bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of physicochemical interactions in metal–polymer systems
Authors: Belyi V. A. , Goldade V. A. , Neverov A. S. , Pinchuk L. S. 
Published: April 2003

AbstractThis article deals with the investigation of adhesive joints of unlike metals separated by layers of thermoplastics. Experimental data are presented on electrical conductivity of polymers at temperatures of 333–573 K in the electric field of 1–102 V/cm. Infrared (IR) spectroscopy data have been used to establish correlation between the parameters of the voltage generated on the metal–polymer specimens and the existence of groups that can form hydrogen bonds. Adhesive strength of the adhesive joints is discussed in connection with the performance of a metal–polymer–metal voltaic couple when the adhesive joints are being formed. The results presented allow a conclusion that polymeric dielectrics exhibit properties of electrolytes when heated in contact with metals. Therefore electrochemical interactions between components of metal–polymer systems should be taken into consideration when predictions are made of performance characteristics of industrial materials based on polymers and metals.
Kinetics and mechanism of the formation of glycol esters: Benzoic acid–ethylene glycol system
Authors: Reimschuessel H. K. , Debona B. T. , Murthy A. K. S. 
Published: April 2003

AbstractEsterification‐hydrolysis and condensation‐glycolysis are the principal equilibria entailed in a system comprised of benzoic acid, ethanediol, ethanediol monobenzoate, ethanediol dibenzoate, and water. These equilibria are characterized by three interrelated equilibrium constants that pertain to the hydrolysis of both ethanediol monobenzoate and ethanediol dibenzoate and to the condensation of ethanediol monobenzoate. The rate constants related to these reactions and to the corresponding reverse reactions were all found to be functions of the concentration of carboxy groups. Antimony triacetate, a well‐known transesterification catalyst, catalyzed the condensation reaction strongly but did not affect the esterification reaction. Based on a mechanism that entailed the considered three principal equilibrium reactions, a set of both the kinetic and thermodynamic parameters was obtained by a nonlinear regression procedure. With these parameters the nonlinear rate equations were integrated numerically, using the fourth‐order Runge‐Kutta method. Excellent agreement between the values thus calculated and the experimental data were obtained in all cases except when considerable concentrations of both benzoic acid and ethanediol dibenzoate were present in the system. It has been concluded that in these instances the formation of the dibenzoate is paralleled by a pyrolysis reaction that is strongly catalyzed by carboxy groups.
Terephthalic acid esterification kinetics: 2‐(2‐methoxyethoxy)ethyl terephthalates
Authors: Reimschuessel H. K. , Debona B. T. 
Published: April 2003

AbstractThe process of esterification of terephthalic acid is characterized by a mechanism that involves three equilibrium reactions. Two are esterification‐hydrolysis equilibria entailing the reactions of the two terephthalic acid carboxyl groups with alcoholic hydroxyl groups, whereas the third one is a transesterification‐acidolysis equilibrium that is concerned with the reaction between two terminal terephthalic acid moieties. The products of these three interrelated equilibria are terephthalic acid, its monoester and diester, the particular alcohol, and water. The alcohol used in the present study was 2‐(2‐methoxyethoxy)ethanol. Equilibrium constants and rate constants were developed from experimental data obtained at 230°C. The esterification‐hydrolysis reactions were found to be catalyzed by carboxyl groups, and the rate of transesterification was found to be a function of the terephthalic acid concentration. With the constants developed, the system of nonlinear differential equations, as derived from the mechanism postulated, was integrated numerically using the Runge‐Kutta method. Good agreement between calculated and experimental values was observed.
The viscoelastic behavior of poly(isobutylene oxide) exposed to UV irradiation
Authors: Yoshinari Makoto , Murakami Kenkichi 
Published: April 2003

AbstractThe stress relaxation of poly(isobutylene oxide) in air was measured while it was exposed to UV irradiation. It was found that the relative stress increased markedly and the polymer degraded extensively with UV irradiation time. In other crystalline polymers that degrade easily, e.g., polyoxymethylene and polypropylene, the relative stress increased somewhat. However, such behavior was not found in another crystalline polymer that was difficult to degrade, polyethylene. It was also found that the increase in the relative stress depended on the strain imposed on the sample, exposure temperature, the degree of crystallinity of the sample, the degree of initial degradation of the sample, and the degree of orientation of the chain molecules in the sample. However, these changes were insignificant in experiments performed under N2.
Effect of the fine structure of viscose hydrocellulose on its adsorption properties
Authors: Shinouda H. G. , Abdel Moteleb M. M. 
Published: April 2003

AbstractFrom the heat of wetting in water and the iodine adsorption measurements of certain hydrolytic residues prepared by the acid hydrolysis of viscose rayon in the absence and presence of FeCl3, a comparison was made between their water adsorption capacity and iodine molecules. The data obtained revealed first that in the initial stages of acid action of the fibers the adsorption cites accessible to water or iodine molecules decrease to some extent, depending on the hydrolytic condition. Second, in the inner fine structure of the various residues examined, there remains a high proportion of cites accessible to water molecules that are inaccessible to iodine. These results are explained by the fact that the water molecules can penetrate the submicroscopic structure of cellulose chains by molecular forces and the swelling effect.
Evaluation of monomer reactivity ratios of more complex copolymerization schemes, with application to the penultimate unit effect in methyl acrylate–butadiene copolymerization
Authors: van der Meer R. , Alberti J. M. , German A. L. , Linssen H. N. 
Published: April 2003

AbstractA generally applicable computational procedure, which permits the accurate evaluation of the kinetic parameters of intricate and extended copolymerization schemes to be made, is described. This method is based on a numerical integration of the differential equation, and, according to the (improved) curve‐fitting I procedure, experimental errors in both measured variables are considered. Furthermore, a description is given of theFtest, in which a statistical comparison between the resulting residual sums of squares of two different schemes offers a possibility of selecting the most probable kinetic scheme for a given copolymerization system. The capability and applicability of the methods developed is demonstrated for the free radical copolymerization kinetics of methyl acrylate (MA) (M1) and butadiene (BD) (M2) with toluene as solvent. Here, the simple copolymer equation is unsatisfactory because a significant penultimate unit effect in BD macroradical reactivity shows up:k222/k221= 0.84, andk122/k121= 0.53, andk11/k12= 0.088. The microstructure of the copolymer samples, determined by infrared (IR) spectroscopy, shows a decreasing fraction of BD units in the vinyl configuration in favor of the fraction of BD units in thecis‐vinylene andtrans‐vinylene configuration at increasing MA (m) content. Statistical considerations indicate a strongly diminished probability of finding BD (b) in the vinyl configuration in ∼mb∼ transitions. Steric hindrance or polar repulsion of the ester side group of the penultimate MA unit probably account for the increased preference for monomer addition to the C4site over the C2site of the BD macroradical.
Coupling of acrylic polymers and collagen by use of a water‐soluble carbodiimide. I. Optimization of reaction conditions
Authors: Lloyd Douglas R. , Burns Charles M. 
Published: April 2003

AbstractA means of coupling synthetic polymers of biomedical interest with collagen under mild conditions was investigated as a part of preliminary studies in the development of a biomedical adhesive. The coupling agent, 1‐cyclohexyl‐3‐[2‐morpholinyl‐(4)‐ethyl]carbodiimide, provides a covalent bond between the acrylic polymer and collagen. The variables affecting the establishment of this bond in solution are concentration of the carboxylic group on the acrylic polymer, concentration of the acid‐soluble collagen, concentration of the coupling agent, pH, and time of reaction. Optimum values of these variables have been obtained experimentally.
A new synthetic route to α‐alkylacrylic esters and α‐alkylacrylonitriles
Authors: Ponticello I. S. 
Published: April 2003

Abstractα‐Alkylacrylic esters and α‐alkylacrylonitriles have been synthesized by cracking their cyclopentadiene adducts. The latter were derived by treatment of the lithium enolates of cyclopentadiene‐blocked acrylates or acrylonitriles with alkyl halides.
Crosslinking of polystyrene via pendant maleimide groups
Authors: Stevens Malcolm P. , Jenkins Aubrey D. 
Published: April 2003

AbstractMaleimide groups were incorporated into polystyrene by a mild Friedel–Crafts procedure using N‐chloromethylmaleimide. Films and solutions of the modified polymer underwent photocrosslinking at a rate that was not appreciably affected by addition of photosensitizer. Free radical, thermal, and Diels–Alder crosslinking were also investigated.
Photooxidation of polyolefins and their light stability
Authors: Karpukhin O. N. , Slobodetskaya E. M. 
Published: April 2003

AbstractIt is shown that all peculiarities of polypropylene photooxidation and alteration of its mechanical properties in this process are a process of second‐order termination reaction. The influence of natural conditions (varied temperature and light intensity) on this process are considered.
Photochemistry of ring‐substituted polystyrenes. II. Photolyses of poly(p‐fluoro‐, p‐chloro‐, and p‐bromostyrene)s
Authors: Weir N. A. , Milkie T. H. 
Published: April 2003

AbstractThe photodegradation of thin films of p‐fluoro (PPFS), p‐chloro (PPCS), and p‐bromo (PPBS) styrenes brought about by exposure to 254‐nm radiation under high vacuum was studied. Mass spectroscopic measurements indicated that hydrogen and hydrogen halides were the only gaseous products because yields of H2 and HF from poly(p‐fluorostyrene) were much smaller than the corresponding yields of chloro‐ and bromo‐substituted polymers. UV and visible spectra of degraded films indicated the presence of unsaturated species, for the initial rates of formation were comparable in PPFS and PS but considerably greater in PPCS and PPBS. Solubility and molecular weight data indicated simultaneous crosslinking and chain scission; both PPCS and PPBS showed an inordinately high susceptibility to crosslinking. These observations can be rationalized in terms of the energetics of abstraction reactions by H and halogen atoms and in terms of scission of the Ph–Br and Ph–Cl bonds which lead to the participation of radicals in the para position in crosslinking. Some qualitative correspondence between the Hammett parameters of the p‐substituents and rates of H2 formation in the substituted polymers was observed. Quantum yields of gaseous product formation and probabilities of crosslinking and chain scission were also determined for the three polymers. Mechanisms of the various reactions are discussed.
Singlet oxygenation of 1,2‐poly(1,4‐hexadiene)s
Authors: Golub Morton A. , Rosenberg Mark L. , Gemmer Robert V. 
Published: April 2003

AbstractThe microstructural changes that occur in cis and trans forms of 1,2‐poly(1,4‐hexadiene) during methylene blue‐photosensitized oxidation were examined by infrared (IR) and 13C‐NMR spec‐troscopy. The singlet oxygenation of these polymers yielded the expected allylic hydroperoxides accompanied by double bond shifts to new vinyl and trans‐vinylene double bonds. The photosensitized oxidation exhibited zero‐order kinetics; the relative rates for the cis‐ and trans‐1,2‐poly(1,4‐hexadiene)s were approximately 3.8:1.0.
Substituent parameters for radical reactions: Cerium(IV)‐substituted acetophenones–acrylonitrile system
Authors: Rout Swoyam P. , Mallick Nigamananda , Rout Anuradha , Rout M. K. 
Published: April 2003

AbstractThe present investigation describes a new approach for the determination of radical substituent parameters σ. The technique has been developed by an ingenious combination of two equations, one proposed by Yamamoto and Otsu and the other by Streitwieser and Perrin. The σ values for different substituents were first evaluated by application of this newly developed technique to the Ce(IV)‐substituted toluenes–acrylonitrile system. The validity of these values was then tested by application to another system, the Ce(IV)‐substituted acetophenones–acrylonitrile system, which is the subject of the present study.
Poly(β‐Amino acids). VI. Synthesis and conformational properties of poly[(r)‐3‐pyrrolidinecarboxylic acid]
Authors: Yuki Heimei , Okamoto Yoshio , Kobayashi Yoshiko 
Published: April 2003

AbstractRacemic and optically active 3‐pyrrolidinecarboxylic acids (β‐proline) were synthesized, and their polymers, poly[(RS)‐β‐proline] and poly[(R)‐β‐proline], were prepared by the polycondensation reaction of the p‐nitrophenyl esters. Model compounds, N‐cyclopentylcarboxylic acid pyrrolidide and N‐cyclopentylcarbonyl‐(R)‐3‐pyrrolidinecarboxylic acid pyrrolidide, were synthesized to elucidate the conformation of the polymer. The solution properties of poly[(R)‐β‐proline] and the model compounds were investigated by means of circular dichroism (CD) and NMR spectroscopy. The spectral patterns of the polymer and model compounds were similar in various solvents. Poly[(R)‐β‐proline] and poly[(RS)‐β‐proline] showed identical NMR spectra. These results suggest that poly[(R)‐β‐proline] may exist in a random conformation consisting of mixtures of cis and trans amide bonds. The conformational study of cyclopentanecarboxylic acid pyrrolidide by NMR spectroscopy with a shift reagent, Eu(fod)3, in CDCl3 implied that the plane containing the amide group bisects the cyclopentane ring. This suggests that each amide plane in the polymer in chloroform may also bisect the pyrrolidine ring.
Cyclic acetal‐photosensitized polymerization. VIII. Photopolymerizations of diallylidene pentaerythritol and its derivatives
Authors: Ouchi Tatsuro , Tatsumi Masakazu , Oiwa Masayoshi 
Published: April 2003

AbstractThe photopolymerization of diallylidene pentaerythritol (DAPE) was carried out in benzene at 40°C without the use of the usual initiator. DAPE was polymerized with the ester radical generated from DAPE by photoirradiation. To investigate the effect of dimethyl groups at the α,α‐ or β,β‐positions of vinyl groups on the polymerization, photopolymerizations of dimethallylidene pentaerythritol (DMPE) and dicrotylidene pentaerythritol (DCPE) were carried out and kinetically studied from the standpoint of the degradative chain transfer by the allylidene group and cyclization by two double bonds. The results can be summarized as follows: (1) The relation between the rate of polymerization, Rp, and the monomer concentration [M] can be expressed as [M]/Rp = (A[M] + B)/(2[M] + C), where A, B, and C are constants. (2) The ratios of the rate constant of unimolecular cyclization to the total rate constants of bimolecular propagation and the chain transfer of uncyclized radical were estimated as 1.12, 0.26, and 0.16 mole dm−3 for DAPE, DMPE, and DCPE, respectively; the cyclizations hardly took place. (3) The rate of polymerization and the molecular weight of the polymer were small because of the degradative chain transfer by the allylidene group.
Effect of polyion conformation on dye binding. IV. Fluorescence of auramine O in relation to its binding to synthetic polyacids
Authors: Erny B. , Muller G. 
Published: April 2003

AbstractThe effect of polymer conformation, polymer concentration, and added salt concentration on the quantum yield ϕ of Auramine O (AuO) is discussed in connection with dialysis equilibrium data. The quantum yield per bound dye molecule (ϕ/q) assumes different values which are related principally to solvation changes in the environment of the binding sites. Binding to globular compact a states results in high ϕ/q, whereas low ϕ/q (of the order of magnitude of ϕ of free AuO) are observed for the binding to expanded solvated b states. The quantum yield of bound AuO is therefore affected by the organic nature of the environment, but shows little or no relation to the amount of bound dye molecules.
Effect of inititiator on the molecular weight distribution in dispersion polymerization of styrene
Authors: Almog Yaacov , Levy Moshe 
Published: April 2003

AbstractDispersion polymerization of styrene in the particle size range of 10 μ with lauroyl peroxide as initiator results in a double‐peak molecular weight (MW) distribution. The high‐MW fraction was due to emulsion polymerization. The same phenomenon also exists in AIBN and benzoyl peroxide initiation, although it is less obvious. The kinetics of the reaction for dispersion polymerization was dependent on the concentration of the dispersing agent and the nature of the initiator.
Synthesis of highly branched perfluoroethers by direct fluorination, promising new materials based on the hexafluoroacetone–ethylene copolymer
Authors: Gerhardt G. E. , Dumitru E. T. , Lagow R. J. 
Published: April 2003

AbstractDirect fluorination of the hexafluoroacetone‐ethylene copolymer, [CH2CH2OC(CF3)2]n, under conditions designed to promote fragmentation of the polymer chain has led to the synthesis of a number of structurally unusual branched perfluoropolyethers [CF2CF2O‐C(CF3)2]n. These new perfluoropolyethers have been characterized by 19F‐NMR, and their physical properties are reported. Direct fluorination under milder conditions yields a high‐molecular‐weight perfluoropolyether.
Radiation‐induced polymerization at high dose rate. II. α‐Methylstyrene in bulk
Authors: Hayashi Kanae , Kotani Noritaka 
Published: April 2003

AbstractBulk polymerization of α‐methylstyrene was carried out in a wide dose rate range, 7.6–256 rad/sec by γ rays and 8.5 × 103–2.1 × 105 rad/sec by electron beams. At high dose rate by electron beams, cationic polymerization took place along with formation of oligomeric product of DPn = ∼4. At low dose rate by γ rays, radical polymerization was found to occur in water‐saturated monomer. The cationic polymerization at high dose rate proceeds with essentially the same mechanism as was already known in γ‐ray polymerization of dry monomers. Relatively low reaction rate of the cationic polymerization compared with that of styrene is explained with the fact that the propagation of α‐methylstyrene is much more easily inhibited by a slight amount of water.
Polymerization of coordinated monomers. XVI. Stereoregulation in the alternating copolymerization of methyl methacrylate with styrene in the presence of metal halides
Authors: Hirai Hidefumi , Tanabe Tsuneaki , Koinuma Hideomi 
Published: April 2003

AbstractTriad cotacticities of alternating copolymers of methyl methacrylate with styrene prepared in the presence of zinc chloride, ethylaluminium sesquichloride, and ethylboron dichloride are investigated from the mechanistic point of view by means of 1H‐ and 13C‐NMR. The cotacticities from 1H‐NMR spectra are obtained accurately by using α‐d‐styrene in the place of styrene and by measuring the spectra on the copolymer in o‐dichlorobenzene at 170°C. The relative intensities of three peaks of the splitting signal for the methoxy protons in the nonalternating copolymers obtained by the use of benzoyl peroxide in the absence of metal halides agree well with the cotacticity distribution calculated theoretically by the Lewis‐Mayo mechanism with the stereoregulation following Bernoullian statistics. The splitting signals in the 1H‐ and 13C‐NMR spectra of the alternating copolymers prepared in the presence of metal halides cannot be explained by the same mechanism. The relative intensities of three peaks of the splitting signals for the methoxy protons and for the carbonyl carbon in the methyl methacrylate unit (the contents of cotactic triads centered by the methyl methacrylate unit) are not equal to those for the aromatic C1 carbon in the styrene unit (the contents of cotactic triads centered by styrene unit). The value of f2Y ‐ 4fxfz is not equal to zero, where fx, fy, and fz are the cosyndiotactic, coheterotactic, and coisotactic triad contents, respectively, in the alternating copolymer. Copolymers obtained in the presence of zinc chloride are not exactly equimolar alternating but always contain a methyl methacrylate unit in excess, and the relative intensities of the three peaks for the aromatic C1 carbon change with the copolymer composition. These results are explained by a proposed mechanism: the alternating copolymerization proceeds through the homopolymerization of a ternary molecular complex composed of a metal halide, methyl methacrylate, and styrene, accompanied with the stereoregulation following first‐order Markovian statistics; the increase of methyl methacrylate content in the copolymer prepared in the presence of zinc chloride is caused by the participation of the binary molecular complex composed of a metal halide and methyl methacrylate in addition to the ternary molecular complex.
Functional polymers. II. Synthesis and properties of new polymeric cinchona alkaloids
Authors: Kobayashi Norio , Iwai Kiyoko 
Published: April 2003

AbstractNew polymeric cinchona alkaloids having favorable structures and properties for asymmetric catalysts have been prepared by radical copolymerization of the alkaloids with acrylonitrile using azobisisobutyronitrile (AIBN) as an initiator. Of the many reaction solvents tried, dimethylformamide (DMF) was found to be the solvent of choice especially for a large‐scale synthesis. Alkaloid monomers employed were free dalkaloids, such as quinine, quinidine, cinchonidine, and cinchonine, and modified ones including 9‐O‐ethoxycarbonylquinine and quinine salts. The copolymers were thermally stable powders, soluble in DMF and DMSO, and insoluble in common organic solvents. They were found to be converted into water‐soluble polymeric alkaloids by hydrolysis with alkaline hydrogen peroxide.
High conversion polymerization. VI. Detailed examination of the kinetic model
Authors: Dionisio Jose M. , O'driscoll Kenneth F. 
Published: April 2003

AbstractA previously developed model which has been used to describe the kinetic behavior of free radical polymerization in the region of the gel effect is here subjected to a detailed quantitative examination. It is shown, using data for the polymerization of methyl methacrylate, that the quasi‐steady‐state assumption is valid during the gel effect, and that the model provides a good description of the chain lengths and concentrations of different species present in the reaction. The postulate that primary radical termination becomes important as the gel effect advances is tested and found to be true.
Comparison of the precision of estimation of copolymerization reactivity ratios by current methods
Authors: McFarlane Randall C. , Reilly Park M. , O'driscoll Kenneth F. 
Published: April 2003

AbstractSix recently proposed methods for analyzing copolymerization composition data have been compared to a nonlinear least‐squares analysis to ascertain the precision of the six methods in determining reactivity ratios. Data used were simulated for five hypothetical monomer pairs with three different types of experiment design and contained error structures similar to those observed experimentally. The results of the comparisons suggest that retrospective analyses of existing copolymerization data should only be done with a nonlinear least‐squares analysis. For new data, the design of experiments is of great importance, and when done properly allows the use of some of the linear least‐squares methods of analysis.