bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermotropic copolyesters. II. Synthesis and characterization of liquid‐crystal copolyesters containing the bicyclo[2.2.2]octane ring system
Authors: Polk Malcolm B. , Nandu Mahendra , Phingbodhipakkiya Metha 
Published: April 2003

AbstractThe syntheses and characterizations of poly(oxy‐trans‐1,4‐cyclohexyleneoxycarbonyl‐1,4‐bicyclo[2.2.2]octylenecarbonyl) (I) and poly(oxy‐trans‐1,4‐cyclohexyleneoxycarbonyl‐1,4‐bicyclo[2.2.2]octylenecarbonyl‐co‐oxy‐trans‐1,4‐cyclohexyleneoxysebacoyl) (II) are described. The polymer systems were characterized by infrared spectroscopy, proton magnetic resonance spectroscopy, solution viscosity, and differential scanning calorimetry. The random copolyester prepared from 1:0.65:0.35 mol of trans‐1,4‐cyclohexanediol, bicyclo[2.2.2]octane‐1,4‐dicarbonyl chloride, and sebacoyl chloride, respectively, formed a birefringent fluid state in the melt.
Synthesis of dihydroxamic acid chelating polymers and the adsorptive property for uranium in sea water
Authors: Hirotsu Takahiro , Katoh Shunsaku , Sugasaka Kazuhiko , Sakuragi Masako , Ichimura Kunihiro , Suda Yoshio , Fujishima Mitsugi , Abe Yoshimoto , Misonoo Takahisa 
Published: April 2003

AbstractPreparation of new chelating polymers bearing dihydroxamic acid groups and the adsorptive ability for uranium in sea water are described. Chloromethylated polystyrene crosslinked with divinylbenzene was treated with diethyl malonate in N, N‐dimethylformamide to give the polymer having diethyl malonate groups. This polymer was then treated with hydroxylamine in methanol to afford the dihydroxamic acid polymer. The presence of hydroxamic acid groups was confirmed by the appearance of IR absorption band at 1680 cm−1. The dihydroxamic acid polymer contained carboxylic acid groups as well as hydroxamic acid ones, and the contents of carboxylic acid and hydroxamic acid groups were estimated from elemental analysis to be 2–3 and 2–4 mmol/g, respectively. The polymer showed the adsorptive ability of 40 μg‐U/g in 8 days for uranium in sea water. In addition, the polymer showed the selective adsorptivity for iron, nickel, copper, and zinc as well as uranium. The macroreticular‐type polymer showed much higher adsorption rate for uranium in sea water than the gel‐type ones did, suggesting that the rate depends on the diffusion of the uranium in the polymer support.
Magnesium chloride supported high mileage catalysts for olefin polymerization. XIII. Effect of external Lewis base on ethylene polymerization
Authors: Chien James C. W. , Bres Phillipe 
Published: April 2003

AbstractThe effect of external Lewis base (Be) on the polymerization of ethylene by the MgCl2/ethyl benzoate/p‐cresol/AlEt3/TiCl4 catalyst was studied by activation with AlEt3 alone without the use of methyl‐p‐toluate. The initially formed active site concentration, [Ti], is about doubled in the absence of Be; at 50°C about 93% of the total titanium became catalytic. The same increment of [Ti] was observed without Be. The rate constants of propagation are not appreciably affected by Be; the values are the same at 50° with and without Be. At other temperatures the kp values are somewhat smaller without Be. One major effect was the very large k values for chain transfer with aluminum alkyls in the absence of Be as compared to those with Be. This can be attributed to the greater monomeric AlEt3 concentration in the former, but in much smaller amounts in the presence of Be due to complexation. The rate constants of chain transfer with hydrogen are not much affected by Be. However, the termination rate constants are generally much smaller when Lewis base is not present.
Preparation and thermal properties of polyquinazolone containing 4‐substituted phenyl groups on the quinazolone ring
Authors: Kubota Shigeru , Moriwaki Toshimoto , Ando Torahiko , Etoh Shohei , Fukami Akira 
Published: April 2003

AbstractPolyquinazolones containing 4‐substituted phenyl groups (H, Cl, CH3, CH3O, NO2) on the quinazolone ring were synthesized in m‐cresol and their thermal properties were studied by using dynamic thermogravimetry and isothermal weight loss in nitrogen and air. Polyquinazolones were synthesized with intrinsic viscosities in the range of 0.2–0.7 dL/g when phosphorus pentoxide was used as a catalyst. In TGA studies, there was a difference in the initial decomposition temperature of polyquinazolones with varying substituted groups. The introduction of substituted groups reduced oxidative thermal stability of the polymers. Furthermore, the thermal degradation mechanism was investigated by infrared spectrophotometry.
Radiation‐induced copolymerization of hydrophilic monomers with vinyl acetate: Synthesis and thermal properties
Authors: Ramakrishna M. S. , Dhal P. K. , Deshpande D. D. , Babu G. N. 
Published: April 2003

AbstractRadiation‐induced copolymerization of hydrophili+ monomers, viz., 2‐hydroxyethyl methacrylate (HEMA), 2‐hydroxypropyl methacrylate (HPMA), and N‐vinyl‐2‐pyrrolidone (NVP) with vinyl acetate (VAc) was carried out in bulk at 25°C. The copolymer composition was determined from the acetoxy content. The copolymerization parameters were determined by a graphical method and compared with those determined by the Yezrielev, Brokhina, and Roskin (YBR) method. Thermal properties of copolymers were studied by GC‐MS. Probable mechanisms were suggested from the products obtained.
Polymerization of methyl methacrylate with ceric ion‐methanol redox system
Authors: Coutinho Fernanda M. B. , Guimarães Maria José O. C. , Gomes Ailton S. 
Published: April 2003

AbstractThe polymerization of methyl methacrylate initiated by Ce4+ methanol redox system was studied in aqueous solution of nitric acid at 15°C. The polymerization was initiated by primary radicals formed from Ce4+/alcohol complex. Poly(methyl methacrylate) chains containing the alcohol residue were obtained. Variations in the temperatuare and concentration of the components of the redox system allowed the control of the rate of polymerization and molecular weight of the polymer. The concentration of the hydroxyl end groups in the poly(methyl methacrylate) of low molecular weight was determined by titration and by spectrometric method.
Polymerization of lignin model compounds with formaldehyde in acidic aqueous medium
Authors: Van Der Klashorst G. H. , Strauss H. F. 
Published: April 2003

AbstractThe reaction of formaldehyde with lignin model compounds in acidic medium was shown to give fast crosslinking of alkyl‐substituted phenolic and etherified phenolic lignin model compounds at positions meta to the aromatic hydroxy groups. This reaction differs from the reaction of formaldehyde with phenolic lignin model compounds in alkaline conditions, where the reaction with formaldehyde always occurs at positions ortho/para to the aromatic hydroxy group., The reaction of formaldehyde with lignin in acidic medium have considerable potential for the crosslinking of lignin, particularly heavily condensed alkali lignin, for use in polymeric products.
Gamma radiation induced graft copolymerization of vinyl monomers onto poly(vinyl alcohol)
Authors: Misra B. N. , Kishore J. , Kanthwal M. , Mehta I. K. 
Published: April 2003

AbstractIn an attempt to modify water‐soluble synthetic polymers, graft Copolymerization of methylmethacrylate (MMA) and ethyl acrylate (EA) onto poly(vinyl alcohol), PVA, has been studied by using gamma irradiation from a Co60 source as initiator. The graft copolymerization was carried out in an aqueous medium by the mutual method in air. The effect of total dose and concentration of vinyl monomers on percentage of grafting has been determined. Water plays a significant role in the enhancement of graft copolymerization and the optimum amount of water to afford maximum grafting has been evaluated. The effect of CH3OH on aqueous grafting of MMA and EA by radiation method has been studied. The graft copolymer has been characterized by IR spectroscopic and thermogravimetric methods.
Magnesium chloride‐supported high‐mileage catalysts for olefin polymerization XI. Determinations of poly(decene‐1) molecular weight chain dimension and thermal transitions
Authors: Chien James C. W. , Ang Tsunle 
Published: April 2003

AbstractDecene‐1 was polymerized with the CW catalyst and fractionated by precipitation technique. Light‐scattering and viscometric measurements on these fractions established the relationship [η] = 5.19 × 10−3 M. The unperturbed mean square end‐to‐end distance is (〈R〉/M)1/2 = (6.17 ± 0.34) × 10−9. Light‐scattering data is consistent with a relatively stiff molecule with length of L = 1.75 × 10−5 cm for poly(decene‐1) with MW = 397,000. Its mean square radius of gyration 〈R〉 is 2.79 × 10−11 cm.2 The ratio of L2/〈R〉 = 11 is close to the theoretical ratio of 12 for this kind of macromolecule.
Polymerization using palladium (II) salts II: Polymerization of 2‐ethynyl‐5‐bromothiophene
Authors: Trumbo D. L. , Marvel C. S. 
Published: April 2003

AbstractThe title monomer was polymerized using a bis(triphenyl phosphine) palladium (II) chloride, cuprous iodide, triphenyl phosphine catalyst system. The products are low‐molecular‐weight materials with thermal stabilities somewhat inferior to corresponding phenylacetylene‐based polymers.
Ion equilibria in THF solutions of models of “living” methacrylonitrile oligomers with Li+ counterion
Authors: Tsvetanov CH. B. , Dotcheva D. T. 
Published: April 2003

AbstractThe electro‐chemical characteristics of isobutyronitrile lithium (P1Li) and 2‐lithio‐4‐cyano‐2,4‐dimethylpentanenitrile (P2Li) are studied. The dissociation constants K of P1Li and P2Li are of the order of 10−11M and show that in THF mainly contact ion pairs exist. The lower value of K for P2Li is an indication for intramolecular complexation between the counterion and the cyano group, next to the active center. Both compounds tend to form ion triples. The results obtained show that in THF the nitrile group of the second monomer unit participates both in intra‐ and intermolecular interactions with the counterion.
Kinetic studies on the radical polymerization of acrylamide initiated by Mn3+–ethoxyacetic acid redox system
Authors: Balakrishnan T. , Subbu S. 
Published: April 2003

AbstractThe kinetics of polymerization of acrylamide (AM) initiated by manganese(III) acetate–ethoxyacetic acid (EAA) redox system in aqueous sulphuric acid was investigated in the temperature range 35–45°C. The effects of variations in [monomer], [Mn3+], [EAA], [H+], and ionic strength on the rates of monomer disappearance (Rp) and Mn3+ disappearance (−Rm) were studied. The polymerization process is initiated by the free radical arising from the oxidation of ethoxyacetic acid by Mn3+ and terminated by the mutual combination of growing polymer radicals. Based on the kinetic results, a suitable reaction scheme is proposed and the rate expressions are derived. The study on degree of polymerization supports the proposed scheme for polymerization. The various rate and thermodynamic parameters are evaluated.
Poly(alkylene oxide) ionomers IX. Polymerization of methyl ω‐epoxyalkanoates and characterization of the polymers
Authors: Muggee John , Vogl Otto 
Published: April 2003

AbstractPolymerization of linear methyl ω‐epoxyalkanoates of C‐3 to C‐10 carboxylic acids (0 to 7 methylene groups between oxirane ring and carbomethoxy group) was accomplished with a triethylaluminum/water/acetylacetone (1.0/0.5/1.0) initiator system to yield polymers of high molecular weight, apparently via a coordinative anionic mechanism. The rate of polymerization increased as the number of methylene groups between the oxirane ring and the carbomethoxy group increased, up to three methylene groups. When more than three methylene groups separate the polymerizable oxirane group and the carbomethoxy group, the rate of polymerization becomes essentially constant. The polymers were characterized by their infrared and13C‐NMR spectra, DSC, GPC, and inherent viscosity. The lower members of the series (ω‐epoxyalkanoates ofn< 3) gave polymers of lower molecular weight and wider‐molecular‐weight distribution (Mw/Mn> 2), while the higher members had molecular weight distributions between 1.5 and 2. The glass transition temperatures of the polymers also decreased from −26°C forn= 1 to around −50 to −55°C forn≥ 3.
Oxygen diffusion in poly(dimethyl siloxane) using fluorescence quenching. II. Filled samples
Authors: Cox M. E. , Dunn B. 
Published: April 2003

AbstractThe method of fluorescence quenching has been used to measure the transport properties of oxygen in poly(dimethyl siloxane) (PDMS) filled with small weight fractions of fumed silica. The experimental results show that the diffusion coefficient of oxygen and the pre‐exponential term in the Arrhenius relationship are reduced, but the activation energy is not affected. In the pressure and temperature ranges used in these experiments, the diffusion coefficient was found to be independent of both the oxygen and fluorophor concentrations. A discussion concerning the effect of fillers on the pre‐exponential term is presented.
Block copolymers of isotactic polypropylene and 1,4‐polybutadiene
Authors: Drzewinski M. A. , Cohen R. E. 
Published: April 2003

AbstractTwo block copolymers of isotactic polypropylene and 1,4 polybutadiene were synthesized using techniques involving a transformation from anionic to Ziegler–Natta polymerization mechanisms. The yield of block copolymer was about fifteen percent (weight basis) in both polymerizations, the remainder being unreacted polybutadiene from the first block synthesis. Molecular characterization experiments and model reactions were consistent with a block‐like structure for the copolymers; definitive evidence for the proposed molecular structure was obtained through transmission electron microscopy which clearly revealed microphase‐separated morphologies characteristic of block copolymers.
Vinyl polymerization. 432. Initiation mechanism of uncatalyzed polymerization in the presence of copper(II) ion
Authors: Ouchi Tatsuro , Sakamoto Hiroshi , Hosaka Yoshifumi , Imoto Minoru , Konoka Ryusei 
Published: April 2003

AbstractThe initiation mechanisms of the uncatalyzed polymerization of methyl acrylate and methyl methacrylate by the system of starch, α‐amylase or water‐soluble nylon 3/copper(II) ion/H2O were investigated by spin trapping techniques. Using 2,4‐dimethyl‐3‐nitrosobenzene sulfonate d8 and 5,5‐dimethyl‐1‐pyrroline‐N‐oxide as the water‐soluble spin trapping agents, the simultaneous generation of both monomer and hydroxyl radicals has been observed, and the propriety of the initiation mechanism proposed previously was confirmed. Thus, the initiation of polymerization in the presence of copper(II) ion was concluded to take place through a hydrogen atom transfer from the complexed water to the β‐carbon of the complexed monomer.
Factors affecting H2O absorption of the epoxy tetraglycidyl‐4,4′‐diaminodiphenyl methane cured with diaminodiphenyl sulfone
Authors: Yang F. , Gilbert R. D. , Fornes R. E. , Memory J. D. 
Published: April 2003

AbstractIt was found that the amount of water absorbed at room temperature in cured tetraglycidyl‐4,4′‐diaminodiphenyl methane/diaminodiphenyl sulfone epoxy resins increases as the curing time or temperature increases while the amount of tetrahydrofuran‐soluble extractables and the room temperature density decreases. These data suggest that the free volume increases with the extent of cure and the resins become more accessible to water. While the driving force for water absorption is the electrostatic attraction between water and the functional groups in the epoxy, the results suggest that equilibrium H2O absorption is determined primarily by unoccupied volume of the epoxy resin.
Water‐soluble copolymers. XII. Copolymers of acrylamide with sodium‐3‐acrylamido‐3‐methylbutanoate: Synthesis and characterization
Authors: McCormick C. L. , Blackmon K. P. 
Published: April 2003

AbstractThe copolymerization of acrylamide (AM) with sodium‐3‐acrylamido‐3‐methylbutanoate (NaAMB) has been studied. The value of r1r2 has been determined to be 0.56 for the AM–NaAMB pair. The molecular weights of the copolymers were relatively unaffected by monomer feed ratios. The copolymer microstructures, including run numbers and sequence distributions, were calculated from the reactivity ratios. The solution properties of the AM–NaAMB copolymers, as well as the NaAMB homopolymer, will be reported in a subsequent paper.
Poly(2‐imidazolin‐5‐ones)—A new class of heterocyclic polymers
Authors: Rasmussen Jerald K. , Heilmann Steven M. , Krepski Larry R. , Smith Howell K. , Katritzky Alan R. , Sakizadeh Kumars 
Published: April 2003

AbstractThe reaction of bisazlactones (2‐oxazolin‐5‐ones) with primary diamines containing additional secondary or tertiary amine functionality (e.g., diethylenetriamine, triethylenetetramine, or N‐methyliminobispropylamine) readily produces polyamides which serve as precursors to a new class of heterocyclic polymers. Thermal cyclodehydration takes place under relatively mild conditions (180–200°C) to produce water‐soluble polymers containing the 2‐imidazolin‐5‐one heterocycle. Model reactions have been studied to verify this mode of cyclization and confirm the proposed polymer structure.
Catalysis in competing isocyanate reactions. I. Effect of organotin–tertiary amine catalysts on phenyl isocyanate and N‐butanol reaction
Authors: Wong Shaio‐Wen , Frisch Kurt C. 
Published: April 2003

AbstractAn analytical method based on high performance liquid chromatography (HPLC) has been developed to investigate the competing isocyanate reactions under the influence of various catalysts. The kinetics of the model reaction between phenyl isocyanate and n‐butanol was studied in acetonitrile at 50°C. Effects of various catalysts such as an organotin compound, dibutyltin dilaurate, and tertiary amines, 1,4‐diazabicyclo‐(2,2,2)octane,N,N′,N″‐pentamethyldiprophylene triamine,N,N′N″‐tris(3‐dimethyl‐aminopropyl)‐3‐hexahydrotriazine, and N,N,N′‐trimethylaminoethyl‐ethanolamine on the reaction rate and the formation of reaction products were investigated. The reactions were followed by determining the NCO disappearance using the standard di‐n‐butylamine back‐titration method as well as measuring the formation of various reaction products using the HPLC method. The relative specificity of a catalyst in isocyanate reactions can thus be determined from the profile of the model reaction which depends upon the structure of the catalyst employed.
Acid‐catalyzed degradation of poly(2‐butyl‐1, 3, 6‐trioxocane)
Authors: Chien James C. W. , Lillya C. Peter , Xu Bao‐Bei 
Published: April 2003

AbstractAcid‐catalyzed degradation of poly(2‐butyl‐1,3,6‐trioxocane) (1) has been studied. With ethyl tosylate as the catalyst, the cyclic monomer 2 was the major product. The minor products are cis and trans isomers of C3H7CHCHOCH2CH2OCH2CH2OH, and three stereoisomers of C3H7CHCHOCH2CH2OCH2CH2OCHCHC3H7 elucidated by 1H and 13C NMR, IR, electron impact and chemical ionization MS, and in the case of 2 also by comparison with an authentic sample. With 98% H2SO4 as the catalyst 2 is only a minor product. The major products are diethylene glycol, valeraldehyde, and 1,4‐dioxane with some 2‐butyl‐1,3‐dioxolane. Capillary GC/mass spectrometry led to identification of the following less abundant products: tri‐n‐propylbenzene, α,β‐unsaturated aldehydes, and cyclic dimer. The products of H2SO4‐catalyzed decomposition of polymer were also obtained by heating monomer 2 with H2SO4. A detailed mechanism for the formation of the eight‐member ring 2 in the decomposition is proposed which involves unzipping proceeds via open carbocation intermediates. According to the principle of microscopic reversibility, the same open carbocation is the propagating species in the polymerization of 2 under similar conditions.
13C‐NMR spectral studies on the distribution of substituents in some cellulose derivatives
Authors: Takahashi Shin‐Ichi , Fujimoto Tetsuya , Barua Basu M. , Miyamoto Takeaki , Inagaki Hiroshi 
Published: April 2003

Abstract13C‐NMR spectra of trityl cellulose (Tr‐Cell), tosyl cellulose (Ts‐Cell), cellulose S‐methyl xanthate (Cell‐M‐Xan), and cellulose formate (CF) in dimethylsulfoxide‐d6 were analyzed at 50.4 MHz. It was found that the distribution of substituents in the anhydroglucose units of these cellulose derivatives can be estimated from their ring carbon spectra. The results showed that (i) in Tr‐Cell having degree of substitution (DS) lower than 1, the hydroxyl groups at C‐6 carbon position are selectively tritylated, (ii) in the case of Ts‐Cell, the difference in the relative DS value among three different types of hydroxyl groups is not large, although the relative reactivities of hydroxyl groups toward tosylation decrease in the order C‐6 > C‐2 > C‐3, (iii) in Cell‐M‐Xan, the hydroxyl groups at C‐3 carbon position are mainly substituted, and (iv) the ease of formylation is C‐6 > C‐2 > C‐3. The 100.8 MHz 13C‐NMR spectra of O‐methyl cellulose (MC) revealed that the reactivity order in commercial MC prepared from alkali cellulose is C‐6 ⋍ C‐2 > C‐3. Concerning MC, its water solubility was also discussed in terms of the distribution of substituents along the cellulose chain.
Aqueous polymerization of methyl methacrylate catalyzed by corundum and characterization of the obtained polymers
Authors: Moustafa A. B. , Abdel‐Latif Z. H. , Amer L. I. , Sayyah S. M. 
Published: April 2003

AbstractThe aqueous polymerization of methyl methacrylate (MMA) was studied using sodium bi‐sulfite as initiator in the absence and presence of corundum (Al2O3). It was found that corundum has a catalytic effect on the polymerization reaction. The polymers obtained in the presence of corundum were found to have a wider molecular weight distribution than in its absence; this was deduced by thin‐layer chromatographic analysis in a binary mixture (benzene: methanol 1:1.5 by volume) at 25°C. The apparent energy of activation was calculated between 40 and 50°C, and was found to be 4.50 × 104 and 1.70 × 104 J/mol in the absence and presence of 0.5 g corundum (type 600 grit)/105 mL of the reaction mixture, respectively.
XPS studies on the chemical structure of the stabilized polyacrylonitrile fiber in the carbon fiber production process
Authors: Takahagi T. , Shimada I. , Fukuhara M. , Morita K. , Ishitani A. 
Published: April 2003

AbstractIn the carbon fiber production process from polyacrylonitrile (PAN), PAN precursor is heated first in air to secure stabilization in the succeeding carbonization process at higher temperature. The mechanism of the stabilization reaction and chemical structure of the stabilized PAN have been examined by x‐ray photoelectron spectroscopy and elemental analysis. The stabilized PAN was determined to have a ladderlike structure consisting of 40% acridone ring, 30% naphtyridine ring, 20% hydronaphtyridine ring, and others. This structure well explains the stability of the polymer in the succeeding carbonization process on carbon fiber production with conjugated π‐electron systems over the whole polymer chain and intermolecular hydrogen bonds. A comonomer addition to the precursor was found to accelerate the dehydrogenation reaction in the stabilization process.