bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissociation‐association sorption on ion exchangers. I. Experimental study of dependence of equilibrium function of acidity in ion exchanger on activity of hydrogen ions in aqueous phase
Authors: Novák Milan 
Published: April 2003

AbstractEquilibrium coloring of crystal violet, methyl violet, and dimethyl yellow sorbed on ion exchanger Dowex‐50‐WX4 was studied by a spectrophotometric method as a function of the pH of the aqueous phase. From the data obtained, the function of acidity in a ion exchanger was calculated corresponding to individual equilibriums of the exchange reaction. A simple relationship between H̄0′ in a ion exchanger and the pH of the aqueous phase was found.
ESR study of free radicals produced in polyethylene irradiated by ultraviolet light
Authors: Hama Yoshimasa , Hosono Kazuya , Furui Yasuro , Shinohara Kenichi 
Published: April 2003

AbstractESR studies of ultraviolet‐irradiated polyethylene (PE) were carried out. Irradiation effects different from those of high‐energy radiation are observed. Ultraviolet radiation is absorbed selectively, and especially in carbonyl groups in PE produced by oxidation. Radicals produced were identified as \documentclass{article}\pagestyle{empty}\begin{document}$ \hbox{---} {\rm CH}_2 \hbox{---} {\dot {\rm C}} {\rm H} \hbox{---}{\rm CHO}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \hbox{---} {\rm CH}_2 \hbox{---} {\dot {\rm C}} {\rm H} \hbox{---}{\rm CH}_2 \hbox{---}$\end{document}. Some radicals giving a quintet signal stable at room temperature were also observed but remained unidentified. The radical \documentclass{article}\pagestyle{empty}\begin{document}$ \hbox{---} {\rm CH}_2 \hbox{---} {\dot {\rm C}} {\rm H} \hbox{---}{\rm CHO}$\end{document} undergoes a mutual conversion with the acyl radical:
Cationic polymerization of isobutene initiated by stannic chloride and phenols: Polymer endgroup studies
Authors: Bauer R. F. , Russell K. E. 
Published: April 2003

AbstractLow molecular weight polymers of isobutene produced with stannic chloride as catalyst and phenols as cocatalysts have been subjected to ultraviolet and NMR analysis. A high proportion of the endgroups are derived from the phenol cocatalyst when the concentration of free phenol in the reaction mixture at −78.5°C is fairly large. At low concentrations of free phenol, termination to give vinylidene endgroups becomes more significant. The results lend support to the suggestion that an important mode of termination in this polymerization system involves the reaction between a growing carbonium ion and the phenol cocatalyst.
Effect of amines on the ceric ion‐initiated polymerization of vinyl monomers. I. Polymerization of acrylonitrile by ceric ion–triethylamine catalyst system
Authors: Saha Sisir K. , Chaudhuri Ajit K. 
Published: April 2003

AbstractThe polymerization of acrylonitrile was studied in aqueous solution with ceric ammonium sulfate in the presence of triethylamine as initiator at 30, 40, and 50°C. The rate of polymerization was found to be linear with the concentration of the amine and independent of ceric ion concentration. A reaction scheme involving initial complex formation between ceric ion and the amine and subsequent disproportionation of the conplex to produce free radicals is proposed for the initiation reaction. The termination step is postulated as involving oxidation of the polymer chains by ceric ions. The results have been explained in the light of the proposed reaction scheme.
Spectroscopy of irradiated vinyl chloride–propylene copolymers
Authors: Albarino R. V. , Otocka E. P. , Luongo J. P. 
Published: April 2003

AbstractSpectra of vinyl chloride—propylene copolymers irradiated at low temperature in vacuum have been obtained at selected temperatures in the range 130–335°K. Copolymers and PVC homopolymer pass through identical intermediate states of dehydrochlorination in which alkyl, allyl, and polyenyl radicals are observed. Substantial spectral differences between copolymers and PVC appearing in the final states of dehydrochlorination after warming above room temperature are consistent with shorter average polyene lengths in the copolymers. This probably results from termination of polyene growth by propylene comonomer. Spectral differences at long wavelength between copolymers with varying amounts of propylene are minor compared to the basic changes between copolymer and homopolymer.
Mechanism of stabilization of polypropylene by ultraviolet absorbers
Authors: Guillory J. P. , Cook C. F. 
Published: April 2003

AbstractThe ultraviolet screening properties of 2‐hydroxyphenylbenzotriazoles and 2‐hydroxybenzophenones in polypropylene film were investigated by using photochemical and spectroscopic techniques. The effect of light screening on polymer photostability was examined by using filter solutions, and the fraction of ultraviolet light absorbed by stabilized film was calculated and compared to flexural failure times. It was found that the 2‐hydroxyphenylbenzotriazoles behave primarily as screeners of ultraviolet light whereas the 2‐hydroxybenzophenones are both screeners and excited‐state quenchers. The quenching characteristics of the latter have not been isolated and mechanistically examined, but it is probably similar in nature to that of the nickel chelate stabilizers.
Synthesis of poly(arylene ethylene) oligomeric hydroperoxides and their use as initiating agents of radical polymerization
Authors: Chuchin A. E. 
Published: April 2003

AbstractThe oxidation to hydroperoxide of poly(arylene ethylenes) (PAE) by oxygen carried out in solutions at 80–110°C. The effect of initiating additions and the nature of solvent relative to the content of hydroperoxide groups in oxidized PAE were investigated. The oxidation to hydroperoxides in PAE occurs at the methylene groups, and the synthesized hydroperoxides are secondary peroxides. The decomposition of PAE hydroperoxides in toluene and chlorobenzene at concentrations of 0.006–0.03 mole/l. for hydroperoxide in the presence and absence of N‐phenyl‐α‐naphthylamine (PNA) was studied. The decomposition of one hydroperoxide has been studied in the presence of cobaltous and manganese resinates and of PNA in chlorobenzene at 30–50°C. The addition of PNA to a chlorobenzene solution of PAE hydroperoxide containing cobaltous or manganese resinate accelerates the hydroperoxide decomposition, reduces the activation energy, and changes the reaction order from the second‐order to first‐order. The synthesized hydroperoxides initiate the radical polymerization of styrene and methyl methacrylate. The initiating activity of one of the synthesized hydroperoxides of PAE for polymerization of styrene (60°C) in the presence and absence of activating addition of manganese resinate was also evaluated.
Criticisms of claims in the field of isomerization polymerization. II. Polymerization of o‐isopropylstryene
Authors: Kennedy J. P. , Magagnini P. L. , Plesch P. H. 
Published: April 2003

AbstractThe polymerization of o‐isopropylstyrene with free radical (benzoylperoxide, heat) and cationic (AlCl3, AlBr3) initiators has been investigated. It is concluded that, contrary to an earlier prediction and to a claim by Aso et al., both the radical and carbonium ion polymerizations of o‐isopropylstyrene proceed by conventional mechanisms which give the same 1,2 repeat unit.
Thermal degradation of nylon 66
Authors: Peebles L. H. , Huffman M. W. 
Published: April 2003

AbstractThe rate of gel formation and color formation in poly(hexamethylene adipamide), nylon 66, is found to be dependent upon the rate of removal of the volatile products of degradation. If a sample of nylon is heated above its melting point in a sealed tube, the material will remain soluble for extended periods of time as the intrinsic viscosity first passes through a maximum, then a minimum, followed by the abrupt formation of insoluble material. The color remains reasonably white. On the other hand, if the volatile material is permitted to escape, rapid gelation and color formation will occur, even in the complete absence of oxygen. Intermediate rates of gelation and color formation can be obtained by control of the rate of volatile material distillation. The decrease in molecular weight evidenced in the sealed tubes is probably due to hydrolysis and ammonolysis of the amide groups which occur simultaneously with the formation of multifunctional crosslinking agents. The volatile material contains an intense absorption in the 290 mμ region. Analysis of the volatile material shows that it contains inter alia, water, carbon dioxide, ammonia, cyclic monomer, hexylamine, hexamethyl‐eneimine, hexamethylenediamine, cyclopentanone, 2‐cyclopentylcyclopentanone, 2‐cyclopentylidinecyclopentanone, and 1,2,3,5,6,7‐hexahydrodicyclopenta[b,e]pyridine, which has an intense absorption at 287 mμ, ε = 8.87 × 104l./mole‐cm, (methanol).
Organometallic polymers I. Solution polymerization of α‐ferrocenylmethylcarbonium fluoborate
Authors: Gal Alon , Cais Michael , Kohn David H. 
Published: April 2003

AbstractThe self‐condensation of α‐ferrocenylmethylcarbonium ion in nitroethane yielded polymers of Mn up to 20,000. The change of [η] and Mn with the reaction time indicated that the process consisted of a rapid primary growth stage, an induction period, a second growth stage, and a crosslinking stage. The [η]–Mn correlation for a series of polymeric fractions in the Mn = 0.1–7.2 × 104 range points to a highly branched structure.
Thermal stability of hydrogen networks by chemical stress relaxation
Authors: Shaw Montgomery T. , Tobolsky Arthur V. 
Published: April 2003

AbstractThe thermal stability of hydrocarbon networks by chemical stress relaxation was investigated in vacuo and in the temperature range 300–350°C. The polymers studied were low‐density polyethylene, high‐density polyethylene, and ethylene–propylene terpolymer. Carbon‐carbon crosslinked networks were produced either by dicumyl peroxide or by radiation. The results show that the overall thermal stability is in the order: peroxide‐cured EPT > peroxide‐cured LDPE > radiation‐cured HDPE. The results are in apparent contradiction to the belief that linear structures are more stable than branched structures. We believed that this can be explained in terms of weak linkages introduced during curing.
Equilibrium anionic polymerization of α‐methylstyrene in p‐dioxane
Authors: Léonard J. , Malhotra S. L. 
Published: April 2003

AbstractThe equilibrium anionic polymerization of α‐methylstyrene in p‐dioxane, with potassium as initiator, has been investigated at 5, 15, 25, and 40°C by using high‐vacuum techniques. The comparison of these results with those obtained previously for the equilibrium polymerization of α‐methylstyrene in tetrahydrofuran revealed that, although the values of ΔG1c, the free‐energy change upon the polymerization of 1 mole of liquid monomer to 1 bases‐mole of liquid amorphous polymer of infinite chain length, are the same for both systems, there is a distinct effect of the solvent. This effect is reflected in the value of monomer equilibrium concentration and its variation with polymer concentration and is explained in terms of a solvent–monomer and solvent–polymer interaction parameter.
Telechelic diene prepolymers. I. Hydroxyl‐terminated polydienes
Authors: Reed Samuel F. 
Published: April 2003

AbstractTelechelic prepolymers of butadiene, isoprene, and chloroprene with hydroxyl end‐ groups have been prepared by the solution polymerization of the dienes under free‐radical initiation. 4,4′‐Azobis(4‐cyano‐n‐pentanol) was employed as the initiator. Liquid prepolymers were obtained with molecular weights of 2000 to 20,000 and with functionalities usually greater than 2. The preparative procedure and prepolymer characterization are described.
Oxidative crosslinking in poly(ethylene terephthalate) at elevated temperatures
Authors: Nealy D. L. , Jane Adams L. 
Published: April 2003

AbstractPoly(ethylene terephthalate) oxidizes on being heated in air at elevated temperatures to form a crosslinked structure. The crosslinking occurs through a reaction which causes arylation of terephthalate rings to form a biphenyltricarboxylic acid derivative. This reaction is interpreted as a free‐radical cleavage generating a substituted phenyl radical which selectively attaches to a terephthalate residue via substitution.
Synthesis and properties of new polyamide‐imides
Authors: Alvino W. M. , Frost L. W. 
Published: April 2003

AbstractSeveral new amide—imide polymers of good thermal stability have been synthesized by the reaction in solution of diacid chlorides with diamines containing cyclic imide linkages. Since these polymers incorporate preformed imide groups, they are not subject to some of the problems encountered in the preparation of polyimides by cyclizing polyamic acids. Their solutions in polar solvents such as dimethylacetamide are stable and will tolerate considerable proportions of hydrocarbon thinners without precipitation. Thick films can be cast from the solutions without degradation. A high‐temperature cure is not needed to produce tough, flexible films. The powdered polymers can be molded readily.
Influence of temperature on microstructure of anionic‐initiated polybutadiene
Authors: Uraneck C. A. 
Published: April 2003

AbstractApplication of the Arrhenius relationship for temperature and ratio of isomeric units in polybutadiene made in the presence of butyllithium initiator is consistent with the existence of three simultaneous competing reactions. Evidence in the literature is cited to support the possibility that the growing chain end exists in a composite equilibrium producing localized structures which on reacting with monomer result in fixed isomeric units. The compliance of the data with the thermodynamic relationship permits the extrapolation of a narrow set of data to a broad temperature range.
Structure of crystalline polymers with unbranched long side chains
Authors: Platé N. A. , Shibaev V. P. , Petrukhin B. S. , Zubov Yu. A. , Kargin V. A. 
Published: April 2003

AbstractThe structure and thermodynamic properties of atactic and isotactic acrylic and methacrylic polymers containing 16–18 carbon atoms in the n‐aliphatic side chains, and of copolymers of hexadecyl acrylate with isopropyl acrylate were studied by means of x‐ray and differential thermal analysis. The crystallization of branched acrylic and methacrylic polymers and of acrylic copolymers proceeds in the form of a hexagonal crystal, regardless of the configuration of the backbone chain. Methods of ordering branched macromolecules are proposed, and the melting points, heats and entropies of fusion determined. The role of flexibility of the backbone chains in ordering and the crystallization processes was determined. In the case of poly(n‐alkyl acrylates) the backbone chain is involved in the crystalline lattice; this is not the case in methacrylates and copolymers of hexadecyl acrylate with isopropyl acrylate. Some similarity was assumed between the structure of biopolymers and synthetic branched polymers.
Homogeneous polymerization of norbornene catalyzed by ruthenium complex–tertiary phosphine system
Authors: Hiraki Katsuma , Kuroiwa Akihiko , Hirai Hidefumi 
Published: April 2003

AbstractNorbornene is polymerized by ruthenium complex–tertiary phosphine catalysts to polymers consisting of trans‐and cis‐olefinic groups and 1,3‐cyclopentylene group. The system derived from dichloro(dodeca‐2,6,10‐triene‐1, 12‐diyl)ruthenium‐(IV) (1) and triphenylphosphine has a fairly high activity for the polymerization, while I itself has only a very low activity. The system derived from dichlorodi‐μ‐chlorobis‐(2,7‐dimethylocta‐2,6‐diene‐1,8‐diyl)diruthenium(IV) (II) and more moles of triphenyl‐phosphine than four shows almost the same activity as the I‐triphenylphosphine system does. However, II and dichloro(2,7‐dimethylocta‐2,6‐diene‐1,8‐diyl)‐(triphenylphosphine)ruthenium(IV) each polymerizes norbornene in a very high yield, in contrast with I. In addition, both dichlorotris(triphenylphosphine)ruthenium(II) and dichlorotetrakis(triphenylphosphine)ruthenium(II) have been found to display a considerably high activity for polymerization of norbornene. On the basis of these facts and the NMR data of the I– and II–triphenylphosphine systems, the mechanism for the polymerization of norbornene has been discussed.
Sodium salts of sulfonated poly(phenylene ethers) as polysoaps
Authors: Cooper James E. 
Published: April 2003

AbstractPolysoaps are of interest because, unlike most polyelectrolytes, their aqueous solutions become more viscous and often form gels upon the addition of salt. A new kind of polysoap was made by sulfonating phenylene oxide polymers that have a pendant alkyl group containing at least 14 carbon atoms on every phenylene unit. Copolymers made from a mixture of 2,6‐dimethylphenol and 2‐methyl‐6‐tetradecylphenol have the same composition as the monomer mixture. Tetradecyl substituents in the copolymer act as internal plasticizing agents and, by varying the number of substituents, a gradation in physical properties of the unsulfonated copolymer from rigid solid to heavy oil is possible.
60Co‐initiated polymerization of styrene, vinyl acetate, and their mixtures in the presence of a radical initiator
Authors: Niezette Joseph , Desreux Victor 
Published: April 2003

AbstractStyrene and vinyl acetate have been polymerized by γ‐radiation in the presence of α,α′‐azobisisobutyronitrile or benzoyl peroxide. Benzoyl peroxide does not affect the vinyl acetate polymerization, but the rate of polymerization is greatly increased by the action of the initiator in the case of the following systems: styrene–α,α′‐azobisisobutyronitrile, styrene–benzoyl peroxide, and vinyl acetate–α,α′‐azobisisobutyronitrile. For these three systems, the experimental results are in good agreement with a kinetic scheme obtained by assuming an energy transfer process from monomer excited molecules to the initiator; this process does not occur in the first system, and the initiation rate is determined only by the vinyl acetate concentration. In the case of the polymerization of mixtures of the two monomers, the action of α,α′‐azobisisobutyronitrile and that of benzoyl peroxide are practically the same; that is, the shape of the polymerization curve may be understood on the basis of an energy transfer from styrene excited molecules to the initiator.
Effect of alkoxides on chain termination and chain transfer of sodium‐catalyzed polybutadiene
Authors: Cheng Tai Chun , Halasa A. F. , Tate D. P. 
Published: April 2003

AbstractThe reaction of butadiene with n‐butylsodium or metal alkoxide‐modified n‐butylsodium was studied. A loss of “live ends” was observed when the polymerization of butadiene‐1,3 with n‐butylsodium was conducted in hexane solvent. This occurs, presumably, by elimination of NaH or Na metal in the allylic system. Similar results were obtained when the polymerization was carried out in the presence of sodium‐tert‐butoxide‐modified n‐butylsodium. However, the modification of n‐butylsodium by lithium or potassium tert‐butoxide in the butadiene‐1,3 polymerization showed no loss of live ends for a period of two weeks. The results and an explanation are discussed.
Chemical thermodynamics of polymerization of formaldehyde in an aqueous environment
Authors: Bryant W. M. D. , Thompson John B. 
Published: April 2003

AbstractA self‐consistent set of chemical thermodynamic values for the polymerization of formaldehyde in the gas phase and in aqueous solution is obtained with the aid of recent experimental thermochemical results and the use of selected methods of calculation of data not otherwise available. Enthalpies, entropies, and Gibbs free energies of formation are derived for the various intermediates and products, including the first six hydroxyl‐terminated oligomers. Simple equations for the logarithm of the equilibrium constant as a function of temperature are presented for a number of polymerization reactions, permitting comparison with experimental results. Reasonable agreement is obtained in almost all cases, even though ideal solutions are assumed.
Mechanism of initiation of methyl methacrylate with lithium tert‐alkoxides
Authors: Trekoval J. 
Published: April 2003

AbstractAn investigation of the solution polymerization of methyl, butyl, isobutyl, sec‐butyl, and tert‐butyl methacrylates and the polymerization of methyl and butyl methacrylates in the presence of methyl, butyl, and tert‐butyl isobutyrate and methyl pivalate showed that the complex order of the initiation reaction with respect to the monomer (about 2) has its cause in the ability of the ester group in the monomer and of methyl or butyl isobutyrate to activate lithium tert‐alkoxide. Owing to conjugation, the ester group in the monomer is less active than the ester group in isobutyrate. Steric hindrances of the formation of a complex between lithium tert‐alkoxide and ester were also investigated, because this complex is intermediate product necessary for the formation of an activated lithium tert‐alkoxide, capable of initiating the polymerization of alkyl methacrylates of the type CH2(CH3)COOCH2R.
Copolymers of vinyl chloride and vinylidene chloride with some acid chlorides
Authors: Janovič Z. , Marvel C. S. , Diamond M. J. , Kertesz D. J. , Fuller G. 
Published: April 2003

AbstractVinyl chloride and vinylidene chloride were copolymerized with 10‐acryloxydecanoyl chloride and 12‐acryloxystearoyl chloride by use of free‐radical initiator in solution to obtain copolymers with active chlorine groups. Alternative routes for making such copolymers which consisted of making the corresponding acrylic acid or acrylyl chloride copolymers, followed by reaction with hydroxy acid and finally conversion to the acid chloride by treatment with thionyl chloride, were investigated. The monomer reactivity ratios for the radical copolymerization of vinyl chloride (VCI) and vinylidene chloride (VCl2) with acrylic acid (AA) and acrylyl chloride (ACI) were determined: VCI–AA, r1 = 0.025, r2 = 6.40; VCl–ACl, r1 = 0.017, r2 = 2.65; VCl2–AA, r1 = 0.46, r2 = 1.26; VCl–ACl, r1 = 0.50, r2 = 1.12.
Vinyl polymerization. Part 268. Polymerization of acrylonitrile initiated by the system of tetramethyl tetrazene and bromoacetic acid
Authors: Sugiyama Kazuo , Nakaya Tadao , Imoto Minoru 
Published: April 2003

AbstractThe polymerization of acrylonitrile (AN) initiated by the system of tetramethyl tetrazene (TMT) and bromoacetic acid (BA) in dimethylformamide (DMF) was studied. The TMT–BA system could initiate the polymerization of AN more easily than TMT alone. The polymerization was confirmed to proceed through a radical mechanism. The initial rate of polymerization Rp was expressed by the equation: Rp = [TMT]0.62‐[BA]0.5[AN]1.5. The overall activation energy for the polymerization was estimated as 9.4 kcal/mole. In the absence of monomer, the reaction of TMT with BA in DMF was also studied kinetically by measuring the evolution of nitrogen gas. The reaction was first‐order in TMT and first‐order in BA; the rate data at 49°C were k2 = 9.1 × 10−2l./mole‐sec., ΔH‡ = 17.0 kcal/mole, and ΔS‡ = − 6.6 eu. In addition, the treatment of TMT with BA in benzene led to the formation of tetramethylhydrazine radical cation, which was identified by its ESR spectrum. On the other hand, the relatively strong interaction between TMT and DMF was observed by absorption spectrophotometry.