bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct polyesterification promoted by a complex of diphenyl chlorophosphate with LiBr
Authors: Higashi Fukuji , Hoshio Atsushi , Yamada Yukiharu , Ozawa Michihide 
Published: April 2003

AbstractThe diphenyl chlorophosphate (DPCP)‐promoted polycondensation reaction between aromatic dicarboxylic acids and bisphenols was largely improved by carrying out the reaction in the presence of lithium halides to give high molecular weight aromatic polyesters. Among the halides LiBr, which is capable of forming a complex with hexamethylphosphoramide, was most effective, suggesting that a similar complexation of DPCP with LiBr in pyridine facilitates the complete reaction of DPCP with carboxyl groups. The complex could selectively activate carboxyl groups of hydroxybenzoic acids to give high molecular weight copolyesters from several combinations of aromatic hydroxy acids. The reaction could also be adaptable to the copolycondensations of a mixture of the dicarboxylic acids, bisphenols, and hydroxybenzoic acids.
On the anionic polymerization of cyanogen
Authors: Skarda V. , Ivkovich D. , Labes M. M. 
Published: April 2003

AbstractThe reaction of anionic initiators with cyanogen was investigated by ultraviolet, visible, and infrared spectroscopy. It is argued that the reaction proceeds via formation of an analog of the heterocyclic anion C7N7− previously known from the reaction of KCN with (CN)2. The analytical results and spectra of the final black product were indicative of the possible formation of open‐structured C7N7− dimers. A molecular model of the dimer suggests why the polymerization might terminate at the dimer stage. The pyrolysis of the cyclic acid HC7N7 was studied with the aim of determining the structure and mechanism of the formation of the resulting black product. It is suggested that this thermally induced polymerization reaction probably proceeds via formation of azomethine‐type intermolecular crosslinks and may serve as a model for the investigation of the mechanism of nitrile polymerization in pyrolyzed acrylonitrile polymers.
Sequence‐length distribution in bulk and DMSO‐derived acrylic acid/methylmethacrylate copolymers
Authors: Ekpenyong Kieran I. 
Published: April 2003

AbstractThe mean sequence lengths (l̄) and probabilities (W) in the formation of various structural units were estimated for acrylic acid (AA) and methylmethacrylate (MMA) copolymers obtained in bulk and solution (DMSO) copolymerization. The results show that, although l1:l2 in bulk polymerization ranges from about 1:5 to about 5:1 when moving from lower to higher M1 feeds in DMSO polymerization, the corresponding ranges is 1:25 to about 1:2, all in favor of the monomer M2. The probability of the formation of structural units of a kind (e.g., doublets and triplets) that in bulk polymerization favors M1 more than M2 swings drastically in favor of M2 when the polymerization is carried out in DMSO.
Oligomerization of vinyl monomers 18. Stereochemistry of anionic oligomerization of 4‐vinylpyridine
Authors: Meverden Craig C. , Hogen‐Esch Thieo E. 
Published: April 2003

AbstractOligomers of 4‐vinylpyridine were prepared by reaction in vacuo of 4‐vinylpyridine with lithio‐4‐ethylpyridine at −78°C, followed by reaction with CH3I(13CH3I) or CH3OH. The stereochemistry was studied by NMR and GC. Methylation and the addition of 4‐vinylpyridine occurred in a stereochemically nonselective manner. The data also indicated that in contrast to the oligomerization of 2‐vinylpyridine the stereoisomeric meso and racemic 4‐pyridyl carbanions propagated with equal reaction rates. The stereochemistry was readily explained by an absence of coordination of the Li ion by the nitrogen of the penultimate pyridine ring observed in the corresponding oligomerization of 2‐vinylpyridine.
Moisture effects in lithium‐doped polyimide films
Authors: Khor Eugene , Gay M. Sandra , Taylor Larry T. , Wightman James P. 
Published: April 2003

AbstractThe interaction of lithium‐doped polyimide films with water has been investigated. Contact angle and water absorption/desorption measurements have been performed to obtain an idea of the hygroscopic nature of these lithium‐doped films. Contact angles were found to decrease as the amount of surface lithium increased. Film water content was also found to increase as the weight percent of total lithium content in the film increased. This phenomenon has been used to rationalize the electrical resistivity–temperature profile of certain lithium films which display an increase in electrical resistivity upon drying.
Kinetic study of the polymerization of acrylamide in inverse microemulsion
Authors: Candau Françoise , Leong Yee Sing , Fitch Robert M. 
Published: April 2003

AbstractThe polymerization of acrylamide in inverse microemulsions stabilized by Aerosol OT emulsifier and initiated with azobisisobutyronitrile (AIBN) or potassium persulfate (K2S2O8) has been investigated. The inverse polyacrylamide latexes formed are clear and highly stable. A dilatometric technique was used to follow the conversion of monomer at T = 45°C. The rate of polymerization is first order with respect to initial monomer concentration in the presence of AIBN, and is 1.5 order with K2S2O8. An inverse relationship between molecular weight and emulsifier concentration is found which suggests participation of the emulsifier in the initiation reaction. This is confirmed by the independence of the molecular weight of polyacrylamide on the concentration of the initiators. High values of the rate of polymerization are obtained combined with high molecular weights (up to 107). An important and novel feature of this microemulsion process is that each final latex particle consists of one single molecule of polyacrylamide in a collapsed state. This suggests kinetics which do not follow the Smith and Ewart theory but are characterized by continuous particle nucleation.
Molecular dimensions of polypeptides in helicogenic solvents
Authors: Kim Jong Ryul , Ree Taikyue 
Published: April 2003

AbstractThe dependence of the molecular dimension of polypeptides in helicogenic solvents on molecular weight was calculated by using the Zimm‐Bragg‐Nagai theory in collaboration with the broken‐rod model, in which the excluded volume effect was taken into account by setting the equivalent chain to be a nonintersecting chain. Our calculated results for PBLG in helicogenic solvents were compared with experiment with good agreement. The flexibility of the helices of PCBL and PELG as broken rods corresponded to that of PBLG without excluded volume effect (i.e., the broken rod of a self‐intersecting chain) in a comparison of their experimental data with our calculated results for PBLG of self‐intersecting and nonintersecting chains. Over a wide range of molecular weights M our theory explains the dependence of the length per monomeric residue h on M, even for short chains in which h > 1.5 Å.
The relative reactivity of primary and secondary amine hydrogen atoms of aromatic amines with epichlorohydrin and N‐ and O‐glycidyl compounds
Authors: Johncock P. , Porecha L. , Tudgey G. F. 
Published: April 2003

AbstractThe relative value of the rate constants for the reactions between the secondary and primary amine hydrogen atoms of 3‐trifluoromethylaniline with epichlorohydrin, and of aniline with phenyl glycidyl ether and with some N‐alkyl‐N‐glycidylanilines were determined by HPLC analysis. Values ranged from 0.14 to 0.24 and are in agreement with the findings of earlier workers for the reactions of aromatic amines with O‐glycidyl compounds but in direct conflict with the claim of a recent publication. The value for the reaction between 3‐trifluoromethylaniline and epichlorohydrin was unaffected by the nature of the catalyst, which covered a wide range of strengths and steric requirements.
Thermal decomposition of poly(sec‐amyl methacrylate)
Authors: Kojima Takakazu , Kurotu Takuzo , Masuda Ken‐Ichi , Hosaka Yoshinobu 
Published: April 2003

AbstractThe thermal decomposition of poly(sec‐amyl methacrylate) is studied by simultaneous thermogravimetry–gas chromatography–mass spectrometry and by pyrolysis–gas chromatography. The TG curve has four distinct breaks and a plateau. Results of the identification of the evolved gas at the individual breaks by GC–MS techniques lead to the conclusion that these breaks correspond to the individual processes in the decomposition mechanism like that of poly(tert‐butyl methacrylate): the first break, the depolymerization initiated at the unsaturated chain ends; the second break, the depolymerization initiated at the saturated chain ends; the third break, the ester decomposition; the plateau, the inhibition of decomposition by the formation of poly(methacrylic anhydride); the fourth break, the decomposition of poly(methacrylic anhydride). The extent of ester decomposition is related to the substituent constants based on Hammett equation. The ester decomposition product is separated into three pentene isomers by pyrolysis–gas chromatography: trans‐2‐pentene, cis‐2‐pentene, and 1‐pentene. As raising decomposition temperature, the composition ratio of trans‐2‐pentene decreases and becomes constant above 620 K, and the composition ratios of cis‐2‐pentene and 1‐pentene increase and also become constant above 620 K. These results are accounted for by mobility of atoms included in the substituent at forming a ring transition state.
Curing of epoxy resins with metal(II)4,4′,4″,4‴‐tetraamino phthalocyanines‐modification with elastomers
Authors: Achar B. N. , Fohlen G. M. , Parker J. A. 
Published: April 2003

AbstractThe use of metal phthalocyanine tetraamines in curing epoxy resins to form high‐temperature‐resistant matrix polymers for composites has been reported earlier. The effect of adding carboxy‐terminated butadiene‐acrylonitrile (CTBN) elastomer is now described; preliminary measurements of tensile, flexural, and short‐beam shear strengths, dynamic moduli, resin content, and moisture absorption are presented, and the results of dynamic thermogravimetric analyses are given. In addition to their high char yield (86–87.5% at 800°C in a nitrogen atmosphere) and limiting oxygen index (48.3–50.3), the laminates showed good mechanical properties.
Quantitative determination of the surface composition of acrylate copolymer latex films by XPS (ESCA)
Authors: Pijpers A. P. , Donners W. A. B. 
Published: April 2003

AbstractThe interaction of copolymer latex particles with emulsifiers is governed to a great extent by the monomer composition of the particle surface. In this article it is demonstrated that for methylmethacrylate butylacrylate copolymer latexes this quantity, within certain limits, may be determined by XPS (ESCA) by a detailed analysis of the C(1s) line. It is shown that in this analysis secondary shifts in binding energy caused by the two carboxyl‐oxygen atoms have to be taken into account, a fact that has been neglected in the literature so far.
Grafting of polyesters onto carbon black. VI. Copolymerization of alkylene carbonate with cyclic acid anhydride initiated by alkali metal carboxylate groups on carbon black surface
Authors: Tsubokawa Norio , Ohyama Takeshi , Yamada Akihiro , Sone Yasuo 
Published: April 2003

AbstractThe ring‐opening copolymerization of alkylene carbonate with cyclic acid anhydride was found to be initiated by carbon black containing potassium carboxylate (COOK) groups to give an alternating polymer, i.e., polyester. The polyester was propagated from COOK groups and effectively grafted from carbon black surface: e.g., the grafting ratio of polyester from ethylene carbonate (EC) and phthalic anhydride (PAn) went up to over 100%. On the other hand, the initiating activity of alkali metal carboxylate groups increased, depending on the alkali metal countercation, in the following order: COOLi < COONa < COOK < COORb < COOCs. This order was in agreement with that of increasing electropositivity of the counteraction. The activation energy of the copolymerization of EC with PAn was determined to be 26.3 kcal/mol. The rate of the copolymerization was accelerated in an aprotic solvent such as N‐methyl‐2‐pyrrolidone. Furthermore, the effect of solvent and polymerization temperature on the grafting ratio of polyester was investigated.
Mechanochemically initiated polymerizations. VIII. Influence of chemical nature of monomers
Authors: Simionescu Cristofor I. , Oprea Cleopatra Vasiliu 
Published: April 2003

AbstractThe article presents some results which prove that vinylic, acrylic, dienic, and cyclic monomers, as well as substances which cannot be polymerized by conventional methods (acetonitrile) are activated under the influence of mechanical energy, by vibratory milling, and participate in polymerization and copolymerization reactions.
Conducting carbon‐nitrogen pyropolymers derived from cyanogen
Authors: Chen J. H. , Labes M. M. 
Published: April 2003

AbstractElectropolymerization of cyanogen in acetonitrile containing an electrolyte yields a poly(cyanogen). Its structure involves an open‐structured dimer derived from the heterocyclic anion C7N7− mixed with a sequence of nitrile‐substituted, conjugated carbon–nitrogen bonds. Although this polymer is an insulating solid, pyrolysis in vacuo to 700°C leads to highly conducting carbon–nitrogen pyropolymers via crosslinking and nitrogen elimination. The 700° pyropolymer has a carbon–nitrogen ratio of 5:1, a room temperature conductivity of 1 Ω−1 cm−1, and an activation energy for conduction of ∼0.03 eV.
Bulk polymerization of diallyl benzene‐dicarboxylates I. Influence of temperature on allyl group reactivity
Authors: Kostański L Krzysztof , Króalikowski Wacław 
Published: April 2003

AbstractThe bulk polymerization of the three isomeric diallyl benzene‐dicarboxylates was carried out in the temperature range 80–285°C. The progress of the polymerization process was examined by determination of the conversion of allyl groups double bonds. The reactivity of these groups in the polymerization increases in the following order of isomers: ortho < para < meta at 80–230°C. At temperatures above 200°C the thermal polymerization with activation energies for ortho, meta and para isomers 32, 27, and 28 kcal/mol of allyl group, respectively, has been observed. With the increase of temperature from 80 to 230°C for each of the monomers the number of allyl groups consumed when forming one CC chain (degree of chain polymerization) decreases, but at the same time the kinetic chain length increases several times. The results have been explained by the growing role of chain transfer reactions with simultaneous increase of an ability to reinitiation by occured radicals. The mechanisms of thermal polymerization have been proposed.
Spectroscopic study on chemical structure of plasma‐polymerized hexamethyldisiloxane
Authors: Tajima Ichiro , Yamamoto Minoru 
Published: April 2003

AbstractA plasma‐polymerized material was produced from hexamethyldisiloxane vapor by a glow discharge polymerization technique. Spectroscopic interpretation of the chemical structure of the polymerized hexamethyldisiloxane was studied by spectroscopic means such as IR, XPS, and NMR. The plasma polymer was barely soluble in the usual organic solvents, although it contained a small amount of the monomer and its oligomers. The IR spectrum indicated that the polymer consisted of SiCH3, SiO, SiCH2, and SiH groups. The surface of the polymer was found to retain structural units similar to the monomer from the XPS measurement. On the other hand, the 13C and 29Si high‐resolution, solid‐state NMR measurements revealed that the plasma polymer was highly crosslinked with a variety of conformations and a number of O atoms surrounding a Si atom. Results from the XPS and NMR spectra suggested that the bulk of the polymer was more oxidized than the surface layer; Si atom was preferentially oxidized. A hypothetical chemical structure was proposed for the polymerized hexamethyl‐disiloxane.
Poly(alkylene oxide) ionomers. XII. Hydrolysis of polymers and copolymers of methyl 10,11‐epoxyundecanoate
Authors: Bansleben Donald A. , Vogl Otto 
Published: April 2003

AbstractEster‐substituted oxyethylene polymers and copolymers of methyl 10,11‐epoxyundecanoate were prepared with an aluminumalkyl–water coordination initiator system modified with acetylacetone. Poly(ethylene oxide) ionomers, polyelectrolytes, and polycarboxylic acids were obtained by alkaline hydrolysis of the pendant carbomethoxy groups and by neutralizations with acetic acid. The high molecular weight substituted poly(ethylene oxide)s were characterized by spectral, thermal, and dilute solution measurements. The infrared spectra of carboxylate substituted poly(ethylene oxide)s, both homo‐ and copolymers, show the typical shifts in the carboxyl absorption when going from the ester to the carboxylate group to the free acid. Polymer transitions temperatures, as measured by DSC, changed accordingly. Wide‐angle x‐ray diffraction measurements strongly suggest the existence of ionic domains in the oxyethylene polymer matrix. Dilute solution properties of the ionomers show typical polyelectrolyte behavior, including a substantial change in viscosity when ionic solute is added.
The kinetics of the attachment of polymer chains to reactive latex particles and the resulting latex stabilization
Authors: Huang Yu‐Hui , Li Zhuo‐Mei , Wetz Herbert Mora 
Published: April 2003

AbstractPoly(vinyl benzyl chloride) latex was reacted with ethanolamine and with amine terminated chain molecules containing up to 33 ethylene oxide residues. The kinetics of these reactions were essentially independent of the length of the chain carrying the amine group. An increasing length of the chains bound to the surface of the latex particles produced an increasing latex stabilization.
Heat‐resistant poly(metal phthalocyanine)imide copolymers using benzenetetracarboxylic dianhydride
Authors: Achar B. N. , Fohlen G. M. , Parker J. A. 
Published: April 2003

AbstractNovel poly(metal phthalocyanine)imide copolymers of high thermal stability have been synthesized using metal(II) 4,4′,4″,4‴‐phthalocyanine tetraamine (metal = copper, cobalt, and nickel); diamines: p‐phenylene diamine; 4.4′‐methylene dianiline and 9,9‐bis(4‐aminophenyl)fluorene; and 1,2,4,5‐benzenetetracarboxylic dianhydride. Polymers with medium to high degree of polymerization can be prepared depending upon the metal phthalocyanine concentrations. Effects of temperature, order of addition, solvent type, and metal phthalocyanine concentrations were studied to ascertain the optimum conditions to obtain polymers having good thermal stability with a high degree of polymerization. These polymers had decomposition temperatures greater than 500°C both in air and in nitrogen atmospheres. Their anaerobic char yield at 800°C varied between 65–80%. These new copolymers have promising applications as heat resistant films, fibers, and varnishes.
Vinylsulfonylethyl derivatives of nucleic acid bases and their graft polymers on polyethyleneimine
Authors: Smith Walter T. , Brahme Nanda M. 
Published: April 2003

AbstractVinylsulfonylethyl (VSE) derivatives of the nucleic acid bases adenine, thymine, cytosine, and the nucleosides inosine and uridine have been prepared via a simple Michael reaction with divinyl sulfone. The VSE derivatives were grafted on a polyethyleneimine (PEI) backbone. PEI of different molecular weights (1400, 1800 and 50,000–100,000) were used and also two different molar ratios (1:1 and 1:2) of monomer to PEI were employed. From the 1H‐NMR and elemental analysis, it appeared that in almost all instances the grafting was quantitative. In one case, both 1‐VSE‐thymine and 9‐VSE‐adenine were grafted on the same PEI backbone. Interactions between some of these polymers were investigated by UV spectroscopy. The expected complementary base pairing was observed only in DMSO–ethylene glycol solvent system but not in DMSO. The adenine polymer showed a one‐to‐one interaction with the thymine polymer.
Cationic polyelectrolytes. V. On macromolecular chain conformational state during amination reactions of CMPS
Authors: Drǎgan Stela , Ioan Silvia , Petrariu I. , Dima M. 
Published: April 2003

AbstractThe macromolecular chain conformational state during the amination of chloromethylated polystyrene (CMPS) with two aliphatic amines, namely methyl(2‐hydroxyethyl)amine (MHEA) and N,N‐dimethyl(2‐hydroxypropyl)amine (DM2HPA), has been studied. Viscosimetric and light scattering measurements were performed during reactions in binary solvent mixtures. The observed kinetic deviations have been related with the conformational transformations of the macromolecular chain.
Semiconducting poly(dicyanoacetylenes)
Authors: Chien James C. W. , Carlini Carlo 
Published: April 2003

AbstractPoly(dicyanoacetylene) (PDCA) has been synthesized and characterized. The pristine polymer has EPR g‐value, linewidth, unpaired spin concentration, spin—spin relaxation time (T2), and room temperature dc conductivity (σRT) very similar to those of pristine cis‐polyacetylene (PA), but shorter spin—lattice relaxation time (T1). Saturation doping with iodine has little effect on most EPR characteristics of the polymer except for a slight increase in T1. The doped PDCA has σRT value of only 5 X 10‐9 (Ω cm)‐1, indicating either low carrier concentration and/or carrier mobility. Partial cyclization of the nitrile groups by heating at 400°C of PDCA produces l‐PDCA with significant increases in unpaired spin concentration and σRT but marginal effects on other properties. Saturation doping of l‐PDCA with iodine increases σRT to 7 × 10‐3 (Ω cm)‐1 without appreciable changes in EPR characteristics. The dopants in both polymers can be removed by evacuation indicating only weak charge transfer interactions. The possible stereoelectronic contribution toward the property differences between the PDCA polymers and PA are discussed.
Preparation of amino group‐containing polymers by plasma polymerization
Authors: Inagaki N. , Oh‐Ishi K. 
Published: April 2003

AbstractPlasma polymerizations of bis(dimethylamino)methylsilane (BDMAMVS), bis(dimethylamino) methylvinylsilane (BDMAMVS), and trimethylsilyldimethylamine (TMSDMA) were investigated by elemental analysis, IR spectroscopy, and ESCA. Polymer deposition was fairly faster in the BDMAMVS and TMSDMA systems than in the BDMAMS system, indicating that vinyl and methyl substituents contribute to polymer formation, whereas hydrogen substituents disturb the polymer formation. IR and ESCA spectra for these polymers showed that some dependence of the polymers formed in the chemical composition on the nature of the monomers. A part of methylamino groups in these monomers were oxidized to give amido and amine oxide groups. BDMAMVS and TMSDMA yielded polymers with few fragmentations of methylamino groups, whereas the polymers formed from BDMAMS had no methylamino groups.
The heterogeneity of the network structure of epoxy polymers studied by dynamic and DSC tests
Authors: Kontou E. , Spathis G. , Theocaris P. S. 
Published: April 2003

AbstractThe final network structure of epoxy polymers cured with a crosslinking agent is strongly connected with the type and amount of the curing agent and conditions. Concerning the morphology of this network, it has been reported that cured epoxies are two‐phase systems, containing roughly spherical floccules arranged in a matrix resembling the constituent phases. In this paper and by using an epoxy‐polymer cured with different amounts (i.e., different than the stoichiometric one) of a curing agent, strong indications of their network‐structure heterogeneity have been disclosed. For this study, two different experimental techniques, such as dynamic mechanical measurements and DSC tests have been utilised. It was found that cured epoxy‐polymers consist of two extreme regions, with low and high crosslink densities, whose volume fractions have been estimated by using a mechanical model applicable for two‐phase systems.