bluuebunny/crossref_metadata_2025_split huggingface dataset:
Watching Photoinduced Chemistry and Molecular Energy Flow in Solution in Real Time
Authors: Aßmann Jens , Kling Matthias , Abel Bernd 
Published: May 2003

AbstractEnergized molecules are the essential actors in chemical transformations in solution. As the rearrangement of bonds requires a movement of nuclei, vibrational energy is often the driving force for a reaction. Vibrational energy can be redistributed within the “hot” molecule, or relaxation can occur when molecules interact. Both processes govern the rates, pathways, and quantum yields of chemical transformations in solution. Unfortunately, energy transfer and the breaking, formation, and rearrangement of bonds take place on ultrafast timescales. This Review highlights experimental approaches for the direct, ultrafast measurement of photoinduced femtochemistry and energy flow in solution. In the first part of this Review, we summarize recent experiments on intra‐ and intermolecular energy transfer. The second part discusses photoinduced decomposition of large organic peroxides, which are used as initiators in free radical polymerization. The mechanisms and timescales of their decarboxylation determine the initial steps of polymerization and the microstructure of the polymer product.
Polymerization of propylene using the high‐activity Ziegler–Natta catalyst system SiO2/MgCl2 (ethoxide type)/TiCl4/Di‐n‐butyl phthalate/triethylaluminum/dimethoxy methyl cyclohexyl silane
Authors: Zohuri G. H. , Azimfar F. , Jamjah R. , Ahmadjo S. 
Published: May 2003

AbstractThe bisupported Ziegler–Natta catalyst system SiO2/MgCl2 (ethoxide type)/TiCl4/di‐n‐butyl phthalate/triethylaluminum (TEA)/dimethoxy methyl cyclohexyl silane (DMMCHS) was prepared. TEA and di‐n‐butyl phthalate were used as a cocatalyst and an internal donor, respectively. DMMCHS was used as an external donor. The slurry polymerization of propylene was studied with the catalyst system in n‐heptane from 45 to 70°C. The effects of the TEA and H2 concentrations, temperature, and monomer pressure on the polymerization were investigated. The optimum productivity was obtained at [Al]/[DMMCHS]/[Ti] = 61.7:6.2:1 (mol/mol/mol). The highest activity of the catalyst was obtained at 60°C. Increasing the H2 concentration to 100 mL/L increased the productivity of the catalyst, but a further increase in H2 reduced the activity of the catalyst. Increasing the propylene pressure from 1 to 7 bar significantly increased the polymer yield. The isotacticity index (II) decreased with increasing TEA, but the H2 concentration, temperature, and monomer pressure did not have a significant effect on the II value. The viscosity‐average molecular weight decreased with increasing temperature and with the addition of H2. Three catalysts with different Mg/Si molar ratios were studied under the optimum conditions. The catalyst with a Mg/Si molar ratio of approximately 0.93 showed the highest activity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1177–1181, 2003
Preparation and characterization of the complex latex formed through complexation of two polymer latexes with chemically complementary structure
Authors: Yang Mingjiao , Dan Yi 
Published: May 2003

AbstractIn this study, the intermacromolecular complexation of two polymers with chemically complementary structures in the latex state and the interparticle interactions were probed. Two latexes—a polydimethylsiloxane (PDMS)/poly(vinyl acetate‐co‐butyl acrylate) system, named PA latex, and a PDMS/poly(methacrylic acid) system, named PB latex—were prepared by seeded emulsion polymerization and the complex latexes were obtained through complexation of the PA latex with the PB latex. The properties of the obtained complex latexes were investigated using surface tension and viscosity measurements. The surface structure and composition of coatings obtained from the latexes were analyzed by X‐ray photoelectron spectroscopy and scanning probe microscopy. The results confirmed that there are interactions between the

(or

groups in PA and the

groups in PB. The interactions result in unique properties of the polymer latex and lead to a formation of a new structure of the coatings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1405–1411, 2003
Inhibition of polyketone oxidation
Authors: Kalinina I. A. , Belov G. P. , Gumargalieva K. Z. , Shlyapnikov Yu. A. , Zaikov G. E. 
Published: May 2003

AbstractOxidation of polyketones [poly(ethylene ketone) (CH2CH2CO‐)n and poly(propylene ketone) (CH2CH(CH3)CO‐)n] in the presence of antioxidant [2,2′‐methylene‐bis(4‐methyl‐6‐tert‐butylphenol)] was studied in the temperature range 120–190°C. The effectiveness of the antioxidant in polyketones is much lower than that in polyolefins. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1182–1185, 2003
Preparation and characterization of poly(methyl methacrylate)–clay nanocomposites via melt intercalation: The effect of organoclay on the structure and thermal properties
Authors: Kumar Sandeep , Jog Jyoti P. , Natarajan Upendra 
Published: May 2003

AbstractNanocomposites of poly(methyl methacrylate) (PMMA) with layered silicates were prepared by the melt mixing route. The PMMA–montmorillonite hybrids were characterized by wide‐angle X‐ray diffraction, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Except for the hybrid formed with unmodified sodium montmorillonite, where a change in distribution of clay platelet stacks was observed without polymer intercalation, the use of organically modified montmorillonites produced well‐intercalated systems. An increase in the separation of the clay layers due to polymer intercalation was observed in the range 7–14 Å. TGA thermographs indicated that the onset of decomposition increased by 15–30°C, depending on the organoclay, as compared to PMMA itself. DSC results showed the existence of a glass‐transition temperature (Tg) for all the hybrids and also showed that the Tg of the hybrids were lower (by ∼10%) compared to that of PMMA. Among the various modifiers, the ones that were relatively more polar favored a greater extent of intercalation of PMMA into the clay layers. The thermal stabilities of the nanocomposites were superior to that of PMMA and were controlled by the stability of the organoclay and its interaction with PMMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1186–1194, 2003
Modified polyurethane with improvement of acid dye dyeability
Authors: Wang Huei‐Hsiung , Lin Li‐En 
Published: May 2003

AbstractThis article concerns the modification of polyurethane using polyamide 6,6 prepolymer to improve the dyeability properties of the polyurethane copolymer with acid dye. First, the carboxyl‐terminated polyamide 6,6 prepolymer was synthesized from adipic acid and 1,6‐diaminohexane. The isocyanate‐terminated polyurethane prepolymer was also synthesized from polytetramethylene glycol and 4,4′‐diphenylmethane diisocyanate in N,N‐dimethylformamide. The polyurethane prepolymer was then extended with a mixture of 1,4‐butanediol and the polyamide 6,6 prepolymer (molar ratios of 1,4‐butanediol to prepolymer being 100%, 75%, 50%, and 25%, respectively). Finally, the poly(urethane–amide) copolymers were dyed with acid dyes. The chemical, physical, and the dyeing properties of the poly(urethane–amide) coploymers are discussed. From the experimental results, it is found that the inherent viscosity of poly(urethane–amide) coploymers is increased with the increasing amount of polyamide content. The structure is proven by infrared spectra, which exhibits the absorption peaks of urethane and amide groups as we expected. From the differential scanning calorimetry measurements, it is found that the poly(urethane–amide) coploymers have two‐phase structures and good phase separation. There are four transition temperatures (Tgs, Tgh, Tms, and Tmh), but only those copolymers in PTMG 2,000 series possess Tms. Moreover, the Tgs is found to change with the length of soft segment, and the Tgh is increased with the increasing amount of polyamide content. Also, the dyed copolymers exhibit higher Tgh than those without dyeing of dye molecule, but the Tgs is not obviously changed. For mechanical properties, it is indicated that both the modulus and the strength of the coploymers are higher than those of unmodified polyurethane, but they are lowered after being dyed with dye molecule due to further separation of intermolecular distance of the dyed polyurethanes. For dye uptake in dyeing properties, it is found to increase with increasing amount of polyamide content. For dye fastness, the dyed copolymers exhibit higher grade of water fastness than that of unmodified polyurethane. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1397–1404, 2003
Copolymerization and thermal behavior of methyl methacrylate with N‐(phenyl/p‐tolyl) itaconimides
Authors: Anand Vishal , Choudhary Veena 
Published: May 2003

AbstractThis study describes the synthesis, characterization, and thermal behavior of copolymers of methyl methacrylate (MMA) and N‐p‐tolyl itaconimide (PTI)/N‐phenyl itaconimide (I). Homopolymerization and copolymerization of N‐(phenyl/p‐tolyl) itaconimide with MMA was carried out by use of various mole fractions of N‐aryl itaconimide in the initial feed from 0.1 to 0.5, using azobisisobutyronitrile as an initiator and tetrahydrofuran as the solvent. The copolymer composition was determined by 1H‐NMR spectroscopy using the proton resonance signals attributed to –OCH3 of MMA (δ = 3.5–3.8 ppm) and the aromatic protons (δ = 7.0–7.5 ppm) of N‐aryl itaconimide. The reactivity ratios of the monomers were found to be r1 (PTI) = 1.33 ± 0.05/r2 (MMA) = 0.24 ± 0.03 and r1 (I) = 1.465 ± 0.035/r2 (MMA) = 0.385 ± 0.005. The molecular weight of the copolymers decreased with increasing mole fraction of N‐aryl itaconimide in the copolymers. Glass‐transition temperature (Tg) and thermal stability of PMMA increased with increasing amounts of itaconimides in the polymer backbone. A significant increase in the percentage char yield at 700°C was observed on incorporation of a low mole fraction of N‐aryl itaconimides. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1195–1202, 2003
Melting behavior and crystallization kinetics of starch and poly(lactic acid) composites
Authors: Ke Tianyi , Sun Xiuzhi 
Published: May 2003

AbstractDifferential scanning calorimetry was used to characterize the melting behavior and isothermal crystallization kinetics of pure poly(lactic acid) (PLA) and blends of PLA with various corn starch contents at varying isothermal crystallization temperatures (90–125°C). The experimental data were evaluated using the well‐known Avrami kinetic model. The Avrami exponent, constant, half‐time of crystallization, and degree of crystallinity were obtained. Talc, a nucleating agent, was also blended with PLA at 1% by volume (v/v) as a comparison. Starch effectively increased the crystallization rate of PLA, even at a 1% content, but the effect was less than that of talc. The crystallization rate of PLA increased slightly as the starch content in the blend was increased from 1 to 40%. An additional crystallization of PLA was observed, and it affected the melting point and degree of crystallinity of PLA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1203–1210, 2003
Atomic force and scanning electron microscopic studies of effect of crosslinking system on properties of maleated ethylene–propylene–diene monomer rubber composites filled with short melamine fibers
Authors: Rajeev R. S. , Bhowmick Anil K. , De S. K. , Bandyopadhyay S. 
Published: May 2003

AbstractThis article reports the development of new composites based on maleated ethylene–propylene–diene monomer (EPDM) rubber and melamine fiber. The compositions are cured using three different types of curing systems: conventional covalent crosslinking based on sulfur and an accelerator, fully ionic crosslinking based on zinc oxide/zinc stearate, and mixed crosslinking involving both covalent and ionic bonds. A dry bonding system comprising resorcinol, hexamethylene tetramine, and hydrated silica, popularly known as HRH, is found to increase the mechanical properties of the composites cured using both the sulfur/accelerator and mixed crosslinking systems. However, incorporation of the dry bonding system and/or melamine fiber adversely affects the strength of the composites if the linkages are fully ionic. Among the three crosslinking systems employed, composites prepared by using the mixed crosslinking system give higher tensile strength and modulus. Aging at 150°C for 48 h causes improvement in the strength and modulus of the composites cured by using the sulfur/accelerator system, particularly at higher fiber loading. However, in the case of an ionic system, both the modulus and strength drop with aging; in the case of the mixed crosslinking system, the modulus increases, but there is a drop in strength on aging. Rheological studies of the uncured compounds show that the presence of zinc stearate in the formulations of mixed and ionic crosslinking systems results in reduced viscosity and a smoother extrudate as compared to the sulfur crosslinking system. An atomic force microscopy analysis of the roughness reveals that the fiber surface roughness is reduced because of aging for the ionic crosslinking system. This is attributable to the formation of a zinc stearate layer on the fiber surface, which also reduces the adhesion between the fiber and the matrix, thereby reducing the hysteresis after aging. However, for the sulfur and mixed crosslinking system, the roughness of the fiber surface is increased and there is a concomitant increase in hysteresis. © 2003 John Wiley Periodicals, Inc. J Appl Polym Sci 89: 1211–1229, 2003
Stability and depolymerization of poly(sebacic anhydride) under high moisture environment
Authors: Chan Cheng‐Kuang , Chu I‐Ming 
Published: May 2003

AbstractPolyanhydrides are found to be useful in drug delivery systems; however, these aliphatic polyanhydrides are also unstable under humidity and temperature (greater than 0°C) for their low toxicity and surface eroding mode of drug release. In this research, poly(sebacic anhydride) was synthesized for a stability and depolymerization study in high humidity a surrounding temperature of 35°C. According to the results from gel permeation chromatography, IR spectrophotometry, and differential scanning calorimetry investigations, it was found that both self‐depolymerization and hydrolysis mechanisms existed during the depolymerization process for poly(sebacic anhydride) and they can be monitored directly. These results were further compared with previous research in a depolymerization study of polyanhydrides in a vacuum and in buffer solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1423–1429, 2003
Dose distributions of high‐energy electrons into planar and cylindrical layers of low‐density polyethylene, high‐density polyethylene, poly(vinyl chloride), and copper for industrial applications
Authors: Behjat A. , Gheysari Dj. , Mojrek A. 
Published: May 2003

AbstractHigh‐energy electron irradiation of low‐density polyethylene, high‐density polyethylene, plasticized poly(vinyl chloride) (PPVC), and copper (Cu) of various thicknesses were studied. We measured the dose distributions versus the thicknesses of various layers of these materials. Moreover, we irradiated polyethylene–Cu–polyethylene and PPVC–Cu–PPVC sandwiches and electrical conductors with Cu cores having 1.4–4.8‐mm diameters and polymeric (polyethylene and PPVC) insulation 0.6–1.1 mm thick. The irradiation was carried out with 5 and 10 MeV of electrons. The depth–dose distributions for these materials showed that 10 MeV of electrons penetrated polyethylene (up to Rp ∼ 4.5 cm), PPVC (up to Rp ∼ 3.5 cm), and Cu (up to Rp ∼ 5 mm). For the sandwiches (planar geometry), the largest dose levels were at the surfaces of the polymeric insulation materials close to the Cu sheets. For small wires, one‐sided irradiation gave a relatively uniform dose distribution, especially with 10 MeV of electrons, and excellent uniform dose distribution was obtained by two‐sided irradiation. For wires with comparatively thick insulation, two‐sided irradiation with 5 MeV of electrons provided a relatively uniform dose distribution, and a more uniform distribution for this type of wire and cable was achieved by irradiation from four sides and with 10 MeV of electrons. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1230–1241, 2003
Analysis of the thermodynamic compatibility of poly(vinyl chloride) and nitrile rubbers from inverse gas chromatography
Authors: Huang Jan‐Chan 
Published: May 2003

AbstractThe solubility parameter method was applied to an analysis of the solution thermodynamic data of several solutes (probes) in polymers obtained by inverse gas chromatography. Experimental data previously reported by different authors were analyzed. The polymers used as the stationary phases were poly(vinyl chloride) (PVC), two nitrile rubbers (NBRs), and PVC/NBR blends. From the retention volumes of the probes, the Flory–Huggins interaction parameters at infinite dilution were calculated. The interaction parameters, in turn, were related to the solubility parameters of the solutes and stationary phases. With a series of probes, the solubility parameters of PVC and NBRs were determined. Differences existed between the experimental values of the size‐corrected free energies of solutions and the values calculated with solubility parameters. The differences were generally negative values. When these differences obtained from two NBR rubbers were plotted versus PVC, a correlation was found. Methods for obtaining the interaction parameters of polymer blends were examined. A modified plotting method gave a linear line and an interaction parameter between two polymers consistent with the results of the solubility parameters. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1242–1249, 2003
ZnBr2‐catalyzed chemical effects in poly(acrylonitrile‐ co‐butadiene)
Authors: Vega‐Cantú Yadira , Hauge Robert , Norman Lewis , Billups W. Edward 
Published: May 2003

AbstractThe excellent chemical properties and resistance to oil of poly(acrylonitrile‐co‐butadiene), or nitrile–butadiene rubber (NBR), has led to the extensive use of these elastomers as O‐ring material in the oil extraction industry. The degradation of NBR gaskets is known to occur during the well completion and oil extraction process when they are exposed to bromide fluids such as ZnBr2‐based completion fluid. Samples of NBR, polyacrylonitrile, and polybutadiene were exposed to ZnBr2‐based completion fluid and analyzed by attenuated total reflectance (ATR) and diffuse reflectance IR. These analyses showed that the ZnBr2 completion fluid promoted the hydrolysis of the nitrile group to form amides and carboxylic groups. The carbon–carbon double bonds in NBR were unaffected after short exposure to ZnBr2‐based completion fluid but were quickly hydrated in acidic bromide mixtures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1250–1257, 2003
Fluorocarbon‐containing hydrophobically modified poly(acrylic acid) gels: Gel structure and water state
Authors: Tian Qin , Zhao Xi‐An , Tang Xiao‐Zhen , Zhang Yun‐Xiang 
Published: May 2003

AbstractA series of hydrophobically modified poly(acrylic acid) gels (HM‐PAA gels) were prepared by radical copolymerization of acrylic acid and a small amount of hydrophobic comonomers, 2‐(N‐ethyl perfluorooctane‐sulfonamido)ethyl methacrylate and lauryl acrylate, respectively, in tert‐butanol. The effects of hydrophobic modification on the structure and water state in hydrogels were studied by atomic force microscopy, differential scanning calorimetry, and thermogravimetric analyses. Significant differences in the enthalpy of dissociation of water per molar polymer unit were found between unmodified gel and hydrophobically modified gels (HM gels). Three states of water molecules—free water, nonfreezing water, and freezing bound water—were proven to exist in HM gels. The number of nonfreezing and freezing bound water molecules associated with a polymer unit, n0 and n1, increased with the hydrophobe content and the hydrophobicity of the hydrophobes. The roles of these water molecules are discussed in relation to hydrophobic association. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1258–1265, 2003
Graft copolymers of lignin as hydrophobic agents for plastic (wood‐filled) composites
Authors: Adcock Timothy , Shah Vipul , Chen Meng‐jiu , Meister John J. 
Published: May 2003

AbstractPoly[lignin‐g‐(1‐phenylethylene)] graft copolymers synthesized by free‐radical, graft copolymerization on lignin and verified by fractionation, infrared spectroscopy, and solubility change possess macromolecular surface activity as indicated by their capacity to form stable emulsions between incompatible fluid phases, to adhesively bond to wood surfaces, and to change the contact angle of water on coated wood. The surface activity of the copolymer changes with its composition. As the weight percent lignin in the copolymerization reaction product increases beyond 20 wt %, the amount of the emulsion phase formed in a water–benzene mixture decreases. Maple wood flour could be solvent‐coated with a copolymer and both coated and uncoated maple flour could be extruded through a stranding plate into a wood‐filled composite with polystyrene. Physical property tests show that composite control samples are about 3% stiffer and less deformable than are the copolymer composites when dry and about 5 or more percent more deformable than are the copolymer composites when wet, showing that the copolymer coating increased the wet strength. The copolymer samples are always denser than are the controls. Copolymer coating on wood filler decreases the swelling in the composite, the partial molar volume of the imbibed water, and the dimensional change in the solid. These effects cause increase in the density of the copolymer composite upon imbibition of water. Coating the wood component of the composite with a copolymer creates a hydrophobic barrier that produces a decrease in water imbibition into the composite, which will not disappear in 20 or more years of water immersion. Expansion in water is highly dependent on the direction of extrusion. The length expands about 1%, the width expands about five times as much, and the thickness expands over 10 times as much as does the length. This differential expansion may be due to the 22% reduction in the width and a 71% reduction in the thickness of the melt as it passes through the die and the alignment of the long axis of the fiber with the direction of flow through the die. The reaction product is a thermoplastic solid stable below 200°C and thermoformable at between 150 and 180°C. Products which contain between 10 and 50 wt % lignin are heterogeneous solids. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1266–1276, 2003
Synthesis and fluorescence in solution of polybenzimidazolylphenylenephthalamides
Authors: Fujimura T. , Tsuchiya M. , Koizumi T. , Ishimaru K. , Kojima T. 
Published: May 2003

AbstractSix polybenzimidazolylphenylenephthalamides (PBIPPA), two meta/para isomers, and four meta/para isomers that had different distances between a benzimidazolyl and the adjacent benzimidazolyl in a polymer chain were synthesized. They were soluble in N,N‐dimethylacetamide. In addition to the fluorescence from the π → π* transition of isolated phenylbenzimidazole, a fluorescence from a chromophore complex in the grand state appeared in the fluorescence spectra, which was observed at higher concentrations. The concentration dependence of the intensity of the fluorescence was investigated in order to learn whether the chromophore complex was intermolecular or intramolecular. It was concluded that the chromophore complex is intramolecular, a conclusion supported by the viscometric results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1412–1416, 2003