bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation‐induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. III. A kinetic study
Authors: Bhattacharyya S. N. , Maldas D. 
Published: April 2003

AbstractThe kinetics of graft copolyermization of styrene and acrylamide from their binary monomer mixtures onto gamma‐irradiated cellulose acetate film was studied. The extent of grafting increased with a rise in reaction time and temperature. The nature of the radical site on the trunk polymer was acertained in a study of grafting at different temperatures when the trunk polymer was irradiated in the presence and absence of oxygen. The character of the radical was tested further in a study of the ESR spectrum. The variation in grafting rates and energies of activation required for graft copolyermization at various mole ratios of the monomers was observed. The grafting rates showed a maximum at 1:1 mol ratio of monomers which was also associated with minimum energy of activation. The Kkt values in the system were dependent on the composition of monomers.
Liquid crystal polymers. 15. Synthesis and liquid crystalline properties of alkyl‐substituted polyesters
Authors: Zhou Qi‐Feng , Lenz Robert W. 
Published: April 2003

AbstractAlkyl substitution in a series of main chain, liquid crystal polyesters strongly depressed their glass temperatures, melting points, clearing points, and mesophase thermal stabilities. Polymers with pendant n‐alkyl substituents eight carbon atoms or longer did not form a liquid crystal phase.
The effect of ammonium polyphosphate on the mechanism of thermal degradation of polyureas
Authors: Montaudo G. , Scamporrino E. , Vitalini D. 
Published: April 2003

AbstractThe thermal decomposition of structurally related N–H and N,N′‐disubstituted polyureas (Table I) and their mixtures with ammonium polyphosphate (APP) was investigated by thermogravimetry (TG) and direct pyrolysis in a mass spectrometer (MS). The N–H polyureas (IV–VI) undergo a quantitative depolymerization process with the formation of oligomers with amine and isocyanate end groups. In contrast, the thermal degradation of the N,N′‐disubstituted polyureas (I–III) proceeds by a different mechanism as a function of their chemical structure. The addition of APP lowers the thermal stability of the N,N′‐disubstituted polyureas, whereas that of the N–H polyureas is unaltered. However, our data show that APP does not change the nature of the pyrolytic products. The destabilizing effect of the additive can be attributed to the catalytic action of the acid species formed by its thermal decomposition.
Effect of sulfur on the electrical conductivity of FEF‐loaded SBR during swelling
Authors: Amin M. , Hassan H. H. , Nasr G. M. 
Published: April 2003

AbstractFollowing a series of experiments on the effect of different factors of the electrical conductivity of carbon‐black‐loaded styrene butadiene rubber, an attempt was made to study the effect on electrical conduction of changing the sulfur content. It was found that an optimum sulfur content leads to a swelling‐resistant composite with good electrical insulation. This was done for dry as well as wet specimens of rubber.
Intumescent flame retardants for polymers. II. The polypropylene‐ammonium polyphosphate‐polyurea system
Authors: Montaudo G. , Scamporrino E. , Vitalini D. 
Published: April 2003

AbstractThe mechanism of action of ammonium polyphosphate (APP) and polyurea (PU) as flame retardant (FR) agents for polypropylene (PP) was examined. The APP–PU system behaves as an intumescent flame‐retardant (IFR) formulation. Comparison of the oxygen index (OI) measured on molded pellets and rods, values of the polymer temperature measured just below the burning surface, and visual considerations describe the IFR action of this system. A strong synergism between APP and two of the four polyureas investigated here was ascertained with a maximum 3:1 ratio. Thermogravimetric (TG), OI, nitrous oxide index (NOI), and char‐residue measurements were made. On the basis of our data, it can be concluded that polyurea acts as a catalyst for the charring reactions of the APP on PP.
Spectroscopic investigation of organosilicon polymers. I. Vibrational analysis of poly(tetramethyl‐p‐silphenylene‐siloxane)
Authors: Neto N. , Sbrana G. , Muniz‐Miranda M. , Dobos S. , Zelei B. , Harsányi L. 
Published: April 2003

AbstractThis article is a detailed, normal coordinate analysis of an isolated chain of poly(tetramethyl‐p‐silphenylene‐siloxane), based on results obtained for the corresponding monomer and a recent x‐ray structure. Predicted vibrational frequencies are compared with new experimental infrared (IR) and Raman data obtained from powder and well oriented films. Vibrational spectra were also obtained for a deuterio derivative in which all hydrogens in the benzene rings were replaced with deuterium atoms. The results indicate that an intermode mixing occurs between vibrations of the ring and the saturated part which lead to low frequency normal modes characteristic of the chain. The simplified valence force field obtained for this polymer should provide a useful tool for understanding the vibrational spectra of other members of the class of polysiloxanes.
Charge transfer polymerization of 2‐vinyl pyridine initiated by n‐butyl amine and carbon tetrachloride
Authors: Gogoi A. K. , Dass N. N. 
Published: April 2003

Abstract2‐Vinyl pyridine (2‐VP) can be initiated by a charge‐transfer complex formed by the interaction of aliphatic amines such as n‐butylamine (nBA) and carbon tetrachloride (CCl4) in a solvent like NN‐dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). This article describes the polymerization of 2‐VP by n‐butylamine (nBA) in the presence of carbon tetrachloride in DMSO at 60°C. The rate of polymerization Rp increases rapidly with carbon tetrachloride (CCl4) up to a concentration of 3.93 mol/L, but for a higher concentration it is almost independent of the carbon tetrachloride concentration; Rp is proportional to [nBA]0.5 and [2‐VP]1.5 when [CCl4]>[nBA]. The average rate constant k is 1.03 × 10−5 L/mol s. When [CCl4] < [nBA] the rate constant in terms of [2‐VP] was 1.06 × 10−5 s−1 at 60°C and the overall rate constant was 1.035 × 10−5 L/mol s at 60°C.
New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). XXX. Synthesis and quantitative terminal functionalization of α,ω‐diarylpolyisobutylenes
Authors: Kennedy Joseph P. , Hiza Misao 
Published: April 2003

AbstractNovel aromatic‐telechelic polyisobutylenes were prepared and characterized: α,ω‐diphenylpolyisobutylene, α‐phenyl‐ω‐tolylpolyisobutylene, and α,ωditolylpolyisobutylene. The syntheses involved the preparation of asymmetric telechelic prepolymers (α‐phenyl‐ω‐tert‐chloropolyisobutylene and α‐tolyl‐ω‐tert‐chloropolyisobutylene) by the minifer method and quantitative alkylation of benzene and toluene by the prepolymer. The terminal aromatic rings of these telechelic polyisobutylenes were quantitatively nitrated, acetylated, and chlorosulfonated and a series of further novel telechelic products was obtained. Characterization of these derivatives provided additional proof for the telechelic structure of the starting prepolymers. The quantitative reduction of nitroaryl‐telechelic polyisobutylene by SnCl2/HCl led to aminoaryl‐telechelic polyisobutylene which was used to cure bisphenol‐A diglycidyl ether. These new flexible epoxy networks exhibited outstanding heat and hydrolytic stability combined with satisfactory mechanical properties.
Plasma polymerization. X. A systematic investigation of materials synthesized in inductively coupled plasmas excited in tetrafluoropyridazine
Authors: Clark D. T. , Abu‐shbak M. M. 
Published: April 2003

AbstractA detailed investigation was made by ESCA of the gross structural features and chemical composition of ultrathin plasma polymer films prepared from tetrafluoropyridazine. The data reveal evidence of extensive rearrangement that accompanied polymerization and that the C:F and C:N stoichiometries of the polymer films were similar to those of the starting monomer. From an initially high contact angle with water the surfaces became completely wettable with time and this is attributed to surface hydrolysis. A comparison is made between surface and bulk compositions. Brief consideration is also given to sleeve effects.
Cationic polymerization of 1,4,6‐trioxaspiro [4,4]‐nonane
Authors: Matyjaszewski Krzysztof 
Published: April 2003

AbstractCationic polymerization of 1,4,6‐trioxaspiro [4,4]‐nonane (1) with (CH3)3O+SbF6−(2) and CH3OSO2CF3(3) initiators has been investigated. Although the observed rates of initiation and propagation are relatively slow, they consist of rapid reversible elementary reactions. In 1H‐NMR spectra, a broadening of the monomer signal was observed, indicating a fast exchange between “free” monomer and monomer engaged in the active species. The variety of orthoester bonds were observed in the polymer formed at the early stages of monomer conversion. The final polymer has, however, structure of a linear poly(ester–ether) including two subsequent ester or ether linkages. To account for these new facts, the mechanism of polymerization was proposed, consisting of a rapid reversible opening of one of the rings in the monomer molecule involved in the growing species, followed by the slower opening of the second ring with formation of the ester linkages. It appears that the rings originally present in the chains rearrange into the linear units intramolecularly.
Radiation‐induced copolymerization of phenylvinyl alkyl ethers and maleic anhydride
Authors: Ranogajec F. , Vuković R. , Fleš D. 
Published: April 2003

AbstractAlternating copolymers of phenylvinyl ethyl ether (I) and phenylvinyl sec‐butyl ether (II) with maleic anhydride (MAn) were prepared in bulk or in benzene solution by high‐energy irradiation at dose rates of 42, 160, and 540 Gy/h, respectively. The overall energies of activation in copolymerization of I and II with MAn were 15.5 and 18.8 kJ/mol, respectively. The reaction proceeds by the free‐radical mechanism and was found to be largely dependent on the bulkiness of the alkyl group. In the copolymerization of I and MAn, the molecular weight increases with conversion. By applying the model described by Shirota and co‐workers, it was established that participation of charge‐transfer‐complex monomers increases with the increase of the total monomer concentration and with the bulkiness of the alkyl group in electron donor monomer.
Photoinitiation of cationic polymerization. III. Photosensitization of diphenyliodonium and triphenylsulfonium salts
Authors: Pappas S. Peter , Gatechair Leslie R. , Jilek Josef H. 
Published: April 2003

AbstractPhotoinitiated cationic polymerization by photosensitization of diphenyliodonium and triphenylsulfonium salts is shown to proceed by two distinct electron transfer process: (1) direct electron transfer from excited‐state photosensitizers and (2) indirect electron transfer from photogenerated radicals. The efficiency of the former process is attributed to the instability of the reduction products (from diphenyliodonium and triphenylsulfonium salts), which dissociate in competition with undergoing energy‐wastage reverse electron transfer. Amplification of photons in the production of protons (or other reactive cations) is postulated to account for the high quantum yields observed in the latter process. Potential advantages of utilizing the indirect redox process in the design of UV curable hybrid systems, which contain functionality for both radical and cationic polymerization, are noted. The results also provide evidence against the importance of triplet states of the onium salts in photoinitiator activity.
Attempted polymerization of substituted pipecolic acid NCA's: Dimerization and mechanism
Authors: Shalati Mohamad D. , Overberger C. G. 
Published: April 2003

AbstractRacemic and optically active N‐carboxyanhydrides (NCA)s of 2‐methyl‐ and cis‐6‐methylpipecolic acid, when subjected to polymerization conditions in solution or in bulk whether with “weak” or “strong” base initiators, resisted polymerization under all conditions tried. Instead, the NCA of 2‐methylpipecolic acid gave the corresponding cyclic dipeptide and the NCA of cis‐6‐methylpipecolic acid formed the cyclic dipeptide derived from trans‐6‐methylpipecolic acid. The mechanism of dimerization of these NCA's was investigated. Evidence was provided for the proposed mechanism in which the active moiety is not a carbamate ion but an amino group. Methyl 2‐methylpipecolate underwent an intermolecular SN2‐type reaction upon heating, yielding equimolar quantities of methyl N‐methyl‐2‐methylpipecolate and 2‐methylpipecolic acid.
The binding of organic anions by polyvinylpyrrolidone: Determination of intrinsic binding constant and number of binding sites by competitive binding
Authors: Takagishi Toru , Yoshikawa Kiyoaki , Kuroki Nobuhiko , Kozuka Hiroshi , Mitsuishi Masaru 
Published: April 2003

AbstractThe binding of 4′‐dibutylaminoazobenzene‐4‐sulfonate (butyl orange, BO) and 1‐amino‐4‐methylaminoanthraquinone‐2‐sulfonate (AQ) by crosslinked polyvinylpyrrolidone and the competition between BO and AQ for binding sites of the polymer were examined. The equilibrium data showed competitive binding. Thus the intrinsic binding constants and the number of binding sites can be evaluated easily and precisely by competitive binding. The thermodynamic parameters that accompained the binding were calculated from the intrinsic binding constant and its temperature‐dependence. The thermodynamic data for BO showed that the binding process is athermal and stabilized entirely by the entropy term. The binding of BO to the polymer is entropically favorable as a result of the operation of the hydrophobic effect. In contrast, with AQ a favorable free energy for a dye‐polymer complex formation is associated with a large negative enthalpy and a small entropy. Therefore it is likely that the binding of AQ occurs by energetic forces and that the large aromatic ring of the dye contributes to the binding energy. On the average, BO and AQ can bind to the crosslinked polymer to the extent of 1 dye/ca 73 basemol in 0.1M tris‐acetate buffer, pH 7.0.
Organosilane polymers: Formable copolymers that contain methyl(β‐phenethyl)silylene or cyclohexyl(methyl)silylene units
Authors: Zhang Xing‐Hua , West Robert 
Published: April 2003

AbstractHigh molecular weight polysilane copolymers which contain the units in the title were prepared in high yield by sodium coupling the corresponding organodichlorosilanes in toluene. These copolymers are highly soluble in common solvents and can be drawn into fibers or formed into films by molding or casting. They are also photoactive.
Thermoplastic resins, polyquats, and membranes based on epoxies
Authors: Renner Alfred , Michaelis Klaus Peter 
Published: April 2003

AbstractHigh‐molecular‐weight branched‐addition polymers made from oligomeric solid epoxy resins and amines carrying two active hydrogen atoms are described. The reaction with aliphatic amines like ethanolamine, 2‐ethylhexylamine, or piperazine can easily be controlled carrying out the polymerization in about 15% solutions of boiling 2‐methoxyethanol. Less basic derivatives of aniline and epoxy resins are processed at 200°C in the molten state. Polymers with Mn up to 33,000 and Mw to 720,000 are obtained. Properties of films and injection moldings are described. The tertiary nitrogen atoms present in the polymer chain can be quaternized with alkylating agents, like dimethylsulfate, methyliodide, or trimethyl phosphate. Thin membranes cast from the polyquats thus obtained exhibit a good flow rate for water and a high salt rejection under reverse osmosis conditions.
A Mössbauer study of polymers prepared from polyvinylpyridine and ferric chloride or ferric nitrate
Authors: Coey J. M. D. , Meagher A. , Kelly J. M. , Vos J. G. 
Published: April 2003

AbstractIron‐ion‐containing polymers were prepared by reacting atactic polyvinylpyridine with ferric chloride or ferric nitrate in methanol solution. Molar ratios of Fe3+ to 4‐vinylpyridine (Fe:PVP) were 1:2, 1:6, and 1:20. Three kinds of iron center were characterized from 57Fe Mössbauer spectra recorded over a temperature range of 4.2–290 K. Infrared (IR) spectra of the samples were measured also. All samples contained amorphous hydrated ferric‐oxide particles that exhibited superparamagnetic behavior at low temperatures. The size of the clusters (102–103 iron atoms per particle) was estimated from the average blocking temperatures TBav, which is sensitive to the Fe:PVP ratio. For FeCl3:PVP preparations with Fe:PVP of 1:2, 1:6, and 1:20 TBav was 37, 10, and <4 K, respectively. A small proportion (<10%) of high‐spin ferrous iron centers was found in most samples. A third type of signal attributable to oxygen‐bridged ferric dimers was found in FeCl3–PVP preparations with Fe:PVP of 1:2 or 1:6 but not in Fe(No3)3–PVP samples. This species is probably [Cl3FeOFeCl3]2−. Interactions between the polymer and the various iron centers were weak.
Studies on heat‐resistant poly(metal phthalocyanine)‐imide copolymers
Authors: Achar B. N. , Fohlen G. M. , Parker J. A. 
Published: April 2003

AbstractSeveral new poly(metal phthalocyanine)imide copolymers have been prepared using 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BPTDA), metal(11) 4,4′,4″,4″′‐phthalocyanine tetraamines (MPTA), p‐phenylenediamine, 4,4′‐methylenedianiline, and 9,9‐bis(4‐aminophenyl)‐fluorene (BAF). The attractive feature of these polymers is their high thermooxidative and thermal stability. The polymer decomposition temperatures of all the imide copolymers are greater than 500°C in air and N atomspheres. Another noteworthy property is their high char yield: 60–78% at 800°C in a N2 atmosphere. Variation of the metal phthalocyanine concentration has a remarkable effect on the thermal stability and degree of polymerization. The most preferred molar proportion of the reagents MPTA, diamine, and BTDA is 1.25:7.5:10. These polymers may be useful in the preparation of heat‐resistant films and fibers.
Synthesis and characterization of poly(ethylene glycol) derivatives
Authors: Harris J. Milton , Struck Evelyn C. , Case Martha G. , Paley M. Steven , Yalpani Manssur , Van Alstine James M. , Brooks Donald E. 
Published: April 2003

AbstractFive general routes for the preparation of polyoxyethylene [generally referred to as poly(ethylene glycol) or PEG] derivatives are described. These routes are (1) nucleophilic displacements with the alkoxide of PEG, (2) nucleophilic displacement on PEG–tosylate, –mesylate, or –bromide, (3) reductive amination of PEG–aldehyde, (4) reductive amination of PEG–amine, and (5) nucleophilic displacements on the s‐triazine derivatives prepared from s‐triazine trichloride (cyanuric chloride) and PEG. Eighteen derivatives are prepared and potential applications to catalysis, cell purifications, and other areas are discussed briefly.
IBMA–metal containing polymers
Authors: Gunesin B. Z. , Schulz D. N. , Kang J. W. , Cain A. R. , Hamed G. R. 
Published: April 2003

AbstractA new convenient route to metal containing polymers is described. This method involves emulsion co(ter) polymerization of a polar hydrocarbon soluble monomer, N‐isobutoxymethylacrylamide (IBMA), with styrene or styrene/butadiene, followed by addition of metals. Metal incorporation is effected by latex or solution techniques. Preparative, atomic adsorption, spectroscopic, film observation, and dilute solution data are presented in support of metal complexation. Structures for the complexes are proposed.
ESCA and contact‐angle studies of the surface modification of poly(ethylene terephthalate) film: Photooxidation and aging
Authors: Peeling James , Courval Gregory , Jazzar Mohammad S. 
Published: April 2003

AbstractESCA and contact‐angle (H2O and CH2I2) measurements are used to follow changes in the surface of poly(ethylene terephthalate) film photooxidized (254 nm radiation in O2) for varying times, followed by aging for as many as three weeks or washing with water. Photooxidation occurs uniformly throughout the outermost 50 Å of the film to give a surface stoichiometry that corresponds to C10O6.6. Oxidation produces mainly carboxyl (acid) and alcohol/phenol groups, carbonyls form after extensive treatment. Low molecular weight products formed by chain scission and oxidation are removed by washing and diffuse into the bulk when aged. Oxidized products in higher molecular weight chains are not removed by washing, but can diffuse into the polymer bulk or reorient because of their chain mobility; therefore they are directed toward the polymer bulk rather than the surface. Extended photooxidation produces a stable oxidized surface more resistant to aging changes. The results are compared with those obtained for poly(ethylene terephthalate) film oxidized in an electrical discharge.
Thermal and radiation‐induced polymerizations of N‐tert‐butylacrylamide and (N‐tert‐butylacrylamide)2–ZnCl2 complex
Authors: Kiliç Soner , Baysal Bahattin M. 
Published: April 2003

AbstractThe thermal and radiation‐induced in‐source and postirradiation polymerizations of N‐tert‐butylacrylamide and (N‐tert‐butylacrylamide)2–ZnCl2 complex of this monomer were studied at various temperatures. In in‐source, solid‐state polymerizations of monomer and complex the conversion was about 95% at 21°C in about eight days. Their postirradiation polymerizations were also studied in solid state. The conversion‐time curves of these two systems show an autoacceleration as in‐source polymerization. In both types of polymerization the overall rate of polymerization of complex was higher than that of pure monomer at the same polymerization temperature. In investigations of the thermal polymerization of N‐tert‐butylacrylamide and ZnCl2‐complex it was observed that the ZnCl2‐complex system can be polymerized in air in the molten and solid state. The conversion of monomer to polymer reaches limiting values in solid state in about 1 hr. The thermal polymerization of ZnCl2‐complex in the molten state was also studied and 100% conversion was obtained in 30 min. The thermal polymerization of pure monomer was studied in vacuum and an appreciable amount of polymer was obtained in the molten state; however, the thermal polymerization of this monomer is negligible in solid state. In this work rates of polymerization for N‐tert‐butylacrylamide and (N‐tert‐butylacrylamide)2–ZnCl2 are compared under various experimental conditions and overall activation energies are calculated.