bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new route for synthesis of oligomeric polyurethanes. Alternating copolymerization of carbon dioxide and aziridines
Authors: Kuran W. , Rokicki A. , Romanowska D. 
Published: April 2003

AbstractCarbon dioxide was copolymerized with 2‐methylaziridine and 1‐phenethylaziridine in the presence of organozinc coordination catalysts. Fully alternating copolymers–polyurethanes were obtained. Relations between reaction conditions and polymer yield are given. On the basis of these results a probable scheme of the copolymerization reaction is proposed.
Changes in row structure of extruded polyethylene film in grafting with styrene. II. Copolymer morphology
Authors: Ungar G. , Dlugosz J. 
Published: April 2003

AbstractThe morphology of extruded high‐density polyethylene film grafted with styrene was studied by transmission electron microscopy of thin stained sections. Near the film surface grafted polystyrene was confined to amorphous layers between lamellar crystals of polyethylene. In the film interior separate polystyrene domains were also formed and became predominant in grafting in diluted styrene. The deciding factor for the location of grafted polystyrene is the chain length because only long chains can coalesce in large separate zones. The polystyrene zones expand by cracking the stacks of lamellae along the lamellar normals. Straightening of the twisted crystalline lamellae of polyethylene occurred in grafting. “Bubbles” of styrene homopolymer were formed under conditions of high monomer concentration. The effect of staining the graft by the Kanig method2 was also discussed.
Copolymérisations de l'acrylonitrile. XII. Phénomènes de solvatation préférentielle et effet de conversion dans la copolymérisation (acrylonitrile–styrène)
Authors: Pichot C. , Guyot A. , Strazielle C. 
Published: April 2003

AbstractKinetic deviations with the conversion observed in free‐radical‐initiated [acrylonitrile (A)–styrene (S)] copolymerization carried out in DMF solution have been interpreted in terms of preferential solvation of the polymer by one of the monomers or the solvent. First it is well established that the initial styrene content of the PAS copolymer increases if a slight amount of polymer is introduced before the beginning of polymerization. Next the preferential solvation has been studied and characterized in various solvents (toluene or DMF) from the results of differential refractometry at dialysis equilibrium of the ternary solution (solvent–monomer–polymer) versus its solvent mixture. It was found that the most polar monomer, acrylonitrile, is already adsorbed by the polymer, mostly in copolymerizations carried out in DMF, from initially rich acrylonitrile mixtures. It is suggested that this phenomenon implies a heterogeneous repartition of the monomer mixture in the solution, which may affect the kinetic copolymerization when the conversion increases.
Solid‐state polymerization of long‐chain vinyl compounds. I. Effect of molecular arrangement on polymerizability of octadecyl methacrylate
Authors: Shibasaki Yoshio , Nakahara Hiroo , Fukuda Kiyoshige 
Published: April 2003

Abstractγ‐Ray‐initiated postpolymerization of octadecyl methacrylate in polymorphic crystals and melt has been investigated to clarify the effect of molecular arrangement of the monomer on polymerizability. From thermal, x‐ray, and infrared (IR) analyses this long‐chain monomer exhibited three crystalline modifications that we refer to as α‐, sub‐α, and β‐forms. The β‐form (mp 28.7–29.7°C), which is obtainable from solution, is a stable state with triclinic chain packing. The α‐form (mp 19.5–20.0°C), which is obtained first from the melt but transforms into β‐form on storing, is a metastable state with hexagonal chain packing. The sub‐α‐form appears transiently in α→β transition. The polymerizability of octadecyl methacrylate in the β‐form is extremely low, whereas the α‐form can polymerize easily and the initial polymerization rate, saturated conversion, and polymer molecular weights increase with temperature. Polymerizability in the molten state at fairly high temperature is rather low, however. Thus maximum polymerizability is obtained just above the melting point of α‐form. It has been found that particular orientation and suitable packing mode with some freedom of rotational motion of the monomer molecules in layered structure accelerate the polymerization reaction.
Thermal decomposition of flame retardants: Mixtures of chlorinated polymers with Sb2O3 and (BiO)2CO3
Authors: Ballistreri A. , Foti S. , Montaudo G. , Pappalardo S. , Scamporrino E. 
Published: April 2003

AbstractThe thermal decomposition products that evolve from mixtures of poly(vinyl chloride) (PVC), poly(vinylidene chloride) (PVC2), and chlorinated paraffin (CP) with Sb2O3 and (BiO)2CO3, respectively, have been analyzed by a method of direct pyrolysis in the ion source of a mass spectrometer. This method allowed us to detect volatile products with masses as high as 226 (SbCl3), 314 (BiCl3), 484 (Sb4), 580 (Sb4O6), and 836 (Bi4). Except for SbCl3, this is the first direct evidence of the presence of these species in the gas phase. The volatilization rate profiles of these species versus the pyrolysis temperature have been also determined. Our data confirm that the effectiveness of the title mixtures as flame‐retardant agents depends on the transport of volatile metal products in the flame and provide direct evidence of the presence of metallic Sb and Bi below the polymer ignition temperatures.
Synthesis of hydroxyl‐containing polyamides by ring‐opening polyaddition of 3,3′‐disubstituted bis‐β‐propiolactone with diamines
Authors: Ueda Mitsuru , Takahashi Masayoshi , Imai Yoshio 
Published: April 2003

AbstractA new bis‐β‐lactone monomer, 3,3′‐p‐phenylenebis(2,2‐dichloro‐β‐propiolactone), was synthesized by the cycloaddition of dichloroketene with terephthalaldehyde. Hydroxyl‐containing polyamides with inherent viscosities as high as 1.1 were prepared by the ring‐opening polyaddition of the bis‐β‐lactone with various diamines in tetrahydrofuran at room temperature. They were readily soluble in a wide range of solvents, which included tetrahydrofuran and acetone. The polymers melted and decomposed at temperatures around 200°C.
Multichain copoly(α‐amino acid). III. Multichain copoly(α‐amino acid) prepared by the reaction of copoly(L‐lysine γ‐methyl‐L‐glutamate) with N‐carboxy anhydride of β‐benzyl L‐aspartate
Authors: Sakamoto Munenori , Kuroyanagi Yoshimitsu 
Published: April 2003

AbstractGraft copolymerization of N‐carboxy anhydride of β‐benzyl‐L‐aspartate onto copoly(L‐lysine γ‐methyl‐L‐glutamate) was carried out in N,N‐dimethylformaide which contained 3 v/v% of dimethyl sulfoxide to obtain multi‐Nε‐poly(β‐benzyl‐L‐aspartyl)copoly(L‐lysine γ‐methyl‐L gluta mate). The degree of polymerization of the branch chain attained was much influenced by the interval of the grafting sites of the copoly(L‐lysine γ‐methyl‐L‐glutamate). The solvent‐induced two‐step conformational transition of the multichain copoly(α‐amino acid) was observed in the chloroform‐dichloroacetic acid system at 25°C by the ORD technique. The stability of the α‐helical conformation of the backbone polymer chain was decreased by the presence of poly(β‐benzyl‐L‐aspartyl) branch chains that could form unstable α‐helical conformations of opposite spirals.
The structure of chlorinated poly(vinyl chloride). VI. Comparison of the chlorination of poly(vinyl chloride) and β,β‐d2‐poly(vinyl chloride) with 1H‐NMR and 13C‐NMR spectroscopy
Authors: Lukáš R. , Kolínský M. , Doskočilová D. 
Published: April 2003

AbstractSamples of chlorinated poly(vinyl chloride) (CPVC) and chlorinated β,β‐dideuterated poly(vinyl chloride) (β,β‐d2‐CPVC) were prepared under identical reaction conditions. The microstructure of CPVC and β,β‐d2‐(CPVC) was characterized by a combination of 1H‐NMR, 13C‐NMR spectroscopy, and analytically determined chlorine content. A difference was observed in the reaction rates of chlorination of PVC and β,β‐d2‐PVC, and, in their thermal chlorination in solution, also in the structure of the chlorinated products. It was proved that in the chlorination of β,β‐d2‐PVC a new chlorine atom can also enter the originalCHCl group. The results are discussed from the standpoint of the chlorination mechanism.
Photobleaching of chemically degraded poly(vinyl chloride)
Authors: Owen Eryl D. , Read Roger L. 
Published: April 2003

AbstractDilute (0.23%) tetrahydrofuran solutions of chemically degraded poly(vinyl chloride) were irradiated with monochromatic light (307,320, or 354 nm) after being degassed or saturated with oxygen. The rates of the resulting photobleaching reactions of the polyene sequences present depended in a complex way on the wavelength of the light used and on the presence or absence of oxygen. During 307‐nm irradiation an initial fast decrease in absorbance at 307 nm, which proceeded with a rapidly decreasing quantum yield and which was unaffected by oxygen, was followed by a slower reaction with constant quantum yield that was strongly inhibited by oxygen. The same general trend was observed for solutions irradiated with 320‐ or 354‐nm light but in each case the rates of changes in absorbance at wavelengths other than those irradiated were complex. A mechanism that involves intra‐ and intermolecular reactions of the polyenes is suggested to explain the observed effects.
Cationic polymerizations by aromatic initiating systems. II. Correlation between cationic model and polymerization reactions with the p‐CH3C6H4CH2Cl/Et3Al system
Authors: Reibel Leonard , Kennedy Joseph P. , Chung David Y. L. 
Published: April 2003

AbstractModel experiments and subsequent polymerization runs have been carried out to elucidate the mechanism of cationic olefin polymerizations initiated by aromatic carbenium ions. Thus, the p‐methylbenzylation of 2,4,4‐trimethyl‐1‐pentene, a nonpolymerizable model olefin for isobutylene, was investigated by using the p‐CH3C6H4CH2Cl/Et3Al initiating system and CH2Cl2 solvent under various conditions. All the important organic reaction products were identified and most of them, quantitatively determined. Analysis of the nature of the products and their distributions gave important mechanistic information about the chemistry of elementary events and their relative rates; for example, hydridation and ethylation by the Et3AlCl⊖ counteranion of various cations occurs and these processes mimic termination in carbocationic polymerizations. Hydridation and ethylation are much faster than proton elimination (chain transfer in polymerization) and experimental conditions (e.g., Al/Cl ratio and temperature) influence the relative rates of these processes. According to model experiments, the p‐CH3C6H4CH2Cl/Et3Al system may initiate olefin (isobutylene) polymerization; chain transfer to monomer should be relatively unimportant, but rapid hydridation or ethylation should reduce the kinetic chain and give low conversions. Predictions derived from model experiments were substantiated by polymerizations with isobutylene and the aromatic initiating system.
Polymerization photosensitized by carbonyl compounds
Authors: Lissi E. A. , Encina M. V. 
Published: April 2003

AbstractThe polymerization of methyl methacrylate and styrene photosensitized by acetone, aldehydes, ethyl pyruvate, 2,3‐butanedione, and 2,3‐pentanedione has been investigated and the effect of several additives (carbon tetrachloride, cumene, diethyl amine, triethyl amine, 2‐pentanol, and tetrahydrofuran) on initiation efficiency has been evaluated. The initiation efficiency of a given system depends on several factors, the most important of which are the relative rates of quenching by the monomers and the additives and type of product obtained.
Organosilane polymers. I. Poly(dimethylsilylene)
Authors: Wesson J. P. , Williams T. C. 
Published: April 2003

AbstractPoly(dimethylsilylene) higher polymers prepared by alkali metal coupling of purified dimethyldichlorosilane were found to be high melting, largely crystalline polymers, soluble in solvents at temperatures above 200°C.
N‐(monohalogenphenyl) maleimides and their copolymers with styrene and butadiene
Authors: Bezděk M. , Hrabák F. 
Published: April 2003

AbstractN‐(Monohalogenphenyl)maleamic acids (I) and N‐(monohalogenphenyl) maleimides (II) which contained bromide or chlorine atoms in the 2‐, 3‐, or 4‐position of the phenyl ring and their respective isoimides (III) were prepared. The radical copolymerization of Pairs II + styrene and II + butadiene in benzene solution initiated with 2,2′‐azobisisobutyronitrile at 50°C was used to determine the monomer reactivity ratios of II. Their values, which are close to zero, indicated an alternating addition of the two monomers on the polymer radical. The thermal stability of the copolymers was characterized by thermogravimetric analysis; their flammability was determined by the method of limiting oxygen index. The copolymerizability of III with styrene and isobutylene was verified at 30°C.
Influence of tertiary aromatic diamines on the n‐buLi‐initiated polymerization of isoprene in hexane solution
Authors: Cheminat A. , Friedmann G. , Brini M. 
Published: April 2003

AbstractThe influence of three aromatic tertiary diamines, bis(4‐dimethylamino phenyl) methane (DMAPM), N,N,N′,N′‐tetramethyl‐p‐phenylenediamine (p‐TMPDA), and N,N,N′,N′‐tetramethyl‐o‐phenylenediamine (o‐TMPDA), on the kinetics of polymerization of isoprene in hexane solution, with n‐BuLi as initiator, was studied for different values of ratio r = [amine]/[n‐BuLi]. It is shown that added amine increases initiation rate according to its complexing ability (DMAPM < p‐TMPDA « o‐TMPDA); this result is explained by the formation of complexes between amine A and n‐BuLi, (n‐BuLi, A)x, where x = 6, 4, and 1 for the three amines, respectively. The propagation rate and the structure of polyisoprene are modified with o‐TMPDA only; the decrease in propagation rate and the increase in 3,4 units in the polymer obtained when r increases are assigned to the formation of solvated ion pairs PI−Li+, o‐TMPDA.
Synthesis of polysulfonamides from aromatic disulfonyl bromides and diamines
Authors: Imai Yoshio , Ueda Mitsuru , Iizawa Takashi , Kudo Shuichi 
Published: April 2003

AbstractSolution polycondensations of aromatic disulfonyl bromides with diamines in tetramethylene sulfone at room temperature by the use of organic or inorganic acid acceptors yielded polysulfonamides with moderately high molecular weights. Preferred acid acceptors were 2‐methylpyridine and propylene oxide and lead oxide. The high activity of lead oxide was discussed in relation to the principle of hard and soft acid and bases.
Polyamides of 2,5‐bis(amino methyl) 1,4‐dioxane and dicarboxylic acids
Authors: Akkapeddi Murali K. 
Published: April 2003

AbstractNovel polyamides of 2,5‐bis(amino methyl) 1,4‐dioxane (cis/trans‐BAMD) with adipic/sebacic acids and of 2,5‐bis(carboxy methyl)/2,5‐bis(carboxy) 1,4‐dioxane with 1,6‐hexane diamine have been prepared. Because of the slightly higher conformational flexibility of the 1,4‐dioxane ring in comparison with that of the cyclohexane ring, the BAMD polyamides have lower Tg and Tm than the corresponding 1,4‐bis(amino methyl) cyclohexane (BAMC) polyamides. The symmetry of the trans‐dioxane moiety permits high crystallinity in the trans‐BAMD polymers. The crystallinity Tg and Tm of the trans polymers are decreased with the incorporation of the cis‐dioxane moiety which lacks a plane of symmetry. Because of the hydrophilic nature of the dioxane ring, t‐BAMD‐6 has good moisture‐regain properties, yet is melt processable (Tm = 292°C).
Particle nucleation in emulsion polymerization. III. Nucleation in systems with anionic emulsifier investigated by seeded and unseeded polymerization
Authors: Hansen F. K. , Ugelstad J. 
Published: April 2003

AbstractStudies of seeded and unseeded polymerization of styrene using sodium dodecylsulfate as emulsifier have been carried out in order to investigate the mechanism of particle nucleation in such systems and to test the theory presented in Part I of this series. The rate of capture of water‐soluble oligomeric radicals was considered to be governed by absorption of oligomers with chain length one less than the critical chain length. It was concluded that the micelles became the dominating loci for particle nucleation above CMC for the emulsifier. A complete nonsteady‐state model for particle initiation above CMC which takes into account radical desorption and reabsorption has been developed. It was indicated that, even for styrene, desorption of radicals may play a role in controlling the radical and particle number of interval I under certain conditions. The model also showed that the efficiencies of particles in absorbing radicals could be calculated from physical parameters, such as diffusion constants and surface charge densities, which are available for the system.
Phase separation in the interpenetrating polymeric network on the basis of polyurethane and polyurethane acrylates
Authors: Shilov V. V. , Lipatov Yu. S. , Karabanova L. V. , Sergeeva L. M. 
Published: April 2003

AbstractInterpenetrating polymer networks (IPN) of polyurethane and polyurethane acrylate were obtained. A small‐angle x‐ray scattering technique was used to study the character of the microheterogeneities in IPN and their variation with composition. It was shown that IPN formation is accompanied by phase separation of constituent components. On the basis of experimental data, which involved the mean square of fluctuations of electron densities in IPN, scattering intensity extrapolated to the zero angle, thickness of the transition layer between two phases, degrees of component segregation and diffuseness of phase boundary, degree of miscibility of components on the molecular level, specific inner surface, and the extent of the heterogeneous regions and their mean radius were determined. Parameters that characterize the intensity of microphase separation are dependent on composition: at a higher content of PUA the segregation degree is higher than that of low content. The dimensions of the heterogeneous regions, which extend from one network to the matrix of the other, depend on the composition of IPN and changes most sharply in the range of mean composition due to phase inversion. Thickness of the transition layer ranges from 20 to 40 Å.
Epoxy resins. II. The preparation, characterization, and curing of epoxy resins and their copolymers
Authors: Lin S. C. , Pearce E. M. 
Published: April 2003

AbstractA polymer with high aromatic ring content in the chain backbone usually has high heat and flame resistance. Three diglycidyl ethers of epoxy resins were prepared from bisphenol A (DGEBA), phenolphthalein (DGEPP), and 9,9‐bis(4‐hydroxyphenyl)fluorene (DGEBF) in a study of the relation between the cured polymer structure and properties. The epoxy resin prepared from phenolphthalein was separated by liquid chromatography and three fractions were obtained. The fractions had a basic structure of 3,3‐disubstituted phthalide and differed only in molecular weight. The DGEPP resin changed color from yellow to red after mixing with trimethoxyboroxine (TMB), the curing agent, and to orange after completing the curing cycle. To prepare a highly crosslinked material with good thermal stability, TMB with three active Lewis sites in a molecule was used as the curing agent. The reactivity of the three different resins toward TMB, measured by differential scanning calorimetry (DSC), was DGEBA > DGEBF > DGEPP. For the same curing conditions the order of crosslink density was DGEBA > DGEPP > DGEBF. To modify the flammability of DGEBA, the conventional epoxy resin, it was copolymerized with DGEPP and DGEBF, the higher‐performance epoxy resins. The glass transition temperatures of poly(DGEBA‐co‐DGEPP) and poly(DGEBA‐co‐DGEBF) systems deviated from this relationship. The DGEBF copolymers showed an increased char residue (40 wt % at 700°C) at 20 mole % of DGEBF. This deviation may be due to the lower crosslinking density of this system.
Hydrophobic interactions in the binding of polyvinylpyrrolidone
Authors: Maruthamuthu Meenakshi , Sobhana Meenakshi 
Published: April 2003

AbstractA spectrophotometric method was used for the quantitative determination of binding in the poly‐vinylpyrrolidone–rose bengal system. Binding of tiron, another anionic dye, onto polyvinylpyrrolidone was investigated by equilibrium dialysis. Comparison of binding constants of the two systems indicated the importance of hydrophobic interactions in binding. Because rose bengal can serve as a fluorescent probe, a fluorimetric method was also used and the increase in fluorescence confirmed the significance of hydrophobic interactions in the binding of the dye onto the polymer.
Polymerizations of substituted cyclopropanes. I. Radical polymerization of 1,1‐disubstituted 2‐vinylcyclopropanes
Authors: Cho Iwhan , Ahn Kwang‐Duk 
Published: April 2003

AbstractDiethyl 2‐vinylcyclopropane‐1,1‐dicarboxylate (Ia), 2‐vinylcyclopropane‐1,1‐dicarbonitrile (Ib), ethyl 1‐cyano‐2‐vinylcyclopropanecarboxylate (Ic), and 1,1‐diphenyl‐2‐vinylcyclopropane (Id) were radically homo‐ and copolymerized. Ia, Ib, and Ic polymerized cleanly in 1,5‐type ring‐opening fashion to yield polymers of high molecular weight. Id failed to homopolymerize but copolymerized with common monomers which included maleic anhydride. Infrared (IR) spectra indicated that the double bonds of the polymer chains were in trans form. All polymers were soluble in solvents and solution‐cast films were clear and flexible, showing Tg values in the 25–40°C range. Model reactions of those monomers with benzenethiol also indicated predominant 1,5‐addition reactions. From the results of our investigation it was concluded that the driving force for the facile radical 1,5‐polymerization of Ia, Ib, and Ic was the stabilization of growing radicals by two substituents.
Chain transfer in vinylpyridine polymerizations
Authors: Howard G. J. , Lai Siu‐Hung 
Published: April 2003

AbstractTransfer constants to monomer at 55°C have been measured in 2 and 4‐vinylpyridine radical polymerizations. In addition, the transfer constants to ethanol, octan‐1‐ol, toluene, benzyl alcohol, chloroform, and nitroethane have been measured. These values, which increase in the order above, show no significant variation between the two isomeric monomers.
Monomer dependence of radiation graft polymerization. V. Poly(ethylene‐g‐4‐vinylpyridine)
Authors: Odian George , Derman Arif 
Published: April 2003

AbstractThe radiation‐initiated graft polymerization of 4‐vinylpyridine to high‐density polyethylene has been studied under diffusion‐free conditions by the mutual irradiation technique. The reaction rate is 1/2 order in radiation intensity over the range 0.00076–0.011 Mrad/hr. The reaction rate is first order in monomer at 0.00076 Mrad/hr, over the complete range of monomer concentrations; at 0.021 Mrad/hr, up to 60 vol % monomer; and at 0.21 Mrad/hr, up to 50 vol % monomer.