bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses and reactions of optically active polymers. II. Preparations of optically active polymers containing quinine, L‐ephedrine, and L‐histidine residues and their reactions with α‐cyanoethylaquocobaloxime
Authors: Narita Mitsuaki 
Published: April 2003

AbstractPreparations of polymers with bis(dimethylglyoximato)cobalt (cobaloxime) were investigated. 4‐Vinylpyridine was reacted with α‐cyanoethylaquocobaloxime to produce α‐cyanoethyl‐4‐vinylpyridinatocobaloxime (I) in 72% yield. It did not, however, polymerize by the use of azobisisobutyronitrile (AIBN) as an initiator. Polymers containing α‐cyanoethylcobaloxime were obtained by reactions of polymers with α‐cyanoethylaquocobaloxime (II). Poly(9‐O‐methacryloylquinine) (III), poly(O‐methacryloyl‐N‐methyl‐L‐ephedrine) (IV), poly[Nα‐(o‐vinylbenzyl)‐L‐histidine] (V), and poly(4‐vinylpyridine) (VI) were prepared and used in these reactions. Polymers V and VI were reacted with II to give polymers X, XI, XII, and XIII containing α‐cyanoethylcobaloxime.
Kinetics and thermodynamics of anionic polymerization of 2‐methoxy‐2‐oxo‐1,3,2‐dioxaphosphorinane
Authors: Łapienis Grzegorz , Penczek Stanisław 
Published: April 2003

AbstractKinetic activation parameters and thermodynamic functions describing the reversible anionic polymerization of 2‐methoxy‐2‐oxo‐1,3,2‐dioxaphosphorinane (1,3‐propylene methyl phosphate) were determined. Enthalpy and entropy of the anionic propagation ⇌ depropagation equilibrium were found to be close to those found previously by the present authors for the cationic polymerization, while the activation parameters of propagation and depropagation differ substantially for both processes and reflect the differences in the involved mechanisms. Thus, data for anionic polymerization (and cationic polymerization in parentheses) are: ΔH1s° = −0.7 kcal/mole (−1.1); ΔS1s° = −2.8 cal/mole‐deg (−5.4); ΔHp‡ = 26.7 kcal/mole, and ΔSp‡ = −6.1 cal/mole‐deg. The polymers obtained have low degrees of polymerization (DPn ≤ 10) because of the extensive chain transfer, leaving cyclic end groups in macromolecules. The presence, structure and concentration of the end groups have been determined by 1H‐, 31P‐, and 13C‐NMR spectra.
Stoichiometric formation of methyl methacrylate oligomer by triethylaluminum in the presence of azobisisobutyronitrile
Authors: Grotewold Juan , Hirschler Marcello M. 
Published: April 2003

AbstractThe yield of methyl methacrylate (MMA) polymerization as a function of triethylaluminum (TEA) concentration for a constant azobisisobutyronitrile (AIBN) concentration at 50°C has been measured. The polymerization yield does not differ markedly from that with AIBN alone as long as the initial TEA concentration is held smaller than four times the initial AIBN concentration. A sudden decrease in yield and molecular weight is observed at TEA/AIBN concentration ratios between 4 and 5. A plot of M̄w−1 vs. TEA gives a rate‐transfer constant of 89 1./mole‐sec. If the reaction mixture is vacuum‐evaporated with a previous addition of water, instead of precipitating the polymer, the formation of a considerable amount of MMA oligomer is detected for TEA/AIBN concentration ratios larger than 4. On the average, each TEA molecule in excess of four times the initial amount of AIBN yields one oligomer molecule. The data are consistent with a radical polymerization mechanism for the high molecular weight polymer and with a nonradical one for the oligomer formation.
Some properties of intermediate regions in interpenetrating polymeric networks
Authors: Lipatov Yu. S. , Chramova T. S. , Sergeeva L. M. , Karabanova L. V. 
Published: April 2003

AbstractThe molecular mobility in an interpenetrating polymeric network (IPN) based on crosslinked polyurethane (1) and styrene–divinylbenzene copolymer (2) was studied by broad‐line NMR spectroscopy and reversed gas chromatography. NMR and infrared investigations show the absence of chemical interaction between the two constituent networks. For an IPN in the temperature range −196 to 120°C transition regions corresponding to the individual networks and to an intermediate region were found, the latter being characterized by an additional transition at 25–60°C (NMR spectroscopy) and 44–78°C (gas chromatography). The existence of an intermediate region, presumably of loosely packed structure, leads to a shift in the beginning of the temperature transition in IPN to lower temperature and to a decrease in activation energies of relaxation in comparison with the individual networks. The activation energies in IPN are decreased with increasing weight fraction of the second network.
Kinetics of diffusion‐free radiation graft polymerization of styrene onto polyethylene
Authors: Rabie Abdelgawad , Odian George 
Published: April 2003

AbstractThe diffusion‐free radiation graft polymerization of styrene onto polyethylene has been studied. The grafting rate shows a dependence on monomer which is far different than what has been assumed. Further, the dependence on monomer changes with increasing dose rate as does the dependence of grafting rate on radiation dose rate. Three different regions of behavior are defined: (1) a region of low dose rate where the grafting rate is 1/2‐order in dose rate and 3/2‐order in monomer; (2) a region of intermediate dose rate where the grafting rate is intermediate between 1/2‐and zero‐order in dose rate and 5/2‐order in monomer; and (3) a region of high dose rate, where the grafting rate is independent of dose rate and at least 5/2‐order in monomer. Various possible mechanisms responsible for these effects are discussed, including the effects of viscosity on the initiation and termination reactions, the possibility of ionic graft polymerization, and energy transfer.
Antimony oxide–PVC synergism: Laser pyrolysis studies of the interaction mechanism
Authors: Lum R. M. 
Published: April 2003

AbstractLaser‐probe pyrolysis is used to investigate the synergistic flame‐retardancy effect observed for antimony oxide (Sb2O3)–PVC combinations. Molecular beam‐mass analysis detection techniques permit direct sampling of the laser‐vaporized species without the need for intermediate product collection stages. Laser pyrolysis of a PVC formulation containing 3 phr Sb2O3 provides the first direct evidence for the production of volatile SbCl3 during thermal decomposition. Selective laser irradiation of PVC in the presence of unheated Sb2O3 in the sample cell reveals that HCl evolved from the polymer substrate rapidly reacts with Sb2O3(s) to form the volatile flame‐retardant species SbCl3. Similar results are observed for SbOCl(s). These reactions are distinct from those previously proposed, which involve the formation and subsequent thermal decomposition of intermediate solid‐phase antimony oxychlorides, and demonstrate that the antimony compounds, rather than serving only as inert sources for SbCl3, readily participate in direct chemical reactions with HCl. In addition to the composition of the reaction products, information is also obtained on their evolution characteristics from the sample cell.
Polystyrene resins with immobilized polyamines: Preparation, characterization, and ability to bind Cu(II) ions
Authors: Shambhu Manvendra B. , Theodorakis Michael C. , Digenis George A. 
Published: April 2003

AbstractThree polyamine ligands, ethylenediamine (EDA), diethylenetriamine (DTA), and triethylenetetramine (TETA), were bound to three chloromethylated “popcorn” polystyrene resins (16, 50, and 100% phenyl ring substitution) with the use of pyridine as the reaction medium. The rate of chloride displacement decreased with increasing molecular weight of the amine and higher degree of resin chloromethylation, while the extent of multiple attachments to the polymer matrix increased. The additional crosslinking, a result of multiple attachments, caused the polyamine resins to swell to a lesser extent in pyridine and water. The ability of the insoluble polyamine–polystyrene resins to chelate Cu2+ ions from dilute solutions (200 ppm) was determined at pH 5. With EDA resins the capacity for Cu2+ increased with increasing amount of the bound polyamine, with DTA it remained unchanged, while with TETA it was found to decrease.
Polymerization of vinyl chloride with organolithium compounds. V. Fractionation and solution properties of high molecular weight poly(vinyl chloride)
Authors: Jíšová V. , Janča J. , Kolínský M. 
Published: April 2003

AbstractA sample of high molecular weight poly(vinyl chloride) (PVC) was fractionated by classical precipitation fractionation and gel‐permeation chromatography (GPC) on a preparative scale. The fractions thus obtained were characterized by light scattering, viscometry, and by the GPC method. The measured weight‐average molecular weights M̄w, intrinsic viscosity [η], and polydispersity index M̄w/M̄n values were used for the determination of the Mark‐Houwink equation, [η] = KMa, for PVC in cyclohexanone (CHX) at 25°C valid for molecular weights from 100,000 to 625,000.
Phosphonylation of a polypentenamer and preparation of its hydrogenated derivatives
Authors: Azuma C. , Macknight W. J. 
Published: April 2003

AbstractPhosphonylated derivatives of a polypentenamer (PP) containing 82% trans and 17% cis double bonds have been prepared by the free‐radical addition of dimethylphosphite to the double bonds and subsequent hydrogenation of the residual unsaturation. In this way derivatives were prepared containing approximately 5 and 10 mole % dimethylphosphonate side groups. These side groups were further reacted by hydrolysis or neutralization to form phosphonic acid and cesium phosphonate salts. Reaction conditions were so chosen that no backbone degradation occurred, and side reactions leading to crosslinking were avoided. The derivatives were characterized by gel‐permeation chromatography (GPC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared spectroscopy, and nuclear magnetic resonance spectroscopy. It was found that increasing substituent concentration decreases the melting point Tm in the case of the hydrogenated derivatives and increases the glass transition temperature Tg in the case of the unhydrogenated derivatives. The free acid derivatives are the least thermally stable of all those studied and the hydrogenated derivatives are generally more stable than the unhydrogenated derivatives.
Determination of unsaturated structures in poly(vinyl chloride) by means of fourier transform 1H‐NMR spectroscopy
Authors: Caraculacu A. , Bezdadea E. 
Published: April 2003

AbstractA method based on the PFT‐NMR technique was developed for a direct determination of unsaturated end groups in PVC. By using NMR proton spectra it was found that the unsaturated groups in PVC contain allylic chlorine atoms. Three types of unsaturated end groups were identified, corresponding to the following models: 3‐chloro‐1‐pentene, 2,3‐dichloro‐1‐pentene, and 1,2‐dichloro‐2‐pentene. The last two types could also correspond to some unsaturated groups on the backbone bearing allylic chlorine atoms. The presence of such groups would partially explain the PVC degradation.
New monomers and polymers. V. Study of the spontaneous polymerization of 5‐ethoxycarbonyl‐3‐formyl‐2‐pyrazoline
Authors: Braham J. N. , Noels A. F. , Teyssié Ph. 
Published: April 2003

AbstractThe 3‐formyl‐2‐pyrazolines (pyrazoline‐3‐carboxaldehyde) obtained by 1–3 dipolar additions of diazoesters to acrolein are unstable and smoothly polymerize through the aldehyde group to a polyacetal polymer. On the basis of spectroscopic data, this paper describes the structure of the isolated polymers, along with their properties and a polymerization mechanism. It is proposed that a nucleophilic attack of an heterocyclic amino nitrogen on another monomer formyl group leads to an internal ion pair, and that this latter promotes a polycondensation of other aldehydic units according to an anionic type of propagation. The results are polyacetal polymers of low molecular weight with conservation of the heterocyclic framework. However, numerous side reactions are possible and account for the relatively low molecular weights observed.
Oligomérisation anionique de l'ethylène. III. Application à la synthèse d'alcools à longue chaine
Authors: Magnin Henri , Rodriguez Firmin , Abadie Marc , Schué François 
Published: April 2003

AbstractLiving oligomers of ethylene obtained by n‐BuLi complexed with TMEDA have been deactivated by ethylene oxide. The nuclear magnetic resonance study of the product obtained allowed us to follow the influence of TMEDA toward the functionalization. Three products have been characterized:

By increasing the ratio [TMEDA]/[n‐BuLi] one obtains a decrease of the functionalization reaction.
D2‐m‐carborane‐siloxanes. III. Preparation and properties of trifluoropropyl‐modified polymers
Authors: Peters E. N. , Stewart D. D. , Bohan J. J. , Moffitt R. , Beard C. D. , Kwiatkowski G. T. , Hedaya E. 
Published: April 2003

AbstractLinear D2‐m‐carborane‐siloxanes with one, two, and three trifluoropropyl moieties per repeat unit were prepared by the condensation reaction between bisureidosilanes and carborane disilanol. Molecular weights between 100,000 and 220,000 were obtained. Compared to fluorosilicones, the trifluoropropyl‐modified carborane‐siloxanes exhibited greater thermal and oxidative stability and in certain cases comparable solvent resistance. The swelling index for carborane‐siloxane elastomers decreased with increasing trifluoropropyl content, although this fluorocarbon moiety did compromise the thermal stability of the carborane system.
Calculation of the elementary rate constants of polymer‐analogous reactions and sequence analysis of products
Authors: Stoy V. 
Published: April 2003

AbstractA method has been developed for the calculation of elementary rate constants of deceleration and acceleration reactions on polymers in which the reactivity of the group is influenced only by the character of the closest adjacent groups. It is suggested that this method may be valid if the calculation yields a rate constant k′3, which is independent of conversion. In this case, the sequence analysis of products can be performed by using Markovian first‐order statistics, and the rate constants thus obtained can be used for calculating the relative frequencies of variously long sequences of reacted and unreacted groups and their number‐average length. For markedly accelerated reactions, a simplified method of estimation of the average sequence length involving use of two of the three elementary rate constants, i.e., k1 and k′2, has been suggested.
Active polycondensation with hexamethylenediamine of sebacates having 1,4‐pyrone nuclei
Authors: Sanui Kohei , Tanaka Saeko , Ogata Naoya 
Published: April 2003

AbstractSebacates from alcohols having a 1,4‐pyrone nucleus were synthesized, and their reactivities toward diamine were investigated. The polycondensation reactions of di(6‐hydroxymethyl‐1,4‐pyron‐3‐yl) sebacate or di(2‐methyl‐1,4‐pyron‐3‐yl) sebacate with hexamethylenediamine took place easily even at room temperature to form a high molecular weight nylon 610 in a quantitative yield. The reactivities of these active diesters with diamine were much higher than that of the corresponding diphenyl ester and were almost comparable to those of acid chlorides. It was also found that inorganic salts such as lithium chloride, zinc chloride, or calcium chloride had a strong influence on the molecular weight of the resulting polyamide. The reactivity enhancement of the active diesters toward aminolysis could be attributed mainly to the acidic character of the leaving group.
Influence of the solvents on the γ‐ray polymerization of acrylic acid. II.
Authors: Laborie Francoise 
Published: April 2003

AbstractThe presence of plurimolecular H‐bonded aggregates in the acrylic acid allows the polymer to involve some stereoregular sequences. This effect is made easier when some polymer is already formed in the reacting medium: the aggregates are stabilized by hydrogen bonds with the polymer which gives rise to a matrix effect. Two groups of solvents have been characterized by examination of the monomer's association forms in solution. In a first group of solvents (methanol–dioxan–water), the aggregates are maintained and reinforced; in the second one, acrylic acid exists only as cyclic dimers (hydrocarbons–chlorinated solvents). The difference between the association forms of the monomer involves some important modifications on the kinetics of polymerization and the structure of the obtained polymers. In the solvents of the first group, the obtained polymers are crystallizable and may involve syndiotactic sequences, while in the presence of the solvents of the second group no crystallization or stereoregularity of the polymer can occur. A very close correlation is thus found between the aggregated structure of the monomer, the polymerization kinetics, and the structure of the polymers.
Effects of lithium bromide on the gel‐permeation chromatography of polyester‐based polyurethanes in dimethylformamide
Authors: Hann Nancy D. 
Published: April 2003

AbstractThe hydrodynamic volume changes of the polyester‐based polyurethanes, as dimethylformamide solutions with and without lithium bromide, were studied. Gel‐permeation chromatographic (GPC) and intrinsic viscosity techniques were employed as methods for characterization. Decreases in intrinsic viscosity as well as dramatic changes in the GPC chromatograms were observed. These observations are explained by the polarity of these polyester‐based polyurethane molecules and the resulting characteristics of molecular expansion, association, and polymer–column interaction normally associated with polyelectrolytes.
Photoinitiated polymerization of methyl methacrylate and methyl acrylate with 14C‐labeled benzoin methyl ethers
Authors: Carlblom L. H. , Pappas S. P. 
Published: April 2003

AbstractThree 14C‐labeled benzoin methyl ether (α‐methoxy‐α‐phenylacetophenone) derivatives were utilized as photoinitiators in the polymerization of methyl methacrylate (MMA) and methyl acrylate (MA). The results of polymer end‐group analysis are in accord with a mechanism of benzoin ether photocleavage into initiator radicals and dispute earlier labeling studies which were interpreted as evidence for copolymerization of excited‐state benzoin ethers with reactive monomers. In MMA polymerization, the results indicate a preference for termination by disproportionation (∼60%) and provide evidence for primary radical termination at 0.041M photoinitiator (optically dense solutions) in neat MMA. Evidence for chain branching by initiator radical hydrogen abstraction from poly(methyl acrylate) (PMA) is also presented. The benzoyl and α‐methoxybenzyl radicals, produced on photolysis of benzoin methyl ether, appear to be equally effective in both initiation and hydrogen‐abstraction processes. Quantum yields at 366 and 313 nm indicate the absence of a wavelength effect.
Functional end‐group polymers derived from free‐radical chain transfer. I. Kinetic prediction of functionality
Authors: Athey R. D. , Mosher W. A. , Weston N. W. 
Published: April 2003

AbstractThe kinetic scheme describing chain transfer in free‐radical polymerizations, the Mayo equation, has been rearranged to yield the probability of generating a functional end group by chain transfer (e.g., to a disulfide). The prediction is that a mixture of functional and nonfunctional ends occurs. Examination of literature data shows a number of systems produce more functionality than predicted. Hence, the challenge to devise a new kinetic scheme to account for the increased functionality is made (e.g., by selective reaction of initiator with chain‐transfer agent).
Alternating ethylene–alkyl acrylate copolymers. II. Polymer properties
Authors: Logothetis A. L. , McKenna J. M. 
Published: April 2003

AbstractProperties such as viscosity correlations and spectral data of alternating ethylene–ethyl acrylate copolymers are described. The proton and 13C‐NMR spectra show that there is a considerable amount of tacticity in these polymers. Although the alternating configuration predominates, there is also some random structure present. Terpolymers were prepared with cure‐site monomers, such as 2‐chloroethyl acrylate. The terpolymers were compounded with carbon black and cured to give vulcanizates with excellent properties. The cured products are resistant to oil, water, heat, and oxidation. They also have good low temperature properties (stiffening temperature −31°C, brittleness temperature −50°C), tensile properties (tensile strength 17.2 MPa, elongation at break 250%) and compression sets (25% at 150°C for 70 hr).
Copolymerization of ethylene with a homologous series of vinyl esters
Authors: Van der Meer R. , Van Gorp E. H. M. , German A. L. 
Published: April 2003

AbstractThe effect of the alkyl group on the relative reactivity of a homologous series of vinyl esters (2) has been studied with ethylene (1) as reference monomer, tert‐butyl alcohol as solvent, at 62°C and 35 kg/cm2. The experimental method was based on frequent measurement of the monomer feed composition throughout the copolymerization reaction by means of quantitative gas‐chromatographic analysis. Highly accurate monomer reactivity ratios were estimated in a statistically justified manner by a nonlinear least‐squares method applied to the integrated copolymer equation. The reactivity of the vinyl ester monomers towards an ethylene radical increased with decreasing electron‐with‐drawing ability of the ester group. All vinyl ester radicals considered turned out to have the same preference for their own monomer over ethylene (constant r2 = 1.50). Reactivity ratios are discussed in terms of the Q–e scheme and the Taft relation. It appeared that chiefly polar factors contribute to the observed relative reactivity, while probably resonance stabilization only plays a minor part. Steric hindrance seems to impair monomer reactivity, only from vinyl pivalate on. Relative reactivities of the vinyl esters are compared with literature values, where other reference monomers have been used.
Electrochemically initiated polymerization of styrene with tetraalkyl and ‐aryl group VA halide support electrolytes
Authors: Smith J. D. B. , Phillips D. C. , Davies D. H. 
Published: April 2003

AbstractThe electrochemically initiated polymerization of styrene in methylene chloride solvent with the use of platinum electrodes and tetraalkyl and ‐aryl group VA halides (i.e., quaternary ammonium, phosphonium, and arsonium compounds) as electrolyte has been investigated. The order of reactivity of the electrolytes with respect to polymerization rate and initiation efficiency was found to be: arsonium > phosphonium > ammonium. Mechanisms involving the electroreduction of the group VA quaternary halides to species capable of electroinitiating polymerization are postulated. The observed losses in solution conductivities during polymerization with the quaternary phosphonium and arsonium electrolytes indicate possible interaction between the initiating radical‐ionic species and the supporting electrolyte. In an attempt to further elucidate the mechanism of initiation in these systems, a separate series of experiments, employing the nonpolymerizing monomer, 1,1‐diphenylethylene, has been carried out.
Polymerization of propiolaldehyde. IV. Synthesis of a functional polymer having an ethynyl group
Authors: Kobayashi Kazukiyo , Sumitomo Hiroshi , Shibata Keiko 
Published: April 2003

AbstractThe cationic homopolymerization and copolymerization of propiolaldehyde were carried out with use of boron trifluoride etherate as an initiator at the temperatures of 0 to −78°C. Poly(ethynyl)oxymethylene was prepared by the homopolymerization at −78°C, but it was readily depolymerized to the monomer. The cationic copolymerization with styrene at −78°C proceeded almost exclusively through the aldehyde addition and a new functional copolymer was obtained. With a rise in polymerization temperature, the ethynyl addition was mixed slightly.