bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymérisation anionique de i'isoprene et du butadiene en presence d'agents complexants
Authors: Alev Samson , Collet André , Viguier Michel , Schué François 
Published: April 2003

AbstractWith the aid of DCHE and [222], solutions of sodium, potassium, rubidium, and cesium have been prepared in tetrahydrofuran (THF) and in benzene. All these new species initiate the polymerization of butadiene and isoprene avoiding the inconvenience of heterogeneous reactions. The presence of free ions and/or complexed ion pairs allows the increase of vinyl structures even in benzene.
Thermostability of polymers containing indanic units in the main chain
Authors: Nishimura J. , Tanaka N. , Yamashita S. 
Published: April 2003

AbstractThe acid‐catalyzed stepwise polymerization of 1,1‐diphenylethylene derivatives, p‐di(1‐phenylvinyl) benzene, bis[p‐(1‐phenylvinyl)phenyl]methane, 1,2‐bis[p‐(1‐phenylvinyl)phenyl]ethane, bis[p‐(1‐phenylvinyl)phenyl]ether, and bis[p‐(1‐phenylvinyl)phenyl]sulfide produced selectively indanic‐unit‐containing polymers in pertinent conditions. Their molecular weights (M̄n) were in the 1600–15, 700 region after the fractionation in hot ethnol. Melting points were in the 214–281°C region. They dissolved fairly well in conventional solvents like benzene, tetrahydrofuran, and carbon tetrachloride. According to TGA they started to decompose at 397–432°C and showed 10% weight loss at 478–502°C in air at a heating rate of 5°C/min. Focusing on the thermostability, we report on their physical properties.
Syntheses of polyethylenimine containing asymmetric nucleic acid base derivatives as grafted pendants
Authors: Overberger C. G. , Morishima Y. 
Published: April 2003

AbstractPreparations of new model polymers of polynucleotides with linear polyethylenimine (PEI) backbones and optically active nucleic acid base derivatives as pending side chains are described. (±)‐2‐(Thymin‐1‐yl)propionic acid (II) and (±)‐2‐(adenin‐9‐yl)propionic acid (IV) were synthesized. These carboxylic acid derivatives were grafted onto PEI at the imino nitrogen by the p‐nitrophenyl active ester method. The enantiomeric pairs of II were optically resolved with quinine to yield (−) and (+)‐2‐(thymin‐1‐yl)propionic acid (VII and VIII). VII and VIII were grafted onto PEI through amide bond by direct coupling with diethylphosphoryl cyanide to give optically active graft polymers. The related monomer and dimer model compounds were also prepared by the same method from diethylamine and dimethylethylene diamine, respectively.
New processable polyaromatic ether–keto‐sulfones curable by Diels‐Alder cycloaddition
Authors: Sankaran V. , Marvel C. S. 
Published: April 2003

AbstractNew Processable polyaromatic ether‐keto‐sulfones were prepared from the acid chloride of bis‐m‐carboxyphenyl acetylene (XII), isophthaloyl chloride (XX), diphenyl ether (XVIII), and 4,4′‐diphenoxydiphenyl sulfone (XIX) in a Friedel‐Crafts‐type polymerization. These polymers were cured by Diels‐Alder cycloaddition with 1,4‐diphenyl‐1,3‐butadiene. The cured polymers showed an increase in Tg and in thermal and heat stabilities. The polymers form colorless, transparent, brittle films and can be cast into a glass fiber laminate. Both meta‐and para‐substituted acid chlorides of biscarboxyphenyl‐1,3‐butadiene yielded insoluble polymers under the same conditions but form processable polymers where combined with acetylene units in the polymer chain. Polymers that contained both acetylene and butadiene units were prepared but could not be cured by an intramolecular Diels‐Alder cycloaddition reaction.
Heat‐resistant polymers with thianthrene analog units. II . Aromatic polyamides
Authors: Niume K. , Nakamichi K. , Toda F. , Uno K. , Hasegawa M. , Iwakura Y. 
Published: April 2003

AbstractA series of polyamides which contained thianthrene, phenoxatiin, and dibenzo‐p‐dioxin units was synthesized from tricyclic fused‐ring diamines and aromatic diacid chlorides by solution polycondensations at a low temperature. The amorphous polyisophthalamides were highly soluble in polar organic solvents, whereas some of the polyterephthalamides with a fair degree of crystallinity were insoluble. The solubility of the series of polyamides increased in the order of the dibenzo‐p‐dioxin‐containing polymers < phenoxatiin‐containing polymers < thianthrene‐containing polymers. The thermal stability increased in the reverse order and the dibenzo‐p‐dioxinpolyamides were more thermostable than the corresponding open‐chain polymers with diphenyl ether linkages. The polyamides derived from 2,8‐oriented tricyclic diamines showed somewhat lower glass transition temperatures than those from 2,7‐oriented diamines.
Photochemistry of polymeric systems. II. Photocrosslinking of polymers and copolymers containing various aromatic N‐oxide groups
Authors: Decout Jean‐Luc , Lablache‐Combier Alain , Loucheux Claude 
Published: April 2003

Abstract2‐Methyl‐5‐vinylpyridine‐N‐oxide, 4‐vinylquinoline‐N‐oxide. 9‐vinylacridine‐N‐oxide, p‐N,N‐dimethylaminostyrene‐N‐oxide units were introduced in polymeric chains as homopolymers or/and as styrene copolymers to study their photocrosslinking. The method used for characterization of photocrosslinked films was a “photoresist test” described in Part I of this series. The photosensitivity of the different chromophores bound to the different polymer has also been studied by UV, IR, and fluorescence spectrophotometries. The use of aromatic amine N‐oxide groups in polymers seems to be a general means to produce their photocrosslinking by radical reactions. Among the different polymeric materials prepared, 4‐vinylpyridine‐N‐oxide and 4‐vinylquinoline‐N‐oxide are the most photosensitive.
Polymerization of cyclic derivatives of uracil and thymine
Authors: Inaki Yoshiaki , Futagawa Hidekazu , Takemoto Kiichi 
Published: April 2003

AbstractCyclic derivatives of uracil and thymine were synthesized from their corresponding 1‐(2′‐chloroethyl) derivatives by dehydrochlorination. These compounds were found to undergo a variety of reactions, giving many valuable derivatives of uracil and thymine. The cyclic derivatives, as monomers, were polymerized with a cationic initiator by a unique ring‐opening process. The polymerization proceeded by ring opening with isomerization of the pyrimidine ring to give a polymer in which pyrimidine rings were connected with ethylene between N‐1 and N‐3 or O‐4 in the pyrimidine ring. The structure of these polymers was determined by nuclear magnetic resonance (NMR), ultraviolet (UV), infrared (IR), and mass spectra. The structure was affected by polymerization temperature.
Enantioselective ester synthesis in the presence of optically active polymers
Authors: Kawakami Yuhsuke , Sugiura Tomiya , Mizutani Yutaka , Yamashita Yuya 
Published: April 2003

AbstractEnantiomer‐differentiating ester syntheses from acid salts, chlorides, and an anhydride were studied in the presence of optically active polyamines. Enantiomer selection occurred in reactions of a racemic salt with an achiral alkyl bromide and vice versa, which is good evidence of the importance of activation of the carboxylate group by complexation of the counterion and activation of alkyl bromide by the formation of a quaternary salt with polyamine under solid–liquid, phase‐transfer reaction conditions. Only small optical activity was observed in the products of acid anhydride or chloride with alcohol.
Kinetics of crosslinking copolymerization of styrene with symmetric divinyl compounds
Authors: Fink Johannes Karl 
Published: April 2003

AbstractGel formation usually occurs in crosslinking systems during polymerization. The critical conversion in this process is dependent on the reactivity ratios of the different kinds of double bond in the system and on the tendency to cyclization. In this article a procedure for estimating the gel point for small amounts of a symmetric divinyl compound is shown in measurements of the degree of polymerization at different conversions. A method is also given to relate the reactivity ratio of the pendent double bonds to the amount of cyclization and to the degree of multiple crosslinking. In m‐divinylbenzene/styrene the results indicate that about 10% of the pendent double bonds is consumed by cyclization due to backbiting of the primary chain, whereas an initial effective crosslink results in about seven multiple crosslink bonds.
Polytetrafluoroethylene surface modification by impregnation with iron and manganese oxides
Authors: Baumhardt‐Neto Ricardo , Galembeck Sérgio Emanuel , Joekes Inés , Galembeck Fernando 
Published: April 2003

AbstractPolytetrafluoroethylene (PTFE) surfaces can be modified by impregnation with Fe and Mn oxides by procedures based on Fe(CO)5 sorption in the polymer and followed by oxidation with H2O2 or KMnO4. The effect of some variables (reagent concentrations and temperature) on the amount of oxides deposited was examined. The oxides incorporated in PTFE can be only partly removed by acid cleaning. Water–PTFE contact angles and PTFE surface resistivity are altered. Electron and x‐ray diffractograms of the oxides were obtained but unambiguous identification was not achieved. Transmission electron microscopy examination of surface replicas showed that impregnation with oxides which covered most of the PTFE surface was fairly uniform.
Transfer constants relative to the cationic polymerization of 1‐ and 2‐vinyl naphthalenes and 3‐vinyl phenanthrene
Authors: Blin Philippe , Bunel Claude , Marechal Ernest 
Published: April 2003

AbstractTransfer and termination constants have been determined for the cationic polymerization of 1‐ and 2‐vinyl naphthalenes and 3‐vinyl phenanthrene. They have been compared with the values obtained for styrene under the same experimental conditions. Experimental values are in good agreement with theoretical determinations.
N‐substituted poly(p‐phenylene terephthalamide)
Authors: Takayanagi Motowo , Katayose Teruo 
Published: April 2003

AbstractN‐substituted poly(p‐phenylene terephthalamide)s (PPTA), such as N‐alkylated, N‐aralkylated, and N‐carboxymethylated poly(p‐phenylene terephthalamide), were synthesized from PPTA and the corresponding halides by the polymer reaction via the metalation reaction in a solution of sodium methylsulfinylcarbanion in dimethyl sulfoxide at low temperature. The introduction of various substitutional groups into the amide groups of PPTA increased their solubilities, but decreased their thermal stabilities compared with PPTA. The effects of various substitutional groups on the thermal properties and the solubilities are discussed. Liquid crystal formation was noticed for PPTA substituted with bulky groups such as 9‐anthrylmethyl group.
Polymerization of acrylonitrile initiated by the redox system 2,2′‐thiodiethanol/Ce4+ in aqueous sulfuric acid
Authors: Jayakrishnan Athipettah , Haragopal Mahadevan , Mahadevan Venkatanarayana 
Published: April 2003

AbstractThe polymerization of acrylonitrile initiated by the redox system 2,2′‐thiodiethanol/Ce4+ in dilute sulfuric acid was investigated in the temperature range of 15–25°C. Oxidation of the substrate in the absence of the monomer has also been studied. The reaction involves the formation of an intermediate complex between the metal ion and the protonated species of the reductant, whose decomposition gives rise to the initiating free radicals. Multual interaction of the growing macroradicals accounts for the termination of polymerization. A suitable kinetic scheme has been proposed and rate and equilibrium constants evaluated.
Mechanism of smoke suppression by metal oxides in PVC
Authors: Ballistreri A. , Montaudo G. , Puglisi C. , Scamporrino E. , Vitalini D. 
Published: April 2003

AbstractThe amount of smoke suppression induced in PVC by some metal oxides was measured as a function of temperature. The amount of CO2 evolved in the combustion was also measured simultaneously with smoke emission. Our results show that in a smoldering condition smoke occurred almost immediately, whereas CO2 occurred at a later stage. A good correlation was found between smoke density and char yield in nitrogen, and the amount of benzene suppression, induced by metal oxides, also correlated well with the char yield. These facts are taken as evidence that crosslinking catalyzed by metal oxides is the principal mechanism of smoke inhibition and that char oxidation is responsible for the reduction of char yield.
Novel thermostable polymers from bis‐o‐aminophenylbenzimidazoles and aromatic tetracarboxylic dianhydrides
Authors: Niume K. , Toda F. , Uno K. , Hasegawa M. , Iwakura Y. 
Published: April 2003

AbstractNovel aromatic hetero polymers, polybenzoylenebenzimidazoquinazolines, were prepared. These polymers were synthesized by the polymerization of bis‐o‐aminophenylbenzimidazoles with aromatic tetracarboxylic dianhydrides in organic solvents, followed by cyclocondensation of the polyamic acids in polyphosphoric acid. In the resulting polymers the o‐phenylenediamine component behaved trifuntionally and the connecting groups were tricyclic fused rings that contained seven‐membered rings. These polymers some of which has a ladder‐type structure, exhibited excellent thermal properties.
Compatibility of cross‐linked polymers with plasticizers by glass transition temperature measurement and swelling tests
Authors: Chi Minn‐Shong 
Published: April 2003

AbstractTo elucidate the compatibility of polymer and plasticizer components of binders a study of polymer–plasticizer interactions by differential scanning calorimetry (DSC) and swelling tests was conducted. The glass transition temperatures (Tg's) of mixtures of polymers and plasticizers, both cured and uncured, were determined with a DSC technique. Results with the PEG polymer systems were complicated by the partial crystallization of the polymer from the polymer/plasticizer mixtures. The PGA polymer system did not exhibit this behavior. However, the Tg's of cured PGA with various plasticizer mixtures made complicated departures from linearity (plots of Tg versus weight fraction of plasticizer) that indicated polymer–plasticizer interaction. By using least‐squares analysis of data plotted by the equation

Values of the interaction parameter K were determined for cured PGA in various plasticizer systems. These K values are in good agreement with the molecular flexibility of the plasticizers based on their molecular structure. The results of swelling tests are discussed to elucidate further the nature of the interaction of these polymers with plasticizers. Calculated polymer‐plasticizer interaction values (χ) from the swelling tests correlated with the solubility parameter (δ) for a given class of polymer (polyether, polyester) and plasticizer (nitrate ester, ether‐type). The efficiency of a plasticizer in reducing the Tg of a polymer (below the linearly interpolated value) was found not to be related to the swelling behavior of the polymer in the plasticizer.
Thermal polymerization of acrylamide by differential scanning calorimetry
Authors: Kishore K. , Santhanalakshmi K. N. 
Published: April 2003

AbstractThermal polymerization of acrylamide was studied by differential scanning calorimetry. Latent heat of fusion ΔHf and enthalpy of polymerization ΔHp values were found to be 36 and −18.0 kcal mol−1, respectively. The overall activation energy E for the polymerization was calculated to be 19 k cal mol−1 up to 60% conversion. The added free‐radical inhibitor (benzoquinone) was found to desensitize the thermal polymerization of acrylamide suggesting the polymerization to be a free‐radical type. The existing rate equation for the heterogeneous bulk polymerization in the presence of initiators has been modified for the thermally initiated bulk polymerization of acrylamide. The experimental overall E value was found to agree well with the calculated E value when considering only the propagation and termination steps, thereby suggesting the process to be similar to postpolymerization of acrylamide.
Microstructure of vinyl acetate–butyl acrylate copolymers studied by 13C‐NMR spectroscopy: Influence of emulsion polymerization process
Authors: Pichot Christian , Llauro Marie‐France , Pham Quang‐Tho 
Published: April 2003

AbstractThe compositions and sequence distributions of vinyl acetate–butyl acrylate copolymers obtained with batch and semicontinuous emulsion polymerizations have been studied by 1H and 13C NMR. The batch process gives heterogeneous copolymers while with the semicontinuous one the sequence distribution is statistical. These differences in sequence distributions have been related to the physical properties of the copolymers.
A 13C‐NMR investigation of plasma polymerized ethane, ethylene, and acetylene
Authors: Dilks A. , Kaplan S. , Van Laeken A. 
Published: April 2003

AbstractSolid‐state 13C‐NMR spectra were obtained by cross‐polarization and magic angle spinning of polymers prepared by injecting ethane, ethylene, and acetylene into a radiofrequency plasma. By use of the delayed decoupling technique to suppress protonated carbon peaks and difference spectroscopy five resolved spectral bands can be distinguished. These bands are assigned to (I) unsaturated nonprotonated, (II) unsaturated CH and CH2, (III) quaternary, (IV) methine and methylene, and (V) methyl carbons by comparison with standard 13C shifts compiled for organic materials. The relative amounts of these structural features in the polymers were determined quantitatively and the possible sources of errors considered.
Polymerization of coordinated monomers. XIX. Kinetic study of the alternating copolymerization of methyl methacrylate with styrene by boron trichloride
Authors: Hirai Hidefumi , Takeuchi Kazuhiko , Komiyama Makoto 
Published: April 2003

AbstractAlternating copolymerizations of methyl methacrylate with styrene in the presence of boron trichloride at 0°C in 1,2‐dichloroethane were carried out by using benzoyl peroxide as an initiator. Conversion increased proportionally with polymerization time, whereas the degree of polymerization was constant irrespective of time. The rate depended linearly on the square root of the concentration of benzoyl peroxide. The equilibrium constants for the formation of the ternary molecular complex composed of methyl methacrylate, styrene, and boron trichloride in 1,2‐dichloroethane at −20, −10, and +4°C were determined by 1H‐NMR spectroscopy. The concentrations of the ternary molecular complex in the polymerization mixtures were evaluated from the equilibrium constant of the formation. The rate of the alternating copolymerization was proportional to the first order of the concentration of the ternary molecular complex. The distribution of methyl methacrylate‐centered triads in the alternating copolymer was different from that of styrene‐centered triads. These results can be explained by a mechanism involving the homopolymerization of a ternary molecular complex.
Resacetophenone oxime–formaldehyde resin and its metal chelates. III
Authors: Parmar J. S. , Patel M. R. , Patel M. M. 
Published: April 2003

AbstractIn this paper the synthesis and properties of resacetophenone oxime–formaldehyde resin are described. The number‐average molecular weights of the resin determined by vapor‐pressure osmometry and nonaqueous conductometric titration are 2200 ± 10% and 2500 g/mol, respectively. Cu(II), Ni(II), and Co(II) chelates of the resin were prepared. Elemental analysis of the chelates indicates a metal to ligand ratio of 1:2. The diffuse reflectance spectra and magnetic moments of Ni(II) and Co(II) chelates show tetrahedral structure, whereas Cu(II) chelate shows a square planar structure. Infrared spectral studies show that the metals are coordinated through the nitrogen of the oximino group and oxygen of the phenolic group. The presence of methylene bridges is also indicated by IR spectral studies. The thermal behavior of the resin and its metal chelates are also discussed.
Cross‐linked polyvinylpyrrolidones with increased affinity and specificity for methyl orange and its homologs
Authors: Takagishi Toru , Hayashi Akiyo , Kuroki Nobuhiko 
Published: April 2003

AbstractPolyvinylpyrrolidones of various degrees of cross‐linkage have been prepared by radical polymerization of N‐vinylpyrrolidone with methylenebisacrylamide to regulate the fraction of cross‐linkage. The insoluble polymers obtained were examined for their ability to bind methyl orange and its homologs, methyl orange, ethyl orange, propyl orange, and butyl orange at 5, 15, 25, and 35°C, respectively, in an aqueous solution. The first binding constants and the thermodynamic parameters that accompanied the binding were calculated. For any particular dye the extent of binding, the absolute magnitude of ΔF°, and the value of ΔS° increased as the degree of cross‐linkage increased, starting with water‐soluble polyvinylpyrrolidone (zero cross‐linkage) and proceeding to the polymer with high cross‐linking density. This behavior can be accounted for in terms of more extensive hydrophobic domains in the cross‐linked polymeric matrix that enhances hydrophobic interactions in the binding process. Moreover, the cross‐linked macromolecule polymerized in the presence of methyl orange and then stripped of the bound methyl orange shows substantially stronger binding for this small molecule than the polymer cross‐linked in the absence of methyl orange. In contrast, the cross‐linked polymer prepared similarly in the presence of the larger molecule, butyl orange, exhibits decreased affinity toward the smaller consolute, methyl orange, than either of the other polymers described. It seems, therefore, that the polymeric matrix provides favorable binding sites or pockets that can accommodate a specific small molecule. The preparative procedure, which uses a small‐molecule template, molds into the polymer some structural specificity in the binding of small molecules.
Vinyl polymerization initiated by peroxydiphosphate. VII. Polymerization of acrylonitrile initiated by peroxydiphosphate–ascorbic acid redox system
Authors: Lenka Subasini , Dhal Akshaya K. 
Published: April 2003

AbstractThe polymerization of acrylonitrile was studied with a peroxydiphosphate–ascorbic acid redox system as the initiator. The rate of polymerization increased with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. It also increased with increasing monomer concentration and the monomer exponent was computed to be unity. The reaction was carried out at three different temperatures and the overall activation energy was computed to be 4.6 kcal/mol. The effect of certain surfactants on the rate of polymerization was investigated and a suitable kinetic scheme is described.
Exactly alternating silarylene‐siloxane polymers. 4. Step‐growth polymerization reactions with dichlorosilane monomers
Authors: Lai Yu‐Chin , Dvornić Petar R. , Lenz Robert W. 
Published: April 2003

AbstractA series of alternating silarylene‐siloxane polymers of moderate molecular weights was prepared by the step‐growth polymerization reactions of 1,4‐bis(dimethylhydroxysilyl) benzene and three different dichlorosilanes: methylphenyldichlorosilane, dimethyldichlorosilane, and methylvinyldichlorosilane. The reactions were monitored by gel permeation chromatography (GPC). The polymers were characterized by 1H‐and 13C‐NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Polymers with number‐average degrees of polymerization ranging from 90 to 350, based on the use of polystyrene standards in GPC analysis, were obtained. For the two homopolymers and a series of copolymers that contained either or both dimethylsiloxyl and methylphenylsiloxyl units, the glass temperatures and thermal stabilities increased substantially with increasing methylphenylsiloxyl unit content.