bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyene sequence distribution in modified poly(vinyl chloride) after thermal degradation
Authors: Martinez Gerardo , Mijangos Carmen , Millan José‐Luis , Gerrard Donald L. , Maddams William F. 
Published: April 2003

AbstractThe products resulting from the reaction of PVC with sodium benzenethiolate were degraded to 0,3% at 180°C in the solid state and at 160°C in solution in trichlorobenzene. The polyene distribution of the polymers after degradation was studied by both UV‐visible and resonance Raman spectroscopies, as a function of the degree of substitution. The results show that there are two types of behaviour: that of the PVC sample prior to the substitution reaction together with the samples modified up to a definite degree of substitution which depends on the starting isotactic content, and that of samples with higher degrees of substitution. The former group exhibits not only a steady improvement in thermal stability but also a preferential formation of polyenes of 7 – 9 double bonds whose concentration decreases with increasing degree of substitution. Conversely, for the second group of samples the thermal stability decreases with the degree of substitution and no specific absorption bands are observed. On the basis of earlier work on the selective substitution of the isotactic GTTG and heterotactic TTTG triads during the first stage of the reaction, the present results show that the bands at 393, 416, and 437 nm are related to specific polyenes which result from initiation by the above quoted conformations in PVC, a conclusion for which confirmatory evidence was obtained by resonance Raman spectroscopic examination of the samples. There is, therefore, clear evidence for the occurrence of two distinct degradation mechanisms, one involving initiation by the unstable triad conformations and the other via random initiation at stable and normal structures. To this may be added the initiation by defect structures, which have been extensively documented in the literature.
Electrochemical preparation and characterization of poly(2,5‐thiophenediyl)
Authors: Tanaka Susumu , Sato Masa‐aki , Kaeriyama Kyoji 
Published: April 2003

AbstractA highly conductive poly(2,5‐thiophenydily) film was obtained when thiophene was electrochemically polymerized at 5°C in nitrobenzene with Bu4NBF4 or Bu4NClO4 as a supporting electrolyte. A platinum plate or indium oxide glass was used as an electrode. The current efficiency was 62%. The IR, UV, and ESR spectra were compared with those of a poly(2,5‐thiophenediyl) obtained from 2,5‐dibromothiophene by polycondensation. The electrochemically prepared poly(2,5‐thiophenediyl) was identified by its IR spectrum. In its UV spectrum, two bands are observed at 440 nm and 740 nm. The band at 740 nm disappears in an undoped film of poly(2,5‐thiophenediyl), which resembles that of the polymer obtained by polycondensation. The ESR spectra were also measured for undoped and partly undoped films. The undoped film shows an asymmetrical signal, Whereas the signal of the polymer resulting from polycondensation is symmetrical. In the air the conductivity decreases by a factor of 10−2 of the initial value in about 70 days, but an undoped film is quite stable. The undoped film can be re‐doped with iodine or sulfur trioxide and attains higher conductivity than the pellets of polymers obtained by polycondensation. This may be attributed to the difference in morphology.
Stereospecific polymerization of methylthiirane in homogeneous phase, 1. Oligomerization step and change in stereocontrol with molecular weight
Authors: Dumas Philippe , Sigwalt Pierre , Guérin Philippe 
Published: April 2003

AbstractThe polymerization of methylthiirane in homogeneous phase initiated by bis(isopropylcysteinato)cadmium is a living process. For low conversions, oligomers (essentially heptamers and octamers) are formed, apparently using one valency of cadmium, the main propagation taking place by using the other one. However, the size of the oligomers may still grow for higher conversions. The mechanism of the oligomer formation depends on the temperature. A “normal” insertion of the monomer is observed at −23°C, whereas at 20°C a disulfide bond is formed. The preferential choice of a different enantiomer in the main propagation reaction may depend on the presence of a particular type of oligomer, in the vicinity of cadmium, linked to the cysteine group. However, stereospecificity (stereoselection and stereoelection) appears only with molecular weights higher than 6000 and also depends on the temperature of propagation: with decreasing temperature, the stereoregularity increases and the stereoelection can be inverted (for a definite oligomer structure).
Segmented block copolymer models of uniform chain length and defined structure, 1. Synthesis and characterization
Authors: Seliger Hartmut , Bitar Mohammed Bassam , Nguyen‐Trong Hao , Marx Alexander , Roberts Rolf , Krüger Jan‐Kristian , Unruh Hans‐Günther 
Published: April 2003

AbstractSegmented block copolymer models of defined structure with molecular weights up to ca. 4000 were synthesized by specific condensation of monofunctional derivatives of oligo condensation products of 4,4′‐isopropylidenediphenol (Bisphenol A) with terephthalic acid and oligomethylenes of uniform chain length. The oligo(arylester) blocks were prepared by stepwise addition of oxyterephthaloyloxy‐1,4‐phenyleneisopropylidene‐1,4‐phenylene units using a suitable protection and activation scheme. Similarly, oligo(arylester)s containing isophthaloyl and phthaloyl units were obtained. Telechelic oligomethylene segments were prepared analogously by combining functional derivatives of decane. All compounds were characterized by chemical, spectroscopic, and chromatographic methods.
Super fast polymerization under high pressure and plastic flow
Authors: Enikolopian Nikolay S. 
Published: April 2003

AbstractSimultaneous action of high pressure and shear deformation on various organic compounds is studied using an apparatus of Bridgeman anvil type. This apparatus allows to work in a temperature range from −196°C to 200°C at different shear forces. It is established that under these conditions the investigated materials are in the plastic flow state. Chemical transformations of more than 300 organic compounds of different chemical classes are observed. Reactions such as polymerization, polycondensation, polyaddition etc. are realized under plastic flow. In addition, copolymerization reactions with the formation of random copolymers occur for some substances. Kinetic peculiarities of the polymerization process under plastic flow are investigated on the example of acrylamide.
Complexation between quaternary ammonium salts and high molecular weight poly(ethylene oxide)
Authors: Bortel Edgar , Kochanowski Andrzej 
Published: April 2003

AbstractComplexation between tetrabutylammonium bromide, or oligomeric tetramethyl‐2,6‐ionene bromide (1), and high molecular weight poly(ethylene oxide) (PEO) was studied viscometrically, using the following media as solvents: water; 0,1 M aq. KCl; 2 M aq. KCl and 0,1 M aq. HCl. It was found that tetrabutylammonium bromide as well as the ionene 1 convert the initially linear ηred vs. cPOE relationships into bent and hunchbacked curves, thus suggesting the formation of water soluble complexes. In aqueous KCl and HCl solutions these complexes behave as typical polyelectrolytes. Contrary to cations of alkali metals, however, protons do not influence the linear ηred vs. cPOE relation, so that it is possible to determine intrinsic viscosities by use of 0,1 M aq. HCl as solvent. These viscosities are rising if the complexation between POE and ammonium salt is accomplished by the polyfunctional ionene. The increase of [η] depends on the unit mole ratio (u.m.r.) of the ionene to POE. With increasing unit mole ratio from 0 to 7 [η] increases from 9 up to 21 dl · g−1. In water the complexation between one unit mole of POE and two unit moles of ionene 1 causes an increase of the reduced viscosity ηred from 11,2 up to 80,2 dl · g−1.
Solution properties of a polydiacetylene with pyridine substituents. Formation of pyridinium salts and complexes with transition metal salts in solution
Authors: Tieke Bernd 
Published: April 2003

AbstractThe solution properties of polymeric 10,12‐pentacosadinyl 4‐pyridinecarboxylate (polymer 1), obtained by UV‐ or γ‐ray initiated solid state polymerization, are described, as studied by UV/VIS‐ and 13C‐NMR spectroscopy, and by viscosity measurements. Treatment of the polymer solution with non‐solvents of the polymer, protic acids, or transition metal halides induces a colour change from yellow to red, accompanied by a protonation or metal complex formation of the pyridine substituent groups, respectively. Reverse colour changes occur, if bases (e.g. triethylamine) or complexing agents, able to form metal complexes more stable than those of the polymer (e.g. 2,2′‐bipyridine), are added to the red polymer solutions. The origin of the colour changes and the structures of the protonated polymer and of the polymer‐metal complexes are discussed.
Metal‐containing initiator systems, 34. Polymerization of vinyl monomers initiated by the binary system cobaltocene/bis(ethyl acetoacetato)copper (II)
Authors: Mun Yang‐Un , Sato Tsuneyuki , Otsu Takayuki 
Published: April 2003

AbstractThe effect of some metallocenes such as ferrocene (Fe(C5H5)2), nickelocene (Ni(C5H5)2), and cobaltocene (Co(C5H5)2), on the vinyl polymerization initiated with bis(ethyl acetoacetato)‐copper(II) (Cu(eacac)2) was investigated. Co(C5H5)2 was found to exert a markedly accelerating effect on the polymerization of methyl methacrylate (MMA) with Cu(eacac)2. The polymerization of MMA with the system Co(C5H5)2/Cu(eacac)2 at 50°C was found to be fairly affected by the solvent used. The results of copolymerization of MMA with styrene (St) and the effect of hydroquinone (HQ) on the polymerization of MMA with Co(C5H5)2/Cu(eacac)2 showed that the polymerization proceeds via a radical mechanism. The polymerization of MMA with Co(C5H5)2/Cu(eacac)2 was studied kinetically in acetone. The overall activation energy of the polymerization was calculated to be 86,3 kJ/mol (20,6 kcal/mol). This value was somewhat higher than that (17,6 kcal/mol) obtained for the polymerization of MMA with Cu(eacac)2 alone. The polymerization rate (Rp) is represented by the following equation: Rp = k[Co(C5H5)2]0,5 [Cu(eacac)2]0,2 [MMA]1,3. The high order in monomer concentration suggests a participation of the monomer in the initiation process of this polymerization. This is supported by the examination of the ESR spectrum of the system Co(C5H5)2/Cu(eacac)2/MMA/acetone, where reduction of Cu(II) to Cu(I) occurs. To elucidate the initiation mechanism, the spin trapping technique was applied to the system Co(C5H5)2/Cu(eacac)2/methyl acrylate. From these results, an initiation mechanism for the binary initiator system Co(C5H5)2/Cu(eacac)2 is proposed and discussed.
Metal‐containing initiator systems, 35. Synthesis of block copolymers by using the binary initiator system cobaltocene/bis(ethyl acetoacetato)copper(II)
Authors: Mun Yan‐Un , Sato Tsuneyuki , Otsu Takayuki 
Published: April 2003

AbstractPolymerization of methyl methacrylate (MMA) with the binary initiator system cobalt‐ocene (Co(C5H5)2)/bis(ethyl acetoacetato)copper(II)(Cu(eacac)2), was studied kinetically at 25°C in acetonitrile. The relationship between yield and molecular weight of the resulting poly(MMA) was suggestive of a living polymerization character in this system. The synthesis of block copolymers of MMA with styrene (St) was attempted by adding St as the second monomer to the polymerization system of MMA. The block copolymer was formed in a yield of 20% when MMA was polymerized for 1 day, while the yield went up to 80% when the MMA polymerization was carried out for 3 days. The resulting block copolymer was characterized by IR spectroscopy and gel‐permeation chromatography.
Polyarylenealkenylenes and polyheteroarylenealkenylenes, 16. Syntheses and electrical conductivities of poly[(alkoxy‐1,4‐phenylene)vinylene‐1,4‐phenylenevinylene]s
Authors: Koßmehl Gerhard , Samandari Massoud 
Published: April 2003

AbstractPoly[(2‐alkoxy (or 2,5‐dialkoxy)‐1,4‐phenylenevinylene‐1,4‐phenylene)vinylene]s containing alkyl groups of different lengths (8a, b or 9a – c), were prepared by Wittig‐reaction of terephthalaldehyde with “bis(Wittig‐salt)s”. To establish the structure of the polymers, alkoxy(and dialkoxy)di‐α‐styrylbenzenes 10a, b and 11a – c were prepared as model compounds under similar conditions. Electrical conductivities, σ288K, of the polymers and their charge transfer (donor‐acceptor) complexes with iodine were studied. The doped polymers show increased room temperature conductivities by several orders of magnitude.
Télomérisation du chlorure de vinylidène, 2. Réaction avec des télogènes du type RCCL3et préparation de composés dérivés
Authors: Belbachir Mohamed , Boutevin Bernard , Piétrasanta Yves , Rigal Gérard 
Published: April 2003

AbstractThe telomerization of vinylidene chloride with CHCl3, CCl3Br, Cl3CCO2CH3, Cl3CCF3, Cl3CCF2CFClX (X = Cl, Br), and CCl3CF2CCl3 was carried out by redox catalysis. The first adducts of each reaction were isolated and identified. The hydrolysis of these telomers containing a CCl3 group at the chain‐end by means of oleum led to a series of halogenated acids, some of them being olefinic ones.
Effect of the temperature on the chemical healing of poly(ethylene terephthalate)
Authors: Fakirov Stoyko 
Published: April 2003

AbstractThe effect of temperature on the chemical healing of poly(ethylene terephthalate) (PET) – healing as a result of chemical reactions between neighboring macromolecules located in the interface surface — was studied. The healing process was carried out in vacuum on pressed partially overlapped strips of commercial PET, previously annealed at 258°C, at temperatures between 140 and 250°C for 24 h. It is demonstrated that the fracture behavior of the welded samples depends strongly on the healing temperatureTh. AtTh> 200°C the strips break beyond the contact area, at 160 <Th< 200°C debonding occurs, and atTh< 160°C no bonding is observed. It is assumed that the bonding effect is mainly a result of chemical reactions (solid state postcondensation and transreactions) taking place during the healing procedure.
Chiral interaction of chitosan with azo dyes
Authors: Yamamoto Hiroyuki 
Published: April 2003

AbstractAbsorption and circular dichroism (CD) spectra were measured on complexes of highly deacetylated chitosans with azo dyes in 0,08% acetic acid. Blue and red shifts of the absorption peaks in the visible region were observed. The induced CD results suggest two different chiral configurations of the transition dipole moments of the dyes. Since the random sequence of amino and acetamido groups in deacetylated chitosan does not affect the induced CD per amino side‐chain, intermolecular interactions of the dye molecules are most probable in these chitosan/dye systems.
Kinetics of free radical polymerization of ortho‐ and para‐alkylaryl esters of methacrylic acid
Authors: Vrhovac Ljubica , Veličković Jovan , Filipović Dragoljub 
Published: April 2003

AbstractThe kinetics of free radical polymerization in bulk of alkylphenyl methacrylates with ethyl‐,isopropyl and tert‐butyl groups in the ortho‐ and para‐positions of the phenyl ring with dilauroyl peroxide as initiator were investigated. For comparison and completion of the investigation, ortho‐ and para‐tolyl methacrylates were reinvestigated with this particular initiator. Most of the results obtained do not obey classical kinetics of polymerization. The results were treated according to the concept of degradative chain transfer and it was concluded that this mechanism is responsible for the non‐ideality. The ortho‐substitution with increasing size of the substituents decreases the overall rate of polymerization and strengthens chain transfer to monomer.
Thermisch und UV‐photochemisch initiierte hochdruckpolymerisation des ethylens, 2. Molmassen‐verteilung
Authors: Buback Michael , Choe Chul‐Rim , Franck Ernst‐Ulrich 
Published: April 2003

AbstractThe molar mass distribution of polyethylenes synthesized at pressures up to 2500 bar and temperatures to 255°C with thermal and partly with photochemical initiation is determined by GPC. In the limiting situation of high pressure, low temperature, and small conversion a distribution function based on a limited set of kinetic equations provides a fair representation of the experimental data. The transfer constant with the monomer is derived as a function of pressure and temperature. The logarithmic normal distribution reasonably represents the molar mass distribution of the high pressure polyethylenes if the conversion is low and if both empirical parameters are taken as temperature dependent. The degree of long chain branching is analyzed for the ethylene polymerization as a function of pressure and temperature and to maximum conversions of 30%. It turns out that even at conversions as low as 2% long chain branching is not negligible.
Herstellung und eigenschaften von polyacenaphthylen, 3. Photoabbau von polyacenaphthylen
Authors: Stelter Thomas , Springer Jürgen 
Published: April 2003

AbstractThermally prepared polyacenaphthylene when irradiated in solution undergoes random chain scission. The photodegradation is solvent‐ and temperature‐dependent and leads to a lower limit of the degree of polymerization. Polymeranalogous reactions and crosslinking can be found to occur simultaneously. A certain fraction of „weak links”︁ was detected in the polymer.
Metalloesters, 11. “Disproportionation” of living (lithiated) oligomers of methyl methacrlylate
Authors: Lochmann Lubomír , Trekoval Jiří , Müller Axel H. E. 
Published: April 2003

AbstractThe decomposition reactions of the lithiated dimer, trimer, and tetramer of methyl methacrylate (MMA) in THF at 25°C were investigated. The decomposition of the lithiated dimer proceeds via depolymerization to lithiated monomer and MMA, addition of MMA to residual lithiated dimer, resulting the trimer (“disproportionation” of the dimer), and subsequent autocondensation of the products. The lithiated trimer almost exclusively undergoes cyclo‐autocondensation, whereas for the lithiated tetramer both reactions proceed simultaneously to a remarkable degree. It is shown that the relative rate of autocondensation, which is highly dependent on the degree of polymerization of the oligomer, controls the distribution of products formed. The results indicated that the depolymerization of living PMMA is an important factor even at room temperature, potentially affecting the MWD of the polymers.
Functional polymers and sequential copolymers by phase transfer catalysis, 2. Synthesis and characterization of aromatic poly(ether‐sulfone)s containing vinylbenzyl and ethynylbenzyl chain ends
Authors: Percec Virgil , Auman Brian C. 
Published: April 2003

AbstractA simple method for the synthesis of α,ω‐bis(vinylbenzyl) aromatic poly(ether‐sulfone)s (2) and their transformation into α,ω‐bis(ethynylbenzyl) aromatic poly(ether‐sulfone)s (4) is presented. This method involves a fast and quantitative Williamson etherification of the α,ω‐bis(hydroxyphenyl)polysulfone with a mixture of p‐ and m‐chloromethylstyrenes in the presence of tetrabutylammonium hydrogen sulfate as phase transfer catalyst, a subsequent bromination, and then a dehydrobromination with potassium tert‐butoxide. The DSC study of the thermal curing of these α,ω‐bis(vinylbenzyl)polysulfones and α,ω‐bis(ethynylbenzyl)polysulfones demonstrates high thermal reactivity for this new class of styrene‐terminated oligomers.
Structure‐reactivity relation for polymines and derivatives in activated ester hydrolysis
Authors: Everaerts Albert , Samyn Celest , Smets Georges 
Published: April 2003

AbstractThree polymeric amines, poly(1‐aminoethylene) (polyvinylamine) (PVNH2) and linear and branched poly(iminoethylene)s (polyethylene(imines)) (1‐PEI and b‐PEI) as well as their dodecyl (D) and imidazolylmethyl (Im) substituted derivatives were used for the hydrolysis of p‐nitrophenyl acetate (PNPA), 4‐acetoxy‐3‐nitrobenzoic acid (ANBA) and some of their homologues in order to elucidate the relations between their overall structures and their catalytic activities. In each series polymers of similar degree of substitution were compared, namely PVNH2‐D18 and PVNH2‐D18‐Im16; b‐PEI‐D20 and b‐PEI‐D20‐Im18; 1‐PEI‐D20 and 1‐PEI‐D20‐Im16. The degree of branching of b‐PEI was 41%. All reactions were carried out at 28,7°C in aqueous solution, and followed spectrometrically. Using a catalyst concentration in large excess with respect to the substrate concentration (10−4 mol · l−1) the reactions were found to obey pseudo‐first order kinetics. By plotting log [Substrate] against time, k2 (cat) and consequently k2 rate constantes were evaluated. For each series of polymers, k2 increases considerably by dodecyl substitution (hydrophobic‐), imidazolylmethyl substitution (catalytic‐) and by the use of a charged substrate (electrostatic effects). At similar degree of substitution the catalytic activity is always in the following order: l‐PEI < PVNH2 < b‐PEI. Using the method of Kosower‐Mikes the polarity of the microenvironment of l‐PEI and b‐PEI was found to be almost equal. Substitution of l‐PEI with ethyl or 2‐diethylaminoethyl side groups (40% substitution) modifies only slightly the catalytic effect of l‐PEI. It is, therefore, concluded that the primary amino groups of the side chains in b‐PEI are reponsible for its much higher reactivity than that of l‐PEI and PVNH2. Experiments with [Substrate] > [Catalyst] were carried out with b‐PEI, b‐PEI‐D20‐lm18 and l‐PEI‐D20‐Im16. Under these conditions the reactions follow Michaelis‐Menten kinetics and permit the comparison of the complexation constant and rate constant of hydrolysis for the three systems. In the case of b‐PEI hydrolysis, reactions towards PNPA carried out at different temperatures, indicate a low enthalpy of activation, ΔH≠ = −196 j · mol K−1 is strongly negative. On the contrary the enthalpy and entropy of complexation are low, indicating low hydrophobic effects.
Polyurethanes containing binaphthyl groups
Authors: Tanaka Mamoru , Nakaya Tadao 
Published: April 2003

AbstractPolyurethanes containing binaphthyl groups were synthesized by reaction of diisocyanates – 4,4'‐diphenylmethane diisocyanate (MDI), 2,4‐toluylene diisocyanate (TDI) and hexamethylene diisocyanate (HDI) – with 2,2'‐(1,1'‐binaphthyl‐4,4'‐ylenedioxy)diethanol (3). The polyurethane obtained from 3 with MDI has an intrinsic viscosity [η]90DMSO90°C of 0,14 dl · g−1 and a melting point of 244 – 260°C, that from 3 with TDI has an [η]90°CDMSO of 0,12 dl · g−1 and a melting point of 181 – 191°C, and that from 3 with HDI has an [η]90°CDMSO of 0,11 dl · g−1 and a melting point of 222 – 241°C. These polymers were found to be crystalline. Segmented polyurethanes (SPU) from 3 with prepolymers of poly(tetramethylene glycol) (PTG), (M = 1079) and MDI or HDI (mole ratio PTG:MDI (or HDI) = 1:2) were also synthesized. The SPU from MDI has an intrinsic viscosity [η]90°CDMSO of 0,56 dl · g−1 and a melting point of 260–275°C, and that from HDI has an [η]90°CDMSO of 0,50 dl · g−1 and a melting point of 231 – 253°C. These polymers show slight crystallinity.
Etude par résonance magnétique nucléaire du 1H et 13C des télomères du chlorure de vinyle et du tétrachlorure de carbone
Authors: Bessière Jean Marie , Boutevin Bernard , Taha Mohamed 
Published: April 2003

AbstractThe adducts and bi‐adducts of the reaction of vinyl chloride with carbon tetrachloride, CCl3(CH2CHCl)nCl and Cl(CHClCH2)CCl2(CH2CHCl)pCl respectively, have been studied by 13C and 1H NMR. The identification of the characteristic peaks of each product enables of much better control of the purity of the telomerization reactions. Moreover, it was possible to resolve complex spin systems in 1H NMR (up to 9 non‐equivalent spains). In particular the threo and erythro conformation of the tri‐adducts could be assigned without any ambiguity. Thanks to model molecules, the chemical shifts were specified in 13C NMR for all carbon atoms with similar groups.