bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on polymers from cyclic dienes. XII. Cationic polymerization of spiro[2,4]hepta‐4,6‐diene
Authors: Ohara Osamu , Aso Chuji , Kunitake Toyoki 
Published: April 2003

AbstractPolymerizations of spiro[2,4]hepta‐4,6‐diene were carried out with cationic initiators and Ziegler‐type catalysts. This monomer polymerized very rapidly with a variety of cationic initiators, and low monomer and initiator concentrations had to be employed in order to avoid formation of crosslinked polymers. The polymer contained 1,2 and 1,4 addition units, and there was no indication of the opening of the cyclopropyl ring in the monomer unit. The following relationship was obtained: [η] = 4.5 × 10−8M̄n1.71. The exponential coefficient of this equation is much greater than those typical of vinyl polymers, suggesting that the polymer chain is very stiff. The polymer showed much enhanced resistance to autoxidation as compared with polycyclopentadiene, and its softening point was above 200°C. These interesting physical and chemical properties of the monomer and the polymer can be associated with their spiro structures.
Thermal analysis of polystyrenes crosslinked by p‐di(chloromethyl)benzene
Authors: Grassie N. , Gilks J. 
Published: April 2003

AbstractSeries of progressively crosslinked polystyrene have been prepared by the reaction off linear polystyrene with p‐di(chloromethyl)benzene in dichloroethylene solution with stannic chloride as catalyst. By using a DTA technique it has been shown that the glass transition temperature Tg increases with crosslinking very much faster than is accounted for purely by increase in molecular weight. This type of crosslink is only about half as effective in increasing Tg as are crosslinks introduced by copolymerization of styrene with divinylbenzene. Thermal analysis by use of the thermal volatilization analysis (TVA) technique shows that stability, as measured by the evolution of volatile products, decreases as crosslinking progresses, and thermal gravimetric analysis (TGA) confirms this.
Poly α‐ester degradation studies. IV. Rheological studies of polymer degradation
Authors: Lovett A. J. , O'Donnell W. G. , Sutton G. J. , Tighe B. J. 
Published: April 2003

AbstractThe Farol‐Weissenberg rheogoniometer has been used to follow molecular weight changes during the degradation of certain poly‐α‐esters in the melt state. By observing the change in melt viscosity at low shear rates it had been shown that the decomposition of the poly(isopropylidene carboxylate) is substantially first‐order with respect to the molecular weight of the residual polymer. The derived kinetic parameters are in good agreement with those previously obtained by other techniques. This provides a substantial piece of supporting evidence for the view that degradation takes place predominantly by intramolecular ester interchange involving the formation of 1,1,4,4,‐tetramethylglycollide. The introduction of β‐chlorine atoms into the polymer structure leads to a more complex degradation pattern. Thus the presence of a single β chlorine atom per repeat unit, as in poly(3‐chloro‐2‐methyl‐2‐hydroxypropionic acid) leads to a substantially similar dependence on molecular weight with the added complication of progressive crosslinking which becomes more apparent in later stages of the reaction. This crosslinking reaction plays an increasingly important part as the extent of chlorination of the polymer is increased. In addition, the presence of chlorine leads to an increased sensitivity of the degradation reaction to the presence of oxygen.
Carbon‐13 nuclear magnetic resonance of ethylene–propylene copolymer and the determination of sequence distribution of monomeric units
Authors: Tanaka Yasuyuki , Hatada Koichi 
Published: April 2003

AbstractThe 13C‐NMR spectra of ethylene–propylene copolymers and their model compounds were measured at 15.1 MHz. Assignments of the signals were carried out by using the equation of Grant and Paul and also by comparing the spectra with those of squalane, hydrogenated natural rubber, polyethylene, and atactic polypropylene. The accuracy and the precision of intensity measurements, that is, the deviation from the theoretical values and the scatter of the measurements, respectively, were checked for the spectra of squalane and hydrogenated natural rubber and were shown to be at most 12% for each of the signals. On the basis of these results the mole fractions of the four types of the dyad sequences, that is, the propylene–propylene (head‐to‐tail and head‐to‐head), the ethylene–propylene, and the ethylene–ethylene sequences, were determined together with the average sequence lengths of both monomer units.
Electron spin resonance study of ethylene–acrolein copolymer irradiated with ultraviolet light
Authors: Tsuji Kozo 
Published: April 2003

AbstractWhen ethylene–acrolein copolymer was irradiated at −196°C with ultraviolet light, a sharp singlet spectrum with a g value of about 2.001 was predominant. This spectrum is attributed to acyl radicals, which are produced by dissociation of a hydrogen atom from an aldehyde group. At the same time it is supposed that dissociation of formyl groups also took place to give alkyl radicals, CO, and H2. The alkyl radicals reacted with CO molecules to give acyl radicals at −78°C under vacuum. Peroxy radicals were produced when the sample irradiated at −196°C in the presence of air was treated at −78°C. The sample irradiated at −196°C was warmed to near 0°C and an apparent singlet spectrum with a g value of about 2.004 was observed. This spectrum was tentatively assigned as due to free radicals of the type
Vinyl acetate emulsion polymerization. I. Effect of ionic strength and temperature on monomer solubility in the ionically stabilized polymer particle
Authors: Klein A. , Kuist C. H. , Stannett V. T. 
Published: April 2003

AbstractSolubility of monomer in the polymer was strongly affected by ionic strength; with increasing ionic strength, solubility was found to increase. At constant temperature, this was entirely due to the decrease in interfacial tension, as the condensation of surfactant proceeded at the interface. The temperature affected both the polymer–solvent interaction parameter as well as the interfacial tension. These are the two parameters on which solubility depends. The variations of interfacial tension with temperature was found to be complex, but entirely dependent on the entropic consideration of adsorption. The polymer–solvent interaction parameter–inverse temperature dependence was found to be linear, as expected.
Inorganic glasses as crosslinked polymers: The relationship between crosslink density and transformation temperature in phosphate glasses
Authors: Ray N. H. 
Published: April 2003

AbstractMost substances that form stable glasses are polymers, and inorganic oxide glasses are no exception. Because most oxide glasses are highly crosslinked polymers it is not possible to measure properties in solution, and parameters such as molecular weight and molecular weight distribution which are used to characterize organic polymers are meaningless in the context of oxide glasses. Instead, the network connectivity or a measure of crosslink density must be used to characterize their structure. In silicate glasses, the network connectivity can be changed significantly only by altering the composition, but phosphate glasses of fixed composition can be prepared with variable hydroxyl contents and consequently different crosslink densities. In this paper it is shown that the relationship between the transformation temperature T(x) and crosslink density x of phosphate glasses is similar to that observed for organic polymers and can be described by an equation of the form

where T(0) is the transformation temperature of the corresponding linear polymer and K is a constant which is approximately the same for three different phosphate glasses that have been studied.
Organometallic condensation polymerization: Carbon–carbon bond formation by coupling of 1‐phenylcyclohexenyl chromophores
Authors: Relles Howard M. 
Published: April 2003

AbstractDiolefins XV and XVII have been successfully polymerized with metallic lithium in tetrahydrofuran by a radical‐anion, carbon–carbon coupling reaction. The coupling takes place in the mode known for the dimerization of α‐methylstyrene and 1,1‐diphenylethylene and shown herein for 1‐phenylcyclohexene.
Chemical structure of poly(ethylene terephthalate)–styrene and nylon–styrene graft copolymers prepared by radiation techniques
Authors: Sakurada I. , Ikada Y. , Kawahara T. 
Published: April 2003

AbstractThe graft copolymerizations of styrene onto poly(ethylene terephthalate) (PET) and nylon fibers were carried out by the mutual irradiation and preirradiation methods. True graft copolymers were isolated from the products by extraction and characterized by hydrolysis and osmometry. Among the swelling agents employed, methanol was most effective for increasing the extent of grafting onto PET. In both methods of the grafting, the molecular weight of polystyrene formed in the substrate matrix was higher than one million if no chain‐transfer agent was added to the monomer solution. Similar to the case of radiation grafting onto poly(vinyl alcohol) and cellulose, the isolated graft copolymer carried only one branch per copolymer molecule in both cases. Of great interest is the particularly low extent of grafting in the case of PET–styrene. This should be attributed to the low sensitivity of PET to radiation. The grafting site on the mother polymer molecule is discussed on the basis of the solution behavior of the branch polymers separated from the backbone.
Studies of the polymerization of diallyl compounds. XIX. Further discussion of the cyclocopolymerizations of diallyl phthalate with monovinyl monomers by the use of the model compounds
Authors: Matsumoto Akira , Aso Takayuki , Tanaka Seiji , Oiwa Masayoshi 
Published: April 2003

AbstractIn the cyclocopolymerizations of diallyl phthalate (DAP) with monovinyl monomers the reactivity ratio of the cyclized radical, rc, was smaller than that of the uncyclized radical, r1; this was ascribed to steric hindrance in the addition reaction of the cyclized radical with DAP. In this paper, the validity of the values of rc and r1 is discussed on the basis of model experiments, i.e., the copolymerization of DAP in dilute solution corresponding to rc and that of allyl propyl phthalate, to r1. The copolymerizations of methyl allyl phthalate and allyl octyl phthalate with vinyl acetate are also presented.
Adsorption of polymers at the solution–solid interface. X. Reinforcement studies of nitrile rubbers by silicas
Authors: Clark P. J. , Howard G. J. 
Published: April 2003

AbstractVulcanizates of three acrylonitrile–butadiene copolymers were prepared by γ‐ray irradiation. Two pyrogenic silicas of differing surface areas and with surface modifications were incorporated as fillers. Measurements of initial modulus, stress–strain hysteresis, tear energy, and swelling show little differences between the reinforcement effects of the various fillers, although the extent of filler reinforcement is related to the acrylonitrile content of the rubber. The considerable range of interaction energies implied by solution adsorption studies are not reflected in the reinforcement phenomena.
Kinetics of grafting acrylonitrile onto starch
Authors: Gugliemelli L. A. , Swanson C. L. , Doane W. M. 
Published: April 2003

AbstractAcrylonitrile (AN) was graft copolymerized onto gelatinized and granular wheat starch in aqueous media in the presence of ceric ammonium nitrate initiator at 91‐364 anhydroglucose units (AGU) per cerium (IV) and at 1.08‐4.33 AN to AGU ratios. Molecular weights and dispersities of polyacrylonitrile side chains were determined by gel‐permeation chromatography. Conversion‐time plots of AN polymerizations in both gelatinized and granular starch systems show characteristics common to heterogeneous polymerizations that could be explained on the basis of buried polymer radicals. The rates of polymerizations were directly related to the square root of the corrected cerium(IV) concentration and to the 1.3 power of the AN concentration. Graft copolymerization of AN onto starch, at least during initial stages, is not suitably explained by a kinetic scheme involving termination by polymer radical with cerium(IV) ion.
2‐alkyl‐1,3‐butadiene polymerization under the influence of π‐allylic complexes of transition metals
Authors: Vasiliev V. A. , Kalinicheva N. A. , Kormer V. A. , Lobach M. I. , Klepikova V. I. 
Published: April 2003

AbstractStereoregulation in the polymerization of 2‐alkyl‐1,3‐butadienes with transition metal π‐allylic complexes has been studied. The direction of isoprene polymerization is shown to be a function of the nature of the metal and ligands in the allylic compound. The presence of acidic ligands in π‐allylic complexes of Zr, Cr, Mo, and Co contributes to 1,4‐addition and increases the selectivity of π‐allylic nickel complexes, favoring cis‐1,4‐structure formation. Investigation of the model reaction of 2‐alkyl‐1,3‐butadienes with bis(π‐perdeuterocrotyl nickel iodide) revealed that active sites have an π‐allylic type structure. The mechanism of formation of π‐allylic adducts and the main factors which determine the dependence of direction and rate of polymerization on the nature of a monomer in the diene series: 2‐methyl‐1,3‐butadiene(isoprene), 2‐ethyl‐1,3‐butadiene, 2‐isopropyl‐1,3‐butadiene, and 2‐tert‐butyl‐1,3‐butadiene, are discussed.
Synthesis of polyesters from active diesters
Authors: Ogata Naoya , Okamoto Shinji 
Published: April 2003

AbstractEster‐exchange and polycondensation reactions of active diesters such as diphenyl, dithiophenyl, or dipyridinyl esters of adipic or terephthalic acids with glycols were carried out in order to investigate the reactivity of these active diesters toward nucleophilic replacement. Catalysts such as potassium carbonate were required for the esterexchange of these active diesters. Comparison of the reactivity of these active diesters with that of ordinary diesters in the presence of potassium carbonate as a catalyst indicates the rates or the equilibrium constants of the exchange reactions of these active diesters were much larger than those of ordinary diesters, indicating that polyesterification reactions favorably occur. Polyesters were obtained in good yield either by solution or bulk methods in mild conditions.
Kinetics of radiation‐induced grafting reactions. II. Cellulose acetate–styrene systems
Authors: Yasukawa T. , Sasaki Y. , Murakami K. 
Published: April 2003

AbstractKinetics of grafting reactions of styrene to preirradiated cellulose acetate have been studied by labeling the active sites with bromine atoms. The dilution of styrene monomer with methanol affected grafting reactions remarkedly: e.g., as the concentration of methanol in monomer solutions increased, the growth rates of individual graft radicals decreased while the average lifetimes increased. The integrated amounts of active sites which participated in grafting reactions were also affected by the constitution of monomer solutions and varied roughly in proportion to the extents of swelling of cellulose acetate. Grafting yields for styrene/methanol = 1/1 were higher than for 3/1 and 1/3 throughout the duration of grafting reactions, which is due not only to the high molecular weight of graft chains but also to the large number of graft chains for the 1/1 system compared to the other systems.
Anionic polymerization and copolymerization in heterogeneous systems on surfaces with aromatic structure
Authors: Panayotov Ivan M. , Rashkov Ilya B. 
Published: April 2003

AbstractMethacrylaldehyde, methyl methacrylate, methacrylonitrile, styrene and isoprene readily polymerize on potassium–graphite inclusion compounds in ethereal and hydrocarbon solvents. The structure of polymethacrylaldehyde, poly(methyl methacrylate), and polyisoprene as well as the composition of styrene–acrylonitrile and styrene–isoprene copolymers have been investigated. The copolymers have a high content of styrene units which is interpreted in terms of selective adsorption of styrene on the initiator surface.
Conformational properties of structurally rigid polyamides. I. Conformation of polyamides and model diamides derived from optically active cyclic 1,2‐dicarboxylic acids
Authors: Montaudo G. , Finocchiaro P. , Overberger C. G. 
Published: April 2003

AbstractThe conformational equilibria of piperidine diamides derived from five cyclic 1,2‐dicarboxylic acids (I–V) have been investigated by dipole moment measurements and a priori conformational energy estimates. Since these diamides represent the building blocks of the polyamides derived from the above cyclic diacids and piperazine or trans‐2,5‐dimethylpiperazine, the results obtained in the study of the models have been used to investigate the conformation of the polymers. The overall evidence suggests that cyclopentane, cyclohexane, and bicyclooctane piperazine polymers behave as rigid rods in which the structural units possess approximately the same conformational preference exhibited by the respective model diamides.
Conformational properties of structurally rigid polyamides. II. Effect of strong acids on the circular dichroism spectra of asymmetric polyamides with varying degree of structural rigidity
Authors: Montaudo G. , Overberger C. G. 
Published: April 2003

AbstractWe have investigated the effect of methanesulfonic acid (MSA) on the circular dichroism (CD) spectra of some stereoregular polyamides derived from three cyclic 1,2‐dicarboxylic acids (I–III) and piperazine (PIP), trans‐2,5‐dimethylpiperazine (DMPIP), or N,N′‐dimethylethylenediamine (DMED). On the basis of a detailed knowledge of the conformational properties of these polymers, we have attempted an essentially empirical interpretation of the CD spectra and of their relative changes. A striking dependence of the optical properties from the conformational properties and/or transitions in the polymers has been found. Although far from suggesting a 1:1 correspondence between CD spectra and conformational changes, we wish to stress their general correspondence.
Anionic polymerization initiated by diethylamide in organic solvents. I. The use of lithium diethylamide as a polymerization catalyst and the effect of solvent type on the polymerization of isoprene and styrene
Authors: Angood A. C. , Hurley S. A. , Tait P. J. T. 
Published: April 2003

AbstractLithium diethylamide has been found to be an active initiator for the polymerization of isoprene both in hydrocarbon media and in a variety of polar solvents, such as diethyl ether and tetrahydrofuran. The successful initiation of styrene polymerization is, however, strongly dependent upon the type of solvent employed. Thus no polymerization is observed in hydrocarbon media or in diethyl ether solution, but polymerization occurs rapidly in either tetrahydrofuran or 1,2‐dimethoxyethane solution. These polymerization processes are anionic in nature and are characterized by sigmoidal conversion–time plots, indicating that the initiation reactions are relatively slow compared to chain propagation.
Crystallization‐induced reactions of copolymers. III. Ester interchange reorganization of poly(cis/trans‐1,4‐cyclohexylenedimethylene terephthalate)
Authors: Lenz R. W. , Go S. 
Published: April 2003

AbstractRandom copolymers of cis‐ and trans‐1,4‐cyclohexylenedimethylene terephthalate were permitted to undergo ester‐interchange reorganization at temperatures just below the melting point. As predicted from the principles of crystallization‐induced reactions of semicrystalline copolymers proposed in the first two papers of this series, the copolymers were observed to undergo changes in physical properties which are associated with the conversion of a random to a block copolymer. The driving force for this antiequilibrium ordering process is believed to be the irreversible expansion of the crystalline regions following replacement of cis by trans glycol units. Solubility, crystallinity, and crystallization properties were monitored to determine the effects of copolymer composition, temperature, catalyst, and molecular weight on the reorganization rate. This type of process is also believed to be responsible for the direct preparation of block copolymers by a solid‐state polycondensation reaction used in this study.
Cyanopolyesters
Authors: Banucci Eugene G. 
Published: April 2003

AbstractThe reaction of alkyl acyl cyanides with electron‐rich aromatic substrates in highly acidic media was found to give high yields of bisadducts. Reactions with phenol produced two new eyanobisphenols which readily underwent polycondensation with acid chlorides. The resultant polyesters can be directly compared to the polyesters of bisphenol‐A (BPA) strictly on the basis of polar effects since steric differences are nominal. Thermal, mechanical, electrical and solubility characteristics are reported for the cyanopolycarbonates, which show higher thermal transitions and thermal stability than BPA polycarbonate.
Infrared spectra of three crystalline forms of cationically synthesized poly‐3‐methyl‐1‐butene
Authors: Elliott J. J. , Kennedy J. P. 
Published: April 2003

AbstractPoly‐3‐methyl‐1‐butene has been synthesized by Et2AlCl/tBuCl initiator at −130°C. A cast film of this material gave three well defined crystalline phases, α, β, and γ, characterized by infrared spectroscopy. The γ polymorph could not be obtained independently of the other two. Synthesis and/or manipulative procedures that would consistently give only one of the polymorphs are still unavailable. Evidently, the three crystalline phases have very similar lattice energies, and the subtle factors that determine the ultimate nature of the crystal lattice are not yet understood.
Time dependence of shear and normal stresses of polystyrene and poly(ethylene oxide) solutions
Authors: Laufer Z. , Jalink H. L. , Staverman A. J. 
Published: April 2003

AbstractThe time dependence of shear and normal stresses during constant shearing of some polystyrene and poly(ethylene oxide) solutions in Aroclor 1248 was measured by means of a Weissenberg rheogoniometer. The stresses of the poly(ethylene oxide) solutions first increase rapidly with the increase of strain, then decrease to a value lower than the value in the stationary state, pass another maximum smaller than the first one, and finally reach a steady value. At the end of the shearing of these solutions at high shear rates, the formation of aggregates was clearly evident. The polystyrene solutions became time‐dependent only after a certain shear rate and then showed a rheopectic behavior. The difference in behavior is explained qualitatively by the differing tendencies of these polymer chains to form a network.
Thermodynamic aspects of the partitioning of a solute in a gel–solvent system
Authors: De Ruvo A. 
Published: April 2003

AbstractAn expression is derived for the partitioning of a solute molecule in a two‐phase system: swollen gel and free solvent. The approach is thermodynamic, and no specific mechanism for the accessibility of the solute to the gel is assumed. Instead, general interaction terms between the components, i.e., polymer–solvent–solute, are introduced.