bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metal ion‐promoted hydrolyses of ligand esters in the presence of polycarboxylates
Authors: Takeishi Makoto , Watanabe Toshio , Niino Shogo , Hayama Shigeru 
Published: April 2003

AbstractCopper(II), nickel(II), cobalt(II), and zinc(II) accelerated the carboxylate‐catalyzed hydrolyses of 2,4‐dinitrophenyl isonicotinate (DNPI) and 2,4‐dinitrophenyl picolinate (DNPP). The rate enhancement effect of the metal ions in the partially neutralized poly(methacrylic acid)‐ or poly(acrylic acid)‐catalyzed hydrolysis of DNPI was greater than that in the monomeric acetate ion‐catalyzed hydrolysis of this ester. This feature of the reactions was explained by the formation of a ternary complex composed of the polymer, the metal ion, and the substrate, in which the metal ion serves as a template for the nucleophilic reaction between the carboxylate groups along the polymer chain and the coordinated substrate. In DNPP the metal ion effect on the polycarboxylate‐catalyzed hydrolysis was smaller than that on the acetate ion‐catalyzed hydrolysis. This was interpreted as the result of differences in the structure of the complex.
Synthesis and thermomechanical properties of alternating copolymers containing bisphenol‐A
Authors: Pacansky T. J. , Schank R. L. , Gruber R. J. , Brandt K. A. , Bernardo M. 
Published: April 2003

AbstractAlternating copolymers containing 4,4‐isopropylidene‐bisphenol (BPA) and comonomers with various degrees of polarity have been evaluated to find comonomer structures which provide low melt viscosity and good thermal stability. The materials were prepared by pyridine‐catalyzed nucleophilic displacement reactions similar to that for the preparation of BPA polycarbonate. The molecular weights of the polycarbonates depend on the concentration and nucleophilicity of the attacking diol and the concentration and stability of a colored pyridine‐chloroformate adduct formed during polymerization. The greatest thermal stability occurs for BPA–DMS and BPA–DEG. Thermomechanical flow measurements and Tg measurements were used to evaluate melt viscosity. The shapes and magnitudes of the Tg vs. Tf curves are sensitive to the copolymer chemical structure.
Polymerization of 2,7,8‐trioxabicyclo[3.2.1]octane and 2,8,9‐trioxabicyclo[3.3.1]nonane
Authors: Yokoyama Y. , Hall H. K. 
Published: April 2003

AbstractTreatment of 2,7,8‐trioxabicyclo [3.2.1] octane (I) with electrophilic initiators gave polyorthoester composed of five‐ (70‐86%), six‐, and seven‐ (the sum, 14‐30%) membered rings. Treatment of 2,8,9‐trioxabicyclo [3.3.1]nonane (VI) with electrophilic initiators gave mainly oligomers. Trifluoromethane sulfonic acid in dichloromethane was particularly effective for the formation of dimer, 2,8,10,16,17,18‐hexaoxatricyclo[11.3.1.1]hexadecane. The analysis of the structures of poly‐I and oligomer‐VI suggests that I and VI are polymerized through an SN1 mechanism.
New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). VII. Synthesis and characterization of α,ω‐di(hydroxy)polyisobutylene
Authors: Iván Béla , Kennedy Joseph P. , Chang Victor S. C. 
Published: April 2003

AbstractA new telechelic polyisobutylene diol, HOCH2PIBCH2OH, carrying two terminal primary hydroxyl end groups has been prepared from α,ω‐di(isobutenyl)polyisobutylene, CH2C(CH3)‐ CH2PIBCH2C(CH3)CH2, by regioselective hydroboration followed by alkaline hydrogen peroxide oxidation. Infrared (IR) spectra, 1H‐NMR analysis of the pure and silylated products, and ultraviolet (UV) spectra of phenylisocyanate‐treated diols indicate quantitative yields and two CH2OH termini per polyisobutylene chain. The viscosity of HOCH2PIBCH2OH is higher than that of the starting α,ω‐diolefin. The telechelic diol prepolymer opens new avenues to the synthesis of many new materials, e.g., polyurethanes.
Estimation of morphology of composite polymer emulsion particles by the soap titration method
Authors: Okubo Masayoshi , Yamada Akira , Matsumoto Tsunetaka 
Published: April 2003

AbstractThe occupied area (Am) of a sodium dodecyl benzene sulfonate molecule adsorbed on particles was measured by the soap titration method. The Am values are 214, 133, and 53 Å2 for poly(methyl acrylate) (I), poly(methyl methacrylate) (II), and polystyrene (III), respectively. For methyl metharylate‐styrene copolymer emulsions the additivity was established between the Am value and copolymer composition. Composite emulsion particles consisting of I/II, I/III, and II/III were prepared by seeded emulsion polymerization. For these emulsions the relationship between polymer composition at the surface layer calculated from the Am value and that in a particle calculated from the polymerization process was investigated. This relationship is remarkably affected by the order of polymerization, the hydrophilicity of polymer, the flexibility of the seed polymer, and the monomer addition method. The models of the morphology of these composite particles explain the results successfully.
Photoreactions of radicals during polyolefin photooxidation
Authors: Garton A. , Carlsson D. J. , Wiles D. M. 
Published: April 2003

AbstractPolypropylene (PP) and polyethylene (PE) peroxy radicals undergo photoreactions, but under commonly encountered photodegradation conditions these reaction rates are much lower than those of conventional radical reactions; for example, for PP peroxy radicals in noon summer sunlight at 25°C their rate of photolysis to alkyl radicals is less than one‐tenth of their rate of hydrogen abstraction from the polymer. At lower temperatures( < −10°C) or when more intense radiation is used, however, peroxy radical photolysis becomes a proportionately more important source of alkyl radicals. In addition, occurrence of photoinduced radical combination is confirmed but is shown to be important only when photolysis generates an alkyl radical sufficiently close to a peroxy radical that termination can occur before oxygen reconverts the alkyl radical to a peroxy radical. This termination mechanism therefore becomes more important for radicals generated at lower temperatures when the average separation of a radical pair is lower.
Studies on stable free radicals. XVI. Copolymerizationo of a stable N‐oxyl biradical with p‐xylylene
Authors: Fujita Takashi , Yoshioka Takao , Soma Nobuo 
Published: April 2003

AbstractSix copolymers were obtained by the reaction of a sterically hindered N‐oxyl biradical with pseudodiradical p‐xylylene using the reactivity of an N‐oxyl toward the carbon radical. The feed ratio of the N‐oxyl biradical to α‐chloro‐p‐xylene, which was used as the precursor of the pseudodiradical p‐xylylene, governed the properties of the copolymers produced. The copolymers with a terminalN‐oxyl group, were obtained when a 0.4‐1.2 molar ratio of the N‐oxyl biradical to α‐chloro‐p‐xylene. The polymerization process was also discussed.
Preparation of esters of styrene sulfonic acid and their emulsion copolymerization with isoprene
Authors: Siadat B. , Lenz R. W. 
Published: April 2003

AbstractSulfonate‐containing rubbers were prepared by emulsion copolymerization of isoprene and the secondary butyl ester of styrene sulfonic acid. Substantially gel‐free copolymers of relatively high sulfonate content were prepared. It was shown that hydrolysis of the ester copolymers with a suitable base can lead to the formation of ionically crosslinked elastomers.
Radiation‐induced polymerization at high dose rate. IV. Chloroprene in bulk
Authors: Hayashi Kanae , Tachibana Michhinori , Okamura Seizo 
Published: April 2003

AbstractBulk polymerization of chloroprene was studied at 25°C in a wide does rate range. Variations of the rate of polymerization (Rp) and molecular weight as a function of does rate were essentially the same as those in several monomers that are capab;e of radical and cationic polymerizations. The polymerization proceeds with radical mechanism at low dose rate ans with radical and cationic mechanism concurrently at high dose rate. The number‐average molecular weight of the high‐dose‐rate was ca. 2400. Microstructure of the polymers was mainly of trans‐1,4 unit with small fraction of cis‐1,4 and 3,4‐vinyl unit. Fractions of the vinyl unit and the inverted unit in trans‐1,4 sequence which increased at high does rate inflected the change of dominant mechanism of polymerization.
The characteristics of lanthanide coordination catalysts and the cis‐polydienes prepared therewith
Authors: Zhiquan Shen , Jun Ouyang , Fusong Wang , Zhenya Hu , Fusheng Yu , Baogong Qian 
Published: April 2003

AbstractThe stereoregularity of polydienes is almost the same in regard to the individual elements of the lanthanide series, whereas the activity of the Ln catalysts in diene polymerization varies from one to the other within the series. The latter may be attributed to the difference in the number of electrons that occupy the 4f orbitals. It has been proved that the polymerization of dienes with Ln catalysts under certain conditions proceeds by a “living polymer” mechanism. With regard to the polymerization of butadiene, the most active catalyst is a Nd3+species a new binary system of NdCl3‐3ROH + AlR3 has been discovered. The cis‐ 1,4 content in polybutadiene is about 97% and the 1,2 content, less than 1%. For the polymerization of isoprene with a Nd3+ catalyst system, the effects of ligand and alkyl groups in AIR3 on cis‐1,4 content (ca. 95%) in polyisoprene can be neglected. For the copolymerization of butadiene and isoprene, the cis‐1,4 contents of these two monomeric units in the copolymer are greater than 95% the reactivity ratios r1 and r2 are determined. and the Tg's of the copolymers of various compositions deviate slightly from the calculated values for random copolymers. A linear relationship exists between the yield strength from the stress‐strain curve of Ln‐polvbutadiene and its [n] This relationship is verified by Ln‐polyisoprene and natural rubber but different slopes are obtained
Complex formation of poly(4‐vinyl‐N‐alkylpyridinium) salts or polymer containing flavin mononucleotide with indole derivatives
Authors: Ishiwatari Tsutomu , Okubo Tsuneo , Ise Norio 
Published: April 2003

AbstractA charge‐transfer‐type complex formation between poly(4‐vinyl‐N‐propylpyridinium bromide) (C3PVP), poly(4‐vinyl‐N‐butylpyridinium bromide) (C4PVP) or poly(4‐vinyl‐N‐benzylpyridinium chloride) (BzPVP), and indole derivatives or between polymer containing flavin mononucleotide residues and indole derivatives was studied in the presence of simple and polyelectrolytes. The association constant (K) of the complex formation with indole acetate increased in the order BzPVP > C4PVP > C3PVP, which indicated an important contribution by hydrophobic interaction. The addition of simple and polyelectrolytes decreased the association constants. This was explained by the “secondary salt effect” of the salts. The importance of the electrostatic interactions in the complexation systems was obvious. The influence of simple electrolytes on the K values was discussed theoretically according to Manning's theory.
Kinetics of the metal‐catalyzed condensations of phenols and polyflavonoid tannins with formaldehyde
Authors: Pizzi A. , Van Der Spuy P. 
Published: April 2003

AbstractThe rate constants and free energies of activation of Zn2+ ‐accelerated and Cr3+ ‐retarded condensations of resorcinolic A rings of polyflavonoid wattle tannins, as well as of the model compounds resorcinol and catechol with formaldehyde, were determined. A quantitative indication of the effect of strong metallic ion catalysts on phenol/aldehyde reactions was obtained. Second‐order kinetics have been found to fit these metallic ion‐catalyzed reactions. The dependence of the tannin/formaldehyde reaction on the concentration of Zn2+ and Cr3+ under acid and alkaline reaction conditions has been investigated and the respective catalytic coefficients determined. In the presence of the metallic ions used the reaction proved to be considerably less sensitive to variations of OH‐concentration, hence of pH.
Adsorption of charged diblock copolymers on porous silica
Authors: Pefferkorn E. , Tran Q. , Varoqui R. 
Published: April 2003

AbstractBlock copolymers of styrene and 2‐vinylpyridine of different molecular weights were synthesized and chemically modified to poly(vinyl pyridine)/poly(styrene sulfonate) or polystyrene/poly(2‐vinyl pyridinium) salts. Adsorption on “Spherosil” silica with a high specific surface area was performed from aqueous solutions of polyelectrolyte copolymers or from noncharged copolymer in an organic medium and subsequent sulfonation or quaternization in the adsorbed state. The adsorption mechanism was studied under various solvent conditions to give silica maximal ion‐exchange properties. Modification of silica resulted in a highly stable coated material which combines the mechanical properties of the porous beads and the ion‐exchange properties of the “supported” and “pellicular” ion‐exchangers and should have potential use in chromatography.
Anionic synthesis of poly[ethylene methylene bis(4‐phenyl‐carbamate)‐g‐acrylonitrile]
Authors: Adibi K. , George M. H. , Barrie J. A. 
Published: April 2003

AbstractA relatively high‐molecular‐weight polyurethane based on MDI and ethylene glycol was prepared and characterized. This polymer was metalated with sodium hydride in N,N‐dimethylformamide (DMF) at about 0°C. Metalation was confirmed principally by spectroscopic identification of the N‐methyl derivative obtained by coupling the metalated polymer with methyl iodide. Under appropriate reaction conditions the metalated polyurethane was used for the anionic graft polymerization of the reactive monomers acrylonitrile and ethylene and propylene sulfides. Attempted anionic graft polymerizations with other monomers, including styrene and ethylene and propylene oxides, were unsuccessful. The polyurethane grafted with acrylonitrile was separated by fractionation from accompanying small amounts of polyacrylonitrile, a low‐molecular‐weight homopolymer. One sample of polyurethane grafted with acrylonitrile was identified by microanalysis, IR, NMR, and increase in weight and was also characterized by differential thermal analysis.
Dispersion polymerization of styrene: Effect of surfactant
Authors: Almog Yaacov , Levy Moshe 
Published: April 2003

AbstractThe influence of poly(vinyl alcohol) (PVA), a steric stabilizer, and sodium dodecyl sulfate (SDS), an electrostatic stabilizer, on the stability of styrene dispersion polymerized systems was studied. It was shown that in stabilization by PVA there was pronounced bridging of the submicron emulsion particles to 10‐μ dispersion particles and that the emulsion particles could not be washed off. In SDS stabilization, on the other hand, the emulsion formed was easily washed off because bridging with SDS does not occur. The surface tension of the aqueous phase measured during polymerization showed different characteristics for stable and unstable systems.
Thermal degradation of polyurethane based on MDI and propoxylated trimethylol propane
Authors: Gaboriaud F. , Vantelon J. P. 
Published: April 2003

AbstractA polyurethane based on diphenyl methane diisocyanate (MDI) and propoxylated trimethylol propane was thermally degraded by using the techniques of pyrolysis and thermogravimetric analysis (TGA) in an inert atmosphere. Identification of pyrolysis gaseous products at 600°C showed that the first degradation step consists of a reversal of the polycondensation process, i.e., dissociation into starting polyol and diisocyanate, followed by the polyol degradation and a probable diisocyanate polymerization. Kinetic parameters were determined using dynamic and isothermal TGA curves. It is shown that the degradation can be closely compared with a random chain scission process.
Polymerization of N‐acryloyl pyrrolidone and synthesis of graft copolymer by using the mechanism of initiation of anionic ring‐opening polymerization
Authors: Sur G. S. , Noh S. K. , Choi Sam K. 
Published: April 2003

AbstractN‐acryloyl pyrrolidone (NAP) was synthesized by reaction of pyrrolidone with acryloyl chloride. First, the polymerization of NAP and copolymerization of NAP with styrene (St) were carried out at 60°C, using 2,2′‐azobisisobutyronitrile (AIBN) as an initiator. Kinetic studies showed that the rate of polymerization (Rp) could be expressed by Rp = K [AIBN]0.5 [NAP]1.0. The reactivity of NAP was found to be larger than that of N‐methacryloyl pyrrolidone. The overall activation energy was calculated to be 24.3 kcal mole−1. The following monomer reactivity ratio and Q and e values were obtained. NAP(M1)—St(M2): r1 = 1.50, r2 = 0.35, Q1 = 0.42, and e1 = 1.60. Second, graft copolymers were synthesized by reacting pyrrolidone, in the presence of a catalytic amount of its potassium salt, with poly(NAP‐co‐St).
Solid‐state polymerization of long‐chain vinyl compounds. V. Two‐step postpolymerization of octadecyl acrylate by temperature increase and by stepwise γ‐ray irradiation
Authors: Shibasaki Yoshio , Fukuda Kiyoshige 
Published: April 2003

AbstractThe mechanism of two‐dimensional polymerization of octadecyl acrylate in lamellar crystal was investigated in two‐step postpolymerizations by temperature increase and stepwiseγ‐ray irradiation in lieu of the usual one‐step reaction. Two‐step postpolymerizations by these procedures are interpreted satisfactorily by the cone model, which assumes that the polymerization probability of the monomer molecules in a single layer is distributed conically around the initiation point. It was found that the propagating radicals were living, even in the saturated stage, and the effect of the polymer chains already formed on the propagating and terminating reactions was evident. Furthermore, molecular weight distributions of the resultant poly(octadecyl acrylate) measured by gel permeation chromatography (GPC) were broad. The values of Mw/Mn for the two‐step post polymerizations were 4.71–7.03, whereas those for one‐step reactions were 3.26–5.54.
Synthesis and properties of conjugated enyne polysulfones
Authors: Reinhardt Bruce A. , Arnold Fred E. 
Published: April 2003

AbstractHigh‐molecular‐weight polysulfones that contained 1,3‐enyne linkages in the polymer backbone were prepared by the reaction of potassium salts of (E)‐1,3‐bis(3‐hydroxyphenyl)‐1‐buten‐3‐yne and 4,4′‐dihydroxybiphenyl with 4,4′‐dihalodiphenylsulfones in DMSO‐sulfolane solvent mixtures. The polymers were soluble in methylene chloride and exhibited intrinsic viscosities as high as 0.74 (in DMAC at 30°C) with glass transition temperatures ranging from 179 to 214°C. It was postulated that on heating the polymers would cure via a intramolecular cycloaddition reaction to from a 2‐phenylnaphthalene fused ring system along the polymer backbone. Thermal analytical data studies on cured polymer films and investigations of the products obtained from the thermal reactions of model compounds indicated that the primary curing reaction was intermolecular rather than intramolecular in nature. Additional data from testing fabricated composites indicated that the enyne polysulfones have suitable properties for use as high‐temperature thermoplastic composite materials.
Self‐consistency of fractional precipitation method for determining molecular weight distribution in a polymer sample
Authors: Lei George Y. 
Published: April 2003

AbstractMolecular weight distribution curves have been determined for two samples of polystyrene by fractionating them with a conventional single‐stage precipitation technique and followed by measurement of the average molecular weights of the fractions by viscometry. The experimental results obtained were analyzed by the usual method of plotting cumulative distribution curves. Subsequently, the distribution curve for a mixture of aliquots of the two samples was obtained and found to agree with the expected curve, which would be the sum of the curves in the two constituent samples. This finding confirms the internal self‐consistency of this method for determining molecular weight distribution curves.
Binding heavy metal ions with polymerized onion skin
Authors: Kumar Pawan , Dara S. S. 
Published: April 2003

AbstractRed onion skin is highly effective for binding heavy metal ions from aqueous solutions. Color leaching can be prevented and the physical characteristics of the substrate can be improved by treatment with formaldehyde in an acidic medium. Batch and column experiments have been conducted with Cu2+, Cd2+, Zn2+, Ni2+, Hg2+, and Pb2+. Almost quantitative removal of the metal ions from solution can be achieved by using columns of the treated onion skin. Competition of the various metal ions for the substrate has been investigated. The capacity of the substrate in the majority of the metal ions studied is well above 1 meq/g. The use of polymerized onion skin to remove heavy metal ions from domestic and industrial wastewater to safe levels has been recommended as a cheap and effective alternative for commercial ion‐exchange resins.
Functional monomers and polymers. LXXXVI. Photochemical reactions on synthetic polymers with pendant thymine bases: Effect of solvents
Authors: Kita Yasuo , Uno Taizo , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractPhotodimerization of thymine bases present on the side chain of acryloyl and methacryloyl‐type polymers was studied in dimethyl sulfoxide, dimethylformamide, and dimethyl sulfoxide—ethylene glycol mixture. Quantum efficiencies for photodimerization and quenching with isoprene were influenced by the solvents. The self‐association of thymine bases estimated from their ultraviolet (UV) spectra and intrinsic viscosity were related to the effect of solvent on the photodimerization.
Telomerization kinetics by redox catalysis
Authors: Boutevin Bernard , Maubert Claude , Mebkhout Ahmed , Pietrasanta Yves 
Published: April 2003

AbstractA new formula for redox catalyzed telomerization kinetics was set up: 1/DPn = CMe(Me)/(M) + CXY(XY)/(M), where CMe is the transfer constant for the metallic ion Me, CXY is the transfer constant for the telogen XY, M the monomer, and DPn is the degree of polymerization. This study has shown that classic transfer and termination reactions can be neglected because of their slow rates and that the metal transfer constant (CMe) is the predominant factor influencing telomer molecular weight. This formula was verified by telomerizations of three monomers [chlorotrifluoroethylene (CTFE), acrylic acid, and ethyl acrylate] with CCl4, catalyzed with ferric chloride‐benzoin. In this last case the initiation rate constant (fKi), the initiation and termination rates, and the radical concentration were measured.
Synthesis and properties of ABA propylene‐ethylene block copolymers
Authors: Prabhu P. , Schindler A. , Theil M. H. , Gilbert R. D. 
Published: April 2003

AbstractExperimental data, which includes catalyst lifetimes, thermal analyses, fractionation by urea complexation, x‐ray diffraction, and 13C‐NMR spectroscopy, are presented to confirm the successful synthesis of ABA propylene‐ethylene block copolymers. A dry catalyst system of DEAC‐TiCl3(AA) and a gas‐phase polymerization technique was used to prepare the copolymers. PRP‐and ERE‐type copolymers (P‐isotactic polypropylene, E‐polyethylene, and R‐random propylene‐ethylene copolymer block) were prepared. Some preliminary physical property data are given which indicate that PRP‐type copolymers can behave as elastomeric fibers. The stress‐strain behavior also indicates block copolymer formation.