bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation between the effect of sonic irradiation on the microfibrils of chitin and cellulose and the polarity of their chains
Authors: Colvin J. Ross 
Published: April 2003

AbstractThe effect of sonication on the morphology of microfibrils of chitins and celluloses was correlated with the polarity of their constituent chains. For given conditions, fibrillation of the microfibrils takes place when the polarity of the chains is antiparallel but not when it is parallel. If this correlation may be extended to cases of unknown structure, it permits an inference about the parallelity or antiparallelity of the chains of samples of both polymers where polarity cannot be determined directly.
Formation of free radicals in photoirradiated cellulose. VIII. Mechanisms
Authors: Hon Nyok‐Sai 
Published: April 2003

AbstractPhotoinduced free radicals in cellulose were studies by means of ESR spectroscopy. Plausible mechanisms have been suggested for each type of intermediate radical to account for the ESR spectra observed and for the product balances. Based on the principles of photochemistry of cellulose, coupled with the findings of the ESR spectra, it becomes evident that localization of the energy absorbed in the cellulose molecule leads to formation of free radicals in terms of chain scission, dehydrogenation, dehydroxylation, and dehydroxymethylation. Emphasis has been placed on the correlation of the mechanisms of photodegradation and the mechanisms of photoinduced graft copolymerization.
220‐MHz NMR spectra of acrylic monomer–2‐substituted 1,3‐diolefin alternating copolymers
Authors: Furukawa Junji , Kobayashi Eiichi , Arai Yoshihiro , Suzuki Toshimitsu , Takegami Yoshinobu 
Published: April 2003

AbstractAn investigation by 220‐MHz NMR spectroscopy was carried out on the alternating copolymers of acrylic monomer with 2‐substituted 1,3‐diolefin. The chain structures were determined. The acrylic monomers used were methyl methacrylate (MMA), acrylonitrile (AN), and methacrylonitrile (MAN); isoprene (IP) and chloroprene (CLP) were the 1,3‐diolefins. In the MAN–IP alternating copolymer, the 1‐position methylene protons of IP showed an AB quartet peak, confirming the α‐1 linkage structure. Similarly, in the MMA–CLP and AN–CLP copolymers, the 1‐position methylene protons of CLP showed and AB quartet and an ABX pattern, respectively, confirming the α‐1 linkage structure in both these cases also. The α‐1 linkage structure was also revealed by the decoupling technique in the MAN–CLP alternating copolymer. The AN–IP and MMA–IP alternating copolymers also possess a bond between the α‐position of the acrylic monomer and the 1‐position of IP. The monomeric units in the alternating copolymers of acrylic monomers with 2‐substituted 1,3‐diolefins were generally linked at the α‐position of acrylic monomer and the 1‐position of 1,3‐diolefin. On the other hand, in the Diels‐Alder adducts of acrylic monomer with 2‐substituted 1,3‐diolefin, the reaction takes place between the α‐position of acrylic monomer and the 4‐position of 1,3‐diolefin.The regioselectivity of the alternating copolymers and the Diels‐Alder adducts is quite compatible with the expectations from molecular orbital theory.
Phenylethynyl‐pendant polyphenylquinoxalines curable by an intramolecular cycloaddition reaction
Authors: Hedberg F. L. , Arnold F. E. 
Published: April 2003

AbstractPolyphenylquinoxalines containing 2,2′‐bis(phenylethynyl)diphenylene moieties along the polymer backbone have been synthesized. As anticipated, these polymers were found to undergo a novel curing reaction consisting of an intramolecular cycloaddition (IMC) of pendant groups to a dibenzoanthracene backbone structure. The IMC reduces chain mobility, and the fused ring structure increases the glass transition temperature of the polymer. The potential of this approach to curing high‐temperature polymers was demonstrated in the processing of one such polymer having an initial Tg of 215°C. Curing at 245°C with no evolution of volatiles produced a Tg of 365°C. This very significant increase in potential use temperature via a volatiles‐free IMC cure provides promise for a tough phenyiquinoxaline resin system which can be used to fabricate reinforced composites that have use temperatures far exceeding processing temperatures.
Vinyl polymerization. CCCXXXIX. Effect of chain length of nylon 3 on the polymerization of methyl methacrylate initiated with the system of nylon 3, copper(II) ion, and water
Authors: Ouchi Tatsuro , Nishimura Tamio , Imoto Minoru 
Published: April 2003

AbstractIt was found recently that the system of nylon 3, copper(II) ion, and water could initiate a radical polymerization of methyl methacrylate(MMA). In the present paper, the effect of average chain length of the molecules of nylon 3 on the rate of polymerization of MMA was studied. The rate increased with the chain length of nylon 3. This result was explained well by the fact that the shorter nylon 3 forms a complex with copper (II) ion more easily than longer nylon 3. It was assumed that the shorter nylon 3 fills three or four coordination sites of copper(II) ion and loses the ability to initiate the polymerization. The efficiency of grafting of MMA and the degree of polymerization of MMA homopolymer were independent of the chain length of nylon 3.
Rotating ring‐disk electrode studies of the reaction of stable radical cations with styrene and isobutyl vinyl ether
Authors: Funt B. Lionel , Severs Wendy , Glasel Arnold 
Published: April 2003

AbstractAn electroanalytical technique has been utilized in a new method for the study of reactive intermediates in polymerization reactions. A ring‐disk electrode system generated persistent carbocation radicals whose stability decreased in the order: 1,3,6,8‐tetraphenylpyrene (TPP), rubrene (Ru), 9,10‐diphenylanthracene (DPA), and 9,10‐dimethylanthracene (DMA). Radical cations from these parent compounds flowed to a collecting ring which was controlled potentiostatically to reduce unreacted cations. When styrene or isobytyl vinyl ether was added to the solution, the concentration of carbocation radicals reaching the electrode was reduced. Current collection efficiencies N were determined as a function of rotation speed ω for each monomer concentration. Plots of N−1 as ω−1 in the absence of monomer show no dependence on ω (indicative of stable intermediates), but a linear dependence is found with each concentration of monomer. This indicates a first‐order dependence on radical cation concentration. The rate constants show a trend in cation reactivities which is in agreement with that obtained by other methods. This technique, however, extends the range of investigation to a much shorter time scale.
Oligomeric polyaromatic ether‐ketone‐sulfones with acetylenic end groups. X
Authors: Huang Frank , Marvel C. S. 
Published: April 2003

AbstractTwo new oligomeric polyaromatic ether‐ketone‐sulfones with acetylenic end groups have been synthesized. These acetylene‐terminated oligomers are soluble in common organic solvents and can be cured under thermal conditions to give the crosslinked polymers which do not soften below 240°C. In the case of oligomer which is incorporated with terephthaloyl chloride, the cured polymer shows almost no penetration below 400°C. Isothermal aging studies show that the cured polymers are stable in circulating air at 300°C with less than 10% weight loss in 3 days.
Photochemistry of fiber‐forming polymers. II. Ketone‐containing poly(ethylene terephthalates)
Authors: Alexandru L. , Guillet J. E. 
Published: April 2003

AbstractPoly(ethylene terephthalate) copolymers were prepared containing minor amounts of comonomers containing backbone and side‐chain ketone groups. The photochemistry of these polymers was studied at 313 nm, both in film and fiber form. It was demonstrated that only the comonomer, dimethyl‐γ‐ketopimelate (DMKP), gave a copolymer with enhanced sensitivity to ultraviolet degradation in air. Since this sensitivity is reduced in a nitrogen atmosphere, it is suggested that the mechanism involves main‐chain scission to form two free radicals by the Norrish type I mechanism, and that recombination of these radicals is reduced by reaction with oxygen. The use of copolymers of this type provides a method for the controlled photodegradation of polyester fibers.
Applications of ESCA to polymer chemistry. XII. Structure and bonding in commercially produced fluorographites
Authors: Clark David T. , Peeling James 
Published: April 2003

AbstractA series of fluorinated graphites, Fluorographites, of varying fluorine content has been examined by ESCA, and the chemical shifts and relative intensities of the core electron lines yield a consistent picture of the compositions and structures in the surface regions of the materials. Fluorographites of composition (C1F0.81)n to (C1F1.00)n are fully fluorinated in the outermost ∼40 Å and consist of a bulk structure composed of tertiary →CF groups with CF2 groups at the prismatic edges of the fluorinated graphite layers. This is also the case for (C1F1.05)n, but, in addition, some of the CC bonds involving edge →CF carbons are broken and replaced by CF bonds, giving a higher concentration of CF2 groups at the outermost surfaces of the particles of this material. The ESCA data for (C1F0.25)n are consistent with a structure comprising six‐membered aromatic rings in which each ring carbon is attached to a →CF group acting as a bridge among three similar rings, with the CF bonds alternately pointing up and down with respect to the plane defined by the carbon atoms. At the immediate surface the valence requirements of the carbon atoms at the prismatic edges of the graphite‐like layers are satisfied by bonding with oxygen. This is also the apparent structure of (C1F0.37)n, but in addition there exist discrete regions of composition (C1F1)n distributed uniformly throughout this material. The Fluorographites (C1F0.34)n, and (C1F0.40)n, and (C1F0.63)n consist of blocks of C1F1 stoichiometry and blocks of unreacted graphite. The presence of CF2 groups and the complete absence of oxygen in the surface regions of these Fluorographites suggests that the prismatic edge sites are fully fluorinated. The inhomogeneous block‐like structures of (C1F0.37)n, (C1F0.37)n, and (C1F0.34)n, (C1F0.40)n, and (C1F0.63)n, give rise to differential sample charging, resulting in apparent shifts in the binding energy scales between the spectral components originating from different regions of the samples. Such differential sample charging is also described for a number of mixtures of the Fluorographites and of graphite with the Fluorographites. It is pointed out that in view of these results it is necessary to exercise considerable caution in using the ESCA lines of an added compound as a reference in measuring core electron‐binding energies.
Synthesis of polystyenes with different stereoregularities by anionic polymerization
Authors: Uryu Toshiyuki , Seki Toshiyuki , Kawamura Tokiji , Funamoto Akashi , Matsuzaki Kei 
Published: April 2003

AbstractThe stereoregularity of polystyrene prepared by anionic polymerization was determined by means of 13C‐NMR spectroscopy. The stereoregularity changed with such polymerization conditions as catalyst, solvent, and temperature. Sodium naphthalene as catalyst gave a syndiotactic‐rich polystyrene of 66–68% syndiotactic dyads independently of solvent and temperature, while potassium and cesium naphthalenes as catalyst produced polystyrenes with different stereoregularities ranging from syndiotactic‐rich to isotactic‐rich configurations, depending on solvent and temperature. The mechanism of anionic polymerization which caused the difference in stereoregularity was discussed from the viewpoint of growing ionic species.
ESCA studies of polymers. XIII. Shake‐up phenomena in substituted polystyrenes
Authors: Clark D. T. , Dilks A. 
Published: April 2003

AbstractShake‐up phenomena in a series of para‐substituted polystyrenes have been studied by ESCA. Comparison with other spectroscopic data and with theoretical calculations within the sudden approximation, equivalent cores model, and CNDO SCF MO formalism identifies the shake‐up structures as arising predominantly from π*← π transitions involving the highest occupied and lowest unoccupied orbitals of the pendant phenyl groups.
Thermodynamics of binding of methyl orange and its homologs by poly(vinylpyrrolidone): The effect of inorganic electrolytes
Authors: Takagishi Toru , Imajo Koichi , Nakagami Kimio , Kuroki Nobuhiko 
Published: April 2003

AbstractThe extent of binding of methyl orange, ethyl orange, propyl orange, and butyl orange by poly(vinylpyrrolidone) has been measured in aqueous solutions of inorganic electrolytes such as NaCl, LiCl, NaSCN, and NaClO4 by an equilibrium dialysis method. The effect of the salts on the first binding constants and the thermodynamic functions which are accompanied by the dye—polymer association process was investigated relative to the corresponding values in the absence of such salts. It was found that in aqueous solutions of NaCl and LiCl the enthalpy change accompanying the binding is small and the largest contribution to the free energy of binding is from the positive entropy gain. For NaSCN and NaClO4, the values of ΔF° and ΔH° were both large and negative and the value of ΔS° was small and negative. Thus, the favorable free energy for the complex formation was due entirely to the negative enthalpy term. These characteristics of the thermodynamic quantities are discussed in terms of changes in structural properties of water in the vicinity of the binding entities and conformational changes of the polymer to which the dye is bound due to the added foreign electrolytes.
Reactivity ratios for acrylonitrile–vinyl chloroacetate copolymerization systems
Authors: Miller Andrzej , Szafko Jerzy , Turska Eligia 
Published: April 2003

AbstractReactivity ratios for acrylonitrile—vinyl chloroacetate systems have been determined for radical copolymerization at 60°C in dimethylformamide. The values of the ratios calculated by the linear graphical method of Kelen and Tüdös were as follows: r1 = 4.05 ± 0.1 and r2 = 0.001 ± 0.001 for acrylonitrile (AN)—vinyl monochloroacetate (VCAc), r1 = 7.0 ± 0.25 and r2 = 0.05 ± 0.015 for acrylonitrile—vinyl dichloroacetate (VDAc), r1 = 7.13 ± 0.25 and r2 = 0.06 ± 0.015 for acrylonitrile—vinyl trichloroacetate (VTAc). The penultimate model of the copolymerization and the effect of the vinyl chloroacetate structure were discussed.
Chemiluminescence from polytetrafluoroethylene
Authors: Mendenhall G. David , Hassell John A. , Nathan Richard A. 
Published: April 2003

AbstractThe chemiluminescence emission from commercial samples of polytetrafluoroethylene, PTFE (Halon G‐80 and Halon G‐10), was studied at temperatures between 25 and 172°C. The emission intensity decreased on extended heating, removal of the surface layer, solvent extraction, or changing from an atmosphere of oxygen to an inert atmosphere. Films of PTFE deposited from the vapor phase showed comparatively little chemiluminescence under these conditions. Ozone‐induced chemiluminescence was observed at 37°C from G‐10 but not from G‐80, or from films deposited from the vapor phase. The chemiluminescence intensity from ozone and G‐10 was not reduced by solvent extraction.
Photochemical reactions of high polymers. XIV. Syntheses and photochemical reactions of copolymers bearing O‐acyloxime groups
Authors: Tsunooka Masahiro , Kotera Kohei , Tanaka Makoto 
Published: April 2003

AbstractCopolymers bearing pendant O‐acyloxime groups were synthesized by two methods: copolymerizations of oxime acrylate (methyl β‐naphthyl ketone oxime acrylate or benzophenone oxime acrylate) and styrene, condensation of acrylic acid—styrene copolymer with oximes (benzophenone oxime, p‐nitrobenzophenone oxime, methyl β‐naphthyl ketone oxime, benzalacetone oxime or 9‐fluorenone oxime). The photochemical behavior of the O‐acyloxime copolymers changed markedly with the irradiation conditions: irradiation of benzene solutions led to degradation in air and crosslinking under nitrogen, while irradiation of solid films in air resulted in simultaneous degradation and crosslinking. Photolysis of methyl β‐naphthyl ketone oxime acetate, a model for the O‐acyloxime copolymer, in benzene solution under nitrogen resulted in scission of the NO bond. The same reaction was observed in the irradiation of the O‐acyloxime copolymers. It is suggested that formation of free radicals on the polymer chains via scission of the NO bond is followed by decarboxylation. In the absence of oxygen, crosslinking of the polymer by recombination of the free radicals competes with degradation via β‐scission. In the presence of oxygen, autoxidative degradation predominates.
Evidence of crosslinking and chain scission in the degradation of poly(tert‐butyl crotonate) by γ‐irradiation
Authors: O'Donnell J. H. , Rahman N. P. , Winzor D. J. 
Published: April 2003

AbstractThe effect of γ‐irradiation on poly(tert‐butyl crotonate) has been investigated by velocity sedimentation and solubility studies. Evidence of significant crosslinking as well as of chain scission has been obtained, the estimates of G(X) and G(S) being 0.66 and 0.59, respectively.
Reactivity of fluorostyrenes in cationic polymerization
Authors: Laval F. , Marechal E. 
Published: April 2003

AbstractReactivity ratios relative for cationic copolymerization of three fluorostyrenes and styrene were studied. The values of r1 and r2 for various experimental conditions were determined. The influence of the nature of the solvent and of the polymerization temperature were studied in particular. Relative activation entropies and enthalpies were determined, and an isokinetic relationship was found for 2‐, 3‐, and 4‐fluorostyrenes. There is a fairly linear correlation between the C8 chemical shift and the values of 1/r2. All the experimental reactivities were correlated with the quantum chemistry parameters. From this correlation, interaction with C8 and also with C7 and F, was found to be possible, depending on the nature of the monomer.
Conformation of syndiotactic poly(styrenesulfonic acid)
Authors: Aylward N. N. 
Published: April 2003

AbstractA conformational energy map for syndiotactic PSSA indicates that a planar trans sequence of chemical repeat units with a side‐chain orientation of χ ≃ 10° is favored over helix or glide‐plane sequences. As the electrostatic potential of this planar sequence is greater than for the (0°,−120°) or (0°, −80°) sequences it is especially favored under conditions of high ionic strength. Only a very small energy is needed to cause rotational transitions from a planar trans sequence, so that many different sequences exist at any one time in solution. Sequences such as (0°,−20°) are calculated to be hypochromic with respect to the other probable sequences, and this seems consistent with some experimental evidence on the apparent hypochromicity of the band near 261.5 nm under conditions of high ionic strength.
Hydrothermal contraction–dilation of polymer networks by reversible complexation with a complementary macromolecule
Authors: Osada Yoshihito 
Published: April 2003

AbstractA mechanochemical system which works by complexation between a poly(methacrylic acid) (PMAA) network and poly(ethylene glycol) (PEG) was studied. A PMAA membrane swollen with an aqueous PEG solution, to which a load 100 times the weight of the membrane was attached, contracts by over 90% of its length when heated from 10°C to 60°C. The work per contraction was 5 × 10−3 cal/g of membrane. The temperature at which the mechanochemical system undergoes a specified contraction can be regulated by the PEG concentration of the swelling fluid. The sign of the temperature coefficient of the membrane dimension can be reversed by addition of a small amount of ethanol to the swelling solution of PEG. A simple method for calculating the stability constant and thermodynamic parameters for the complexation is outlined.
Synthesis of hydroxyl‐containing polyamides by ring‐opening polyaddition of 4,4′‐disubstituted bis(4‐butanolide) with aliphatic diamines
Authors: Ueda Mitsuru , Yabuuchi Masahiko , Imai Yoshio 
Published: April 2003

AbstractHydroxyl‐containing polyamides have been prepared by the ring‐opening polyaddition of 4,4′‐oxydi‐p‐phenylenebis(4‐butanolide) with aliphatic diamines in alcoholic solvents at 65–80°C. These polymers having inherent viscosities ranging from 0.1 to 0.5 were soluble in a variety of solvents including dimethylformamide, formic acid, and m‐cresol. Transparent and flexible films cast from these solutions were highly hygroscopic. All the polymers had low softing temperatures in the range of 115–130°C, and began to decompose at around 250°C, both in air and under nitrogen.
Selective dimerization of styrene to 1,3‐diphenyl‐1‐butene by acetyl perchlorate
Authors: Higashimura Toshinobu , Nishii Hideo 
Published: April 2003

AbstractThe linear unsaturated dimer of styrene, 1,3‐diphenyl‐1‐butene, was obtained exclusively in the oligomerization of styrene by acetyl perchlorate in various solvents. In benzene, the linear dimer was produced in more than 90% yield at 50°C. In n‐hexane and cyclohexane, the yield of the linear dimer was lower. The yield of the linear dimer was strongly dependent on the nature of solvent. When an increasing amount of 1,2‐dichloroethane was added to benzene, the yield of the linear dimer gradually decreased. On the other hand, when a small amount of 1,2‐dichloroethane was added to n‐hexane or cyclohexane, the yield of the linear dimer increased. The yield of the linear dimer was almost independent of the reaction temperature and the initiator concentration. For comparison, the dimerization of α‐methylstyrene was carried out, and the effects of the initiator and the solvent on the structure of dimers were investigated. On the basis of these results, the mechanism of the dimerization of styrene initiated by acetyl perchlorate is discussed.
Some aspects on the polymerization of N‐vinylpyrrolidone in the presence of poly(methacrylic acid) templates
Authors: Bartels T. , Tan Y. Y. , Challa G. 
Published: April 2003

AbstractN‐Vinylpyrrolidone (NVP) was polymerized in dimethylformamide (DMF) at 60°C in the presence of poly(methacrylic acids) (PMAA) of different tacticities and molecular weights. The rate enhancement, which was ascribed to chain growth of the poly(vinylpyrrolidone) (PVP) radical along the polyacid template, became more pronounced with increasing chain length and syndiotacticity of the PMAA template. The results can be expressed by vR = aPvn, where vR is the polymerization rate relative to that of the blank experiment, Pv is the viscosity‐average degree of polymerization of PMAA, and a and n are constants depending on the reaction conditions and tacticity of PMAA. In the presence of excess monomer the rate enhancement decreased when the quantity of PVP produced corresponded to a stoichiometric ratio of 1:1 with the available PMAA. It is proposed that the template effect is caused mainly by delay of the bimolecular termination step of growing PVP radicals associated with PMAA. Diffusion of polymer radicals, and consequently termination, will be more impaired if the attached PMAA has a greater length (size) and if the binding forces between PVP radical and PMAA template are stronger. The latter implies that PVP forms the strongest complexes with syndiotactic PMAA. This is supported by experiments concerning complex stability.