bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coordination catalysts for the selective hydrogenation of polymeric unsaturation
Authors: Falk John Carl 
Published: April 2003

AbstractThe selective hydrogenation of poly‐1,4‐butadiene in the presence of poly‐1,4‐isoprene is described. Both of these polydienes are hydrogenated more easily than polystyrene. The catalysts which effect these selective hydrogenations are made by the reaction of organoaluminum or lithium compounds with transition metal salts of 2‐ethylhexanoic acid.
Effect of dose rate on the radiation‐induced polymerization of ethylene in tert‐butyl alcohol
Authors: Wada Takeshi , Watanabe Terutaka , Takehisa Masaaki 
Published: April 2003

AbstractThe dependence of the dose rate on the rate of radiation‐induced polymerization of ethylene in tert‐butyl alcohol containing 5 vol‐% water was studied. The reaction was carried out by use of a reactor with a capacity of 100 ml under the following conditions: pressure, 200 kg/cm2; temperature, 24 ± 3°C; dose rate, 3.7 × 104−1.6 × 105 rad/hr; amount of medium, 70 ml. The dose rate exponents for rate of the polymerization, the molecular weight, and the number of polymer chain were found to be about 0.8, −0.1, and 0.9, respectively. These results were well explained with kinetic results (obtained by a novel analytical method) for the polymerization which contain both first‐order and second‐order terminations for the concentrations of propagating radical. The individual values of the rate constants in each elementary reaction were also obtained.
Mechanism of action of some stabilizers in the thermal degradation of poly(vinyl chloride)
Authors: Rasuvaev G. A. , Troitskaya L. S. , Troitskiǐ B. B. 
Published: April 2003

AbstractThe dehydrochlorination of PVC under vaccum has been studied at 170–200°C by a volumetric method. The accelerating effect of HCl is related to its interaction with the forming polyene units of macromolecules. A mechanism is proposed. The effects of various stabilizers, such as organic salts of Ca, Ba, Cd, trialkyl‐ and dialkyltin, trialkyl phosphites, and mixtures of phosphites with metal salts upon the rate of dehydrochlorination, polymer crosslinking, and electron absorption spectra of PVC during degradation in evacuated ampoules were investigated. The stabilizing activity of these compounds depends primarily on the effectivity of absorption of HCl and destruction of polyene units by these compounds.
Structure of chlorinated poly(vinyl chloride). II. Distribution of Cl atoms in the polymer chain
Authors: Doskočilová D. , Schneider B. , Drahorádová E. , Štokr J. , Kolínský M. 
Published: April 2003

AbstractThe distribution of chlorine atoms in the chain of solution‐chlorinated PVC (CPVC) composed of CH2CHCl (1), CHClCHCl (2), and CCl2CHCl (3) monomeric units is described by first‐order Markoffian statistics based on the assumption that the chlorination mechanism is independent of tacticity. In this case, all the statistical parameters can be obtained from experimentally determined concentrations of CH2, CHCl and CCl2 units. Populations of the sequences (11) and (111) calculated from the statistical parameters agree with experimental values determined from infrared and 220 MHz NMR spectra. From infrared spectra, suspension‐chlorinated CPVC contains blocks of intact PVC.
Synthesis and characterization of poly‐β‐hydroxybutyrate. II. Synthesis of D‐poly‐β‐hydroxybutyrate and the mechanism of ring‐opening polymerization of β‐butyrolactone
Authors: Shelton J. Reid , Agostini D. E. , Lando J. B. 
Published: April 2003

AbstractSynthesis of the naturally occurring polyester, D‐poly‐β‐hydroxybutyrate (PHB) was accomplished by using an optically active monomer. Polymerization of D‐(+)‐β‐butyrolactone (β‐BL) of 73% optical purity with a catalyst system of Et3Al–H2O produced a polymer with a similar optical activity and essentially identical to the natural polymer as isolated from bacterial cells. This paper describes the synthesis and characterization of this optically active polyester along with a suggested mechanism to account for the observed stereospecific polymerization of β‐BL with this catalyst system.
Permeability of membranes containing ionogenic groups
Authors: Kopeček J. , Vacík J. , Lím D. 
Published: April 2003

AbstractThe present paper deals with the transport properties of membranes made of hydrophilic gels containing ionogenic groups. Introduction of ionogenic groups into a gel based on 2‐hydroxyethyl methacrylate will affect the permeability of the investigated membranes for sodium chloride by an order or more. Dependences of the permeability on the content of ionogenic groups, three‐dimensional network density, and pH were established. The permeability for NaCl was compared for that for bivalent salt (MgSO4). It is shown, on the basis of independently determined distribution coefficients, that an increase in the permeability of ampholytic membranes in comparison with the neutral ones is primarily due to an increase in the diffusivity of the salt in the membranes with modified structure. It can also be concluded that an approximation of the free volume from the volume of the solvent in the membrane cannot be applied to the poly(2‐hydroxyethyl methacrylate) gel.
Acid‐catalyzed polymerization of 1,6‐anhydro‐β‐D‐glucopyranose
Authors: Wollwage Paul C. , Seib Paul A. 
Published: April 2003

AbstractA number of 1,6‐anhydrides were polymerized in the melt at 115°C by use of monochloroacetic acid as catalyst. In the early stages of polymerization (up to 40–50% monomer consumed), each monomer was found to disappear by a first‐order rate process. The 1,6‐anhydrides investigated and their relative rates of polymerization were: 1,6‐anhydro‐2‐O‐methyl‐β‐D‐glucopyranose, 1.0; 1,6‐anhydro‐3,4‐di‐O‐methyl‐β‐D‐glucopyranose, 1.4; 1,6‐anhydro‐2‐O‐methyl‐β‐D‐galactopyranose, 2.3; 1,6‐anhydro‐3‐O‐methyl‐β‐D‐glucopyranose, 2.6; 1,6‐anhydro‐4‐O‐methyl‐β‐D‐glucopyranose, 6.3; 1,6‐anhydro‐4‐O‐(β‐D‐glucopyranosyl) β‐D‐glucopyranose, 9.0; 1,6‐anhydro‐β‐D‐galactopyranose, 17; 1,6‐anhydro‐β‐D‐glucopyranose, 37; 1,6‐anhydro‐β‐D‐mannopyranose, 91; and 1,6‐anhydro‐2‐deoxy‐β‐D‐arabino‐hexopyranose, 240. The effect of substitution on the rate of polymerization suggests this reaction is mechanistically related to the acid hydrolysis of pyranosides. The results suggest that polymerization proceeds in two stages: (1) an initial build‐up of dimer followed by (2) a slower growth to higher molecular weight material.
Cationic polymerization of cyclic dienes. X. Cationic polymerization of 1‐vinylcyclohexene and 3‐methyl‐1,3‐pentadiene
Authors: Hara Kazuo , Imanishi Yukio , Higashimura Toshinobu , Kamachi Mikiharu 
Published: April 2003

Abstract1‐Vinylcyclohexene (VCH), which has one of the double bonds in the ring and the other outside the ring, was synthesized and polymerized by cationic catalysts. The reactivity of VCH was very large in the polymerizations catalyzed by boron trifluoride etherate (BF3OEt2) and stannic chloride–trichloroacetic acid complex. Similar to other cyclic dienes, the polymerization of VCH was a nonstationary reaction having a very fast initiation step. The polymerization proceeded by either a 1,2‐ or a 1,4‐propagation mode in which vinyl group was always involved. Particularly when BF3OEt2 was used as a catalyst, an intramolecular proton or an intramolecular hydride ion transfer reaction took place, resulting in the formation of methyl groups in the polymer. The degree of polymerization of polymer formed was about 10. This indicates the preponderance of monomer transfer reaction. To investigate the reason for the high reactivity of cyclic dienes, cationic copolymerizations of VCH and 3‐methyl‐cis/trans‐1,3‐pentadiene (cis/trans‐MPD) was carried out. The relative reactivity of monomers decreased in the order VCH > trans‐MPD > cis‐MPD. On the other hand, the resonance stabilization of monomers decreased in the order VCH > trans‐MPD > cis‐MPD. Therefore, it could be considered that the monomer reactivity is mainly determined by the stability of carbonium ion intermediate. The relative stability of carbonium ion must be VCH > trans‐MPD > cis‐MPD. Thus the influence of the conformation of ion on its stability was clearly demonstrated.
Effects of temperature on styrene–methacrylonitrile copolymerization
Authors: Rudin A. , Yule R. G. 
Published: April 2003

AbstractThe free‐radical copolymerization of styrene and methacrylonitrile was studied in toluene solution at 60, 90, and 120°C. Copolymer composition was estimated from gas‐chromatographic measurement of unreacted monomer concentrations. Reactions were carried to about 20% conversion to minimize analytical errors. Reactivity ratios were calculated by using an integrated form of the Mayo‐Lewis simple copolymerization equation. Reactivity ratios were not sensitive to reaction temperature. The values at 90°C are r1 = 0.41 (methacrylonitrile) and r2 = 0.37 (styrene). The r1 values are higher than those reported by other workers, presumably because of advantages in the present analytical technique and calculation method. The negligible temperature dependence of reactivity ratios is in accord with theory. If monomer pairs exhibit pronounced dependence of reactivity ratios on polymerization temperature, this may indicate a change in mode of placement of units in the polymer chain.
Inorganic coordination polymers. XI. A new family of chromium(III) bis(phosphinate) polymers, [Cr(OH)(OPRR′O)2]x
Authors: Nannelli Piero , Gillman H. D. , Block B. P. 
Published: April 2003

AbstractHeating hydroxyaquochromium(III) bis(phosphinates) at temperatures up to 200°C under vacuum yields the corresponding anhydrous polymers [Cr(OH)(OPRR'O)2]x. The infrared and visible spectra and solution properties lead to the following conclusions. When R and R′ are phenyl groups, the hydroxyl groups appear to bridge between adjacent chromium atoms in the chain together with the phosphinate ligands to yield a linear, triple‐bridged polymer. When at least one substituent on the phosphorus is an alkyl group, some of the hydroxyl groups crosslink between chains to yield less soluble polymers. Comparison of the properties of these new polymers with the parent polymers suggests that the latter should be formulated [Cr(H2O)n(OH)(OPRR′O)2]x·pH2O and that they contain more than one kind of monomer unit. The parent polymers can be readily prepared by a new method which involves reaction of a soluble chromium(III) salt with alkali metal phosphinates or of chromium(III) hydroxide with phosphinic acids in a water–tetrahydrofuran mixture.
Cationic polymerization of 2‐vinyl‐1,3‐dioxane
Authors: Sumitomo Hiroshi , Okada Masahiko , Ito Hiroshi 
Published: April 2003

AbstractThe cationic polymerization of 2‐vinyl‐1,3‐dioxane initiated with triethyloxonium tetrafluoroborate was studied with particular emphasis on elucidation of the structure of the polymer. The polymer was a light yellow powdery material with a molecular weight of several thousands which was soluble in most organic solvents. The infrared and NMR investigations on the polymer, together with chemical analyses, showed that the polymer consisted of the three structural units I, II, and III, the contents of which were estimated to be 5–10%, 20–25%, and 65–70%, respectively.
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The formation of the structural units I and II was discussed in detail.
Photochemical and thermal isomerization in polymer matrices: Azo compounds in polystyrene
Authors: Priest W. J. , Sifain M. M. 
Published: April 2003

AbstractPhotochemical and thermal geometrical isomerizations of monoazo compounds have been studied in polystyrene–n‐butylbenzene compositions. Cis–trans isomer ratios established by light absorption were found to depend on matrix viscosity. Where the compositions were above their respective glass temperatures, all thermal isomerizations conformed to first‐order kinetics. Where compositions were below their respective glass temperatures, the initial isomerization rates were abnormally fast, decaying to normal first‐order processes after substantial amounts of reaction had taken place. These effects have been interpreted in terms of the vitreous properties of polystyrene.
Titration curves of p‐aminobenzoic acid–formaldehyde polymer in relation to its structure
Authors: Chatterjee S. K. , Agrawal V. B. 
Published: April 2003

Abstractp‐Aminobenzoic acid and formaldehyde were condensed in the presence of acid catalyst. The linear condensation polymer thus obtained was then separated into four fractions by a fractional precipitation method. Conductometric titrations were carried out on these four polymer fractions and the conglomerate in nonaqueous solvents with acid as well as base. The titration curves indicated a large number of additional breaks before the complete neutralization of COOH or NH2 groups. These observations have been interpreted in terms of degree of polymerization and the structure of the polymer.
Synthesis and characterization of some trithiols
Authors: Overberger C. G. , Scheinfeld I. 
Published: April 2003

AbstractThe preparation of 1,3,5‐pentanetrithiol is described to provide model systems for poly(vinyl mercaptan). In addition, the preparation and identification of the three stereoisomers of 2,4,6‐heptanetriol are reported as models for isotactic, syndiotactic, and heterotactic poly(vinyl mercaptan).
Rotational mobility of nitroxyl radicals in polyesters
Authors: Gross Susan C. 
Published: April 2003

AbstractRotational mobility of nitroxyl radicals in polyester films was investigated at temperatures from −180 to +240°C by ESR spin‐probe techniques. Evidence obtained indicated that mobility of radicals was related to polymer structure and reflected increased volume made available to the probe molecule by the polymer matrix. A single correlation time, which followed the form τC = τ0 exp {Ea/RT}, was calculated for the temperature range of rapid reorientation (∼109 Hz) of nitroxyl radicals. Ea ranged from 5 to 25 kcal/mole for various systems. Uniaxially oriented semicrystalline polymer matrix restricted radical mobility to a greater extent than a semicrystalline biaxially oriented sample. Effective local viscosity encountered by a nitroxyl radical in several polymers was calculated as 9–13 poise.
Radiation‐induced copolymerization of chlorotrifluoroethylene with ethyl vinyl ether
Authors: Tabata Y. , Du Plessis T. A. 
Published: April 2003

AbstractThe radiation‐induced copolymerization of chlorotrifluoroethylene with ethyl vinyl ether was investigated in the liquid phase at 20 and −78°C over a wide range of monomer compositions. A copolymer was obtained in which the monomers alternate with regularity along the polymer chain over the entire range of monomer compositions investigated. Both the rate of copolymerization and the intrinsic viscosity of the resulting copolymer were found to depend strongly on the initial monomer composition, both reaching a maximum value at an equimolar concentration of the monomers. The monomer reactivity ratios were determined and correspond well with calculated values. A decrease in the irradiation temperature was accompanied by a marked decrease in the rate of copolymerization and the intrinsic viscosity of the copolymer.
Kinetics of heterogeneous free‐radical polymerization of vinylidene chloride
Authors: Wessling Ritchie A. , Harrison I. R. 
Published: April 2003

AbstractPoly(vinylidene chloride) precipitates as a crystalline phase during the polymerization reaction. Under the conditions studied, this phase is made up of complex particles with a lamellar substructure. The detailed morphology is very sensitive to reaction medium. The morphology developed by particles formed during polymerization of vinylidene chloride in dioxane suggests a mechanism of polymerization followed by crystallization. The morphology observed in mass polymerization suggests that both processes occurs simultaneously. Kinetic data, however, suggest a solid‐phase reaction mechanism for both cases. The results are analyzed by comparison with a model that takes into account the solid‐phase morphology. The theoretical analysis is consistent with experimental results if it is assumed that polymerization occurs on the edges of the lamellar crystals.
Estimation of parameters of the scattering particles in elastoidin by low‐angle X‐ray methods
Authors: Ratho T. , Misra T. 
Published: April 2003

AbstractLow‐angle x‐ray scattering methods have been used to evaluate some parameters like specific inner surface of the dispersed phase, transverse lengths, the length of in homogeneity, the length of coherence, and the air‐fraction of the scattering particles in Elastoidin. The low‐angle Kratky camera of the latest design was used for the experimental measurements. Since the sample under investigation is a densely packed solid polymer, the theories of Kratky and Kratky and Porod have been used to evaluate these parameters.
Preparation and properties of some water‐soluble cobalt (III)–poly‐4‐vinylpyridine complexes
Authors: Kurimura Yoshimi , Tsuchida Eishun , Kaneko Masao 
Published: April 2003

AbstractWater‐soluble cobalt(III) chelates having a polymeric ligand such as cis‐[Co(en)2‐PVPCl]Cl2 and cis‐[Co‐(trien)PVPCl]Cl2 (PVP = poly‐4‐vinylpyridine) were prepared by substitution reactions between cobalt(III) chelate and PVP in water–alcohol solution. PVP of different degrees of polymerization was used as the ligand in preparation of these complexes. The PVP complexes were identified and their properties ascertained by microanalysis and by a study of the infrared, ultraviolet, visible, and PMR spectra. Most of the characteristic properties of these complexes may be ascribed to the polymeric structure of the PVP ligand.
Imidization reaction in polyvinylamides
Authors: Haas Howard C. , Macdonald Ruby L. 
Published: April 2003

AbstractDepending on their method of preparation, polyvinylamides can have nitrogen contents which vary from the theoretical value to considerably lower values. Cyanamer P‐250, a polyacrylamide, manufactured by American Cyanamid Corporation, had a nitrogen content of 17.67% compared to the theoretical value of 19.7%. A polyacrylamide prepared in dioxane at 60°C and initiated by benzoyl peroxide, had a nitrogen content of only 15.5%. These low values are ascribed to loss of ammonia via intramolecular imide formation. We have found that when the intramolecular imidization reaction in poly acrylamide and in polymethacrylamide is driven to completion by heating the polymers in dilute solution, very close to 33% of the amide groups remain unreacted. Thus, unlike poly(methyl vinyl ketone) and poly(vinyl chloride), the poly‐vinylamides do not obey Flory's statistical calculation for the random reaction of 1,3 groups in a head‐to‐tail polymer which predicts isolation of only 13.53% of the vinyl residues. Of the various possible explanations, the hypothesis of larger ring formation seems the most plausible, since specific interactions have been shown to exist between widely spaced amide groups in low molecular weight diamides. The infrared spectra of polyacrylimide and polymethacrylimide are presented and compared with those of the corresponding polyvinylamides. When the nitrogen content of polyacrylamide falls to the 14.9–15.4% N range due to imide formation, the polymer becomes water‐insoluble. Because imidization stiffens the polymer chain and introduces weakly acidic groups, the imide content of a polyvinylamide should affect its compatibility with other polymeric systems.
Studies of the polymerization of diallyl compounds. XII. Cyclocopolymerization of dimethallyl phthalate with vinyl acetate
Authors: Matsumoto Akira , Oiwa Masayoshi 
Published: April 2003

AbstractDimethallyl phthalate was copolymerized with vinyl acetate at 60°C with the use of benzoyl peroxide as an initiator. The rate and degree of copolymerization increased with an increase in the mole fraction of vinyl acetate. The residual unsaturation of the copolymer was nearly constant, regardless of the feed molar ratio. The monomer reactivity ratios (MRR) were obtained on the basis of the copolymer composition equation in which the intramolecular cyclization reaction was considered: γ1 = 1.08 (MRR of the uncyclized radical), γ2 = 0.99 (MRR of vinyl acetate radical), γc = 0.73 (MRR of the cyclized radical). The difference between γ1 and γc is discussed.
Synthesis and properties of anthracene‐containing polybenzyls
Authors: Montaudo G. , Finocchiaro P. , Caccamese S. 
Published: April 2003

AbstractA number of alternating copolymers containing anthryl and aryl units in the polymer chain have been prepared by Friedel‐Crafts arylation of the anthracene (polymer type B) or by condensation of 9,10‐bis(chloromethyl) anthracene with opportune aromatic substrates (polymer type A). Polymers of type A were all found to contain 9,10‐disubstituted anthracene units, but polymers of type B were found to contain 1,4‐disubstituted anthracene units. Structure of the polymers were established through their NMR and ultraviolet spectra, and through analogy with appropriate model compounds. It has been found that the inclusion of anthracene units in the polymer chain yields higher melting and more soluble materials with respect to polybenzyls containing only aryl units. Anthracene units introduce, also, some interesting fluorescence characteristics in the polymers, which show intense emission at about 440 mμ.
Radiation‐induced polymerization of 1,2‐cyclohexene oxide in the plastic crystalline state
Authors: Hiramoto Tetsuo , Nishii Masanobu , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractRadiation‐induced solid state polymerization of 1,2‐cyclohexene oxide has been investigated. By the differential thermal analysis and x‐ray diffraction analysis, it was found that this compound has a phase transition point at −81°C and behaves as a plastic crystal in the temperature range from −81°C to −36°C (melting point). The in‐source polymerization proceeded not only in the plastic crystalline state but also in the ordinary crystalline state at temperatures below the phase transition point. The overall rate of polymerization and the rate of chain transfer to monomer in the plastic crystalline state were larger than those in the ordinary crystalline state by a factor of about forty, but the kinetic mechanisms were identical, i.e., the termination mechanisms were unimolecular in both solid states. In contrast, the kinetic mechanisms in the plastic crystalline state and in the liquid state were different. From these observations, the effects of molecular motion and molecular arrangement on the polymerizations of 1,2‐cyclohexene oxide in the three phases were discussed.
Synthesis of titanium polyesters
Authors: Carraher Charles E. 
Published: April 2003

AbstractTitanium polyesters of the form
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where Cp denotes cyclopentadiene, have been synthesized by utilizing both the interfacial and solution techniques. Polymer yield increases with reaction time. The reactive titanium reactant in the solution polycondensations is believed to be the Cp2Ti+2 cation.
Orientation in nylon 6 films as determined by the three‐dimensional polarized infrared technique
Authors: Sibilia John P. 
Published: April 2003

AbstractA three‐dimensional polarized infrared technique was used to obtain information about molecular orientation in both uniaxially and biaxially drawn nylon 6 films. The 835 and 930 cm−1 bands were used to describe the orientation of the A (extended chain) conformation while absorptions at 1175 cm−1, and 1120 cm−1 and 1075 cm−1 were used to give some information about orientation of the B (twisted chain) conformation. On the basis of the 835 and 930 cm−1 bands, it was shown that the hydrogen‐bonded sheets made up of chains in the A conformation are parallel to the film surface in the biaxially drawn film. Uniaxially drawn films obtained by drawing both at 100 and 150°C showed a high degree of chain alignment in the draw direction for the A conformation at draw ratios greater than 2.5. Some planar orientation was also observed in these uniaxially drawn films for both the A and B conformations at high draw ratios.