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Efforts to find stick-slip flow in the land of a die under sharkskin melt fracture conditions: polybutadiene

macromolecular Symposia 2001年第1期158卷

作者： Yong Woo Inn Liangshi Wang Montgomery T. Shaw Polymer Program Institute of Materials Science University of Connecticut Storrs CT 06269-3136 USA Department of Chemical Engineering

Because stick-slip or other flow disturbances inside the die land have been suggested as a possible mechanism of the sharkskin, our effort was to observe any relevant periodic changes inside the die land during the sharkskin condition. We used particle tracking and time-resolved birefringence and two-dimensional light scattering in conjunction with a slit die attached to an extruder and a tubular glass die attached to a pressurized reservoir. Both dies could be observed up to the exit; both could also be directly observed downstream of the exit. While periodicities were easily seen in the slip-stick regime, none of the methods revealed any periodicity in the sharkskin regime. Direct observation of the sharkskin formation outside the die suggests a tearing and rolling mechanism as the origin of the sharkskin ridges found on polybutadiene extrudates.

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Spherical and vesicular ionic aggregates in Zn-neutralized sulfonated polystyrene ionomers

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Journal of Polymer science 2001年第5期39卷

作者： Brian P. Kirkmeyer Robert A. Weiss Karen I. Winey Department of Materials Science and Engineering University of Pennsylvania 3231 Walnut Street Philadelphia Pennsylvania 19104-6272 Polymer Science Program and Department of Chemical Engineering University of Connecticut Storrs Connecticut 06269-3136

Ionic aggregates in a series of Zn-neutralized poly(styrene- co -styrene sulfonate) (SPS) random ionomers have been imaged using scanning transmission electron microscopy. The Zn-rich aggregates were found to have two shapes: solid spheres (Type I) and shells or vesicles (Type II). Type I aggregates range in a maximum diameter from 4 to 10 nm, whereas Type II aggregates range in a maximum diameter from 9 to 55 nm with a vesicle wall thickness of ∼ 3 nm. Lightly neutralized ionomers exhibited only Type I aggregates, whereas higher neutralization levels exhibited both Type I and II aggregates. Lightly neutralized ionomers also showed evidence of macrophase separation at the micron size scale. These direct observations of ionic aggregates contradict previous interpretations of small-angle X-ray scattering data with respect to size, size dispersity, shape, and spatial distribution. In addition, the aggregates observed in SPS differ markedly from the nearly monodisperse ∼ 2-nm spherical aggregates observed in Zn-neutralized poly(ethylene- co -methacrylic acid). The presence of vesicular aggregates encourages a re-examination of the morphologies and properties of styrenic ionomers. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 477–483, 2001

关键词： ionomers sulfonated styrene STEM morphology

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Decision analysis frameworks for life-cycle impact assessment

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Journal of Industrial Ecology 2001年第4期5卷 45-68页

作者： Seppälä, Jyri Basson, Lauren Norris, Gregory A. Environ-mental Technology Program Finnish Environment Institute Helsinki Finland Centre for Risk Environment Systems Technology and Analysis (CRESTA) Department of Chemical Engineering University of Sydney Sydney NSW Australia Sylvatica North Berwick ME United States Environmental Science and Engineering Program Harvard University School of Public Health Boston MA United States Complex Systems Research Center University of New Hampshire Durham NH United States Finnish Environment Institute SF-00251 Helsinki Kesäkatu 6 Finland

Life-cycle impact assessments (LCIAs) are complex because they almost always involve uncertain consequences relative to multiple criteria. Several authors have noticed that this is precisely the sort of problem addressed by methods of decision analysis. Despite several experiences of using multiple-attribute decision analysis (MADA) methods in LCIA, the possibilities of MADA methods in LCIA are rather poorly elaborated in the field of life-cycle assessment. In this article we provide an overview of the commonly used MADA methods and discuss LCIA in relation to them. The article also presents how different frames and tools developed by the MADA community can be applied in conducting LCIAs. Although the exact framing of LCIA using decision analysis still merits debate, we show that the similarities between generic decision analysis steps and their LCIA counterparts are clear. Structuring of an assessment problem according to a value tree offers a basis for the definition of impact categories and classification. Value trees can thus be used to ensure that all relevant impact categories and interventions are taken into account in the appropriate manner. The similarities between multiattribute value theory (MAVT) and the current calculation rule applied in LCIA mean that techniques, knowledge, and experiences derived from MAVT can be applied to LCIA. For example, MAVT offers a general solution for the calculation of overall impact values and it can be applied to help discern sound from unsound approaches to value measurement, normalization, weighting, and aggregation in the LCIA model. In addition, the MAVT framework can assist in the methodological development of LCIA because of its well-established theoretical foundation. The relationship between MAVT and the current LCIA methodology does not preclude application of other MADA methods in the context of LCIA. A need exists to analyze the weaknesses and the strengths of different multiple-criteria decision analysis metho

关键词： Decision analysis Life-cycle impact assessment (LCIA) Methods Multiple attribute Multiple-criteria decision analysis (MCDA) Normalization

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Effect of albumin on brushite transformation to hydroxyapatite

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Journal of Biomedical Materials Research Part B: Applied Biomaterials 2001年第3期57卷

作者： Jing Xie Clyde Riley Krishnan Chittur Materials Science Program and Chemistry Department The University of Alabama-Huntsville Huntsville Alabama 35899 Chemical and Materials Engineering Department The University of Alabama-Huntsville Huntsville Alabama 35899

Brushite (CaHPO 4 · 2H 2 O) is a precursor to hydroxyapatite [HA, Ca 5 (PO 4 ) 3 OH]. It has been shown that a modified form of brushite, with potassium substituting for calcium at specific sites, demonstrated accelerated transformation to HA when exposed to nonproteinaceous Hanks’ balanced aqueous salt solutions (HBSS). The biocompatibility of a transforming material is related to cellular response to the process, which is initiated by protein adsorption. The effect of adsorbed protein on the kinetics and chemistry of brushite transformation to HA, when exposed to HBSS containing bovine serum albumin (BSA), was examined using Fourier transform IR spectroscopy, X-ray diffraction, and energy dispersive spectrometry techniques. The effect of solution pH was also studied. Results show that, in the presence of a protein-free environment, transformation is faster in buffered medium than in nonbuffered medium. Moreover, curve fitting and second derivatives of the IR spectra show that some bands shift depending on whether the brushite transforms in a buffered or nonbuffered medium. Therefore, variation in pH affects both transformation rate and the associated chemistry. The presence of BSA in either buffered or nonbuffered medium retards the transformation in comparison to the corresponding BSA-free medium. The extent of this retardation increases with the increase in bulk concentration of BSA but does not alter the transformation chemistry. This suggests the retardation on the transformation rate is due to BSA adsorption coverage on the calcium phosphate ceramic. This may be due to the shielding of Ca 2+ and PO 4 −3 sites, preventing their interaction with the HBSS. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res 57: 357–365, 2001

关键词： brushite hydroxyapatite protein adsorption transformation and dissolution studies of calcium phosphates

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Growth of ZnO Thin Film by Laser MBE: Lasing of Exciton at Room Temperature

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physica status solidi (b) 2001年第2期202卷

作者： Y. Segawa A. Ohtomo M. Kawasaki H. Koinuma Z. K. Tang P. Yu G. K. L. Wong Photodynamics Research Center Frontier Research Program The Institute of Physical and Chemical Research 19-1399 Koeji-Nagamachi Aoba Sendai 980 Japan Research Laboratory of Engineering Materials Tokyo Institute of Technology 4259 Nagatsuda Midori-Ku Yokohama 226 Japan Physics Department Hongkong University of Science and Technology Clear Water Bay Kowloon Hong Kong

High quality ZnO thin film was grown by Laser MBE. A pure ceramic ZnO target was ablated by the KrF laser pulses (248 nm, 10 Hz, 1 J/cm 2 ) in an ultra high vacuum to deposit ZnO film on sapphire (0001) substrate. The lateral grain size was about 50 nm for the sample with thickness of 55 nm. At room temperature, the peak of the exciton absorption and the photoluminescence have the same energy. Under high density excitation (355 nm, 35 ps, 10 Hz), an exciton–exciton collision process was observed as P 2 and P lines where 2S exciton and ionized exciton remain. From the edge of the sample, a very rapid increase of the P line was observed with the increase of the excitation power. A fine structure that comes from the cavity mode was also observed. These facts suggest that the lasing of the exciton was observed at room temperature.

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Molecular design of polyimides toward high proton conducting materials

Molecular design of polyimides toward high proton conducting...

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Washington,DC. Meeting

作者： Zhang, Yue Lilf, Morion Savinell, Robert F. Wainright, Jesse S. Vendramini, Jerome Department of Macromolecular Science Case Western Reserve University Cleveland OH 44106 United States Department of Chemical Engineering Case Western Reserve University Cleveland OH 44106 United States

In this study, high proton conductivities were obtained for sulfonic acid containing, linear, rigid rod liquid crystalline copolyimides having bulky comonomer units. The observed conductivities force the polymer chains to pack loosely. With larger interchain spacing, more unoccupied volume is available for water to occupy, and higher proton conductivities at low relative humidity are found, compared to homopolymer.

关键词： Polyimides

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Abstracts of presentations at the 18th Conference of the Entomological Society of Israel - May 18, 2000 - ARO, The Volcani Center, Bet Dagan, Israel

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PHYTOPARASITICA 2001年第1期29卷 51-89页

作者： [Anonymous] Dept. of Cell and Animal Biology The Hebrew University of Jerusalem Jerusalem Israel Dept. of Entomology Israel Dept. of Chemistry The Volcani Center ARO Bet Dagan Integrated Pest Management Fruit Crops Experiment Station Agriculture Company in Upper Galilee Kibbutz Yiron Ministry of Agriculture and Rural Development Extension Service Qiryat Dept. of Stored Products Pheromone Research Lab. ARO The Volcani Center Bet Dagan Israel Div. of Bioresource and Bioenvironmental Sciences Graduate School Kyushu University Fukuoka Japan Mitrani Dept. for Desert Ecology Blaustein Institute for Desert Research Ben-Gurion University of the Negev Sede Boqer Campus Israel Dept. of Chemistry University of Hamburg Germany Dept. of Entomology ARO The Volcani Center Bet Dagan Dept. of Zoology Faculty of Life Science Tel-Aviv University Tel Aviv Israel Plant Protection and Inspection Services Ministry of Agriculture and Rural Development Bet Dagan Israel Carmel Mizrahi Rishon LeZiyyon Ministry of Agriculture and Rural Development Extension Service Rehovot Israel Agricultural Department Agan Chemical Manufacturers Ashdod Israel Dept. of Entomology ARO Gilat Research Station M.P. Negev Israel Entomology Laboratory Ministry of Health Jerusalem Israel Kimron Veterinary Institute Bet Dagan Israel USDA/ARS Gainesville USA Dept. of Stored Products ARO The Volcani Center Bet Dagan Israel Dept. of Plant Protection Southwest Agricultural University Chonqing China Makliteshim Chemical Works Ltd. Be’er Sheva Israel Dept. of Entomology ARO The Volcani Center Bet Dagan Israel Jerusalem Bet Dagan Israel Plant Protection Division Extension Service Ministry of Agriculture and Rural Development 1 ha ’Hamaqim District Bet Dagan Dept. of Plant Science Faculty of Life Science Tel-Aviv University Tel Aviv Israel Dept. of Plant Sciences Tel-Aviv University Tel Aviv Vitality Biotechnologies (Israel) Ltd. Carmel Industrial Park Tirat HaCarmel Israel Max-Planck-Institut Cologne

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Synthesis and microstructural characterization of POSS-based triblock copolymers prepared using atom transfer radical polymerization

American Chemical Society, Polymer Preprints, Division of Po...

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American chemical Society, Polymer Preprints, Division of Polymer Chemistry 2000年第1期41卷 582-583页

作者： Mather, Patrick T. Chun, Seung B. Pyun, Jeffrey Matyjaszewski, Krzysztof Jeon, Hong G. Polymer Program Institute of Materials Science University of Connecticut Storrs CT 06269-3136 United States Ctr. for Macromolecular Engineering Department of Chemistry Carnegie Mellon University 4400 Fifth Avenue Pittsburgh PA 15213 United States Systran Corp. AFRL/MLBP Wright Patterson AFB Dayton OH 45433-7750 United States

A polyhedral silsesquioxane (POSS)-methacrylate and poly(n-butyl acrylate) triblock copolymer (poly(MA-POSS)-b-BA-b-(MA-POSS)) prepared by atom transfer radical polymerization (ATRP) were synthesized and characterized. The molecular weight and composition of the triblock copolymer was determined from size exclusion chromatography and H NMR spectroscopy. The study aims to develop an understanding of the thermoplastic elastomeric properties as influenced by hard-block interactions and nanometer-scale organization in the materials.

关键词： Block copolymers

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Synthesis of side chain liquid crystalline copolymers and characterization of their polar structure

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Journal of Polymer science 2000年第8期37卷

作者： Toemsak Srikhirin J. Adin Mann Jr. Jerome B. Lando Polymer Microdevice Laboratory Department of Macromolecular Science Case Western Reserve University Cleveland Ohio 44106 Department of Chemical Engineering Case Western Reserve University Cleveland Ohio 44106

A series of side chain liquid crystalline copolymers having different spacer lengths, copolymer compositions, and chromophore types were synthesized and characterized both in the bulk and at the gas-water interface. Liquid crystalline properties were identified by differential scanning calorimetry (DSC), optical microscopy, and X-ray diffraction (XRD). Copolymer with spacer lengths 4, 5, 10, and 11 showed smectic A (S A ) phases with a bâtonnet texture. The liquid crystalline (LC) phase stabilized as the spacer increased. Copolymers with different compositions were investigated both as monolayers and transferred films. The isotherms suggest nanodomain formation at the gas-water interface in copolymers with high nitrobiphenyl (NBP) content. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1057–1070, 1999

关键词： Langmuir-Blodgett films polysiloxane liquid crystal nonlinear optics

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Functionalized diacetylenes for nonlinear optical applications: Synthesis, characterization, and the properties of their monolayers

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Journal of Polymer science 2000年第12期37卷

作者： Toemsak Srikhirin Pak-Meng Cham J. Adin Mann Jr. Jerome B. Lando Polymer Microdevice Laboratory Department of Macromolecular Science Case Western Reserve University Cleveland Ohio 44106-7202 U.S.A. The Dow Chemical Company Freeport TX 77541-3257 USA Department of Chemical Engineering Case Western Reserve University Cleveland Ohio 44106-7202 U.S.A.

Synthesis and characterization of DA(8/1)OMe (14-{4′-[(methoxy)methoxy] biphenyl}-10,12-tetradecadiynoic acid) and DA(8/1)NBP (14-{4′-[(nitro)methoxy] biphenyl}-10,12-tetradecadiynoic acid ) are presented. Monolayers of DA(8/1)OMe at gas-water interface were investigated. It does not form a stable monolayer nor does it undergo polymerization at the gas-water interface. However, the Ba 2+ and Cd 2+ salts formed stable monolayer that polymerized. Polymerization was confirmed by Raman spectroscopy. The diacetylene analog with the more polar tail group, DA(8/1)NBP, does not form a monolayer and undergo polymerization regardless of the subphase condition. A mixed monolayer of DA(8/1)OMe and DA(8/1)NBP forms a true monolayer if the composition of DA(8/1)NBP is 50% or less. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1771–1779, 1999

关键词： polydiacetylene Langmuir–Blodgett film nonlinear optic

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