bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle formation in interval III of the emulsion polymerization of styrene with aerosol‐MA as an emulsifier
Authors: Sajjadi Shahriar 
Published: August 2002

AbstractParticle nucleation in the seeded emulsion polymerization of styrene in the presence of Aerosol‐MA emulsifier micelles and in the absence of monomer droplets (interval III) was investigated. The seed particles were swollen with different amounts of the styrene monomer before the experiments. A larger number of polymer particles formed in interval III than in the corresponding seeded batch operation in the presence of monomer droplets. The increase in the number of particles could be attributed to the reduced rate of growth of new particles, which retarded the depletion of emulsifier micelles. The number of secondary particles initially increased with the initial polymer weight ratio in the seed particles (wp0) but decreased at a higher range of wp0, after reaching a maximum at wp0 = 0.60, and eventually was reduced to zero. At high values of wp0 (>0.75), polymerization occurred in the seed particles, whereas few or no new particles were formed despite the presence of micelles. The cessation of particle formation at high conversions was ascertained with a semibatch process in which the neat monomer feed was added to the reaction vessel containing the seed particles and emulsifier micelles. For wp0 > 0.85, the emulsifier micelles were disintegrated to stabilize the seed particles with no secondary particle formation. The possible reasons for the cessation of particle formation at high wp0 were examined. The size distribution of secondary particles showed a positive skewness in terms of volume because of the declining rate of growth for particles, together with a low rate of growth for small particles. The distribution breadth of new particles sharpened with increasing wp0. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1652–1663, 2002
Grafting of polymers onto a carbon‐fiber surface by ligand‐exchange reaction of poly(vinyl ferrocene‐co‐vinyl monomer) with polycondensed aromatic rings of the surface
Authors: Tsubokawa Norio , Abe Nobuyuki , Wei Gang , Chen Jinhua , Saitoh Satoshi , Fujiki Kazuhiro 
Published: August 2002

AbstractTo improve the surface of carbon fiber, the grafting reaction of copolymer containing vinyl ferrocene (VFE) onto a carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber was investigated. The copolymer containing VFE was prepared by the radical copolymerization of VFE with vinyl monomers, such as methyl methacrylate (MMA) and styrene, using 2,2′‐azobisisobutyronitrile as an initiator. By heating the carbon fiber with poly(VFE‐co‐MMA) (number‐average molecular weight: 2.1 × 104) in the presence of aluminum chloride and aluminum powder, the copolymer was grafted onto the surface. The percentage of grafting reached 46.1%. On the contrary, in the absence of aluminum chloride, no grafting of the copolymer was observed. Therefore, it is considered that the copolymer was grafted onto the carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber. The molar number of grafted polymer chain on the carbon‐fiber surface decreased with increasing molecular weight of poly(VFE‐co‐MMA) because the steric hindrance of grafted copolymer on the carbon‐fiber surface increases with increasing molecular weight of poly(VFE‐co‐MMA). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1868–1875, 2002
Synthesis of a novel methacrylic monomer iniferter and its application in surface photografting on crosslinked polymer substrates
Authors: Luo Ning , Hutchison J. Brian , Anseth Kristi S. , Bowman Christopher N. 
Published: August 2002

Abstract(Methacryloyl ethylenedioxycarbonyl) benzyl N,N‐diethyldithiocarbamate (HEMA‐E‐In) was synthesized and used as a monomer iniferter to develop a novel, photopatternable grafting technology. This molecule functions as both a methacrylic monomer and a photoiniferter (photoinitiator–transfer agent–terminator). The structure of HEMA‐E‐In was characterized by 1H NMR, Fourier transform infrared, and ultraviolet–visible spectroscopies. In the presence of the monomer iniferter, methyl methacrylate was polymerized by exposure to 365‐nm ultraviolet radiation, confirming the initiation capability of HEMA‐E‐In. After the copolymerization of HEMA‐E‐In into a methacrylate‐based polymer, attenuated total reflectance Fourier transform infrared spectra revealed that the photoiniferter functionality was present at the surface of this polymeric substrate. Photografting of poly(ethylene glycol) monomethacrylate monomer from the surface caused a significant change in the hydrophobicity of the surface as demonstrated by contact angle measurements. The novel monomer photoiniferter HEMA‐E‐In initiates the polymerization of bulk monomer and provides a reactive functionality that facilitates further initiation and polymer modification by the polymerization of different monomers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1885–1891, 2002
Chemical structure of composites derived from poly(silicic acid) and 2‐hydroxyethylmethacrylate
Authors: Habsuda J. , Simon G. P. , Cheng Y.‐B. , Hewitt D. G. , Toh H. , Diggins D. R. 
Published: August 2002

AbstractOrganic–inorganic hybrids from 2‐hydroxyethylmethacrylate (HEMA) and poly(silicic acid)s were prepared and characterized. The molecular architecture of the inorganic phase was studied with 29Si NMR spectroscopy, and the effect of acid concentration and reaction time on the properties of poly(silicic acid) were elucidated. Interactions between phases were studied with NMR spectroscopy and gel permeation chromatography, and the coexistence and connectivity of the two phases were investigated. Contrary to previous assumptions, evidence was found that indicated that the organic and inorganic phases of this class of sol–gel materials were not covalently linked. The curing process was studied by infrared spectroscopy, by which the disappearance of terminal double bonds of HEMA monomer were monitored. Thermogravimetric analysis profiles showed that the inorganic phase content was about 10 wt %, and it was varied slightly by changes in the molar ratio of the components. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1342–1352, 2001
From metal‐catalyzed radical telomerization to metal‐catalyzed radical polymerization of vinyl chloride: Toward living radical polymerization of vinyl chloride
Authors: Asandei A. D. , Percec V. 
Published: August 2002

AbstractThe metal‐catalyzed radical polymerization of vinyl chloride (VC) in ortho‐dichlorobenzene initiated with various activated halides, such as α,α‐dihaloalkanes, α,α,α‐trihaloalkanes, perfloroalkyl halides, benzyl halides, pseudohalides, allyl halides, sulfonyl halides, α‐haloesters, α‐halonitriles, and imidyl halides, in the presence of Cu(0)/2,2′‐bipyridine, Fe(0)/o‐phenantroline, TiCp2Cl2, and other metal catalysts is reported. The formation of the monoadduct between the initiator and VC was achieved with all catalysts. However, propagation was observed only for metals in their zero oxidation state because they were able to reinitiate from geminal dihalo or allylic chloride structures. Poly(vinyl chloride) with molecular weights larger then the theoretical limit allowed by chain transfer to VC were obtained even at 130 °C. In addition, the most elemental features of a living radical polymerization, such as a linear dependence of the molecular weight and a decrease of polydispersity with conversion, were observed for the most promising systems based on iodine‐containing initiators and Cu(0), that is, ICH2PhCH2I/Cu(0)/bpy (where bpy = 2,2′‐bipyridyl), at 130 °C. However, because of the formation of inactive species via chain transfer to VC and other side reactions, the observed conversions were in most cases lower than 40%. A mechanistic interpretation of the chain transfer to monomer in the presence of Cu species is proposed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3392–3418, 2001
Polymorphic behavior in syndiotactic polystyrene/clay nanocomposites
Authors: Wu Tzong‐Ming , Hsu Sung‐Fu , Wu Jeng‐Yue 
Published: August 2002

AbstractX‐ray diffraction methods were used in an investigation of the structural changes in syndiotactic polystyrene (sPS)/clay nanocomposites. sPS/clay was prepared by the intercalation of sPS polymer into layered montmorillonite. Both X‐ray diffraction data and transmission electron microscopy micrographs of sPS/clay nanocomposites indicated that most of the swellable silicate layers were exfoliated and randomly dispersed in the sPS matrix. The X‐ray diffraction data also showed the presence of polymorphism in the sPS/clay nanocomposites. This polymorphic behavior was strongly dependent on the thermal history of the sPS/clay nanocomposites from the melt and on the content of clay in the sPS/clay nanocomposites. Quenching from the melt induced crystallization into the α‐crystalline form, and the addition of montmorillonite probably increased heterophase nucleation of the α‐crystalline form. The effect of the melt crystallization of sPS and sPS/clay nanocomposites at different temperatures on the crystalline phases was also examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 736–746, 2002
Temperature dependence of the fluorescence quantum yields of diphenylsiloxane‐based copolymers in dilute solutions
Authors: Itoh Takao , Yang Mei‐Hui 
Published: August 2002

AbstractThe monomer and excimer fluorescence quantum yields of well‐defined poly(dimethylsiloxane‐co‐diphenylsiloxane)s with different diphenylsiloxane (Ph2SiO) contents have been determined, along with those of 1,1,3,3‐tetraphenyl‐1,3‐dimethyldisiloxane and 1,1,3,3,5,5‐hexaphenyltrisiloxane‐1,5‐diol used as model compounds, in a dilute organic solvent at different temperatures. The measured fluorescence quantum yields of the copolymers are correlated with the fraction of the (CH3)2SiO (Ph2SiO)n(CH3)2SiO structures. The monomer fluorescence yield for copolymers with low Ph2SiO contents is dominated mainly by the isolated (CH3)2SiO (Ph2SiO)(CH3)2SiO unit, and the apparent mean binding energy of the excimer does not increase significantly with increasing Ph2SiO content. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 854–861, 2002
Phase separation induced by shear quenching in polymer blends with a diblock copolymer
Authors: Jeon H. S. , Kim S. , Han C. C. 
Published: August 2002

AbstractThe effects of adding A–B diblock copolymer to a polymer blend (A/B) on phase‐separation kinetics and morphology have been investigated in a fixed shallow‐quench condition (ΔT = 1.5 °C) by in situ time‐resolved light scattering and phase‐contrast optical microscopy. A shear‐quench technique was used in this study instead of a conventional temperature‐quench method. Mixtures of nearly monodisperse low relative‐molecular masses of polybutadiene (Mw = 2.8 kg/mol), polystyrene (Mw = 2.6 kg/mol), and a near‐symmetric butadiene–styrene diblock copolymer (Mw = 6.3 kg/mol) as an interfacial modifier were studied. We observed that the addition of the diblock copolymer could either retard or accelerate the phase‐separation kinetics depending on the concentration of the diblock copolymer in the homopolymer blends. In contrast to the conventional temperature quench, we observed complex phase‐separation kinetics in the intermediate and late stages of phase separation by the shear‐quench technique. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 819–830, 2001
Configurations conducive to the formation of intramolecular excimers in poly(N‐vinyl carbazole) and its copolymers
Authors: Gallego Javier , Pérez‐Foullerat David , Mendicuti Francisco , Mattice Wayne L. 
Published: August 2002

AbstractThe ratios of the intensity of excimer and monomer emissions, denoted IE/IM, in poly(N‐vinyl carbazole) and copolymers of N‐vinyl carbazole and methyl methacrylate were measured with steady‐state fluorescence. Measurements were performed in dilute solutions of several fluid solvents at 25 °C and in a solid matrix of poly(methyl methacrylate) at room temperature. The values of IE/IM depended on the nature of the solvent, the emission wavelength, and the copolymer composition. Molecular dynamics simulations were performed for diastereoisomers of 2,4‐di(N‐carbazolyl)pentane and for isotactic and syndiotactic trichromophoric copolymer fragments to assist in the identification of the thermally accessible conformations capable of forming intramolecular excimers and the configurational relationship of the carbazole units in these complexes. Nearest neighbor carbazole groups made the dominant contribution to the excimers. Excimers were more likely in isotactic sequences than in syndiotactic sequences, as was also the case for the low‐energy excimer arising from the complete overlap of two carbazole units. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1272–1281, 2001
Thermal and infrared spectroscopic studies on hydrogen‐bonding interactions between poly‐(ε‐caprolactone) and some dihydric phenols
Authors: Li Jianchun , He Yong , Inoue Yoshio 
Published: August 2002

AbstractThe effects of three dihydric phenols on the thermal properties of poly‐(ε‐caprolactone) (PCL) were investigated by DSC. The thermal properties of PCL were found to be greatly modified by the addition of 4,4′‐dihydroxydiphenyl ether (DHDPE). When the content of DHDPE reached 40%, PCL that was a semicrystalline polymer in the pure state changed to a fully amorphous elastomer. Fourier transform infrared (FTIR) spectroscopy was also applied to investigate the specific interaction between PCL and DHDPE. The formations of intermolecular hydrogen bonds between the carbonyl groups of PCL and the hydroxyl groups of DHDPE were discovered. By applying the Beer–Lambert law and a curve‐fitting program, the fractions of hydrogen‐bonded carbonyl groups were quantitatively analyzed. Although one DHDPE molecule had the potentiality to form two hydrogen bonds with PCL chains, the values of the fraction of the hydroxyl group involved in the intermolecular hydrogen bond were so little that from a statistical point of view, the formation of two hydrogen bonds was very difficult for every DHDPE molecule. Both DSC and FTIR revealed that 4,4′‐dihydroxydiphenyl methane and 4,4′‐dihydroxyphenyl had the ability to form hydrogen bonds with PCL, which were strongly affected by the polarity of the group linking two hydroxyphenyls and the flexibility of the molecular chain. The stronger the polarity of the group and the better the flexibility of molecular chain, the more tendencies dihydric phenol had to form intermolecular hydrogen bonds with PCL. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2108–2117, 2001
Soil moisture conditions during thawing on a slope in the Daisetsu Mountains, Hokkaido, Japan
Authors: Matsumoto Hotaka , Kurashige Yoshimasa , Hirakawa Kazuomi 
Published: August 2002

AbstractPrecise monitoring of total potential, thawing front depth and groundwater level indicate the soil moisture conditions in a turf‐banked terrace during the thawing season in the Daisetsu Mountains, Japan. During thaw, the soil was in an almost unsaturated condition, and unsaturated soil water infiltrated downward. A small saturated zone sometimes appeared on the frost table with a duration of less than one day. In such cases the water in the saturated zone moved upward to a low total potential layer. The saturated zone was formed not by vertical water infiltration from the surface, but most likely by melting of ice lenses. Copyright © 2001 John Wiley & Sons, Ltd.RÉSUMÉDes enregistrements précis du potentiel hydraulique total, du front de dégel du sol et du niveau de l'eau ont révélé quelles étaient les conditions d'humidité pendant la saison de dégel dans une terrasse à front végétalisé des montagnes de Daisetsu au Japon. Pendant le dégel, le sol a été presque insaturé et l'eau de ce sol insaturé s'est infiltré en profondeur. Une petite zone saturée apparaît parfois pendant moins d'un jour au dessus de la table gelée. Dans de teles situations, l'eau de la zone saturée se déplace vers le haut vers une couche de potentiel moins élevée. La zone saturée ne résulte pas d'une infiltration verticale de l'eau depuis la surface, mais plus probablement de la fusion de lentilles de glace. Copyright © 2001 John Wiley & Sons, Ltd.
New geophysical methods of investigating the nature and distribution of mountain permafrost with special reference to radiometry techniques
Authors: Mühll Daniel Vonder , Hauck Christian , Gubler Hansueli , McDonald Robert , Russill Nick 
Published: August 2002

AbstractA series of geophysical surveys were undertaken within the PACE geophysical work package. Various methods were applied including refraction seismics, DC resistivity, ground penetrating radar (GPR), electromagnetic induction, radiometry and bottom temperature of snow cover (BTS). The focus of the surveys was to determine the internal structures and distribution of mountain permafrost. This paper gives a preliminary overview of progress. The two‐dimensional DC resistivity tomography combines the geoelectrical sounding and mapping and makes it possible to model internal structures. This method was applied at all PACE drill sites. Electromagnetic induction methods showed good results, in particular the EM‐31 for determining the permafrost distribution and the PROTEM to assess the overall permafrost thickness. A major new development discussed here is the use of passive microwave (11.4 GHz) for airborne remote measurement of the bottom temperature of snow cover (BTS). Manual BTS measurements agreed very well with the BTS determined by radiometry. To reduce ambiguity, several geophysical methods should be deployed at the same locality. As a further step, such measurements could be interpreted using joint inversions. Copyright © 2001 John Wiley & Sons, Ltd.RÉSUMÉUne série de levés géophysiques a été réalisé dans le cadre des travaux de PACE. Différentes méthodes ont été utilisées y compris la séismique réfraction, la résistivité DC, le radar pénétrant le sol (GPR), l'induction électro‐magnétique, la radiométrie et la température à la base de la couverture nelgeuse (BTS). Le but de ces levés était de déterminer les structures internes et la distribution du pergélisol de montagne. Le présent article donne une vue générale préliminaire des progrès réalisés. La tomographie en deux dimensionns par résistivité. DC qui combine le sondage géoélectrique et la cartographie, rend possible la reconnaissance des structures internes. Cette méthode a été appliquée dans tous les sites de sondage. Les méthodes par induction électromagnétique ont donné de bons résultats, en particulier la méthode par EM‐31 pour déterminer la distribution du pergéllisol, tandis que la méthode PROTEM a été utile pour estimer l'épaisseur totale du pergélisol. Un imporant nouveau développement discuté ici est l'emploi de micro‐ondes passives (11.4 GHz) dans des mesures aéroportées de la température de la base de la converture de neige (BTS). Des mesures manuelles BTS se sont révélées bien en accord avec les données BTS obtenues par radiométrie.Pour diminuer les ambiguités, plusieurs methodes géophysiques devraient toujours être utilisées. Copyright © 2001 John Wiley & Sons, Ltd.
Results of permafrost modelling of the lowlands and shelf of the Laptev Sea Region, Russia
Authors: Romanovskii Nikolai N. , Hubberten Hans‐W. 
Published: August 2002

AbstractPermafrost thickness evolution models for the Laptev Sea shelf and coastal lowlands describe a palaeogeographic scenario, a geological model, and the choice of lower and initial boundary conditions. The model covers four climatic and glacio‐eustatic cycles. The temperature zonation of permafrost, the freezing of seawater‐saturated deposits, and the accumulation of ice‐rich syncryogenic sediments with fresh ice on the emergent shelf surface are all included into the model. Different values of geothermal heat flow are used. Results indicate an increase in the magnitude of oscillations of the permafrost bottom, an increase in differences in permafrost thickness during the warmer parts of climatic cycles, a lag in the appearance of the maximum permafrost thickness after the climate extreme, and a degradation of permafrost on the shelf and coastal lowlands at the present time. Copyright © 2001 John Wiley & Sons, Ltd.RésuméDes modèles d'évolution de l'épaisseur du pergélisol sur la plate‐forme de la mer de Laptev et sur les basses terres côtières décrivent un scénario paléogéographique, un modèle géologique et imposent le choix de conditions de départ. Les modèles couvrent quatre cycles climatiques et glacio‐eustatiques. La zonation des temératures du pergélisol, le gel des dépôts saturés en eau de mer et l'accumulation de sédiments riches en glace sur la plate‐forme émergente sont des données incluses dans ce modèle. Différentes valeurs sont employées pour le flux géothermique. Les résultats indiquent une augmentation de l'ampleur des oscillations de la base du pergélisol, une augmentation des différences d'épaisseur du pergélisol pendant les parties chaudes des cycles climatiques, un retard dans l'apparition de l'épaisseur maximum du pergélisol après le minimum climatique et une dégradation actuelle du pergélisol sur la plate‐forme et les basses terres côtières. Copyright © 2001 John Wiley & Sons, Ltd.
Temperature regime of a small sandstone tor, latitude 80 °N, Ellesmere Island, Nunavut, Canada
Authors: Lewkowicz Antoni G. 
Published: August 2002

AbstractNear‐surface rock temperatures were recorded hourly for more than one year around a sandstone tor located on a ridge‐crest at an elevation of 270 m asl. There were significant differences between air and rock temperatures except during the polar night. The SSE‐ and WSW‐facing sides experienced large amplitude diurnal temperature cycles in the late‐winter and spring, and these crossed through 0 °C from mid‐April to May, well before air temperatures rose above freezing. Rock temperatures at a depth of 15 mm on the SSE‐face exceeded air temperature by up to 31 °C. During most of the summer, rock faces and air temperatures remained above 0 °C. Diurnal temperature cycles were smaller in amplitude in the autumn and few cycles through 0 °C were measured because of persistent cloud cover and the absence of a radiation‐reflecting snowpack. Modelling using a constant environmental lapse rate shows that although the timing and number of temperature cycles through 0 °C are influenced by altitude, the importance of rock‐face orientation on the relative numbers of cycles is independent of tor elevation. The average rate of micro‐weathering measured on several tors over four years was 0.012 mm a−1. No loss of larger clasts was observed at the monitored tor over 11 years suggesting that the combined rate of all types of weathering is low. Copyright © 2001 John Wiley & Sons, Ltd.