bluuebunny/crossref_metadata_2025_split huggingface dataset:
The synthesis of bisitaconamic acids and isomeric bisimide monomers
Authors: Galanti Anthony V. , Liotta Franic , Keen Brian T. , Scole Daniel A. 
Published: April 2003

AbstractMembers of a series of N,N′‐alkylene bisitaconamic acids were synthesized from the reaction between itaconic anhydride and a homologous group of aliphatic diamines with the general formula H2N (CH2)n NH2, where n = 4–12. Cyclodehydration of the acids in toluene gave the isomeric imides: bisitaconimide, biscitraconimide, and citra‐itaconimide. The isomeric imides were isolated, purified, and characterized for each diaminoalkane studied.
A simplified data treatment for dead‐end and high conversion polymerization kinetics
Authors: Hill D. J. T. , O'Donnell J. H. 
Published: April 2003

AbstractA simplified approximation method for the treatment of dead‐end and high conversion polymerization kinetics is presented. The method is based on the treatment of dead‐end polymerization first described by Tobolsky. In appropriate circumstances, by contrast with Tobolsky's method, this method provides measurements of kd and kp/kt1/2 without recourse to the measurement of the monomer conversion at infinite time.Kinetic studies of free radical polymerizations are normally confined to measurements of initial rates. At low conversions the predictions of the general mechanism for chain‐growth polymerization involving initiation, propagation, and termination steps are generally obeyed. Thus the polymerization rate should be first order in the vinyl monomer and half‐order in the initiator concentrations.At high conversions, however, large deviations which can be ascribed to various effects can occur; for example, (1) the effect of the increasing viscosity of the polymerization medium on the termination rate constant kt, and possibly also on the propagation rate constant kp, which have been considered by North1 and Cardenas and O'Driscoll,2 or (2) depletion of the initiator as the polymerization progresses. This depletion will occur in all polymerizations but its significance will depend on the magnitude of the rate constant for initiator decomposition (kd) and the period of polymerization. Appropriate conditions will lead to limiting monomer conversion even after infinite polymerization time; this phenomenon has been called dead‐end polymerization by Tobolsky.3Free radical polymerizations to high conversion are particularly important in the industrial context when initial kinetics are obviously inadequate. Suitable treatment of the conversion/time relationship is highly desirable.Senogles and Woolf4 have examined the polymerization of n‐lauryl methacrylate at 60°C with 2‐azobisisobutyronitrile as initiator under dead‐end conditions.Here we propose a modification of Tobolsky's treatment of such polymerizations by using an approximation for the exponential decay in the initiator concentration. This method permits easy manipulation of the experimental data and the estimation of values for the kinetic parameters in favorable circumstances without recourse to the measurement of the conversion at infinite time or the evaluation of complicated functions of the monomer conversion. The method thus allows the duration of the laboratory experimentation to be significantly shortened and the complexity of the subsequent data analysis to be considerably reduced.
Syntheses of amphiphilic block copolymers. Block copolymers of methacrylic acid and p‐N,N‐dimethylaminostyrene
Authors: Morishima Yotaro , Hashimoto Toshihiko , Itoh Yoshihiro , Kamachi Mikiharu , Nozakura Shun‐Ichi 
Published: April 2003

AbstractAmphiphilic block copolymers consisting of methacrylic acid (MA) sequences and p‐N,N‐dimethylaminostyrene (DMS) sequences were prepared by living anionic polymerization. DMS was polymerized by lithium naphthalene in tetrahydrofuran to yield a living polymer solution, to which trimethylsilyl methacrylate (TMSM) was added to allow the block copolymerization. The conversion of TMSM was dependent on the countercation, i.e., with Na+ as counterion, no quantitative conversion was reached owing to premature termination, whereas with Li+ the conversion was quantitative. The role of the counterion was discussed in some detail in connection with self‐termination by the backbiting mechanism. The trimethylsilyl ester groups in the block copolymer were quantitatively hydrolyzed by treatment with aqueous methanol at room temperature, yielding MA sequences. The block copolymer of MA and DMS exhibited micellar properties in an aqueous solution.
Some aspects of curing novolac with hexamethylenetetramine
Authors: Aranguren M. I. , Borrajo J. , Williams R. J. J. 
Published: April 2003

AbstractCuring novolac with hexamethylenetetramine in closed molds at T = 190°C was studied. Cured products were examined with the following experimental techniques: sol fraction determination, % N fixed in sol and gel fractions, and IR spectra. The fraction of fixed N decreased from 1 to 0.5 when the hexa mass fraction was increased from 0 to 0.3 in the mixture with novolacs. A segregation of the fixed N in the sol fraction was observed. Azomethine derivatives were present, their amounts increasing with the hexa mass fraction. Curing was described by a reaction scheme similar to the one derived from studies with model phenols. A simplified scheme was adequate for the prediction of the minimum hexa amount necessary to gel the system at full conversion.
Studies of particle size distribution and adsorption of stabilizers in dispersion polymerization
Authors: Almog Yaacov , Levy Moshe 
Published: April 2003

AbstractThe conditions for obtaining stable dispersions of 10‐μ droplets of monomer in an aqueous phase using steric and electrostatic stabilizers, were studied. The nature and concentration of the surfactant in the aqueous phase has an important effect on the size of the droplets and the stability of the dispersion during the polymerization reaction. The amount of polyvinylalcohol adsorbed on the interface was measured and the rate of desorption was shown to be very slow. It was also shown that sodium dodecyl sulfate, on the other hand, is more readily desorbed. These findings have an effect on the amount of the submicron emulsion particles formed during the polymerization process.
Polymer‐supported phosphines: Reactivity of pendant and crosslink groups
Authors: McKenzie W. M. , Sherrington D. C. 
Published: April 2003

AbstractTwo groups of phosphine‐containing resins were prepared by bead copolymerization. In one the phosphine residues were introduced as pendant groups with p‐styryldiphenylphosphine, whereas in the other the phosphine residues were located specifically at crosslinked points with bis(p‐styryl)phenylphosphine. Both groups of resins were used to convert alcohols to alkyl chlorides in the presence of carbon tetrachloride and benzaldyhyde to benzal chloride and β,β‐dichlorostyrene. In the first reaction an increase in the crosslink ratio of the support reduced the reactivity of the resins, although both octanol and octadecanol substrates behaved similarly. No clear difference emerged between resins with pendant phosphine groups and those located on crosslinks and the absence of a strong substrate size effect or substrate selectivity with both series of resins was apparent. The production of benzal chloride and β,β‐dichlorostyrene requires interaction of two phosphine residues to generate the reactive intermediate, and inhibition of phosphine–phosphine interactions in these highly crosslinked networks does indeed inhibit this reaction. Again both series of resins behaved similarly. Among the possible routes by which PPh3/CCl4 converts alcohols to chlorides one involving phosphine‐phosphine interactions must also be inhibited in these supported systems.
The solubility of cellulose in liquid ammonia/ammonium thiocyanate solutions: Thermoreversible gelation and a preliminary report on fiber formation
Authors: Hudson Samuel M. , Cuculo John A. 
Published: April 2003

AbstractThe melting temperatures of thermoreversible gels formed from solutions of cellulose in liquid ammonia/ammonium thiocyanate mixtures were measured over a volume fraction range of .01–.004. Three samples of cellulose with Mw ranging from 1 × 105 to 1.64 × 105 were used. The findings show that the structural makeup of the gels is strongly reflected in their time‐dependent behavior. The reciprocal of their melting temperature is a nearly linear function of the logarithm of the cellulose concentration. The relation between the logarithm of Mw and the reciprocal temperature of gel melting was also nearly linear. Exothermic heats of reaction ranging from 150 to 460 kcal/mol were calculated from the Ferry‐Eldridge relationship (∂ ln C/∂) = ΔHx/R for the formation of cross‐links, assuming that they result from a binary association of chains. It is inferred that the cross‐linking loci in the gel were crystallites that consisted of glucose units. In addition, an initial study is reported of the fiber‐forming potential of the liquid ammonia/ammonium thiocyanate system. Rudimentary fiber extrusion from a modified syringe was readily demonstrated. Operable coagulation systems involved proton‐donating agents as well as methanol. Tenacities of these unstretched, as spun fibers, ranged as high as 0.89 g/d.
Interaction between dyes and polyelectrolytes. XIII. Effect of dye aggregation on the excitation energy transfer between bound dyes
Authors: Shirai Masamitsu , Ohyabu Motoshi , Ono Yoshiki , Tanaka Makoto 
Published: April 2003

AbstractEffect of polyanions on the aggregation of methylene blue (MB) was investigated spectrophotometrically. The following polyanions were used: potassium poly(vinyl sulfate), potassium poly(styrenesulfonate), sodium poly(methacrylate), and sodium poly(acrylate). The state of aggregation was largely dependent on the kind of polyanion and polyanion‐MB ratio. MB‐photo‐sensitized isomerization of cis‐p‐(phenylazo)phenyltrimethylammonium iodide(cis‐PTA) to the transisomer was used advantageously to investigate the effect of dye aggregation on the triplet excitation energy transfer between cationic dyes bound to polyanions. Although the efficiency of the excitation energy transfer between MB and cis‐PTA was enhanced by the addition of polyanions, the formation of highly aggregated MB reduced the efficiency of the excitation energy transfer. Correlation with the dye aggregation induced by polyanions and the efficiency of excitation energy transfer between dyes was discussed.
Studies on polyyne polymers containing transition metals in the main chain. VII. Synthesis and characterization of palladium‐polyyne polymers
Authors: Takahashi S. , Morimoto H. , Murata E. , Kataoka S. , Sonogashira K. , Hagihara N. 
Published: April 2003

AbstractMetal‐polyyne polymers consisting of palladium and conjugated acetylenic systems,
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where PD and R represent the —Pd(PBu3)2—moiety and alkyl groups, respectively, were prepared by polycondensation between palladium chlorides and α,ω‐diethynyl compounds in amines using a catalytic amount of cuprous iodide. The molecular weights of the polymers formed were greatly affected by the basicity of the amines and the addition of free phosphines to the polymerization system. Under the optimum conditions, i.e., in the presence of CuI and PBu3 (in molar ratio 1/4) in piperidine at room temperature, polymer Ia (R1 = R2 = H) having M̄w = 29,000 was obtained.
Vinyl polymerization initiated by peroxydiphosphate. V. Polymerization of acrylonitrile initiated by peroxydiphosphate‐cyclohexanol redox system in the presence of silver ion
Authors: Lenka Subasini , Dhal Akshaya K. 
Published: April 2003

AbstractThe polymerization of acrylonitrile was carried out using peroxydiphosphate‐cyclohexanol redox system in the presence of silver ion. The rate of polymerization increases with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. The rate of polymerization increases with increasing monomer concentration and the monomer exponent was computed to be unity. The plot of Rp vs [Ag+]1/2 was linear, indicating 0.5 order with respect to [Ag+]. The reaction was carried out at three different temperatures and the overall activation energy was calculated to be 7.60 kcal/mol. The effect of certain surfactants on the rate of polymerization has been investigated and a suitable kinetic scheme has been pictured.
Intramolecular charge transfer complexes. VIII. Poly[N‐(2‐hydroxyethyl) carbazolyl acrylate‐co‐2,4‐dinitrophenyl methacrylate]
Authors: Simionescu C. I. , Percec V. , Natansohn A. 
Published: April 2003

AbstractRadical copolymerization of N‐(2‐hydroxyethyl) carbazolyl acrylate (HECA, M1) with 2,4‐dinitrophenyl methacrylate (DNPM, M2) can be described by a simple terminal mechanism having the relative reactivities r1 = 0.14, r2 = 1.10 (at 60°C); 0.28, 0.96 (80°C); and 0.41, 0.79 (100°C), respectively. The dependence of the reactivity ratio values on copolymerization temperature, analyzed by Arrhenius equation, takes place mainly through the frequency factor. The copolymers obtained are intramolecular charge transfer complexes. The intramolecular interaction is evidenced by the shift of the aromatic protons from the DNPM structural unit in the copolymers' 1H‐NMR (nuclear magnetic resonance) spectra. This shift depends on sequence distribution and chain conformation, but is not affected by the copolymerization temperature.
Polybenzimidazoles containing anthracene photodimer
Authors: Niume K. , Toyofuku K. , Toda F. , Uno K. , Hasegawa M. , Iwakura Y. 
Published: April 2003

AbstractPolybenzimidazoles that contained anthracene photodimer were prepared. The molecular weights of the polymers prepared by the photopolymerization of bis‐anthrylbenzimidazoles were limited by the precipitation of the resulting polymers from the reaction organic solvents. Higher molecular weight polymers were obtained by the photopolymerization of bis‐anthryl‐Schiff's bases, followed by the oxidation of the resulting polymers. These polymers were soluble in acidic solvents such as formic and sulfuric acids but were insoluble in organic solvents.
Mixed ligand complexes in vinyl polymerization. I. [N,N′‐ethylenebis (salicylideneiminato)](acetylacetonato)cobalt(III) as an initiator
Authors: Thiagarajan R. , Kalpagam V. , Nandi U. S. 
Published: April 2003

AbstractPolymerization of methyl methacrylate in the presence of a mixed ligand complex, [N,N′‐ethylenebis(salicylideneiminato)](acetylacetonato)cobalt(III) in benzene was studied. The rate of polymerization was proportional to the square root of the concentration of the chelate and the monomer exponent was 1.67 and 1.69 at 60 and 70°C, respectively. The activation energy and the kinetic and transfer constants were evaluated. A free‐radical mechanism has been proposed.
Preparation and properties of ordered and random polyamide‐esters from 4‐(4‐amino‐α,α‐dimethylbenzyl)phenol and aromatic diacyl chlorides
Authors: Imai Yoshio , Abe Shigemitsu , Takahashi Takeyoshi , Ueda Mitsuru 
Published: April 2003

AbstractRandom polyamide‐esters were prepared directly by the interfacial and solution polycondensation of 4‐(4‐amino‐α,α‐dimethylbenzyl)phenol (I) with iso‐ and terephthaloyl chlorides. Authentic samples of ordered polyamide–esters with an amide‐amide–ester‐ester structure were synthesized by the two‐step procedure; that is, the preparation of amide–bisphenol monomers from I and subsequent polycondensation with aromatic diacyl chlorides. The random and ordered polyamide–esters differed from one another with respect to solubility in organic solvents and glass transition temperature, whereas all the random and ordered polymers were of equal low crystallinity. All of these polymers began to decompose around 350°C in both air and nitrogen atmospheres.
The chemistry and kinetic behavior of Cu‐Cr‐As/B wood preservatives. III. Fixation of a Cr/As system on wood
Authors: Pizzi A. 
Published: April 2003

AbstractThe kinetic behavior of a Cr/As system in its reaction with wood is described, as are its reactions with lignin and carbohydrates of wood for CrVI alone. ChromiumIII arsenate complexes with the guaiacyl units of lignin, as well as the usual chromic acid/guaiacyl unit complexes already characterized, was formed. The interference of As concentration on the various zones of fixation of chromium are identified. Complexes between guaiacol and chromium arsenates indicate that in this Cr/As system CrIII can also be linked to the guaiacyl units of lignin when in the form of CrAsO4·6H2O contrary to what obtained with systems not containing As. An initial increase in the rate of reduction CrVI → CrIII by the carbohydrates fraction in wood is ascribed to the catalytic effect of the arsenic. The percentages of chromium fixed onto lignin and cellulose of wood compare well with experimental values.
Some of the dielectric properties of cotton cellulose and viscose
Authors: Moteleb M. M. Abdel , Naoum M. M. , Shinouda H. G. , Rizk H. A. 
Published: April 2003

AbstractComplex dielectric constants were measured at frequencies of 0.1–10,000 kc/s over the temperature range of 0–60°C in medicated cotton cellulose and viscose. In these fibers evidence is found for a new secondary relaxation process within the frequency region of 0.1–1 kc/s. The significance of the results is discussed.
Some 1‐substituted quaternary imidazolium compounds and related polymers: Qualitative and quantitative infrared analysis
Authors: Petrak K. , Degen I. , Beynon P. 
Published: April 2003

AbstractIt was found that 1‐substituted quaternary imidazolium compounds show some characteristic infrared (IR) activity. On quarternization of 1‐substituted imidazoles strong absorption bands appeared at about 1150 and 1550 cm−1 in the IR spectra of these compounds. The band at 1150 cm−1 was assigned to the position 2 C−H bending mode and the 1550 cm−1 band was attributed to a ring vibration mode of the quaternary imidazolium compounds. The concentration of the quaternary imidazolium units in a polymer can be determined by measuring the intensity of the absorption bands at 1150 or 1550 cm−1 in relation to another suitable absorption band of the spectrum.
A free‐volume model for photopolymerizable/cross‐linkable dry‐film systems
Authors: Molaire Michel F. 
Published: April 2003

AbstractA photopolymerizable/cross‐linkable dry‐film system is generally a compatible mixture of three main ingredients: a preformed polymeric binder, a multifunctional polymerizable monomer, and a photoinitiating system. The photographic speed of systems sensitized with certain free‐radical sensitizers which undergo intermolecular hydrogen‐abstraction (e.g., benzophenone/Michler's ketone) is proportional to the excess fractional free volume (Vf − Vfg), of the dry coating. Free‐volume dependence appears to be determined by the molecular size or configuration of the actual initiating species. We used as a working model the copolymer system poly[4,4′‐isopropylidenediphenylene‐1,1,3‐trimethyl‐3‐phenylindan‐5,4′‐dicarboxylate:azelate] and tri(6‐acryloyloxyhexyl)‐1,3,5‐benzenetricarboxylate as the polymerizable/cross‐linkable monomer. A mathematical model based on experimental data and the free‐volume theory was developed. The photographic speed of a photopolymerizable/cross‐linkable dry‐film system suffering from free‐volume dependence can be correlated with the glass transition temperatures of the polymeric binder and the monomer, the volume fraction of the monomer, and the temperature of exposure.
Kinetics and mechanism of the anionic polymerization of cyclohexadienes initiated by naphthalene radical anions and dianions
Authors: Sharaby Z. , Jagur‐Grodzinski J. , Martan M. , Vofsi D. 
Published: April 2003

AbstractThe anionic polymerization of 1.3‐cyclohexadiene (1.3‐CHD) was investigated in temperatures that ranged from 25 to −77°C. Initiation by lithium naphthalene (N−·,Li+) in tetrahydrofuran at −20°C yields polymers with fairly narrow molecular weight distribution. The M̄w of these polymers so prepared is ca. 20,000. Polymerization of 1.3‐CHD conducted at room temperature is accompanied by the dehydrogenation and disproportionation of the monomer, especially when N−·,K+ acts as initiator. Oligomers are formed when hexamethylphosphoramide is used as a solvent. The mechanism of the initiation of the polymerization of 1.3‐CHD by N−·,Li+ was elucidated and the rate constants at −20°C in tetrahydrofuran of the elementary reactions were determined. It was established that the dianions formed by disproportionation of N−·,Li+ act as effective initiators for 1.3‐CHD. The adducts formed constitute the cyclohexanyl and naphthyl carbanionic groups. The former carbanions (λmax ∼ 275 nm) propagate the polymerization. The initially formed dimeric adducts are stabilized by the separation of the carbanionic end groups by the additional monomer units. Chain transfer to the monomer limits the growth of the polymers. The isomerization of the cyclohexadienyl anions, formed as result of chain transfer, may be followed by the elimination of lithium hydride. The latter reaction represents a termination step. Addition of 1.4‐CHD to the reaction mixture enhances the chain transfer and the termination.
Amylose–polyester block copolymers
Authors: Lee K. S. , Stannett V. T. , Gilbert R. D. 
Published: April 2003

AbstractThe synthesis of amylose–polyester block copolymers is described. 2,3,6‐Tri‐0‐allyl amylose was synthesized by amylose alkoxide and allyl bromide and hydrolyzed by hydronium ions to give an hydroxyl‐terminated allyl amylose oligomer (HTAA). The allyl groups were isomerized with t‐BuoK to yield the prop‐1‐enyl isomer (HTPA). The HTPA was capped with a diisocyanate. The HTPA prepolymer was reacted with hydroxy‐terminated poly(ethylene‐co‐propylene adipate) and poly‐(ethylene terephthalate) to form block terpolymers. Block terpolymer formation was demonstrated by intrinsic viscosity increases, gel permeation chromatographic results, and infrared (IR) and PMR spectroscopy. The products were depropenylated by HgCl2 to yield amylose block terpolymers. These polymers were readily degraded by α‐amylase.
Thermal degradation study of isotactic polypropylene using factor‐jump thermogravimetry
Authors: Dickens Brian 
Published: April 2003

AbstractThe degradation of isotactic polypropylene in the range 390–465°C was studied using factor‐jump thermogravimetry. The degradations were carried out in vacuum and at pressures of 5 and 800 mm Hg of N2, flowing at 100–400 standard mL/s. At 800 mm Hg this corresponds to linear rates of 1–4 mm/s. In vacuum bubbling in the sample caused problems in measuring the rate of weight loss. The apparent activation energy was estimated as 61.5 ± 0.8 kcal/mol (257 ± 3 kJ/mol). In slowly flowing N2 at 800 mm Hg pressure the activation energy was 55.1 ± 0.2 kcal/mol (230 ± 0.8 kJ/mol) for isotactic polypropylene and 51.1 ± 0.5 kcal/mol (214 ± 2 kJ/mol) for a naturally aged sample of atactic polypropylene. For isotactic polypropylene degrading at an external N2 pressure of 5 mm Hg the apparent activation energy was 55.9 ± 0.3 kcal/mol (234 ± 1 kJ/mol). A simplified degradation mechanism was used with estimates of the activation energies of initiation and termination to give an estimate of 29.6 kcal/mol for the ß‐scission of tertiary radicals on the polypropylene backbone. Initiation was considered to be backbone scission ß to allyl groups formed in the termination reaction. For initiation by random scission of the polymer backbone, as in the early stages of thermal degradation, an overall activation energy of 72 kcal/mol is proposed. The difference between vacuum and in‐N2 activation energies is ascribed to the latent heat contributions of molecules which do not evaporate as soon as they are formed. At these imposed rates of weight loss the average molecular weights of the volatiles in vacuum and in 8 and 800 mm Hg N2 are in the ratios 1–1/2–1/9.