bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mixed ligand five coordinate cobalt(II) complexes of a polymer‐bound schiff base derived from 2‐aminobenzimidazole
Authors: Yusuff K. K. Mohammed , Sreekala R. 
Published: April 2003

AbstractThe complexes resulting from the interaction of a new Schiff base ligand derived from crosslinked polystyrene bound benzaldehyde and 2‐aminobenzimidazole with a square planar complex [Co(TPP)] (where TPP = meso‐tetraphenylporphyrin), and also with tetrahedral complexes [Co(BPBI)2X2] (where BPBI = 1‐benzyl‐2‐phenylbenzimidazole, X = Cl, Br, or NCS) have been isolated and characterized. The percentages of cobalt and nitrogen in the complexes show that only one Schiff base unit is coordinated to cobalt. Infrared spectra suggest that the bonding of the polymer ligand to cobalt is through the N‐3 atom of the benzimidazole moiety. The EPR spectra indicate that all the complexes are in the low‐spin state and have a square pyramidal environment around cobalt(II). © 1992 John Wiley & Sons, Inc.
Emulsion polymerization of vinyl acetate using a polymerizable surfactant. II. Polymerization mechanism
Authors: Urquiola M. B. , Dimonie V. L. , Sudol E. D. , El‐Aasser M. S. 
Published: April 2003

AbstractThe mechanism of growth of latex particles in the emulsion polymerization of vinyl acetate using a polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (TREM LF‐40; Henkel) was investigated. Both the aqueous phase and the particle/water interface were found to be loci for the copolymerization of TREM LF‐40 with vinyl acetate. Competitive growth experiments using TREM LF‐40 and its nonpolymerizable derivative were conducted to separate the effects of aqueous phase and particle surface. Particle size analysis of the seeded and unseeded polymerizations coupled with kinetic results suggested that the reactions at the particle/water interface are more important and that the particle size of the latexes is a key parameter controlling the polymerization rate through copolymerization and chain transfer to the polymerizable surfactant at the particle surface. A decrease in particle size lead to an increase in the amount of TREM LF‐40 polymerized at the particle surface and to a decrease in polymerization rate. © 1992 John Wiley & Sons, Inc.
Dithiadiazolium salts as initiators for the cationic ring‐opening polymerization of tetrahydrofuran
Authors: Banister Arthur J. , Luke Anthony W. 
Published: April 2003

AbstractMono‐, bis‐ and tris‐(1,3,2,4‐dithiadiazolium) salts [R‐(CNSNS+)n]n+[AsF‐6]n (R = aryl, n = 1, 2, 3) were found to initiate the cationic ring‐opening polymerization of tetrahydrofuran (THF) at room temperature to give clear gels from which the pure polymer was precipitated. 1,3,2,4‐Dithiadiazolium cations associated with the hard [AsF6]‐ anion thus constitute a new class of cationic polymerization initiators. The poly(THF) formed by initiation with 1,3,2,4‐dithiadiazolium cation was characterized by gel permeation chromatography, infrared spectrophotometry, and 13C‐NMR spectroscopy. Number‐average molecular weights of 198 700 g mol‐1 (polydispersity 1.96) and 190 000 g mol‐1 (polydispersity 1.61) were obtained using [PhCNSNS] [AsF6] and [C6H3‐1,3,5‐(CNSNS)3][AsF6]3, respectively, as initiators. The use of multifunctional dithiadiazolium salts as initiators suggests that they may be useful in the preparation of starburst and dendritic polymers. © 1992 John Wiley & Sons, Inc.
Polymer‐supported palladium and platinum species as hydrogenation catalysts
Authors: Xavier Regina , Mahadevan V. 
Published: April 2003

AbstractThe synthesis of new hydrogel copolymers and their use for anchoring Pd and Pt species is described. The supported catalysts are effective for the reduction of alkenes, dienes, alkynes, and nitroaromatics under mild conditions. The catalysts have been characterized by chemical analysis, particle size measurement, IR, TGA, and x‐ray photoelectron spectra. Relative reactivities and the effects of substrate structure, solvents, catalyst loading, particle size of the catalysts, and partial pressure of hydrogen have been determined. The kinetics of hydrogenation have been analyzed using concepts useful under slurry reaction conditions. The recycling efficiencies of the catalysts and product analysis to establish selectivities have been assessed. © 1992 John Wiley & Sons, Inc.
Photooxidation of polystyrene by O2 and N2O
Authors: Wells R. K. , Badyal J. P. S. 
Published: April 2003

AbstractStrips of polystyrene held in a flowing O2 or N2O atmosphere have been exposed to 240‐600 nm radiation. The extent of photooxidation has been followed by x‐ray photoelectron spectroscopy (XPS). Although N2O is a more reactive gas than O2, it produces a less oxidized polymer surface. This surprising observation can be correlated to the photochemistry occurring at the gas/polystyrene interface. © 1992 John Wiley & Sons, Inc.
Plasma copolymerization of ethylene and tetrafluoroethylene
Authors: Golub Morton A. , Wydeven Theodore , Cormia Robert D. 
Published: April 2003

AbstractThe plasma copolymerization of ethylene (ET) and tetrafluoroethylene (TFE) was investigated by means of IR and XPS analyses. The deposition rates for plasma ET/TFE copolymers, when plotted versus mol % TFE in the feed gas, gave a concave‐downward curve situated above the straight‐line joining the deposition rates for the respective plasma polymers, PPET and PPTFE, with the maximum rate at ∼ 70‐80 mol % TFE. This result, coupled with the finding that normalized absorbances of the CH and CF IR bands of ET/TFE copolymers had maxima at ∼ 20 and 80 mol % TFE, respectively, indicated a positive interaction between ET and TFE such that each monomer “sensitized” the plasma copolymerization of the other. As analyzed by XPS, CF groups dominated over CF2 and CF3 groups at 5‐70 mol % TFE, but at ≥ 80 mol % TFE, these moieties approached the relative proportions in PPTFE (CF2 > CF3 > CF). The plot of F/C ratio versus mol % TFE was concave‐upward and situated below the hypothetical straight‐line plot representing noninteracting, independent polymerization of ET and TFE, while the % F in the plasma copolymers was linear with mol % TFE. The F1s mean binding energies of the ET/TFE plasma copolymers, which increased monotonically with % F, were consistently higher than those for several commercial polymers of fluorinated olefins at comparable values of % F. This result suggested clustering of CFn moieties in the plasma copolymers or the presence of F atoms in highly fluorinated environments. © 1992 John Wiley & Sons, Inc.
Thermal oxidation of blends of poly(ethylene oxide) and poly(methyl methacrylate)
Authors: Makhija S. , Pearce E. M. , Kwei T. K. 
Published: April 2003

AbstractThermal oxidation of poly(ethylene oxide) (PEO) and its blends with poly(methyl methacrylate) (PMMA) were studied using oxygen uptake measurements. The rates of oxidation and maximum oxygen uptake contents were reduced as the content of PMMA was increased in the blends. The results were indicative of a stabilizing effect by PMMA on the oxidation of PEO. The oxidation reaction at 140°C was stopped at various stages and PMMA was separated from PEO and its molecular weights were measured by gel permeation chromatography (GPC). The decrease in the number‐average molecular weight of PMMA was larger as the content of PEO increased in the blends. The visual appearance of the films suggested that phase separation did not occur after thermal oxidation. The activation energy for the rates of oxidation in the blends was slightly increased compared to pure PEO. © 1992 John Wiley & Sons, Inc.
Optically‐active polyurethanes containing coumarin dimer component: Synthesis, characterization, and chiral recognition ability
Authors: Chen Yun , Lin Jiann‐Jang 
Published: April 2003

AbstractOptically‐active polyurethanes (2a‐2c) were prepared by polyaddition reaction of diamide (1a, 1b) and diester (1c) derivatives of chiral coumarin dimer with 4,4′‐diphenylmethane diisocyanate (MDI) in chloroform and methyl ethyl ketone, respectively. The inherent viscosity of the polyurethanes are between 0.13 and 0.21 dL/g in N,N‐dimethylacetamide (DMAc) at 30°C. Treated silica gels were absorbed with ca. 25 wt % of the polyurethanes, and packed as chiral stationary phases for direct optical resolution of 16 racemates with aromatic groups by high‐performance liquid chromatography (HPLC). Polyurethanes 2a and 2b, obtained from diamide derivatives, show efficient resolution ability to some of the racemates (α = 1.06‐1.79), especially the atropic (R5) and trans (R6‐R9) isomers. The recognition ability of the polyurethanes can be attributed to the simultaneous aromatic stacking and hydrogen‐bonding interactions with racemates. © 1992 John Wiley & Sons, Inc.
Molecular weight distribution of emulsion‐polymerized polyethylene
Authors: Starkweather Howard W. , Han Mark C. 
Published: April 2003

AbstractEmulsion polymerizations of ethylene were run using potassium persulfate as the initiator and either an anionic or a cationic surfactant, usually at five times the critical micellar concentration. The molecular weight distributions had at least two major peaks. The broadly distributed lower molecular weight component is formed in the early stages of polymerization. The higher molecular weight component has a narrow distribution characteristic of termination by the combination of chain radicals. The weight‐average molecular weight of this component was about 400,000 when the surfactant was sodium laurate and 33,600,000 when the surfactant was dodecyl amine hydrochloride. © 1992 John Wiley & Sons, Inc.
Shrinkage effects in photopolymerizable resins containing filling agents: Application to stereophotolithography
Authors: Karrer P. , Corbel S. , Andre J. C. , Lougnot D. J. 
Published: April 2003

AbstractThe influence of porous additives with various structures on the shrinkage of resins used for stereolithographic applications was studied by measuring the dependence of the specific gravity of the charged polymer material as a function of the charge fraction. The investigations were conducted on difunctional monomers photopolymerized either by a radical (acrylate) or a cationic (epoxy) mechanism. The improvement resulting from the incorporation of charges in the formulation is accounted for in a semi‐quantitative way by an adsorption‐desorption equilibrium of monomer molecules between the pores and the bulk phase. Thus, the pores of the charges which are initially filled with monomer molecules play the role of buffers which discharge their content as the photopolymerization develops in the liquid phase. It is also worth mentioning that the viscosities of the photosensitive charged resins used in these experiments are quite suitable for use in stereophotolithography. © 1992 John Wiley & Sons, Inc.
Interpenetrating polymer networks of polycarbonate‐urethane and polybutadiene
Authors: Frisch Harry L. , Zhou Peiguang 
Published: April 2003

AbstractInterpenetrating polymer networks (IPN's), pseudo IPN's and linear blends of urethane‐containing aliphatic polycarbonate (PCU) and polybutadiene (PB) have been prepared and characterized. The simultaneous full IPN's of PCU and PB over the whole composition range (15‐85% by weight PCU) exhibit a single phase morphology even though the linear chain blends are completely immiscible, as determined by DSC and confirmed by transmission electron microscopy (TEM). However, in both pseudo IPN's of PCU and PB there appeared multiple (melting and glass) transitions in DSC measurements and phase separation was observed by TEM. © 1992 John Wiley & Sons, Inc.
Photocrosslinking of silicones. VI. Photocrosslinking kinetics of silicone acrylates and methacrylates
Authors: Müller Uwe , Jockusch Steffen , Timpe Hans‐Joachim 
Published: April 2003

AbstractThe photoinduced radical crosslinking of silicones containing pendant acrylate and methacrylate groups has been investigated with calorimetric and ESR measurements. Oxygen very strongly influences this process, which leads to a prolonged induction period and a pseudo first‐order termination reaction between polymer radicals and oxygen. Kinetically, such reaction steps are responsible for light intensity and monomer exponents, both of unity. In the absence of oxygen, second‐order processes take place between polymer and primary radicals. The results of conversion‐time and reaction‐rate time measurements using stationary irradiations and postpolymerization experiments agree with the corresponding kinetic expressions. Long‐lived polymer radicals and their decay have also been determined with ESR techniques. Long‐chain spacer groups, which link the unsaturated ester moiety at the silicone backbone, increase the crosslinking rate. The final conversions of the double bonds exceed high values in each case. © 1992 John Wiley & Sons, Inc.
Thermal degradation of poly((E,E)‐[6.2]paracyclophane‐1,5‐diene)
Authors: White Robert L. , Sikabwe Emmanuel C. 
Published: April 2003

AbstractThermal degradation of poly((E,E)‐[6.2]paracyclophane‐1,5‐diene) is studied in inert and oxidative environments by using thermogravimetric analysis, pyrolysis GC/MS, pyrolysis GC/FT‐IR, and variable temperature‐diffuse reflectance infrared spectroscopy (VT‐DRIFTS). Thermal degradation in helium begins by depolymerization yielding a volatile product capable of abstracting hydrogens from the polymer residue. Multiple hydrogen abstractions result in a variety of volatile species containing benzyl‐benzyl bonds. In the presence of oxygen, polymer decomposition is dictated by reactions of peroxy and hydroperoxy radicals. At low temperatures, oxygenated species are the primary products. At higher temperatures, increased unsaturation is detected in the polymer residue. In both inert and oxidative environments, the strain associated with alignment of paracyclophane aromatic rings is lost during the initial stages of thermal degradation. © 1992 John Wiley & Sons, Inc.
Chemical reactions occurring in the thermal treatment of polymer blends investigated by direct pyrolysis mass spectrometry: Polycarbonate/polybuthyleneterephthalate
Authors: Montaudo Giorgio , Puglisi Concetto , Samperi Filippo 
Published: April 2003

AbstractThe chemical reactions occurring in the thermal treatment of polycarbonate/polybuthyleneterephthalate (PC/PBT) blends have been investigated by gradual heating (10°C/min) using thermogravimetry and direct pyrolysis into the mass spectrometer. Exchange reactions occur already in the temperature range below 300°C but the transesterification equilibrium is affected by the evolution of thermal degradation products. Buthylenecarbonate, was detected in the first decomposition stage (320–380°C), which is evolved together with a series of cyclic compounds containing units of PC and PBT, in varying ratios. The overall thermal reaction evolves towards the formation of the most thermally stable polymer, i.e., a totally aromatic polyester (polymer III, Table I), which was found to be the end‐product of the thermal processes occurring in the system investigated. The thermal decomposition products obtained from the PC/PBT blends in the range 320–600°C have mass sufficiently high to be structurally significant, since they contain at least one copolymer repeating unit. The reactions occurring in the thermal treatment of the PC/PBT blend are discussed in detail. © 1993 John Wiley & Sons, Inc.
Alginate polyelectrolyte ionotropic gels. XIV. Kinetics and mechanism of formation of intermediate complex during the oxidation of alginate polysaccharide by alkaline permanganate with a spectrophotometric evidence of manganate(VI) transient species
Authors: Hassan Refat M. 
Published: April 2003

AbstractThe kinetics and mechanism of the [Alg.Mn VIO] intermediate complex formation during the oxidation of alginate polysaccharide at pHs ≥ 12 have been investigated spectrophotometrically. The reaction showed a first‐order dependence in permanganate and a fractional order with respect to the alginate concentration (Alg). Kinetic and spectrophotometric evidence revealed the formation of manganate(VI) as transient species. The results obtained indicated the dependence of the rate of formation on the pH of the medium where the complex formation was base catalyzed. A mechanism consistent with the experimental results is discussed. © 1993 John Wiley & Sons, Inc.
Solvent effects on the polymerization of multi‐armed vinyl biphenyl derivatives containing pendant oligo(oxyethylene)cyclotriphosphazenes
Authors: Inoue Kenzo , Nakahara Hisanori , Tanigaki Teiichi 
Published: April 2003

AbstractPolymerization of vinyl biphenyl derivatives containing a pendant oligo(oxyethylene)cyclotriphosphazene (VBMEP, (OCH2CH2)nOCH3, n = 1; VBDEP, n = 2; VBTEP, n = 3) was carried out in various solvents. The conversions of these monomers increased with increasing β values, solvent hydrogen bond acceptor abilities, indicating that the hydrogen bond formation is the most important factor in the polymerization. 13CNMR study showed that the reactivity of the monomer is influenced by the hydrogen bond interaction. In ethanol, the kinetic orders of monomer and initiator concentrations for the polymerization of VBDEP were different from those in 1,2‐dichloroethane (DCE), which suggest the predominant occurrence of primary radical termination. The intrinsic viscosity of poly(VBDEP) with M̄n = 22 000 in DCE was two times higher than that in ethanol, and plots of intrinsic viscosity versus conversion of VBDEP gave a straight line. The results suggest that the polymer chains in ethanol are in a coiled conformation, whereas in DCE they are in a relatively extended structure, and that the propagation is affected by the conformational change. These behaviors originated from the hydrogen bond formation between polymers and solvents are discussed. The copolymerization of styrene with multiarmed monomers and the properties of polycascade polymers obtained are also described. © 1993 John Wiley & Sons, Inc.
Cyclopolymerization of dipropargyl isopropylidene malonate and characterization of the product
Authors: Jin Sung‐Ho , Cho Hyun‐Nam , Choi Sam‐Kwon 
Published: April 2003

AbstractThe polymerization of dipropargyl isopropylidene malonate (DPIPM) was polymerized by WCl6 and MoCl5 associated with various organometallic cocatalysts. MoCl5 was found to be the most effective catalyst and Ph4Sn was observed to have a high cocatalyst activity. Structure and physical properties of poly(DPIPM) were investigated. The spectral data indicated that poly(DPIPM) contains alternating double and single bonds along the polymer backbone and a cyclic recurring unit. The poly(DPIPM) was partially soluble in common organic solvents. The M̄n values of the polymer from soluble fraction were in the range of 5100–8000 relative to polystyrene standards by GPC. In addition, poly(DPIPM) possesses good stability to air oxidition. When poly(DPIPM) is exposed to iodine vapor, the electrical conductivity was increased from 4.5 × 10−11 to 7 × 10−2 S/cm. © 1993 John Wiley & Sons, Inc.
Mathematical models of the initial stage of the thermal degradation of poly(vinyl chloride). II. The thermal degradation of poly(vinyl chloride) with effective removal of HCl
Authors: Troitskii B. B. , Troitskaya L. S. 
Published: April 2003

AbstractThe dehydrochlorination of different samples of PVC under vacuum with continuous removal of HCl by freezing, has been studied at 180–210°C. The comparison of the kinetic curves of the dehydrochlorination of various samples of PVC which were obtained by us and other investigators, with the theoretical curves for the thermal degradation of idealized PVC in the absence of HCl has been carried out. This had made it possible to evaluate the influence of unstable fragments present in the original polymer on the initial rate of PVC degradation quantitatively. It has been shown that the distinction between the stationary rates of the dehydrochlorination of various samples of PVC is determined by the difference of the values of the average length of dehydrochlorination chain, lav. The most probable interval of the values of lav has been ascertained to be 4–12. It is established that the most probable value of the constant of the rate of dehydrochlorination of normal links of PVC, k0, is 2.1 × 10−7−2.5 × 10−7 s−1 at 200°C. © 1993 John Wiley & Sons, Inc.
Photochemically induced oxidative surface modification of polyimide films
Authors: Meier Ingrid K. , Langsam Michael 
Published: April 2003

AbstractPolyimide membranes that contain both the phthalimide chromophore and abstractable hydrogens undergo photochemically‐induced oxidative surface modification when they are irradiated with ultraviolet (UV) light for 0.5–30 min in air. The reaction requires 200–300 nm light and the presence of oxygen, and the surface‐modified membranes show much higher oxygen/nitrogen selectivities than the untreated films. A mechanism for the photochemical reaction that is based on the photochemistry of structurally‐similar monomeric phthalimides is proposed. The observed selectivity increases can also be explained by this mechanism. © 1993 John Wiley & Sons, Inc.
Photochemical addition reaction of a polymer‐bearing pendant vinyl ether with various thiol compounds
Authors: Nishikubo Tadatomi , Kameyama Atsushi , Sasano Mikio , Sawada Masa‐Aki 
Published: April 2003

AbstractPhotochemical addition reaction of the pendant vinyl ether group in the polymer (P‐1), which was synthesized by the alternate ring‐opening copolymerization of glycidyl vinyl ether with phthalic anhydride, with various thiol compounds such as benzenethiol, phenylmethanethiol, 2‐mercaptoacetic acid, ethyl 2‐mercaptoacetate, N‐acetyl‐L‐cysteine (AcCys), and 1,4‐phenylenedi(methylthiol) was carried out using benzophenone (BP) as the photosensitizer in the THF solution. Each reaction proceeded very smoothly to give the corresponding polymers with high conversion, although the degree of reaction of the pendant vinyl ether group in P‐1 was affected by the molar ratio between the thiol compounds and the vinyl ether group, and the amounts of photosensitizer BP added. Furthermore, it was also found that optically active polymer containing pendant N‐acetyl‐L‐cysteine residue was synthesized by the photochemical addition reaction of P‐1 with AcCys. The reactions of P‐1 with dithiol or bisazide compounds occurred effectively to give gel products in the film state, and it was found that the polymer film containing P‐1 and those compounds can be applied as negative‐type photoresists with high practical photosensitivity. © 1993 John Wiley & Sons, Inc.
Synthesis and gas transport properties of high molecular weight block copolymers of styrene and vinyltrimethylsilane
Authors: Rickle Greg K. 
Published: April 2003

AbstractPoly(styrene‐b‐vinyltrimethylsilane) of high molecular weight and varying composition suitable for membrane applications has been synthesized at 50–60°C. The copolymer could be made as a tapered block copolymer by polymerizing both monomers at the same time (r1 and r2 = 0.08 and 13) or as a pure block copolymer with some homopolymer contaminant by sequential addition of monomers. However, in both methods the copolymer phases out of solution before the reaction is complete. The copolymers can exhibit phase separation in the solid and dissolved states. Poly(styrene‐b‐vinyltrimethylsilane) membranes have some unique gas transport properties. The poly(vinyltrimethylsilane) segments are phase separated and dispersed in a continuous polystyrene matrix so the resultant membranes can have over twice the permeability of polystyrene but also retain the high selectivity of polystyrene. These results should be applicable to other biphasic systems where the low permeability phase is also the continuous phase. © 1993 John Wiley & Sons, Inc.