bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tailored heterogeneity indices in anionic polymerization
Authors: Eisenberg A. , McQuarrie D. A. 
Published: April 2003

AbstractEquations are derived for the differential molecular weight distribution curve and for the heterogeneity index for several types of delayed initiator addition in anionic polymerization. All the results are in closed and easily used form, and depend only upon the product of the rate constant of the propagation reaction, the total initiator concentration, and a parameter representative of the rate of initiator addition. The results are plotted versus the above‐mentioned product, so that one can determine the heterogeneity index to be expected under a wide range of the variables involved.
Catalysis in the polymerization of silicic acid
Authors: Moulik S. P. , Mullick D. K. 
Published: April 2003

AbstractSome aspects of the condensation polymerization of silicic acid have been discussed in a systematic manner. Empirical relationships between the time of gelation and the catalyzer concentration, with both H+ and OH− catalysis, have been suggested. These are found to be consistent with the observations of various authors. Also the activities of both the ionized and un‐ionized species present in the system account for some anomalous observations and the pH optimum for the maximum time of gelation. The idea of a secondary salt effect, introduced by Brönsted, has been found to be helpful in understanding catalyst function.
Macroreticular redox polymers. III. Characterization of some hydroquinone–quinone redox polymers
Authors: Kun Kenneth A. , Kunin Robert 
Published: April 2003

AbstractA series of hydroquinone–quinone redox polymers on highly and lightly crosslinked macroreticular styrene–divinylbenzene matrices was characterized for redox capacity, reactivity, equilibria, and redox potential. The effects of cerium(IV), iron(III), and oxygen on determinations of redox capacity are described.
Cationic polymerization of cyclic olefins
Authors: Mizote A. , Tanaka T. , Higashimura T. , Okamura S. 
Published: April 2003

AbstractThe polymerization and the polymerizabilities of indene, benzofuran, and 1,2‐dihydronaphthalene are discussed from the point of view of ring strain, ring stabilization, and steric hindrance in the transition state. Monomer reactivities of these olefins were estimated from copolymerization with styrene and from the rate of addition of iodine bromide in acetic acid. Rates and degrees of polymerization are compared with monomer reactivities and resonance energies of indene, 1,2‐dihydronaphthalene, and benzofuran as a measure of ring strain and stabilization. It is found that indence is 1.5–2.0 times more reactive than styrene. This high reactivity of indene is attributed to the ring strain in the monomer state and to the low amount of steric hindrance in the transition state of the coplanar five‐membered cyclic olefin. 1,2‐Dihydronaphthalene is strained and therefore reactive, but propagation to higher molecular weight products is impeded due to the steric hindrance. The reactivity of benzofuran is decreased by conjugative stabilization of CC double bonds at the reaction site.
Polymers from aryl glycidyl ethers
Authors: Gibb T. B. , Clendinning R. A. , Niegisch W. D. 
Published: April 2003

AbstractHigh molecular weight, linear polyethers were prepared by polymerizing a series of ring‐substituted phenyl glycidyl ethers by using the ferric chloride–propylene oxide and dibutylzinc–water catalyst systems. The α‐naphthyl, β‐naphthyl, p‐phenylphenyl, the o‐, m‐, and p‐methyl, and the o‐ and p‐chlorophenyl polymers resemble the parent polymer in that they are readily crystallizable polyethers which have melting points above 170°C. The other substituted poly(phenyl glycidyl ethers), including the o‐ and p‐isopropyl, p‐tert‐butyl, p‐octyl, and 2,4,6‐trichloro derivatives show much less tendency to crystallize and are lower melting. The x‐ray and electron diffraction data established that poly(o‐chlorophenyl glycidyl ether) crystallizes in an orthorhombic unit cell; data obtained in a parallel study of unsubstituted poly(phenyl glycidyl ether) did not allow assignment of a specific structure.
Application of the flory‐mandelkern equation to individual unfractionated polymer samples
Authors: Kalfus Maurycy , Mitus Jan 
Published: April 2003

AbstractA method is developed for the application of the Flory‐Mandelkern equation to the determination of the weight‐average molecular weights of individual, broad, unfractionated polymer samples. The method includes appropriate averaging of the sedimentation constants and of the intrinsic viscosity of an unfractionated polymer sample in a θ solution from the velocity sedimentation data. By means of the method, individual samples of polystyrene, poly(isooctyl methacrylate) and of the copolymer of styrene with 20% isooctyl methacrylate prepared under the same emulsion polymerization conditions from commercial monomers have been investigated. Appropriate θ solvents have been found by the Elias method. Equations for the dependence of the sedimentation constants and of the intrinsic viscosities in the θ solvents on the molecular weights have been established for the polymers without fractionation. Osmometric and light‐scattering measurements as well as Archibald experiments have shown that by the proposed method the molecular weight cut‐off effect is eliminated in the above equations and in the polydispersity parameter Mw/Mn. Molecular weight distributions have been determined for the polymer samples.
Molecular vibrations of irregular chains. I. Analysis of infrared spectra and structures of polymethylene chains consisting of CH2, CHD, and CD2 groups
Authors: Tasumi M. , Shimanouchi T. , Kenjo H. , Ikeda S. 
Published: April 2003

AbstractVarious samples of irregularly deuterated polyethylene were prepared and their infrared spectra were studied. The results support the previously proposed view that poly‐trans‐CHDCHD or ‐cis‐CHDCHD obtained with Al(i‐Bu)3–TiCl4 is an irregularly deuterated chain consisting of the CH2, CHD, and CD2 groups. A simplified calculation of the CHD scissors and CDH rocking vibration frequencies has been made for various model chains. The assignments of the CDH rocking vibration bands in the region of 700–500 cm.−1 have been given on this basis.
Molecular vibrations of irregular chains. II. Configurations of polydideuteroethylene
Authors: Tasumi M. , Shimanouchi T. , Ikeda S. 
Published: April 2003

AbstractA simplified calculation of the CHD scissors vibration frequencies has been made for (CHD)n of various configurations. The correlation between the CHD scissors frequency and the local configuration has been established. On this basis the infrared absorption bands of poly‐trans‐CHDCHD and poly‐cis‐CHDCHD appearing in the region of 1350–1280 cm.−1 have been interpreted in greater detail.
Analysis of the base‐catalyzed phenol–epichlorohydrin condensation
Authors: Brode George L. , Wynstra John 
Published: April 2003

AbstractThe amount of abnormal addition of phenoxide to epichlorohydrin and phenyl glycidyl ether was determined as a function of reaction conditions. The isomer distribution resulting from attack at either position of these unsymmetrical epoxides was quantitatively measured by vapor phase chromatography of the resulting product mixtures. While both epoxides reacted predominantly in the expected normal fashion, small quantities of abnormal addition products were found whose concentrations were temperature‐dependent. The analytical method also permitted a study of the effect of temperature on side reactions involving hydrolytic solvents.
Efficiencies of some ethyl acrylate chain terminators
Authors: Levy Leon B. , Fisher Gene J. 
Published: April 2003

AbstractA group of substituted phenols, quinone, and tropone were used to retard AIBN‐initiated ethyl acrylate polymerization in ethyl propionate solution at 44.7°C. in the absence of oxygen. It was concluded that the efficiency of retardation depended upon the ability of the terminator to stabilize a positive charge on its reaction site in the transition state. Tropone was found to be a particularly good retarder. The radical‐trapping efficiency of 2,2‐diphenyl‐1‐picrylhydrazyl in this system was found to be 50–60%.
Reaction of n‐butyllithium with poly(vinyl chloride)
Authors: Shiina K. , Minoura Y. 
Published: April 2003

AbstractThe reactions of poly(vinyl chloride) and butyllithium in tetrahydrofuran were investigated. A deep purple color developed at first with addition of butyllithium to the THF–PVC solution, and a spontaneous color change of the misture occurred successively to blue, green, and finally pale vellow. In these reaction stages, the PVC might be butylated, dehydrochlorinated, and partially lithiated by BuLi. These facts were substantiated by the results of successive reactions with various substances such as Michler's ketone, carbon dioxide, and styrene.
Some polymers of high dielectric constant
Authors: Rosen Robert , Pohl Herbert A. 
Published: April 2003

AbstractA class of highly conjugated macromolecules exhibiting extraordinarily high effective dielectric constants (DK = 50–900) is described. These polymers are of the polyacene radical quinone type, are highly purified, and exhibit electronic semiconduction. The dielectric constant varies only slightly with pressure (up to 20 Kbar), but strongly with frequency (300–300,000 cps) and moderately with temperature and field strength. The latter effect of field strength on the effective dielectric constant (and on the conductivity) required the development of special measurement techniques which are described. The unusual dielectric behavior can be accounted for assuming the presence of what amounts to a thermally generated plasma of electrons and holes, each locally mobile on extended regions of associated π‐orbitals on the molecules. The postulated resulting “hyperelectronic” polarization of the locally mobile charges in external fields fits the observed high magnitude of the polarizability, as well as its field, frequency, and temperature dependence.
Vanadium‐ or vanadylacetylacetonate as a cocatalyst for the terpolymerization of ethylene, propylene, and dicyclopentadiene
Authors: Cunningham Robert E. 
Published: April 2003

AbstractVanadium trisacetylacetonate [V(C5H7O2)3] and vanadyl bisacetylacetonate [VO‐(C5H7O2)2] were found to be satisfactory catalysts (with Al2Et3Cl3cocatalyst) for the terpolymerization of ethylene, propylene, and dicyclopentadiene to unsaturated, sulfurcurable elastomers. Polymerization solvents of heptane or benzene were used. Best yields of terpolymers were obtained in benzene. Terpolymers with unsaturations of greater than ≃0.20 mole CC/kg. can be cured with a sulfur‐based vulcanzing recipe. Both acetylacetonates produced terpolymers, in benzene, with practically equivalent properties. They also appeared to be nearly equal to corresponding terpolymers made with catalysts of VOCl3or VCl4.
Continuous fractionation of polymers in solution by thermal diffusion
Authors: Kössler Ivo , Krauserová Helena 
Published: April 2003

AbstractThe possibility of carrying out continuous fractionation of polymers by the thermodiffusion method was investigated. From the working space of a plate‐type column, fractions of polymer were continuously withdrawn simultaneously with filling of the column with fresh solution from a storage vessel. After equilibrium had been established, the distributions of molecular weights of the fractions were determined by a modified Baker and Williams method. In the same apparatus, and at constant temperature and concentration, fractionation, which may be characterized by a limiting viscosity number, is dependent on the total rate of withdrawal and on the ratios of amounts of polymer withdrawn in various places on the column.
Polymerization of lactam ethers
Authors: Ogata Naoya , Asahara Tomohiko , Tohyama Syunroku 
Published: April 2003

AbstractPreparation and polymerization of lactam ethers which contain an amide and an ether group in the same ring are described. Seven‐membered lactam ethers give relatively low molecular weight polymers with an anionic or cationic catalyst, while with diethylzinc as catalyst, the 2,7‐dimethyl lactam ether of a seven‐membered ring gives a crystalline polymer having a melting point of 220°C. A polymerization mechanism is discussed.
Synthesis and characterization of branched polystyrene. Part I. Synthesis of four‐ and six‐branch star polystyrene
Authors: Gervasi J. A. , Gosnell A. B. 
Published: April 2003

AbstractThe synthesis of very well defined four‐ and six‐branched polystyrene has been carried out. Anionic polymerization initiated by butyllithium in benzene–tetrahydrofuran medium gave single chains of narrow distribution. Coupling this living polystyryllithium with bis(trichlorosilyl)ethane gave a maximum of four branches. Coupling with the cyclic trimer of phosphonitrilic chloride gave a maximum of six branches. The reaction procedures have been discussed and mechanisms suggested for some of the reactions.
Electron paramagnetic resonance of ultraviolet‐irradiated polyolefins
Authors: Browning H. L. , Ackermann Hazel D. , Patton H. W. 
Published: April 2003

AbstractIf films of polyolefins are ultraviolet‐irradiated at liquid nitrogen temperature, alkyl radicals which can be examined by EPR are produced. No EPR spectra are observed from polyolefins irradiated at room temperature in air. Ultraviolet irradiation of polyolefins containing small alkyl side chains generally produces radicals corresponding to the pendant group or methyl radicals if the side chains contain a methyl branch. For some polymers the radical species could not be identified with certainty. Stabilization studies indicate that an optimum concentration of ultraviolet stabilizer is necessary for maximum stabilization of polyolefins. Preliminary results of EPR studies of the ultraviolet irradiation of various polyolefins are given, and some possible radical species are discussed.
Polyamides having long methylene chain units
Authors: Saotome Kazuo , Komoto Hiroshi 
Published: April 2003

AbstractThree series of polyamides having long methylene chain units have been prepared from p‐xylylenebisethylamine and 2,2′‐pphenylenebisethylamine with aliphatic dicarboxylic acids of long methylene chain units; aliphatic diamines of long methylene chain units with terephthalic, p‐benzenediacetic, and p‐benzenedipropionic acids; and aliphatic diamines with aliphatic dicarboxylic acids, both having long methylene chain units. The effects of the length of the methylene chain units on the melting point, the glass transition temperatures and the densities of these polyamides were investigated. The aromatic polyamides, in which even methylene chains are joined between a phenylene and an amide group generally have higher melting points than the corresponding ones with odd methylene chains. On the plots of the melting points and the densities of the aliphatic series against the amide concentrations, both the melting point and the density extrapolated to the zero amide concentration are found below the values for polymethylene.
Structure and physical properties of glow discharge polymers. I. Polymers from hydrocarbons
Authors: Jesch K. , Bloor J. E. , Kronick P. L. 
Published: April 2003

AbstractThe polymers deposited from the vapors of pentane, ethylene, butadiene, benzene, styrene, and naphthalene subjected to glow discharge have been analyzed by infrared absorption techniques. The reaction products show unsaturation, hydrogenation, and branching in the polymer chains. Aromaticity is present only in polymers from aromatic monomers.
Polymerization in the crystalline state. VIII. Polymerization in N‐carboxy anhydrides of γ‐benzyl glutamate, γ‐methyl glutamate, and ϵ‐carbobenzoxylysine
Authors: Kovács Gábor , Kovács Eszter , Morawetz Herbert 
Published: April 2003

AbstractThe kinetics of the solid‐state polymerization of the N‐carboxy anhydrides (NCA) of the L‐ and racemic forms of γ‐benzyl glutamate (BG), γ‐methyl glutamate (MG), and ϵ‐carbobenzoxylysine (CL) were studied as a function of temperature and aqueous vapor pressure. The reaction of the L‐forms of BG and MG was characterized by an induction period, while the CL derivative reached its maximum polymerization rate at the outset of the reaction. Water vapor had only a minor effect in accelerating the reaction and reducing the chain length of the polypeptides formed. The racemic monomers were found to have different crystal structures from those of the L‐isomers and the racemic MG and CL derivatives polymerized much more slowly than the corresponding optically active crystals. All polymers gave diffuse x‐ray diffraction patterns. Infrared spectra of the L‐polypeptides showed that they were largely in the α‐helical form. The polymer derived from the racemic BG–NCA had a content of α‐helical material which suggested that it consisted of polypeptides with long blocks of D and L residues.
Thermally resistant polymers containing the s‐triazine ring
Authors: Anderson D. R. , Holovka John M. 
Published: April 2003

AbstractAromatic dinitriles cyclize to form aromatic polymers containing the s‐triazine ring. In this paper, these polymers are compared thermally with each other and with aromatic melamine polymers prepared via the aromatic diamine and cyanuric chloride. One perfluoroaromatic melamine polymer was prepared and compared with the other two types of polymers. The polymers (triazines and melamine) in which biphenyl was the backbone were increasingly stable up to 1000°C. in nitrogen. The triazine polymers as a group were the most stable. The perfluoroaromatic polymer was the most stable melamine up to 500°C. in air but was very unstable above 700°C.
Degradation of pectin by γ‐radiation under various moisture conditions
Authors: Wahba I. J. , Massey L. M. 
Published: April 2003

AbstractBy using D50 and D37 doses for 50 and 63% decreases in the solution viscosity of pectin, an evaluation was made of the effectiveness of radiation at different moisture levels. The relation between radiation effectiveness, as measured by the D50 value, and the pectin: water ratio was expressed in a simplified empirical equation. The indirect effect of radiation in dilute aqueous solutions decreased progressively with increasing pectin concentration. On the other hand, a protective effect was produced by small additions of water to dry pectin and a minimum in degradation (i.e., maximum D50 and D37 values) was attained at about the 20% moisture level.The relation between the intrinsic viscosity of dilute aqueous solutions of pectin irradiated air‐dry and the number‐average molecular weight and D37 values was determined. By using the former relation, the number of chain scissions per unit of absorbed energy was measured at different moisture levels.The importance of moisture control in comparative radiation studies was emphasized. An approximately 26‐fold increase in the radiation sensitivity of pectin was produced by an increase in the moisture content from the 20 to the 99% level. Varying the moisture content therefore provides a good means of altering the sensitivity of pectin and similar materials to radiation damage.
Macromolecular models for branched PVC. I. Copolymer of vinyl chloride with isopropenyl chloride
Authors: Caraculacu Adrian A. 
Published: April 2003

AbstractA new type of model for study of polymer anomalies by copolymerization is proposed. For branched PVC, the vinyl chloride–isopropenyl chloride copolymer was used as the macromolecular model. A regulatory and inhibitory action of isopropenyl chloride during the polymerization was demonstrated. To determine the composition of the copolymer, methods based on elemental analysis and NMR and infrared spectra were utilized. It was found that the copolymer composition is very close to that of the polymerization mixture. The structure of the copolymer was studied from infrared spectra. It was found that both forms TCHH and THHH are present, the former being present in a larger quantity. The possibility of the utilization of spectral methods on macromolecular systems to determine the structure and content of a chlorine atom bound to a tertiary carbon atom (ClT) in the presence of an excess of chlorine bound to a secondary carbon was verified.
Macromolecular models for branched PVC. II. Reactivity of chlorine bound to a tertiary carbon atom in the copolymer vinyl chloride–isopropenyl chloride
Authors: Caraculacu Adrian A. 
Published: April 2003

AbstractThe selectivity of the phenolysis reaction of a chlorine atom bound to a tertiary carbon ClT on a macromolecular model, i.e., the copolymer of vinyl chloride–isopropenyl chloride, was verified. The phenolysis reaction can be used as a chemical method to determine ClT in the copolymers. Phenolic polyelectrolytes are obtained as products. The increase of the ClT content leads to an appreciable decrease of the thermal stability of the polymer. The thermal decomposition by dehydrochlorination is a chain reaction. The γ and ultraviolet radiolysis processes did not reveal a remarkable influence of ClT; the samples with an increased ClT content showed a decreased stability towards sunlight. One concludes that when ClT is present in PVC it can initiate the decomposition reaction at lower temperatures than would be expected.
Preparation and characterization of syndiotactic polypropylene
Authors: Boor J. , Youngman E. A. 
Published: April 2003

AbstractThe preparation and characterization of syndiotactic polypropylene are reported. The influence of polymerization variables on the syndiotactic regulating capacity of the VCl4–AlEt2Cl catalyst were investigated. Vanadates could be substituted for VCl4, and Al(C6H5)2Cl or AlEt2Br for AlEt2Cl under suitable conditions. Hydrogen functioned as a chain transfer agent for the AlEt2Cl–VCl4 catalyst, and polymerizations which were terminated with tritiated alcohols yielded polymers containing bound tritium. The syndio‐regulating capacity of the AlEt2Cl–VCl4 catalyst was increased under specific conditions when cyclohexene, oxygen, or tert‐butyl perbenzoate was incorporated. A polymerization mechanism is proposed. According to this mechanism, preference for a monomer complexing mode which minimizes steric repulsions between methyl groups of the new and last added monomer unit is responsible for syndiotactic propagation. Characterization included determination of infrared syndiotactic indices, melting points (65–131°C.), glass transition temperature, densities (0.859 to 0.885 g./cc.), nuclear magnetic resonance spectra, birefringence, differential thermal analysis spectrograms, solubility, and heat of fusion (∼450 cal./mole).