bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic Studies of Olefin Epoxidation with Hydrogen Peroxide in 1,1,1,3,3,3‐Hexafluoro‐2‐propanol Reveal a Crucial Catalytic Role for Solvent Clusters
Authors: Berkessel Albrecht , Adrio Jens A. 
Published: March 2004

AbstractThe epoxidation of cyclooctene and 1‐octene with hydrogen peroxide was studied kinetically in HFIP (1,1,1,3,3,3‐hexafluoro‐2‐propanol)/1,4‐dioxane mixtures. In the case of cyclooctene, no additional catalyst was applied, whereas the epoxidation of 1‐octene was run in the presence of phenylarsonic acid as catalyst. For both reaction types, two kinetic regimes can be distinguished: at low HFIP concentration (nHFIP/ntotal≤0.15), both the catalyzed and the uncatalyzed reaction show first order dependence on the HFIP concentration. This result is interpreted by the HFIP “charge template” for the uncatalyzed epoxidation (as postulated by Shaik and Neumann) and by the formation of an arsonic acid mono‐HFIP ester for the catalyzed reaction. At high HFIP concentration (nHFIP/ntotal≥0.5), both reaction types are up to ca. 5 orders of magnitude faster and show ca. 12th order dependence on the HFIP concentration. We propose that the dramatic accelerations observed at high HFIP concentrations are brought about by HFIP clusters. Based on literature data (Fioroni, Roccatano, Hong, Suhm), it is concluded that the epoxidation reactions studied here take place in a HFIP coordination sphere comprising ca. 12 HFIP molecules, and that this coordination sphere effects the enormous increases in epoxidation rates. This mechanistic model bears resemblance to enzymatic reactions taking place in and being catalyzed by a protein matrix.
Solid Materials as Sources for Synthetically Useful Singlet Oxygen
Authors: Wahlen Joos , De Vos Dirk E. , Jacobs Pierre A. , Alsters Paul L. 
Published: March 2004

AbstractSolid materials can generate 1O2 (1Δg) either by irradiation of an immobilized dye in the presence of oxygen, or by catalytic decomposition of H2O2. The methods for obtaining such solid catalysts are described, and the usefulness of the obtained materials in preparative 1O2 oxygenations (“ene” hydroperoxidation, [2+2]‐ and [4+2]‐cycloaddition) is discussed, particularly with respect to substrate scope, solvent scope, reusability and productivity of the catalyst, regioselectivity and chemoselectivity of the oxidation.
Radiational hardening of poly(vinylidene fluoride)–poly(methyl methacrylate)–polystyrene ternary blends
Authors: Mishra A. K. , Agrawal P. , Bajpai R. 
Published: March 2004

AbstractSpecimens of poly(vinylidene fluoride) (PVDF)–poly(methyl methacrylate) (PMMA)–polystyrene (PS) polyblends with different weight percentage ratios of the three polymers were prepared with the solution cast technique. The effect of γ irradiation on the Vicker's microhardness was studied. Among the three pure polymers, PVDF, PMMA, and PS, the γ irradiation imparted crosslinking in PVDF, thereby causing radiational hardening. In the cases of PMMA and PS, the effect of irradiation exhibited a predominance of both the scissioning and crosslinking processes in different ranges of doses. Moreover, at a dose of 5 Mrad, in both PMMA and PS, maximum radiational crosslinking was observed. The effect of γ irradiation seemed to stabilize beyond 15 Mrad in PVDF and beyond 20 Mrad in PMMA and PS. Microhardness measurements on ternary blends of PVDF, PMMA, and PS revealed that the blend with low contents of PMMA, that is, up to 5 wt %, yielded softening, whereas increasing the content of PMMA beyond 5 wt % produced a hardened material because of radiational crosslinking, and a higher content of PMMA in the blend facilitated this crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3107–3111, 2004
Ultraviolet light treatment of thin high‐density polyethylene films monitored with a quartz crystal microbalance
Authors: Øiseth Sofia Kihlman , Krozer Anatol , Lausmaa Jukka , Kasemo Bengt 
Published: March 2004

AbstractUltraviolet (UV) treatment is an effective method for modification of the surface properties of polymeric materials. In this study, the effects of the ozone‐generating UV light treatment of thin high‐density polyethylene (HDPE) films were monitored with the quartz crystal microbalance (QCM) technique both in the presence of ozone and without it. The films were further characterized by X‐ray photoelectron spectroscopy, optical microscopy, and atomic force microscopy. We found that the ozone not only modified the surface properties of the HDPE films but also etched away the polymer layer. An average etching rate of 0.48 nm/min was determined. UV light exposure of the polymer film in an argon atmosphere resulted only in minor degradation of the films; the presence of ozone was needed to cause the destruction and loss of material. The QCM technique was a straightforward method for the monitoring of the kinetics of the ablation induced by the UV–ozone treatment process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2833–2839, 2004
Syntheses of hydroxypropyl methylcellulose phthalate gels in organic solvents by radiation crosslinking
Authors: Xu Ling , Nagasawa Naotsugu , Yoshii Fumio , Kume Tamikazu 
Published: March 2004

AbstractCellulose gels were prepared through the crosslinking of hydroxypropyl methylcellulose phthalate (HPMCP) with electron‐beam irradiation in concentrated organic solvent solutions. The effects of the solvent species, polymer concentration, and irradiation dose on the formation of the gels were investigated. Some organic solvents, such as alcohols with short alkyl chains, alkyl acetates, and ketones, were found to be suitable as media for the radiation crosslinking of the polymer. The prepared HPMCP gels showed excellent swelling in various organic solvents with medium hydrogen‐bonding abilities, such as pyridine, cresol (meta), acetic acid, dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, 1,4‐dioxane, acetone, methyl ethyl ketone, methyl acetate, and chloroform. In an acetone/water mixture, the swelling ratio was significantly dependent on the solvent composition because of the coexistence of both hydrophilic and hydrophobic moieties in HPMCP. These results suggest that HPMCP gels have the potential to be superabsorbents for various kinds of organic solvents. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3002–3007, 2004
Dependence of optical properties on the preparation methods of poly[(9,9′‐dialkylfluorene‐2,7‐diyl)‐alt‐(1,3,4‐oxadiazole‐2,5‐diyl)]
Authors: Yang Nam Choul , Lee Chang Ik , Kim Jong Kyu , Suh Dong Hack 
Published: March 2004

AbstractA blue‐light‐emissive fluorene‐based polyoxadiazole, an n‐type polyfluorene derivative, was synthesized by both one‐step and two‐step methods. Directly polymerized poly[(9,9′‐didodecylfluorene‐2,7‐diyl)‐alt‐(1,3,4‐oxadiazole‐2,5‐diyl)] (PFOx‐DP) exhibited a higher molecular weight and a more efficient photoluminescence quantum yield than poly[(9,9′‐didodecylfluorene‐2,7‐diyl)‐alt‐(1,3,4‐oxadiazole‐2,5‐diyl)] (PFOx) prepared via a polyhydrazide precursor, poly[9,9′‐didodecylfluorene‐2,7‐(2,5‐dihydrazide‐ 1,3,4‐oxadiazole). Both polymers, differently prepared, showed similar photoluminescent properties in 1,2‐dichloroethane. However, in a film state, the influence of the interchain interactions on the photoluminescence of PFOx with the lower molecular weight was larger than on the photoluminescence of PFOx‐DP. The electron‐deficient property of an oxadiazole group in the polymer backbone resulted in low‐lying highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of −6.29 and −3.26eV, respectively, of the polymer suitable for electron‐transport/hole‐blocking layers and emissive layers in multilayer electroluminescence devices. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3112–3118, 2004
Functional barriers in PET recycled bottles. Part II. Diffusion of pollutants during processing
Authors: Pennarun P. Y. , Ngono Y. , Dole P. , Feigenbaum A. 
Published: March 2004

AbstractRecycled plastics may be polluted by various chemicals available to consumers. When such materials are used to manufacture packaging materials intended to be in direct contact with food, these pollutants may migrate into food. The use of multilayer structures with a virgin polymer layer as a functional barrier may prevent such migration. This work deals with the possible diffusion of pollutants into and through the virgin layer during processing at high temperatures. A test is designed to measure diffusion coefficients in elastomeric and glassy polymers, in their molten state; 2.5‐dimethoxyacetophenone was used as a surrogate pollutant, and its concentration profiles are monitored by UV microscopy. Based on diffusion coefficients and on activation energies, glassy polymers appear to be much better barriers than polyolefins, even in their molten state. We then focus on poly(ethylene terephthalate) (PET) bottle preforms, processed by injection molding. In a first approach, a worst case situation was simulated by numerical analysis, using both overestimated diffusion coefficient values and very low values of activation energy. It appears that migration into foodstuffs through functional barriers can only be observed with unrealistic high diffusion coefficients and low activation energies. These results were confirmed by experimental determination of the concentration gradients of model pollutants in multilayer structures. It appears that little diffusion occurs, despite at a very high temperature. The effects of temperature and thickness of the functional barrier are discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2859–2870, 2004
Behavior of poly(ethylene‐co‐olefin) polymers as elastomeric materials
Authors: López‐Manchado Miguel Angel , Valle Marcela , Sapunar Rodrigo , Quijada Raúl 
Published: March 2004

AbstractThe properties of two new ethylene‐α‐olefin copolymers, namely, ethylene–1‐hexene copolymer (EHC) and ethylene–1‐octadecene copolymers (EOC), synthesized via metallocene catalysts were evaluated. The copolymerization was carried out in an autoclave reactor with Et(Indenyl)2ZrCl2/methylaluminoxane as a catalyst system. These single‐site catalysts (metallocene type) allow one to obtain very homogeneous copolymers with excellent control of the molecular weight distribution and proportion of comonomer incorporation. So, copolymers with 18 mol % comonomer in the case of EHC and 12 mol % for EOC were shaped, and activities around 100,000 kg of polymer mol−1 of Zr bar−1 h−1 were reached. The properties of these copolymers were compared with other commercial elastomers, such as ethylene–propylene copolymers synthesized by Ziegler–Natta catalysts and an ethylene–octene copolymer obtained via metallocene catalysts. The results show that these new copolymers, in particular, EOC, had excellent elastomeric properties. Furthermore, they had a relatively low viscosity, which implied a good response during processing. Moreover, the effectiveness of these copolymers as impact modifiers for polyolefins was also studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3008–3015, 2004
Particle size distribution control in emulsion polymerization
Authors: Sood Ashwini 
Published: March 2004

AbstractEffects of the operating policies—the initial initiator amount; the initial emulsifier amount; the monomer addition mode: batch or semibatch; and the monomer addition rate under “monomer‐starved conditions” for the control of particle size distribution (PSD)—were studied through a model that simulates batch and semibatch reactor operations in conventional emulsion polymerization. The population balance model incorporates both the nucleation stage and the growth stage. The full PSDs were reported, which have normally been omitted in earlier studies. It was shown through simulations that the broadness of the distributions, both initial (obtained after the end of nucleation) and final (after complete conversion of monomer), can be controlled by the initial initiator amount and the emulsifier amount. The higher initiator amounts and the lower emulsifier amounts favor narrower initial and final distributions. The shape of the initial PSDs and the trends in the average size and range were preserved with subsequent addition of monomer in the batch or in the semibatch mode, although the final PSD was always considerably narrower than that of the initial PSD. The addition of monomer in the semibatch mode gave narrower distribution compared to that of the batch mode, and also, lower monomer addition rates gave narrower distributions (larger average sizes), which was a new result. It was further shown through simulations that, under monomer‐starved conditions, the reaction rate closely matched the monomer feed rate. These conclusions are explained (1) qualitatively—the shorter the length of the nucleation stage and the larger the length of the growth stage (provided the number of particles remains the same), the narrower is the distribution; and (2) mathematically—in terms of the “self‐sharpening” effect. Experimental evidence in favor of the self‐sharpening effect was given by analyzing the experimental particle size distributions in detail. The practical significance of this work was proposed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2884–2902, 2004
Diffusion of unreacted monomers detected by ATR FTIR spectroscopy in a photosensitive printing plate after the photoreaction
Authors: Sakaguchi Yoshimitsu , Kawahara Keizo , Yamada Takatoshi , Okazaki Yasuyuki , Imahashi Satoshi 
Published: March 2004

AbstractA water‐developable flexographic printing plate consisting of poly(acrylonitrile‐co‐butadiene), polybutadiene, and carboxylated polyurethane as a polymer matrix, hexanediol dimethacrylate and polybutadiene diacrylate as reactive monomers, and benzildimethylketal as a photoinitiator was prepared and its photoreaction followed by structural change caused by the diffusion of unreacted monomers was characterized. Analysis combined 13C‐NMR and attenuated total reflection (ATR) FTIR showed the photoreaction occurred predominantly at the surface of exposure to the light at first, and then the reaction proceeded to the direction of the opposite surface with an increase in the exposure time. Diffusion of unreacted monomers after the photoreaction from the unexposed side to the exposed side was monitored by ATR FTIR. The diffusivity of unreacted monomers was dependent on the extent of photoreaction in the plate and the molecular weight of diffusing monomers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2903–2907, 2004
Immobilization of lipase on hydrogels: Structural aspects of polymeric matrices as determinants of enzyme activity in different physical environments
Authors: Chauhan Ghanshyam S. , Mahajan Swati , Sddiqui Khalid M. , Gupta Reena 
Published: March 2004

AbstractWell‐defined and characterized polymeric matrices showing close chemical similarities but wide differences in water uptake and swellability in aqueous medium were used for lipase immobilization. Biphasic networks of 2‐hydroxypropylcellulose (HPC) were synthesized with acrylamide (AAm), methacrylamide (MAAm),N‐isopropylacrylamide (N‐i‐PAAm), and 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSA) and simultaneously crosslinked withN,N‐methylene bisacrylamide in aqueous medium by using simultaneous γ‐radiation technique. Lipase enzyme was produced from a mesophilic bacterial isolate (HBK‐8) and was immobilized onto all the matrices by adsorption method. The activity of the immobilized enzyme was optimized for pH, temperature, and amount of crude enzyme and effect of dehydration. High relative activity for the immobilized enzymes was observed and loss of activity with time was minimal; reusability was found to be good. The activity of the immobilized enzyme was also observed to be good in both esterification and hydrolysis of esters. In the present study, lipase immobilization, hydrolysis ofp‐nitrophenyl palmitate, and optimum pH and temperature for substrate hydrolysis were evaluated for different matrices to study polymer structure and enzyme activity relationship in diverse physical environments. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3135–3143, 2004
Emulsifier‐minor emulsion copolymerization of BA‐MMA‐St‐MAA (or AA)‐N‐MA
Authors: Tang Linsheng , Yang Jingwei , Zhang Shufeng , Yang Jinzong , Wu Yumin 
Published: March 2004

AbstractA novel emulsion polymerization technique referred to as emulsifier‐minor emulsion polymerization was achieved by the copolymerization of methyl methacrylate, butyl acrylate, and styrene (MMA‐BA‐St) with a combination of water‐soluble ionic monomers [methacrylic acid (MAA) or acrylic acid (AA)] and nonionic monomers (N‐methylol acrylamide). In the technique, water‐soluble monomers play a crucial role in the stabilization of the latex particles as they can be bound to the particle surface and form a hydrate protective layer, which exhibits steric and/or electrostatic effects to prevent particle coagulation. The minor but over its critical micelle concentration emulsifier sodium alkylated diphenyl ether disulfonate (DSB) results in the nucleation of particles mainly by the micelle nucleation mechanism and thus determines the polymerization rate, the particle size, and the number. The film water resistance of the latices can be improved, and the foaming capacity of can be lowered by using technique instead of conventional emulsion polymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2923–2929, 2004
Properties of a new synthetic rubber: High‐trans 1,4‐poly(butadiene‐co‐isoprene) rubber
Authors: He Aihua , Yao Wei , Huang Baochen , Huang Yaqin , Jiao Shuke 
Published: March 2004

AbstractA high‐trans 1,4‐butadiene/isoprene copolymer (TBIP) was synthesized in a 5‐L autoclave with hydrogen as an effective molecular weight modifier. The effects of hydrogen on the catalyst efficiency and molecular weight of the copolymers were investigated. The processability and physicomechanical properties of TBIP and their relationship to the composition, composition distribution, and molecular weight of TBIP were examined in detail. Increasing the H2pressure effectively reduced the molecular weight of TBIP. The optimum Mooney viscosity of TBIP and the 1,4‐butadiene molar content in the feed were 30–50 and 5–25%, respectively. No cis–trans isomerization was observed during the roll processing procedure for TBIP. The vulcanization characteristics of TBIP were similar to those of general rubbers, and no reverse vulcanization was observed for TBIP. A high green strength was the typical characteristic of TBIP. Vulcanized TBIP (TBIR) with an optimum composition and molecular weight presented outstanding antifatigue properties and low heat buildup in comparison with general rubbers. Compared with general sidewall stock [natural rubber (NR)/butadiene rubber (BR) = 50/50], TBIR exhibited a greater than 15‐fold increase in its crack‐initiation resistance. The other mechanical properties of TBIR were similar to those of 50/50 NR/BR. The heat‐aging mechanism of TBIR was crosslinking aging. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2941‐2948, 2004
Ethylenediamine tetraacetic acid modification of crosslinked chitosan designed for a novel metal‐ion adsorbent
Authors: Shimizu Yoshiaki , Izumi Sinya , Saito Yoshihiro , Yamaoka Hitoshi 
Published: March 2004

AbstractNovel chitosan‐based adsorbent materials were synthesized with a higher fatty diacid diglycidyl as a crosslinking agent, and the adsorption ability of the resulting polymers for several metal ions was evaluated. Selective adsorption for Cu2+ in comparison with other divalent metal ions, such as Ni2+, Pb2+, Cd2+, and Ca2+, was observed with the crosslinked chitosan sorbent at pH 6; however, the adsorption power decreased abruptly as the pH value of the solution decreased. The addition of ethylenediamine tetraacetic acid (EDTA) residues to crosslinked chitosan significantly enhanced the adsorption power for metal ions, especially for Ca2+. The adsorptivity of Ca2+ was dramatically improved with the introduction of EDTA residues, and the value was greater than that obtained with a commercial chelate resin (CR11). Although the adsorption power of the EDTA‐derivatized sorbent for other metal ions was just comparable to that of the CR11 material, the newly synthesized adsorbent could be used for the recovery of metal ions from industrial waste solutions with a relatively wide range of pHs, from 4.0 to 6.0. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2758–2764, 2004
Structural characterization of polymer blends based on polysulfones
Authors: Linares A. , Acosta J. L. 
Published: March 2004

AbstractA series of blends with various compositions was prepared on the basis of polysulfone, polyethersulfone, and polyimide. These blends were characterized by different techniques, including Fourier transform IR spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and tensile stress–strain measurements. The results obtained allowed for certain conclusions regarding blend compatibility. In addition, the mechanical properties were subjected to an experimental test design to measure the blends for tensile break strength and Young's modulus with a computer program, which eventually enabled us to obtain the surface response equations of both properties and also to predict the optimum composition presenting the best mechanical behavior. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3030–3039, 2004
Removal of metal ions by water‐soluble polymacromonomers in conjunction with ultrafiltration membrane
Authors: Rivas Bernabé L. , Pooley S. Amalia , Maureira Antonio 
Published: March 2004

AbstractThe macromonomer polyethylene glycol methylether methacrylate was homo‐ and copolymerized with 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid under three feed monomer ratios. The initiator used was ammonium peroxydisulfate (0.2 mol %). All the polymers were completely soluble in water. The copolymer composition was determined by elemental analysis. The metal ion interaction capability of the three polymers was investigated through the liquid‐phase polymer‐based retention (LPR) technique at different values of pH and filtration factor Z. The highest metal ion retention ability was observed at pH 5.0. The homopolymer showed a high selectivity for Ni(II) ions at pH 3.0. The copolymers (PEGMEM)1.51‐co‐(APSA)1.00 and (PEGMEM)1.00‐co‐(APSA)1.95 showed a high selectivity for Cr(III) ions at pH 3.0. The maximum retention capacity, in general, was similar for the homo‐ and copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2955–2960, 2004
Allyl ether‐modified unsaturated polyesters for UV/air dual‐curable coatings. I: Synthesis and characterization of the oligomers and their cured films
Authors: Yuan Huiya , Lu Xueyi , Zeng Zhaohua , Yang Jianwen , Chen Yonglie 
Published: March 2004

AbstractAllyl ether (AE)‐modified unsaturated polyester oligomers were synthesized from polyethylene glycol (PEG), maleic anhydride (MAH), and trimethylolpropane mono allyl ether (TMPAE), and characterized by Fourier transform infrared (FTIR) spectra. The UV/air dual‐curable coatings were prepared from the oligomers using vinyl ether (VE) as a reactive diluent. FTIR spectra showed that CC bonds in the coating composition had polymerized partially after cured by UV or air. The investigation of rheological behavior of the dual curable composition suggested that all the systems belonged to pseudoplastic fluid, and the increasing allyloxy content in oligomer resulted in a higher viscosity. Differential scanning calorimetry (DSC) analysis showed that the increasing TMPAE‐PEG molar ratio resulted in lower Tg, and all samples had the same glass transition temperature irrespective of the type of curing. The results of TGA for cured films indicated that UV‐cured film had better thermal stability than the air‐cured one. The air‐cured film showed superior pencil hardness, impact strength, and flexibility to the UV‐cured counterpart. However, the air‐cured film had poor adhesion and electric resistance properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2765–2770, 2004