bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microanalysis of polymers using a windowless energy‐dispersive X‐ray detector
Authors: Hayat Umar , Bartlett Philip N. , Dodd George H. , Lewis Michael H. 
Published: April 2003

AbstractThe surface compositions of various polymeric films, grown electrochemically on platinum foils, have been investigated by energy‐dispersive x‐ray analysis in conjunction with scanning electron microscopy (SEM/EDS). Comparison of the relative area ratios of peaks for the C and N Kemission lines show that the EDS may be used to study the surface composition of polymers. The evidence presented strongly suggests that there is limited structural degradation and the elemental composition is not changed under the electron beam at relatively low accelerating voltages. This technique statistically samples the repeat units of the polymer. For samples grown in both aqueous and nonaqueous solutions. SEM/EDS provides evidence for extensive contamination with oxygen.
Cationic copolymerization of 3‐methyltetrahydrofuran and 3,3‐dimethyloxetane: Structural study of the copolymers
Authors: Guzmáan J. , García M. , Riande E. 
Published: April 2003

AbstractThe bulk cationic copolymerization of 3‐methyltetrahydrofuran and 3,3‐dimethyloxetane was studied at 0°C using acetylhexafluoroantimonate as initiator. Values of the composition of the copolymers and the dyad and triad probabilities were obtained by 1H‐ and 13C‐NMR spectroscopy. A kinetic scheme was proposed for this copolymerization and the values of the reactivity ratios were directly determined from the dyad probabilities. The experimental values of the triad probabilities were found to be in good agreement with those calculated from the reactivity ratios.
Synthesis of intramolecularly cyclized poly(phenylene sulfide)s of the thianthrene‐type
Authors: Bizzarri P. Costa , Casa C. Della , Fiorini M. , Porzio W. 
Published: April 2003

AbstractOligomers containing thianthrene units in the chain are synthesized by AlCl3‐catalyzed reaction of diphenylsulfide, thianthrene, poly(p‐phenylene sulfide), and poly(m‐phenylene disulfide) with sulfur at 80°C. The products are compared with that obtained by the reaction of diphenylsulfide with AlCl3 at 225°C. IR spectra and elemental analyses are consistent with cyclic chain structures and show a higher cyclization for CHCl3‐insoluble fractions. X‐ray diffraction analysis indicates the same structure for the samples obtained with the different methods of synthesis. A possible structural model is tentatively proposed.
Polymer complexes stabilized through hydrogen bonds. Influence of “structure defects” on complex formation: Viscometry and fluorescence polarization measurements
Authors: Iliopoulos I. , Halary J. L. , Audebert R. 
Published: April 2003

AbstractThe structure of polymer complexes stabilized through hydrogen bonds can be much influenced by the presence of nonactive groups (structure defects) on the polymer chains. In this paper two very simple homopolymer/copolymer systems are studied: the homopolymer is a polybase, polyoxyethylene (PEO) or polyvinylpyrrolidone (PVP), and the copolymer a partially neutralized poly(acrylic acid) (PAA). The acrylate groups on PAA chain behave as structure defects. Viscometry provides information about macroscopic structure of polymer complex in solution while fluorescence polarization is especially adapted for the study of the local mobility of polymer chains. Two kinds of structure are found: the first one is compact and implies a low viscosity of the mixture, eventually precipitation occurs, the second one is a highly branched structure, close to a gel, which leads to a very high increase in viscosity. For instance, the viscosity of the mixture may be several hundred times higher than the sum of the viscosities of the two individual polymer solutions. Such mixtures are especially adapted to be used like thickening agents.
Electro‐initiated polymerization of acrylonitrile in aqueous acetic acid containing Mn(OAc)2·4H2O and CNCH2COOH
Authors: Balasubramanian T. R. , Mahadevan V. 
Published: April 2003

AbstractThe electro‐initiated polymerization of acrylonitrile initiated by the anodic oxidation of an aqueous acid solution (80% HOAc + 20% H2O) containing Mn(OAc)2 · 4H2O/CNCH2COOH has been investigated in the 30–40°C temperature range. The kinetics and mechanism of the process has been investigated as a function of variables and a suitable mechanism proposed. From the experimental observations the rate of polymerization is seen to be proportional to [An]1.5I0.5[Mn+2]0.5 and [CAA]0.5. The rate of polymerization gradually decreases at a higher applied current. The rate was independent of [CAA]0.5. The rate of polymerization gradually decreases at a higher applied current. The rate was independent of CAA at high concentration. The average degrees of polymerization (Pn) increases with increasing AN and decreasing [CAA], [Mn+2] and applied current, I. The initiation is due to the anodic oxidation of Mn+2–CNCH2COOH complex. Both the initiation of polymerization by the primary radical, viz., CNCḢCOOH as well as the oxidation of the primary radical at the electrode are equally significant reactions and neither can be neglected in comparison with the other. Predominant mutual termination accounts for all the observed data.
Backbone‐assisted reactions of polymers. VII. Kinetics of isomerization of poly[(chloromethyl)thiirane] in the absence of solvent
Authors: Zussman Melvin P. , Tirrell David A. 
Published: April 2003

AbstractThe kinetics of the repeating unit isomerization of poly[(chloromethyl)thiirane] have been determined at four temperatures in the absence of solvent. The reaction can be treated as a reversible first‐order process with rate constants and activation energies similar to those observed in analogous reactions of β‐chlorosulfides of low molecular weight. These observations are consistent with a mechanistic scheme that involves rate determining cyclization to a thiiranium ion intermediate, followed by rapid ring opening by chloride ion attack.
Studies on diacetylenic vinyl compounds. II. Copolymerization of phenyl‐4′‐vinylphenylbutadiyne with styrene and methyl methacrylate
Authors: Castillóan Felipe F. , Navarro Rosa E. , Ogawa Takeshi 
Published: April 2003

AbstractThe copolymerizations of phenyl‐4′‐vinylphenylbutadiyne (PVPB) with styrene and methyl methacrylate were carried out under various conditions. PVPB was more readily incorporated in copolymerization than the comonomers, but the diacetylenic group of PVPB interacted with the propagating radical, decreasing the polymerization rate and the molecular weight of copolymer. When the polymerization system became very viscous, crosslinking took place giving light green luminescent gels. The thermal behaviors of copolymers were also studied.
The introduction of hydroxyl functionality into polymers: The synthesis, polymerization, and hydrolysis of vinylbenzyl acetate
Authors: Beihoffer T. W. , Glass J. E. 
Published: April 2003

AbstractVinylbenzyl acetate was synthesized in yields greater than 80% via the reaction of vinylbenzyl chloride with potassium acetate. Radical copolymerization of the monomer with styrene and methylmethacrylate were studied at 60°C. Reactivity ratios determined from FT‐IR analysis of low conversion copolymerizations with styrene (M1) were r1 = 0.78 ± 0.07 and r2 = 1.33 ± 0.13. Polymers and copolymers of vinylbenzyl acetate were found to completely hydrolyze in dioxane/water/base solution to yield hydroxymethyl functionality. Size exclusion chromatography studies indicated that the hydrolysis proceeded without crosslinking. This procedure is a useful method for the introduction of hydroxyl functionality on polymers and avoids crosslinking problems common in previously reported methods.
Comparative study of the absolute reactivity of vinyl monomers: Kinetics of polymerization of vinyl monomers initiated by Mn3+–thiodiglycolic acid redox system
Authors: Balakrishnan T. , Subbu S. 
Published: April 2003

AbstractThe kinetics and mechanism of polymerization of methacrylic acid (MAA) and ethyl acrylate (EA) initiated by the redox system, Mn3+–thiodiglycolic acid (TDGA) were investigated in the 15–35°C temperature range. The polymerization kinetics of both the monomers followed the same mechanism, viz., initiation by primary radical and termination by Mn3+–thiodiglycolic acid complex. The rate coefficients ki/k0 and kp/kt were related to the monomer reactivity and polymer radical reactivity, respectively. It was observed that both monomer reactivity and polymer radical reactivity followed the same order, viz., EA > MAA. The polymer radical reactivity varied inversely with the Q values of the monomers.
Synthesis and characterization of polystyrene–poly(ethylene oxide)–heparin block copolymers
Authors: Vulić I. , Okano T. , Kim S. W. , Feijen J. 
Published: April 2003

AbstractA procedure for the preparation of new block copolymers composed of a hydrophobic block of polystyrene, a hydrophilic spacer‐block of poly(ethylene oxide) and a bioactive block of heparin was investigated. Polystyrene with one amino group per chain was synthesized by free radical oligomerization of styrene in dimethylformamide, using 2‐aminoethanethiol as a chain transfer agent. This amino group was used in the coupling reaction with amino‐telechelic poly(ethylene oxide) to produce an AB type diblock copolymer with one amino group per polystyrene (PSt)–poly(ethylene oxide) (PEO) chain. The amino‐semitelechelic oligo‐styrene was converted into the isocyanate‐semitelechelic oligo‐styrene using toluene 2,4‐diisocyanate and subsequent coupling with H2N–PEO–NH2 afforded AB type block copolymers with terminal amino groups. The coupling of PSt–PEO–NH2 with heparin was performed in a DMF–H2O mixture, first by activating the heparin carboxylic groups with EDC at pH 5.1–5.2 and subsequently reacting the activated carboxylic groups with the amino groups of the PSt–PEO–NH2 at pH 7.5. Depending on the molecular weights of the diblock copolymer used 25–29% w/w heparin was incorporated. These polymers will be further evaluated for their blood‐compatibility.
Synthesis and electrical properties of substituted paracyclophane polymers
Authors: Longone Daniel T. , Glans Jeffrey H. 
Published: April 2003

AbstractWe report the synthesis of three new substituted [6.2]paracyclophane‐1,5‐dienes and their conversion to medium molecular weight polymers by an intra/intermolecular cyclopolymerization. These materials can be oxidatively “doped” by exposure to iodine vapor to give semiconductor properties.
Highly active supported catalysts for olefin polymerization. Supports from a grignard reagent for preparation of highly active catalysts
Authors: Yano Takefumi , Inoue Tokuji , Ikai Shigeru , Shimizu Michimasa , Kai Yoshiyuki , Tamura Masanori 
Published: April 2003

AbstractSupports were obtained by the interaction of C4H9MgCl with the reaction mixture of AlCl3 and CH3Si(OC2H5)3 or Si(OC2H5)4 (Mg/Al/Si = 2/1/1). With the combination of Al(C2H5)3 and methyl‐p‐toluate, immobilized titanium catalysts prepared by the treatment of the supports with TiCl4 and ethylbenzoate showed extraordinary high activity and stereoregularity in the polymerization of propylene.1 By the study of the reaction of AlCl3 with CH3Si(OC2H5)3, the elemental analysis and powder x‐ray diffractometric measurements of the supports, it was found that the supports comprised of Cl, Mg, Al, and Si atoms, OC2H5 groups, C4H9 groups, and ethers, and that they were amorphous solids to the extent that the x‐ray diffraction peak assigned to the 003 plane in MgCl2 crystals completely disappeared.
Crosslinking of epoxy resins at interfaces. IV. Anhydride‐cured resins at carbon and graphite surfaces
Authors: Garton Andrew , Stevenson William T. K. 
Published: April 2003

AbstractDispersions of carbon blacks and chopped carbon fibers in epoxy resins may be characterized by infrared internal reflection spectroscopy (IR–IRS). The high surface areas of the carbons (often ≥ 100 m2/g) ensure a high degree of interfacial contact between the carbon surface and the polymer. The crosslinking kinetics and final crosslinked state of an anhydride‐cured epoxy resin are shown to be affected strongly by the carbons through adsorption of the tertiary amine catalyst at oxidation sites on the carbon surface. Oxidative treatments of the carbons (nitric acid oxidation, air oxidation) increase the effect on the crosslinking chemistry. Carbon dioxide treatment of the carbons, which produces a basic surface, reduces the effect on the crosslinking. The effects on the crosslinking kinetics were confirmed by differential scanning calorimetry (DSC). The relevance of these results to the characterization of the interphase in carbon fiber/epoxy composites is discussed.
Functional polymers. XLVII. Synthesis of various derivatives of ω‐alkenoates
Authors: Purgett Mark D. , Xie Shishan , Bansleben Donald A. , Vogl Otto 
Published: April 2003

AbstractA number of derivatives of ω‐alkenoates were synthesized in preparation for the synthesis of functional polymers based on α‐olefins. For the preparation of most of the methyl esters, the regular esterification of ω‐alkenoic acids, specifically 10‐undecenoic acid with methanol and sulfuric acid as the catalyst, was most effective. For the preparation of thetert‐butyl‐ and 2‐ethylhexyl esters of 10‐undecenoic acid, the acid chloride route was found to be most convenient, whereas for the preparation of the corresponding esters of 5‐hexenoic acid, our method of choice was the synthesis via the imidazolyl derivative of the acid. 2,2,2‐Trifluoroethyl 10‐undecenoate and the 2,2‐dimethyloxazolidine derivative of 10‐undecenoic acid were prepared from the acid and 2,2,2‐trifluoroethanol or 2‐amino‐2‐methyl‐propanol withp‐toluene sulfonic acid as the catalyst. Esters of phenol, 2,6‐dimethylphenol, and 2,6‐diphenylphenol were synthesized from 3‐butenoic and 10‐undecenoic acid with trifluoroacetic anhydride.
Synthesis of aromatic polyethers by Scholl reaction. I. Poly(1,1′‐dinaphthyl ether phenyl sulfone)s and poly(1,1′‐dinaphthyl ether phenyl ketone)s
Authors: Percec Virgil , Nava Hildeberto 
Published: April 2003

AbstractA novel synthetic method for the preparation of high molecular weight aromatic polyethers is presented. It consists in the Scholl reaction of di(1‐naphthyl) ethers of aromatic derivatives exhibiting lower nucleophilicity and higher oxidation potential than the 1‐naphthoxy groups. The examples described in this paper refer to the synthesis of aromatic polyether sulfones and aromatic polyether ketones by the polymerization of 4,4′‐di(1‐naphthoxy)diphenyl sulfone and respectively 4,4′‐di(1‐naphthoxy)benzophenone. Both polymerization reactions are performed at room temperature in nitrobenzene, using anhydrous FeCl3 as catalyst, and apparently follow a “reactive intermediate polycondensation” polymerization mechanism.
Liquid crystal polymers. IX. Copolyesters of trans‐4,4′‐stilbenedicarboxylic acid, 1,4‐butanediol, and aromatic dicarboxylic acids
Authors: Jackson W. J. , Morris J. C. 
Published: April 2003

AbstractCopolyesters of trans‐4,4‐stilbenedicarboxylic acid (SDA), terephthalic acid, and 1,4‐butanediol exhibit thermotropic liquid crystallinity if at least 40 mol % SDA is present (acids total 100 mol %); SDA/2,6‐naphthalenedicarboxylic acid/1,4‐butanediol copolyesters are liquid crystalline if at least 30 mol % SDA is present. The effects of SDA content on the thermal, rheological, plastic, and fiber properties of the copolyesters were determined. The SDA component increases the relaxation times of the polymers and enables injection‐molded plastics and melt‐spun fibers to have significantly increased tensile strength and stiffness.
Participation of water in conformational change of isotactic poly(2‐hydroxyethyl methacrylate) as studied by viscometry in various electrolytic solutions
Authors: Kim Whan Gun , Jhon Mu Shik 
Published: April 2003

AbstractConformational properties of isotactic poly(2‐hydroxyethyl methacrylate) (PHEMA) have been studied by viscometry in various electrolytic solutions. The intrinsic viscosity of isotactic PHEMA at 0.01M salt solution increases with decreasing the B coefficient in Jones—Dole's equation. In respective to water structures, a polymer chain is more expanded in the salt solution including water structure breaker ions. As the concentration of ions increases, the interactions between polymer segments and ions make a major contribution to conformational changes of isotactic PHEMA. Depending on the kind of ions, a salting‐in or out effect is observed at higher concentrations than 0.1M salt solution. We observed that the denaturing effects of various anions in isotactic PHEMA salt solutions are as follows; SO42‐ < F− < I− NO3− < SCN‐. This order is similar to the Hofmeister series. To investigate the influences of denaturing agents on solvent structures, we also compared the guanidine hydrochloride effect with the tetrabutylammonium chloride effect in isotactic PHEMA solution.
Synthesis of polyphthalocyanines by an oxidoreduction reaction initiated by the benzhydrol functional group. I. Model study
Authors: Pascal Thierry , Malinge Jean , Sillion Bernard , Claudy Pierre , Letoffe Jean‐Marie 
Published: April 2003

AbstractA novel route for the thermal conversion of bis(phthalonitrile)monomers into metal‐free phthalocyanine network polymers was investigated on the basis of a model study on the tetramerization reaction of 4‐benzoylphthalonitrile and benzhydrol derivatives into metal‐free phthalocyanine compounds. This procedure of conversion of phthalonitrile derivatives involved an oxidoreduction reaction initiated by the alcohol functional group of benzhydrol coreactant. The influence of molar ratio of phthalonitrile and benzhydrol functional groups, chemical environment of the benzhydrol reducing group has been studied by microcalorimetry and electronic spectroscopy. It was observed that the theoretical 4 : 1 phthalonitrile: benzhydrol molar ratio is respected and the reductive capacity of the benzhydrol group is increased by the electron withdrawing effect of its substituants.
Monte Carlo estimation of kinetic parameters in polymerization reactions
Authors: Duever T. A. , O'Driscoll K. F. , Reilly Park M. 
Published: April 2003

AbstractA general method for estimating kinetic parameters in polymerization reactions using Monte Carlo simulation to represent the models of the reactions is developed. From a statistical point of view, the procedure is a Bayesian one in which a posterior probability density surface (PPDS) is calculated for points on a grid in the parameter space. A smoothing function is fitted to the PPDS, then a posterior probability region, which is similar to a confidence region, is calculated for the parameters. An application to a relatively trivial example, the Mayo–Lewis copolymerization model is shown in detail. Many other potential applications are suggested.
Syntheses and characterization of poly(benzimidazolyl) thiaxanthones
Authors: Reddy T. Ashok , Srinivasan M. 
Published: April 2003

AbstractNovel polybenzimidazoles containing thiaxanthone heterocyclic units were synthesised from 2,7‐thiaxanthonedicarboxylic acid‐5,5′‐dioxide and 2,8‐thiaxanthonedicarboxylic acid‐5,5′‐dioxide and two aromatic tetramine hydrochlorides by PPA solution polycondensation in 60–70% yield. Two model compounds, 2,7‐bis(2‐benzimidazolyl)thiaxanthone‐5,5′‐dioxide and 2,8‐bis(2‐benzimidazolyl)thiaxanthone‐5,5′‐dioxide, were prepared and characterized by spectral methods. The polybenzimidazoles have inherent viscosities in the range 1.13–1.50 dL/g and decomposition temperatures of 495–560°C. The effect of thiaxanthone units on polymer properties are discussed.
Polymérisation radicalaire du pentadiène‐1,3. II. Microstructure des résidus pentadiéniques dans les homo‐ et copolymères des cis et trans pentadiènes‐1,3 avec l'acrylonitrile
Authors: Petit A. , Cung M. T. , Neel J. 
Published: April 2003

AbstractThe microstructure of diene units was investigated in radical homopolymers of the cis and trans isomers of 1,3‐pentadiene and copolymers with acrylonitrile, synthetized in bulk and emulsion. Experiments were carried out by infrared spectroscopy, 100 MHz 1H‐NMR, and 25 MHz 13C‐NMR studies. No difference between the bulk and emulsion samples was noted. The microstructure of poly(1,3‐pentadiene) is practically independent of the cis or trans configuration of the diene monomer and is as follows: 56–59% trans‐1,4, 15–17% cis‐1,4, 16–20% trans‐1,2 7–10% cis‐1,2 and 0% 3,4. On the other hand, up to about 30% of incorporated acrylonitrile (10% in the feed), the microstructure of the pentadiene fraction in the copolymers is not affected. This finding suggests that the penultimate unit has very little influence on the polymerization process involving the terminal pentadienly unit. Beyond 10% of acrylonitrile in the feed, the proportions of the structural units were linearly dependent upon the acrylonitrile content: trans‐1,4 content increased whereas the amounts of cis‐1,4 trans‐1,2 and cis‐1,2 decreased (except the cis‐1,2 fraction, constant in the copolymers from the cis‐diene). These results are discussed on the assumption that the microstructure of pentadiene residues is strongly associated with the acrylonitrile comonomer in the feed.
Emulsion polymerization: On the characterization of the particle size distribution
Authors: Chen Show‐An , Wu Kuo‐Wei 
Published: April 2003

AbstractIn emulsion polymerization, the polymer particles generated exhibit a size distribution. Broadness of the distribution is usually characterized by the uniformity (Dp), a ratio of weight to number average particle sizes, and is found to decrease with reaction time despite the fact that the particle volume distribution is usually broadened. Based on the mathematical model proposed by Lichti, Gilbert, and Napper, detailed analysis using the method of moment shows that standard deviation of the particle volume distribution increases with time, while that of the particle diameter distribution decreases with time. Dp's of both volume and diameter distributions all show decreasing with reaction time. These results are in agreement with those found experimentally. The present analysis indicates that, in the characterization of the broadness of the PSD in the emulsion polymerization, one has to be aware of the difference in meanings among these parameters related to the broadness of the PSD.
Bismaleimides chain‐extended by imidized benzophenone tetracarboxylic dianhydride and their polymerization to high temperature matrix resins
Authors: Melissaris Anastasios P. , Mikroyannidis John A. 
Published: April 2003

AbstractHeat‐resistant polymers were obtained by thermal polymerization of several bismaleimides or their substituted derivatives. The chain of the polymer precursors was extended by incorporation of imidized benzophenone tetracarboxylic dianhydride between the maleimide rings in order to impart a degree of flexibility in the polymers. The bismaleimides and their corresponding tetraamic acids were characterized by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. The differential thermal analysis (DTA) thermograms of the monomers showed exotherms at 200–340°C attributed to the thermally induced polymerization reactions. The influence of different substituents in the maleic double bond on the curing temperature was investigated. The thermal stability of the cured resins was evaluated by thermogravimetric analysis (TGA) and isothermal gravimetric analysis (IGA). They were stable up to 367–433°C both in nitrogen and air atmosphere and afforded 57–68% char yield at 800°C under anaerobic conditions. The structure of the aromatic and aliphatic diamines utilized for imidization was correlated with the thermal stability of the cured resins. The bismaleimide derived from p‐phenylenediamine gave the most heat‐resistant resin because of its higher rigidity.