Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Chemistry Faculty Research and Publications

2005

Articles 1 - 25 of 25

Full-Text Articles in Physical Sciences and Mathematics

Atr-Ftir Spectroscopic Analysis Of Sorption Of Aqueous Analytes Into Polymer Coatings Used With Guided Sh-Saw Sensors, Yolanda K. Jones, Zhonghui Li, Michael M. Johnson, Fabien Josse, Jeanne Hossenlopp Dec 2005

Atr-Ftir Spectroscopic Analysis Of Sorption Of Aqueous Analytes Into Polymer Coatings Used With Guided Sh-Saw Sensors, Yolanda K. Jones, Zhonghui Li, Michael M. Johnson, Fabien Josse, Jeanne Hossenlopp

Chemistry Faculty Research and Publications

Attenuated total internal reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used for the investigation of sorption of aqueous solutions of analytes into polymer coatings. A series of simple model polymers, such as poly(dimethylsiloxane), poly(epichlorhydrin), and poly(isobutylene), and films and analytes, such as aqueous solutions of ethylbenzene, xylenes, toluene, and nitrobenzene, were used to evaluate the use of ATR-FTIR spectroscopy as a screening tool for sensor development. The ratios of integrated infrared absorption bands provided a simple and efficient method for predicting trends in partition coefficients. Responses of polymer-coated guided shear horizontal surface acoustic wave (SH-SAW) sensor platforms to the series …

Go to article

Combined X-Ray Diffraction And Diffuse Reflectance Analysis Of Nanocrystalline Mixed Sn(Ii) And Sn(Iv) Oxide Powders, Hongmei Deng, Jeanne Hossenlopp Dec 2005

Combined X-Ray Diffraction And Diffuse Reflectance Analysis Of Nanocrystalline Mixed Sn(Ii) And Sn(Iv) Oxide Powders, Hongmei Deng, Jeanne Hossenlopp

Chemistry Faculty Research and Publications

Nanocrystalline mixtures of Sn(II) and Sn(IV) oxide powders, potential gas sensor materials, are synthesized via a simple precipitation route using SnCl(2) as the precursor. Materials are characterized by powder X-ray diffraction, thermogravimetric analysis, UV-visible diffuse reflectance spectroscopy (DRS), and Fourier transform infrared spectroscopy. The ratio of Sn(II)/Sn(IV) in powders precipitated at room temperature, as well as the identity of the primary Sn(II) product (SnO or Sn(6)O(4)(OH)(4)), can be varied by adjusting aging time and washing procedures. The identity of the initial Sn(II) product influences the subsequent phase composition and degree of disorder in the tetragonal SnO(2) phase obtained following sintering …

Go to article

Electrochemical Attachment Of Motile Bacterial Cells To Gold, Sergey Rozhok, Richard C. Holz Sep 2005

Electrochemical Attachment Of Motile Bacterial Cells To Gold, Sergey Rozhok, Richard C. Holz

Chemistry Faculty Research and Publications

Selective attachment of Escherichia coli K-12 bacterial cells to charged gold surfaces was demonstrated. Electrostatic binding of E. coli K-12 bacterial cells to positively charged surfaces was observed starting at +750 mV. The binding of E. coli K-12 cells to positively charged gold surfaces is proposed to occur due to long-range electrostatic interactions between the negatively charged O-chain of lipopolysaccharide (LPS) molecules protruding the bacterial cell body and the electrode surface. Removing LPS alters the cellular surface charge and results in cellular attachment to negatively charged surfaces. Thus, applying an electrical potential allows for the direct, real time detection of …

Go to article

Molecular Discrimination Of Type-I Over Type-Ii Methionyl Aminopeptidases, Krzysztof Swierczek, Alicja J. Copik, Sabina I. Swierczek, Richard C. Holz Sep 2005

Molecular Discrimination Of Type-I Over Type-Ii Methionyl Aminopeptidases, Krzysztof Swierczek, Alicja J. Copik, Sabina I. Swierczek, Richard C. Holz

Chemistry Faculty Research and Publications

Two residues that are conserved in type-I methionyl aminopeptidases (MetAPs) but are absent in all type-II MetAPs are the cysteine residues (Escherichia coli MetAP-I:   C59 and C70) that reside at the back of the substrate recognition pocket. These Cys residues are 4.4 Å apart and do not form a disulfide bond. Since bacteria and fungi contain only type-I MetAPs while all human cells contain both type-I and type-II MetAPs, type-I MetAPs represent a novel antibiotic/antifungal target if type-I MetAPs can be specifically targeted over type-II. Based on reaction of the thiol-specific binding reagent 5,5‘-dithio-bis(2-nitrobenzoic acid) (DTNB) with the type-I …

Go to article

A Short Synthesis Of The Common Dihydropyran Segment Of The Antifungal Agents Ambruticin And Jerangolid A, Julie Lukesh, William Donaldson Aug 2005

A Short Synthesis Of The Common Dihydropyran Segment Of The Antifungal Agents Ambruticin And Jerangolid A, Julie Lukesh, William Donaldson

Chemistry Faculty Research and Publications

The dihydropyranyl segment common to ambruticin and jerangolid A was prepared in six steps (31.7% yield) from (S)-2-benzyloxypropanal via silyloxydiene cyclocondensation, followed by C-glycosidation, and eventual epimerization at C18.

Go to article

Analysis Of Liquid-Phase Chemical Detection Using Guided Shear Horizontal-Surface Acoustic Wave Sensors, Zhonghui Li, Yolanda Jones, Jeanne M. Hossenlopp, Richard Cernosek, Fabien Josse Jul 2005

Analysis Of Liquid-Phase Chemical Detection Using Guided Shear Horizontal-Surface Acoustic Wave Sensors, Zhonghui Li, Yolanda Jones, Jeanne M. Hossenlopp, Richard Cernosek, Fabien Josse

Chemistry Faculty Research and Publications

Direct chemical sensing in liquid environments using polymer-guided shear horizontal surface acoustic wave sensor platforms on 36° rotated Y-cut LiTaO3 is investigated. Design considerations for optimizing these devices for liquid-phase detection are systematically explored. Two different sensor geometries are experimentally and theoretically analyzed. Dual delay line devices are used with a reference line coated with poly (methyl methacrylate) (PMMA) and a sensing line coated with a chemically sensitive polymer, which acts as both a guiding layer and a sensing layer or with a PMMA waveguide and a chemically sensitive polymer. Results show the three-layer model provides higher sensitivity than the …

Go to article

Expandable Graphite/Polyamide-6 Nanocomposites, Fawn Marie Uhl, Qiang Yao, Hiroyoshi Nakajima, Evangelos Manias, Charles A. Wilkie Jul 2005

Expandable Graphite/Polyamide-6 Nanocomposites, Fawn Marie Uhl, Qiang Yao, Hiroyoshi Nakajima, Evangelos Manias, Charles A. Wilkie

Chemistry Faculty Research and Publications

Polyamide-6 (PA-6)/graphite nanocomposites were prepared by melt blending, using a variety of graphites, including virgin graphite, expandable graphites and expanded graphite. The resulting nanocomposites were characterized by X-ray diffraction, thermogravimetric analysis, cone calorimetry, and tensile mechanical analysis. Nanocomposite formation does occur, as denoted by the nanometre dispersion of graphite layers in the polymer matrix, and the dispersion depends on the graphite treatment. The material properties of the resulting composites are improved relative to the virgin/unfilled polymer; in particular, there is an enhancement of the thermal stability without any significant deterioration of the mechanical properties.

Go to article

Fire Retardancy Of Vinyl Ester Nanocomposites: Synergy With Phosphorus-Based Fire Retardants, Grace Chigwada, Panchatapa Jash, David D. Jiang, Charles A. Wilkie Jul 2005

Fire Retardancy Of Vinyl Ester Nanocomposites: Synergy With Phosphorus-Based Fire Retardants, Grace Chigwada, Panchatapa Jash, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

Vinyl ester (PVE) nanocomposites were prepared using both clay and polyhedral oligosilsesquioxanes (POSS) as the nano-dimensional material. From cone calorimetric data, it was shown that both POSS and clay affect the flammability of the nanocomposites to the same extent. To improve on the flame retardancy, the nanocomposites were combined with phosphorous-containing fire retardants (FRs) and the result compared to the benchmark halogen-containing system. The use of the cone calorimeter to investigate the fire properties of these nanocomposites showed a great reduction in peak heat release rate (PHRR) in the presence of phosphate and slight improvements in average mass loss rate …

Go to article

Effects Of Surfactants On The Thermal And Fire Properties Of Poly(Methyl Methacrylate)/Clay Nanocomposites, Panchatapa Jash, Charles A. Wilkie Jun 2005

Effects Of Surfactants On The Thermal And Fire Properties Of Poly(Methyl Methacrylate)/Clay Nanocomposites, Panchatapa Jash, Charles A. Wilkie

Chemistry Faculty Research and Publications

Nanocomposites of poly(methyl methacrylate) (PMMA) with layered silicates and with polyhedral oligosilsesquioxanes (POSS) were prepared by bulk polymerization. The thermal and fire stabilities of the various organically-modified clay and POSS nanocomposites were evaluated using both thermogravimetric analysis (TGA) and cone calorimetry. Thermogravimetric analysis is not a good criteria for evaluating nanocomposite formation but cone calorimetry can be. For montmorillonite systems, when more than 4% clay is present, the expected reduction in peak heat release rate is observed. For hectorite, a minimum of 6% clay concentration is required to achieve the same reduction in peak heat release rate. POSS has the …

Go to article

Synergy Between Nanocomposite Formation And Low Levels Of Bromine On Fire Retardancy In Polystyrenes, Grace Chigwada, Panchatapa Jash, David D. Jiang, Charles A. Wilkie Jun 2005

Synergy Between Nanocomposite Formation And Low Levels Of Bromine On Fire Retardancy In Polystyrenes, Grace Chigwada, Panchatapa Jash, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

An organically-modified clay has been prepared using ammonium salts which contain an oligomeric material consisting of vinylbenzyl chloride, styrene and dibromostyrene. The presence of dibromostyrene enhances the flame retardancy of polystyrene nanocomposites compared to both the virgin polymer and polystyrene nanocomposites prepared from non-halogen-containing organically-modified clays. The nanocomposites were prepared both by bulk polymerization and melt blending and they were evaluated by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry measurements. Bulk polymerization produced nanocomposites with reduced peak heat release rate, reduced total heat release and improved thermal stability. It is noteworthy that all these improvements were obtained …

Go to article

An Introduction To The Use Of Fillers And Nanocomposites In Fire Retardancy, Charles A. Wilkie Apr 2005

An Introduction To The Use Of Fillers And Nanocomposites In Fire Retardancy, Charles A. Wilkie

Chemistry Faculty Research and Publications

No abstract provided.

Go to article

Fire Retardancy Of Polystyrene - Hectorite Nanocomposites, Dongyan Wang, Bok Nam Jang, Shengpei Su, Jinguo Zhang, Xiaoxia Zheng, Grace Chigwada, David D. Jiang, Charles A. Wilkie Apr 2005

Fire Retardancy Of Polystyrene - Hectorite Nanocomposites, Dongyan Wang, Bok Nam Jang, Shengpei Su, Jinguo Zhang, Xiaoxia Zheng, Grace Chigwada, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

No abstract provided.

Go to article

Methods For Fabricating Microarrays Of Motile Bacteria, Sergey Rozhok, Clifton K. -F. Shen, Pey-Lih H. Littler, Zhifang Fan, Chang Liu, Chad A. Mirkin, Richard C. Holz Apr 2005

Methods For Fabricating Microarrays Of Motile Bacteria, Sergey Rozhok, Clifton K. -F. Shen, Pey-Lih H. Littler, Zhifang Fan, Chang Liu, Chad A. Mirkin, Richard C. Holz

Chemistry Faculty Research and Publications

Motile bacterial cell microarrays were fabricated by attaching Escherichia coli K-12 cells onto predesigned 16-mercaptohexadecanoic acid patterned microarrays, which were covalently functionalized with E. coli antibodies or poly-L-lysine. By utilizing 11-mercaptoundecyl-penta(ethylene glycol) or 11-mercapto-1-undecanol as passivating molecules, nonspecific binding of E. coli was significantly reduced. Microcontact printing and dip-pen nanolithography were used to prepare microarrays for bacterial adhesion, which was studied by optical fluorescence and atomic force microscopy. These data indicate that single motile E. coli can be attached to predesigned line or dot features and binding can occur via the cell body or the flagella of bacteria. Adherent bacteria …

Go to article

Synthesis Of Cyclopropanes Via Organoiron Methodology: Preparation And Rearrangement Of Divinylcyclopropanes, Nathaniel J. Wallock, William A. Donaldson Apr 2005

Synthesis Of Cyclopropanes Via Organoiron Methodology: Preparation And Rearrangement Of Divinylcyclopropanes, Nathaniel J. Wallock, William A. Donaldson

Chemistry Faculty Research and Publications

Addition of alkenyl Grignard reagents to (1-methoxycarbonylpentadienyl)iron(1+) cation generates the corresponding (2-alkenylpent-3-en-1,5-diyl)iron complexes. Oxidatively induced-reductive elimination of these complexes gives divinylcyclopropanes which can undergo subsequent Cope rearrangement to give 1,4-cycloheptadienes.

Go to article

Hydroxy Double Salt Anion Exchange Kinetics: Effects Of Precursor Structure And Anion Size, Everson Kandare, Jeanne Hossenlopp Feb 2005

Hydroxy Double Salt Anion Exchange Kinetics: Effects Of Precursor Structure And Anion Size, Everson Kandare, Jeanne Hossenlopp

Chemistry Faculty Research and Publications

H NMR spectroscopy and powder X-ray diffraction have been used to explore the details of anion exchange reactions of two layered hydroxy double salts (HDSs), zinc copper hydroxy acetate (ZCA), nickel zinc hydroxy acetate (NZA), and a related layered material, zinc hydroxy acetate (ZHA), at room temperature (21−22 °C). Reactions that followed Avrami−Erofe'ev kinetics with respect to temporal profiles for acetate release, ZCA with butyrate (k = 1.7 × 10-3 s-1), and octanoate (k = 0.79 × 10-3 s-1) anions, as well as ZHA with octanoate (k = 2.6 × 10 …

Go to article

Scope And Mechanistic Study Of The Ruthenium-Catalyzed Ortho-C−H Bond Activation And Cyclization Reactions Of Arylamines With Terminal Alkynes, Chae S. Yi, Young Yun Jan 2005

Scope And Mechanistic Study Of The Ruthenium-Catalyzed Ortho-C−H Bond Activation And Cyclization Reactions Of Arylamines With Terminal Alkynes, Chae S. Yi, Young Yun

Chemistry Faculty Research and Publications

The cationic ruthenium hydride complex [(PCy3)2(CO)(CH3CN)2RuH]+BF4- was found to be a highly effective catalyst for the C−H bond activation reaction of arylamines and terminal alkynes. The regioselective catalytic synthesis of substituted quinoline and quinoxaline derivatives was achieved from the ortho-C−H bond activation reaction of arylamines and terminal alkynes by using the catalyst Ru3(CO)12/HBF4·OEt2. The normal isotope effect (kCH/kCD = 2.5) was observed for the reaction of C6H5NH2 and C …

Go to article

Isolation, X-Ray Structures, And Electronic Spectra Of Reactive Intermediates In Friedel−Crafts Acylations, M. G. Davlieva, Sergey V. Lindeman, I. S. Neretin, Jay K. Kochi Jan 2005

Isolation, X-Ray Structures, And Electronic Spectra Of Reactive Intermediates In Friedel−Crafts Acylations, M. G. Davlieva, Sergey V. Lindeman, I. S. Neretin, Jay K. Kochi

Chemistry Faculty Research and Publications

Reactive intermediates in the Friedel−Crafts acylation of aromatic donors are scrutinized upon their successful isolation and X-ray crystallography at very low temperatures. Detailed analyses of the X-ray parameters for the [1:1] complexes of different aliphatic and aromatic-acid chlorides with the Lewis acids antimony pentafluoride and pentachloride, gallium trichloride, titanium and zirconium tetrachlorides provide unexpected insight into the activation mechanism for the formation of the critical acylium carbocations. Likewise, the X-ray-structure examinations of aliphatic and aromatic acylium electrophiles also isolated as crystalline salts point to the origins of their electrophilic reactivity. Although the Wheland intermediates (as acylium adducts to arene donors) …

Go to article

Isolation And X-Ray Structures Of Labile Benzoic- And Acetic-Acidium Carbocations, Sergey V. Lindeman, I. S. Neretin, M. G. Davlieva, Jay K. Kochi Jan 2005

Isolation And X-Ray Structures Of Labile Benzoic- And Acetic-Acidium Carbocations, Sergey V. Lindeman, I. S. Neretin, M. G. Davlieva, Jay K. Kochi

Chemistry Faculty Research and Publications

New carbocationic salts (via O-protonation of substituted benzoic acids) are prepared for the first time by controlled hydration of the corresponding benzoylium salts and isolated in pure crystalline form. Precise X-ray structural analyses reveal the rather unexpected (electronic) structure of the carboxylic-acidium functionality.

Go to article

Synthesis Of Cyclopropanes Via Organoiron Methodology: Preparation Of The C9–C16 Alkenylcyclopropane Segment Of Ambruticin, Julie Lukesh, William Donaldson Jan 2005

Synthesis Of Cyclopropanes Via Organoiron Methodology: Preparation Of The C9–C16 Alkenylcyclopropane Segment Of Ambruticin, Julie Lukesh, William Donaldson

Chemistry Faculty Research and Publications

A synthesis of the C9–C16 segment of ambruticin is described which relies on organoiron methodology to establish the 1,2,3-trisubstituted cyclopropane ring.

Go to article

Polyethylene And Polypropylene Nanocomposites Based Upon An Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie Jan 2005

Polyethylene And Polypropylene Nanocomposites Based Upon An Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

Montmorillonite clay was modified with an oligomeric surfactant, which was then melt blended with polyethylene and polypropylene in a Brabender mixer. The morphology was characterized by X-ray diffraction and transmission electron microscopy, while thermal stability was evaluated from thermogravimetric analysis and the fire properties by cone calorimetry. The nanocomposites are best described as mixed immiscible/intercalated/delaminated systems and the reduction in peak heat release rate is about 40% at 5% inorganic clay loading.

Go to article

The Effects Of Triphenylphosphate And Recorcinolbis(Diphenylphosphate) On The Thermal Degradation Of Polycarbonate In Air, Bok Nam Jang, Charles A. Wilkie Jan 2005

The Effects Of Triphenylphosphate And Recorcinolbis(Diphenylphosphate) On The Thermal Degradation Of Polycarbonate In Air, Bok Nam Jang, Charles A. Wilkie

Chemistry Faculty Research and Publications

The thermal degradation of polycarbonate/triphenylphosphate (PC/TPP) and PC/resocinolbis(diphenylphosphate) (PC/RDP) in air has been studied using TGA/FTIR and GC/MS. In PC/phosphate blends, the phosphate stabilizes the carbonate group of polycarbonate from alcoholysis between the alcohol products of polycarbonate degradation and the carbonate linkage. Thus, the evolution of bisphenol A, which is mainly produced via hydrolysis/alcoholysis of the carbonate linkage, is significantly reduced, while, the evolution of various alkylphenols and diarylcarbonates increases. The bonds that are broken first in the thermal degradation of both the carbonate and isopropylidene linkages of polycarbonate are the weakest bonds in each, when a phosphate is present. …

Go to article

The Thermal Degradation Of Bisphenol A Polycarbonate In Air, Bok Nam Jang, Charles A. Wilkie Jan 2005

The Thermal Degradation Of Bisphenol A Polycarbonate In Air, Bok Nam Jang, Charles A. Wilkie

Chemistry Faculty Research and Publications

The thermal degradation of polycarbonate in air was studied as a function of mass loss using TGA/FTIR, GC/MS and LC/MS. In the main degradation region, 480–560 °C, the assigned structures of smaller molecules and linear molecules that evolved in air were very similar to those obtained from the degradation in nitrogen; the degradation of polycarbonate follows chain scission of the isopropylidene linkage, in agreement with the bond dissociation energies, and hydrolysis/alcoholysis of carbonate linkage. Compared to the degradation in nitrogen, some differences were observed primarily in the beginning stage of degradation. Oxygen may facilitate branching as well as radical formation …

Go to article

Methyl Methacrylate Oligomerically-Modified Clay And Its Poly (Methyl Methacrylate) Nanocomposites, Xiaoxia Zheng, David D. Jiang, Charles A. Wilkie Jan 2005

Methyl Methacrylate Oligomerically-Modified Clay And Its Poly (Methyl Methacrylate) Nanocomposites, Xiaoxia Zheng, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

A methyl methacrylate oligomerically-modified clay was used to prepare poly(methyl methacrylate) clay nanocomposites by melt blending and the effect of the clay loading level on the modified clay and corresponding nanocomposite was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed intercalated/delaminated morphology with good nanodispersion. The compatibility between the methylacrylate-subsituted clay and poly(methyl methacrylate) (PMMA) are greatly improved compared to other oligomerically-modified clays.

Go to article

Polystyrene Nanocomposites Based On Carbazole-Containing Surfactants, Grace Chigwada, David D. Jiang, Charles A. Wilkie Jan 2005

Polystyrene Nanocomposites Based On Carbazole-Containing Surfactants, Grace Chigwada, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

New organically-modified clays containing a carbazole unit were prepared and the number of long alkyl chains on the surfactant was varied. The clay was used to prepare polystyrene nanocomposites by both bulk polymerization and melt blending. The dispersion of these clays in the polymer matrix was evaluated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal stability of the clays and the nanocomposites were analyzed by thermogravimetric analysis (TGA) while the fire properties were evaluated by cone calorimetry. If more than two alkyl chains were present, the gallery spacing is apparently overcrowded, leading to poor dispersion. Bulk polymerization …

Go to article

The Relationship Between The Solubility Parameter Of Polymers And The Clay-Dispersion In Polymer/Clay Nanocomposites And The Role Of The Surfactant, Bok Nam Jang, Dongyan Wang, Charles A. Wilkie Jan 2005

The Relationship Between The Solubility Parameter Of Polymers And The Clay-Dispersion In Polymer/Clay Nanocomposites And The Role Of The Surfactant, Bok Nam Jang, Dongyan Wang, Charles A. Wilkie

Chemistry Faculty Research and Publications

Nanocomposites were prepared of polymers having different solubility parameters and pristine or organically modified clays, and the dispersion of clay in the polymer was evaluated using X-ray diffraction and transmission electron microscopy. The solubility parameters of both the polymers and surfactants of interest were calculated according to the group contribution method and correlated with the clay morphology. A close relationship between the solubility parameter of the polymer and the clay morphology was observed. The clay has a very polar group, so the higher is the solubility parameter of the polymer, the larger is the d spacing of the clay that …

Go to article