bluuebunny/crossref_metadata_2025_split huggingface dataset:
Redox polymerization of methyl acrylate in absence and in presence of some inorganic silicon compounds
Authors: Badran A. S. , Abd‐El‐Hakim A. A. , Moustafa A. B. , El‐Ghaffar M. A. Abd 
Published: April 2003

AbstractThe polymerization of methyl acrylate in water using ammonium, potassium, and sodium persulphates with sodium bisulphite as redox initiation system was studied. It has been found that ammonium persulphate had the least activity on the rate of polymerization and resulted in the formation of the highest viscosity average molecular weights for the obtained polymers. The rate of polymerization was found to increase with sodium bisulphite concentration in the redox system, but the viscosity average molecular weights were found to decrease with the increase of sodium bisulphite concentration. Addition of some inorganic silicon compounds (containing the same weight equivalent of SiO2) resulted in increasing the rate of polymerization and decreasing the induction period. The average molecular weights obtained in presence of china clay were found to be the highest and those obtained in presence of talc were the least.
Comparison of methods of calculation of 13C‐NMR chemical shifts of diene polymers with applications to isomerized natural rubber
Authors: Bradbury J. H. , Elix J. A. , Perera M. C. S. 
Published: April 2003

AbstractNatural rubber was isomerized by two methods that involved either dehydrobromination of hydrobrominated natural rubber or heating natural rubber with butadiene sulfone. The 13C‐NMR spectra of the methylene region of isomerized natural rubber was interpreted in terms of dyad arrangements for which assignments were made by calculating chemical shifts according to three different published methods. One method [Gronski, Murayama, Cantow, and Miyamoto, Polymer, 17, 358 (1976)] gave the best overall agreement with the experimental chemical shifts; another [Sato, Ono, and Tanaka, Polymer, 18, 580 (1977)] was better for C‐1 and C‐3 methylene carbon atoms; and still another [Khatchaturov, Dolinsky, Prozenko, Abramenko, and Kormer, Polymer 18, 871 (1977)] gave results which deviated considerably from the other methods. From 13C‐NMR intensity measurements it was shown that the elimination of HBr from hydrobrominated natural rubber occurred by a random process. Contrary to literature reports, it was found that the sulphur dioxide catalyzed isomerization of natural rubber was accompanied by a significant amount of double bond migration; a possible reaction scheme was proposed.
Polymerization of oxiranes by polymeric organoantimony oxides
Authors: Nomura Ryoki , Wada Yasunori , Matsuda Haruo 
Published: April 2003

AbstractPolymeric arylantimony(V) oxides [poly(ArSbO2), Ar = phenyl, p‐chlorophenyl (CPh), and p‐methylphenyl (Tol)] were employed as catalysts for the polymerization of oxirane [ethylene oxide (EO)] and also substituted oxiranes [propylene oxide (PO), 1,2‐butylene oxide (BO), and epichlorohydrin (ECH)]. The polymerization of EO by ArSbO2s proceeded 3–60 times faster than that by the other organoantimony and ‐tin compounds such as triphenylstibine oxide (Ph3SbO) and arenestannoic acids (ArSnO2H), respectively. Apparent activation energy for the polymerization of EO was estimated as 13.7, 13.3, and 13.6 kcal/mol for PhSbO2, TolSbO2, and CPhSbO2, respectively. The results of the polymerization as well as 1H‐, 13C‐, and 17O‐NMR spectroscopy suggested that the polymerization was initiated by ArSbO2 or Ar2Sb2O4 fragments, which was derived from a nucleophilc solvation of the polymeric ArSbO2 by oxiranes in situ.
Furanized rubber studied by NMR spectroscopy
Authors: Perera M. C. S. , Elix J. A. , Bradbury J. H. 
Published: April 2003

AbstractThe double bonds of natural rubber latex (stabilized by a nonionic surfactant) were reacted with an approximately equimolar amount of performic acid at room temperature with a limited amount of formic acid present. Product analysis by 1H‐NMR during the course of the reaction showed that 69–90% epoxidation occurred before the advent of ring opening and ring expansion to produce furanized rubber; hence the rate of epoxidation was greater than the rate of furanization. Indeed, at lower concentrations of formic acid and rubber latex, epoxidation occurred to 90% and furanization was prevented; it was subsequently brought about by the addition of a catalytic amount of orthophosphoric acid. Increased formic acid concentration caused early coagulation of the modified rubber latex. By 1H‐ and 13C‐NMR, it was found that the furanized rubber probably consisted of tetrahydrofuran rings linked together by CC bonds at positions adjacent to the hetero atom and contained a terminal hydroxy group. The number average sequence length was 2–9, but only the sample with an average sequence length of 9 was effective as a cation binder.
Functional polymers. XLVIII. Polymerization of ω‐alkenoate derivatives
Authors: Purgett Mark D. , Vogl Otto 
Published: April 2003

AbstractEsters of ω‐alkenoic acids have been homopolymerized with transition metal initiating systems. The key to the successful polymerization was the complexation of the monomer prior to its addition to the initiating system. Titanium trichloride, aluminum activated, was found to be best as the transition metal part of the initiator systems, with diethyl‐, or better, diisobutylaluminum chloride as the reducing agents andn‐hexane or toluene as the solvents. Best results for polymerizations were obtained with 2,6‐dimethylphenyl esters of the functional α‐olefin monomers; however, other phenyl esters also polymerized well. Attempts to polymerize methyl 10‐undecenoate gave the corresponding polymer in only low yields. Polymers of the 2,6‐dimethylphenyl esters, obtained in high molecular weight, were characterized. Polymers were also obtained from 2,6‐dimethylphenyl 7‐octenoate, but not from ω‐alkenoates with less than three methylene units between the ester group and the terminal olefin group.Poly(2,6‐dimethylphenyl 10‐undecenoate) was hydrolyzed in an aqueous sodium hydroxide/1,4‐dioxane solution to poly(sodium 10‐undecenoate) that in turn was neutralized with acetic acid to poly(10‐undecenoic acid).
29Si nuclear magnetic resonance of dimethyl and phenylmethyl containing polysilanes
Authors: Wolff Andrew R. , Nozue Ikuo , Maxka Jim , West Robert 
Published: April 2003

AbstractThe 29Si‐NMR spectra are reported for poly(methylphenylsilylene), 1, poly(1,1,2‐trimethyl‐2‐phenyldisilene) 2, two samples of poly(dimethylsilylene‐co‐phenylmethylsilylene), 3a and 3b, and poly(phenylmethylsilylene‐co‐n‐hexylmethylsilylene), 4. The spectra of 3a, 3b, and 4 indicate that these polymers contain blocklike regions with considerable segregation of RMeSi and PhMeSi groups. The spectrum of 2 shows no evidence for stereospecific polymerization. The preparation of 2 from 1,1,2‐trimethyl‐2‐phenyldichlorosilane is also described.
29Si nuclear magnetic resonance of dialkylpolysilanes
Authors: Wolff Andrew R. , Maxka Jim , West Robert 
Published: April 2003

AbstractThe silicon‐29 nuclear magnetic resonance spectra of a number of dialky‐ and alkylmethylpoly‐silanes are reported. Polysilanes composed of asymmetrically substituted silylenes (i.e., alkylmethylsilylenes) exhibited very broad resonance lines attributed to diastereomeric chemical shifts of stereogenic silylenes alpha and beta to the observed nucles Symmetrically substituted polysilanes showed a single narrow peak. The 29Si chemical shifts for these polysilanes decrease with increasing steric bulk of the substituents, varying inversely with the electronic excitation energy.
Functional polymers and sequential copolymers by phase transfer catalysis. XXVIII. Synthesis and characterization of alternating block copolymers and polyformals of polyisobutylene and aromatic polyether sulfone
Authors: Percec Virgil , Auman Brian C. , Nava Hildeberto , Kennedy Joseph P. 
Published: April 2003

AbstractAlternating—i.e., ‐(A‐B)n‐ type—block copolymers of polyisobutylene (PIB) and aromatic polyether sulfone (PSU) have been prepared by phase transfer catalyzed Williamson polyetherification of α,ω‐di(phenol)PIB with α,ω‐di(chloroallyl)‐ or ‐(bromobenzyl)PSU. Block copolymers of the two prepolymers were also synthesized by the phase transfer catalyzed polyetherification of methylene chloride with α,ω‐di(phenol)PIB and α,ω‐di(phenol)PSU (bisphenol‐A‐terminated PSU). This method leads to ‐[(A)x‐(B)y]n‐ block copolymers with formal linkages between segments. At sufficiently high segment lengths, both types of block copolymers exhibit two distinct Tgs, indicating phase separation into rubbery PIB and glassy PSU domains.
A study of polypyrrole synthesized with oxidative transition metal ions
Authors: Chao Taina H. , March Juan 
Published: April 2003

AbstractPolypyrrole powder and films were chemically synthesized by the reaction of AgNO3, FeCl3, Fe(NO3)3, Cu(NO3)2, or Cu(NO3)2‐AlCl3 with pyrrole in an aqueous solution or a water—toluene two‐phase system. Products were characterized by elemental analysis, IR, scanning electron microscopy with energy dispersive x‐ray analysis (SEM with EDAX), and conductivity measurements. The polypyrrole synthesized from pyrrole with FeCl3 had a composition of C4.00H3.05N0.99Cl0.25. The pressed powder had a conductivity of 2.7 × 10−2 S/cm and the film 2.8 S/cm. All the other metal salts produced films that had the same organic backbone, morphology, and conductivity as the polymer synthesized using Fe(III) salts, regardless of the considerable differences in the reduction potentials of the metal ions. The nature of the anions of the transition metal salts had no effect on the reaction. Anions, however, were retained as the counterions of the cationic polypyrrole backbone and could be easily exchanged with other anions.
Structure characteristics of halouracils containing chiral centers and their polymers with polyethylenimine
Authors: Ye Dakeng , Overberger C. G. 
Published: April 2003

AbstractUracil esters and acids containing both a chiral center and a halogen atom at the 5‐position (fluoro, chloro and bromo) were preapred. The esters of these species were then grafted onto polyethylenimine via an amide bond. The precise nature of this bond was examined using 1H, 13C, 19F, and 13C‐1H coupled spectroscopies. The results show that the polymers obtained under our experimental conditions possess both covalent and ionic bonds at the grafting position.
Preparation and properties of silicon containing copolyamides
Authors: Kiyotsukuri Tsuyoshi , Tsutsumi Naoto , Ayama Koichi , Nagata Minoru 
Published: April 2003

AbstractCopolyamides containing siloxane moieties in main chain were prepared by a melt polycondensation with 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane (E), hexamethylenediamine (N6), and adipic acid (6). Glass transition temperature (Tg), cold crystallization temperature (Tcc), and melting temperature (Tm) were measured by differential thermal analysis (DTA). The depression of Tm for copolyamide was fitted by the Flory curve. Melting peak remarkably broadens with increasing E6 component in copolyamide. The change of Tg was fitted by the Gibbs and Dimarzio's equation in which the number of flexible bond is considered. The difference between Tg and Tcc increased with increasing E6 component. These DTA studies suggest that the crystallization of N66 component in copolyamide is hindered by the bulky siloxane moiety, while the micro‐Brownian motion of amorphous segment is promoted by the flexible siloxane bond. Tensile strength and Young's modulus decreased with increasing E6 component. The solubility in various solvents increased with increasing E6 component. Permeability of oxygen and nitrogen increased with an increase of temperature and E6 component. The separation coefficient of oxygen to nitrogen rapidly increased near 50 mol% of E6 concentration and then leveled out above 70 mol%. The contact angle with water and methylene iodide increased with an introduction of the siloxane moiety into polymer chain.
Graft copolymers from poly(2,6‐dimethylphenylene oxide) and pivalolactone
Authors: Bell Vernon L. , Wakelyn N. T. 
Published: April 2003

AbstractThe copolyether‐polyester system resulting from the anionic graft polymerization of pivalolactone onto poly(2,6‐dimethylphenylene oxide) has been formulated with differing graft densities and graft segment lengths. Wide angle x‐ray scattering studies on these materials indicated an increased crystalline order with increased PVL segments/graft for similarly annealed specimens and a decrease in such order with increasing carboxylation.
Complex radical copolymerization of di‐n‐butylstannyl dimethacrylate with maleic anhydride
Authors: Rzaev Z. M. O. , Mamedova S. G. , Jusifov G. A. , Rustamov F. B. 
Published: April 2003

AbstractMechanisms of radical copolymerization of di‐n‐butylstannyl dimethacrylate with maleic anhydride in the presence of 2,2‐asobisisobutyronitrile are discussed. Complexing (Keq) and copolymerization (r1 and r2) constants have been determined. Quantitative contributions of cyclization and complexing to reactivity ratios of the monomers under study and to propagation reactions have been estimated. The copolymerization has been found to proceed predominantly at the complex radical cyclocopolymerization step, leading to cyclized and linear unsaturated units in the macromolecule chain.
Dissociation of 2,2′‐substituted thioindigo whites, and recombination of their radicals in solution and in polymer matrix
Authors: Leest Yvo , Smets Georges 
Published: April 2003

AbstractThe dissociation of 2,2′‐disubstituted thioindigo whites into captodative radicals and the recombination of these radicals have been examined in solution and in polymeric matrix. For the methyl‐ and ethyl‐substituted TIW the quantum yield of dissociation in solution is equal to 4 × 10−4 and 5 × 10−4, respectively. Using the iodine scavenging method the quantum yield of formation of free radicals was almost 3 to 4 × 10−4, i.e. 20–25% radicals recombine in cage. For the isopropyl and aryl TIWs partial dissociation occurs already at room temperature. Their dissociation enthalpies have been evaluated in solution on the basis of the ESR signal surfaces at different temperatures. For the aromatic substituted Δ Hdiss amounts to 88–95 kJ mol−1, while for i‐PrTIW ΔHdiss is 150 kJ mol−1. The behavior of these compounds was studied in three different matrices: polymethyl methacrylate (PMMA), polypropyl methacrylate (PPMA), and polystyrene (PST). In the cases of the aryl substituted derivatives, cage dimensions of the TIW‐radical pairs were measured at low temperature, and their apparent dissociation enthalpies above their glass transition temperatures were evaluated using ESR spectrometry; they are equal to 118 ± 3 kJ mol−1 in PPMA and around 155 kJ in PMMA and PST. The decay kinetics of the radicals after photolysis of the TIWs below Tg were interpreted on the basis of Waite's equations for diffused controlled reactions. The great influence of steric effects in the cases of the 2‐orthochlorophenyl and the 2,4‐dichlorophenyl TIWs is stressed as well as the importance of the merostabilization of the captodative radicals on these kinetic characteristics. The nature of the polymeric matrix is also underlined; below Tg the diffusion rate constant is only one‐third in PST compared to PMMA. The radicals generated from Ph TIW and its para‐nitro and p‐methoxy derivatives show a strong inhibiting effect toward the polymerization of methyl methacrylate, while the alkyl TIWs behave as free radical initiators.
Interchain electron donor–acceptor complexes. Determination of equilibrium constant and thermodynamic parameters in the solid state
Authors: Percec Virgil , Schild Howard G. , Rodriguez‐Parada José M. , Pugh Coleen 
Published: April 2003

AbstractThe interpolymeric electron donor–acceptor (EDA) complex of donor poly[(N‐ethylcarbazol‐3‐yl)methyl methacrylate] (PHMCM‐2) with acceptor poly‐(2‐[(3,5‐dinitrobenzoyl)oxy]ethyl methacrylate) (PDNBM‐2) presents a single glass transition temperature and a decomplexation endotherm on differential scanning calorimetric (DSC) thermograms. This system is considered a “polymer blend model” which exhibits a lower critical solution temperature (LCST). Phase separation of this blend is kinetically controlled and positive deviations of the glass transition temperatures from weight average values suggest that it behaves as a thermally reversible crosslinked network. Calorimetric methods to determine the heats of mixing of small molecule complexes in solution were adapted for this solid state blend to estimate the equilibrium constant (Keq) and other thermodynamic parameters. Applying a computer iterative procedure and assuming 1 : 1 stoichiometry, a least‐squares fit was found for several different donor molecular weights with three different high molecular weight acceptors. At moderate molecular weights,Keqrises to represent saturation fractions near unity as found in biological systems.Keqdecreases for higher molecular weights, possibly due to trapped chain entanglements. These results are supported by a composition‐independent, “horizontal line” phase diagram, thus resembling the completely complexed/denaturation process in DNA.
Kinetic data on the curing of an epoxy polymer in the presence of lignin
Authors: Feldman D. , Banu Dorina 
Published: April 2003

AbstractIn the present study, dynamic differential scanning calorimetry has been used to investigate the effect of an alkali lignin in amounts up to 20% by weight, on the crosslinking kinetics of an epoxy prepolymer cured with an aliphatic polyamine. Lignin presence does not significantly affect the overall reaction order, but the activation energy increases and the slowing of the overall curing process with lignin content could be explained by the interaction between lignin and the polyamine hardener. The possibility of having a “false compensation” in the case of the use of single DSC scans is also discussed.
Grafting onto chitosan. I. Graft copolymerization of methyl methacrylate onto chitosan with Fenton's reagent (Fe2+−H2O2) as a redox initiator
Authors: Lagos A. , Reyes J. 
Published: April 2003

AbstractPoly(methyl methacrylate) has been grafted onto chitosan by using Fenton's reagent as a redox initiator in an aqueous medium. Initiation by Fenton's reagent was carried out in the presence of atmospheric oxygen. The percentages of grafting, efficiency, and homopolymer were found to depend on chitosan (RchitOH), ferrous ammonium sulfate (FAS), hydrogen peroxide, monomer (MMA) concentrations, reaction temperature, and reaction time.
Direct polyesterification with thionyl chloride in pyridine improved by a modification of monomer sequences in copolymers
Authors: Higashi Fukuji , Sugimori Shigeru , Mashimo Toshio 
Published: April 2003

AbstractThe direct polyesterification with thionyl chloride (SOCl2) in pyridine was further investigated. Copolycondensations of dicarboxylic acids, bisphenols, and hydroxybenzoic acids were significantly affected by the reaction temperatures and combinations of monomers which could change relative rates of alcoholyses of the activated dicarboxylic acids and the hydroxyacids consequently to vary monomer sequences in the copolymers resulted. The sequences were tried to be varied more directly by stepwise reactions of monomers in copolycondensations of dicarboxylic acids, bisphenols, and p‐hydroxybenzoic acid (PHB), as well as PHB and m‐hydroxybenzoic acid (MHB). The reactions proceeded smoothly and satisfactorily when carried out by initial reaction of dicarboxylic acids and PHB followed by bisphenols likely to favor sequential to random distributions of monomers. Reverse addition of PHB and bisphenols, and then dicarboxylic acids resulted in rapid precipitation due to some oligomerization of PHB at an earlier stage of reaction, and largely retarded the reaction. This was also the case for the copolycondensation of PHB and MHB. Copolymers of high inherent viscosities with up to 65 mol% PHB could be obtained by initial reaction of MHB followed by PHB.
Anionic polymerization of N‐substituted maleimide. II. Polymerization of N‐ethylmaleimide
Authors: Hagiwara Tokio , Someno Tsutomu , Hamana Hiroshi , Narita Tadashi 
Published: April 2003

AbstractAnionic polymerization of N‐ethylmaleimide (N‐EMI) was carried out with potassium t‐butoxide, lithium t‐butoxide, n‐butyllithium, and ethylmagnesium bromide as initiators in THF and in toluene. An almost quantitative yield of poly(N‐EMI) was obtained with potassium t‐butoxide as initiator in THF in a wide range of polymerization temperatures. Initiators possessing lithium as counter cation produced poly(N‐EMI) in slightly lower yields and ethylmagnesium bromide gave the polymer only in less than 35% yield in THF. As a polymerization reaction solvent, THF was preferable for the polymerization of N‐EMI compared with toluene with respect to polymer yields. Poly(N‐EMI) obtained with anionic initiators exerted unimodal molecular weight distribution. From 1H‐ and 13C‐NMR spectra of poly(N‐EMI) anionic polymerization of N‐EMI with potassium t‐butoxide was revealed to proceed at carbon–carbon double bond. t‐Butoxide system was found to have a “living” polymerization character, i.e., the observed average degree of polymerization was in good agreement with the one calculated from the initial molar ratio of N‐EMI/initiator and the yield of polymer.
Comparative reactivity of water soluble photoinitiators as viewed in terms of excited states processes
Authors: Lougnot D. J. , Fouassier J. P. 
Published: April 2003

AbstractThe activity of 10 water soluble photoinitiators derived from thioxanthone, benzophenone, and benzil were studied comparatively. The mechanisms of initiation were determined by time resolved laser spectroscopy and steady state polymerization. The characteristic features of each series of compounds are pointed out. The possible contribution of biphotonic processes to the initiation step is considered.
Electroinitiated polymerization of acrylamide in acetonitrile medium
Authors: Samal Seetanshu Kumar , Nayak Bimbadhar 
Published: April 2003

AbstractThe electroinitiated polymerization of acrylamide (AA) has been studied in acetonitrile medium using tetrabutylammonium perchlorate (TBAP) as the electrolyte. Split‐cell experiments showed that the polymer formation takes place both in the anode and the cathode compartments. The polymer yield depends on several factors such as the magnitude of the current flow, the duration of the electrolysis, the monomer concentration, the electrolyte concentration, the temperature of the solution, presence or absence of air, and finally whether or not the cell content was stirred. The current exponent of the polymerization was 0.28 with a reaction rate constant of 1.06 reaction % per hour. The IR and NMR spectra of the polymers suggest that the anodic polymer is polyacrylamide and the cathodic polymer is poly‐β‐alanine (CH2CH2CONH). Based on the experimental results, a radical mechanism for the anodic polymerization and an anionic mechanism for the cathodic polymerization have been proposed.
Synthesis and characterization of polyamides containing heterocyclic thiaxanthone units
Authors: Reddy T. Ashok , Srinivasan M. 
Published: April 2003

AbstractNovel polyamides containing heterocyclic thiaxanthone units were prepared by condensing 2,7‐dichloroformylthiaxanthone‐5,5′‐dioxide and 2,8‐dichloroformylthiaxanthone‐5,5′‐dioxide with various aromatic diamines, under low temperature solution polymerization conditions in DMAc. The model diamide, 2,8‐ditolylcarbamylthiaxanthone‐5,5′‐dioxide was synthesised and characterized by spectroscopic methods. The polyamides were prepared in 70–80% yield and had inherent viscosity in the 0.36–0.73 dL/g range. The poyamides have decomposition temperatures in the 425–510°C range in nitrogen. The effect of thiaxanthone rings on polymer backbone on solubility, crystallinity, and thermal stability is also discussed.