electrical membrane potentials of the membranes in LiCl, NaCl, and KCl solutions were measured in order to obtain information on the mobility of ions within the membranes. In the membranes with α‐helix structure the relative ionic mobilities of Na+ and Li+ to K+ are larger than in aqueous solutions. In the membranes with ß‐sheet structure the mobility of cations within the membrane is extremely restricted. The partition coefficient of KCl in this membrane at low concentrations is greater than 10. The permeability and diffusion coefficients of KCl depend on the concentration of KCl, and the values are higher, when compared with those for the membrane with α‐helix structure. These results reflect the differences between the secondary structures of the polymers. The specific behaviour of the partition coefficient and of the permeability found in the membranes with ß‐sheet structure is explained by an interaction between the carbonyl groups of the main chain and the cations.
Le phényl‐1 éthylpotassium, amorceur de polymérisation anionique: Préparation par clivage de l'oxyde de bis(phényl‐1 éthyle); étude du milieu réactionnel
Authors: Beinert Gérard , Zilliox Jean‐Georges , Herz Jean 
Published: April 2003

Abstract1‐Phenylethylpotassium (5), an efficient anionic polymerization initiator in tetrahydrofuran (THF) solution serving as a substitute for 1‐methyl‐1‐phenylethylpotassium in most of its applications, was obtained by cleavage of bis(1‐phenylethyl) ether (1) with potassium. Ether cleavage reactions were carried out in THF at mole ratios potassium/1 = 2/1 and 1/1, and the resulting solutions were submitted to careful analysis. All by‐products formed in the reaction media were unambiguously identified and their mole fractions in the resulting mixture determined. The presence of these by‐products was found not to influence the initiator efficiency.
Synthesis and properties of (18‐crown‐6)‐bridged phthalocyanine network polymers
Authors: Ahsen Vefa , Yilmazer Emel , Bekâroǧlu Özer 
Published: April 2003

Abstract(18‐Crown‐6)‐bridged phthalocyanine network polymers 4–8 as well as a low‐molecular‐weight model compounds with only one phthalocyanine unit (3a, b) were prepared from tetracyanodibenzo‐18‐crown‐6 (2a). The cyano end groups were partially converted into imido groups during the cyclotetramerization reaction, as detected from the IR spectra. In order to obtain structurally uniform compounds with the same end groups, the C  N groups were hydrolyzed into imido groups with conc. sulfuric acid. The metal‐free phthalocyanine polymer 4a was obtained by the reaction of 2a either with hydroquinone or PbO in ethylene glycol. The chlorides of Cu(II), Ni(II), and Co(II) were empolyed in order to synthesize the corresponding metal‐phthalocyanine polymer, and Fe(CO)5 was used for the preparation of the Fe‐analog 7a. For the preparation of the Co‐containing polymer 8a ammonium molybdate has to be added as catalyst. The selectivity of 7a for Rb+ was found to be highest in the heterogeneous phase extraction experiments. Polymers 4–8 are also capable of binding silver from aqueous and methanolic solutions.
Mechanisms of the thermal degradation of polyesters based on 1,2‐propanediol, phthalic anhydride, maleic anhydride and 1,4,5,6,7,7‐hexachlorobicyclo[2.2.1]hept‐5‐ene‐2,3‐dicarboxylic acid
Authors: Vijayakumar Chinnaswamy Thangavel , Lederer Klaus 
Published: April 2003

AbstractSix different linear polyesters based on phthalic anhydride, maleic anhydride, 1,4,5,6,7,7‐hexachlorobicyclo[2.2.1]hept‐5‐ene‐2,3‐dicarboxylic acid (HET‐acid) and 1,2‐propanediol were synthesized. The polyesters were pyrolysed by heating dynamically at a rate of 10 K · min−1 from 40 to 440°C. Apart from the dynamic pyrolysis, the standard unsaturated polyester was isothermally pyrolysed at five different temperatures (200, 250, 300, 350 and 400°C) for 60 min. The pyrolysis products obtained were separated in a capillary gas chromatograph and identified using a mass‐selective detector. In all the polyesters investigated, the corresponding anhydride was formed in major quantities. A variety of low‐molecular‐weight compounds such as propanoi isomers, isomeric dimethyldioxanes, 1,2‐propanediol, 5‐hydroxy‐2‐pyrone and its 6‐alkyl substituted derivatives, polychlorocyclopentadienes and considerable quantities of complex mono‐ and diesters of the diacid component were identified. The presence of HET‐acid units in the polyester chain alters the course of the degradation of the diol units considerably by suppressing the formation of 1,2‐propanediol and increasing the formation of isomeric dimethyl‐dioxanes, 1‐propanol and 2‐propanol. In the thermal degradation of HET‐acid containing polyesters, the formation of HET‐anhydride is favoured in comparison to the retro‐Diels‐Alder reaction in chain. The mode of formation of the products identified by gas chromatography/mass spectrometry analysis is discussed in the light of the general polyester degradation mechanism.
Determination of primary crystallite size of TiCl3 catalysts by small angle x‐ray scattering
Authors: Kakugo Masahiro , Sadatoshi Hajime , Sakai Jiro , Yokoyama Masakazu 
Published: April 2003

AbstractSmall‐angle X‐ray scattering (SAXS) analysis using MoKα radiation is successfully applied to a determination of the crystallite sizes of TiCl3 catalysts. The sizes of TiCl3 catalysts dispersed in nascent polypropylenes differing in polymer yield are determined by using this technique. It is shown that the original catalyst size does not change during the course of polymerization. This result agrees with the observation by transmission electron microscopy (TEM).