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Articles 481 - 510 of 690
Full-Text Articles in Chemistry
Polystyrene Nanocomposites Based On Quinolinium And Pyridinium Surfactants, Grace Chigwada, Dongyan Wang, Charles A. Wilkie
Polystyrene Nanocomposites Based On Quinolinium And Pyridinium Surfactants, Grace Chigwada, Dongyan Wang, Charles A. Wilkie
Chemistry Faculty Research and Publications
In this paper pyridine and quinoline-containing salts were employed to modify montmorillonite. TGA analysis shows that the quinolinium modified clay has a higher thermal stability than the pyridinium modified clay. Polystyrene nanocomposites were prepared by in situ bulk polymerisation and direct melt blending using both clays. The X-ray diffraction and transmission electron microscopy results show the formation of intercalated structures. The 50% degradation temperature of the nanocomposites is increased and so is the amount of char from TGA analysis compared to the virgin polymer. Cone calorimetric results indicate that clay reduces the peak heat release rate and average mass loss …
Thermal Stability And Degradation Kinetics Of Poly(Methyl Methacrylate)/Layered Copper Hydroxy Methacrylate Composites, Everson Kandare, Hongmei Deng, Dongyan Wang, Jeanne Hossenlopp
Thermal Stability And Degradation Kinetics Of Poly(Methyl Methacrylate)/Layered Copper Hydroxy Methacrylate Composites, Everson Kandare, Hongmei Deng, Dongyan Wang, Jeanne Hossenlopp
Chemistry Faculty Research and Publications
Poly(methyl methacrylate) (PMMA)/copper hydroxy methacrylate (CHM) composites were prepared via solution blending and bulk polymerization. Addition of 3% by weight of the CHM additive using solution blending resulted in a significant increment (~45°C) in thermogravimetric analysis (TGA) T50, the temperature at which 50% of the original polymeric mass is lost. The value T50 increased by 30°C for a PMMA composite with 4% CHM, synthesized via bulk polymerization. Activation energies, Ea, were calculated as a function of conversion fractions (TGA decomposition profile) for the polymeric materials. Analysis of multiple heating rate data using the Flynn–Wall– Ozawa …
Nmr Studies Of Escherichia Coli Acyl Carrier Protein: Dynamic And Structural Differences Of The Apo- And Holo-Forms, Yangmee Kim, Evgenii L. Kovrigin, Ziad Eletr
Nmr Studies Of Escherichia Coli Acyl Carrier Protein: Dynamic And Structural Differences Of The Apo- And Holo-Forms, Yangmee Kim, Evgenii L. Kovrigin, Ziad Eletr
Chemistry Faculty Research and Publications
Two indicators of conformational variability of Escherichia coli acyl carrier protein (ACP) have been investigated, namely backbone dynamics and chemical shift variations of ACP. Hydrophobic interactions between the 4′-PP prosthetic group and the hydrophobic pocket enclosed by the amphipathic helices resulted in chemical shift perturbations in the residues near the prosthetic group binding sites and contact sites in the hydrophobic pockets upon conversion from apo- to holo-forms. At pH 7.9, destabilization of ACP due to negative charge repulsions and the deprotonated state of His 75 resulted in observed chemical shift changes in the C-terminal region. Model-free analysis showed that the …
Flammability Of Styrenic Polymer Clay Nanocomposites Based On A Methyl Methacrylate Oligomerically-Modified Clay, Xiaoxia Zheng, David D. Jiang, Dongyan Wang, Charles A. Wilkie
Flammability Of Styrenic Polymer Clay Nanocomposites Based On A Methyl Methacrylate Oligomerically-Modified Clay, Xiaoxia Zheng, David D. Jiang, Dongyan Wang, Charles A. Wilkie
Chemistry Faculty Research and Publications
Nanocomposites of polystyrene, high impact polystyrene, acrylonitrile–butadiene–styrene terpolymer, polypropylene, and polyethylene were prepared using a methyl methacrylate oligomerically-modified clay by melt blending and the thermal stability and fire retardancy were studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed morphology, depending on the polymer.
Applications Of Acoustic Wave Devices For Sensing In Liquid Environments, Jeanne Hossenlopp
Applications Of Acoustic Wave Devices For Sensing In Liquid Environments, Jeanne Hossenlopp
Chemistry Faculty Research and Publications
Acoustic wave devices such as thickness shear mode (TSM) resonators and shear horizontal surface acoustic wave (SH-SAW) devices can be utilized for characterizing physical properties of liquids and for chemical sensor applications. Basic device configurations are reviewed and the relationships between experimental observables (frequency shifts and attenuation) and physical properties of liquids are presented. Examples of physical property (density and viscosity) determination and also of chemical sensing are presented for a variety of liquid phase applications. Applications of TSMs and polymer-coated guided SH-SAWs for chemical sensing and uncoated SH-SAWs for “electronic tongue” applications are also discussed.
Enzyme Dynamics Along The Reaction Coordinate: Critical Role Of A Conserved Residue, Evgenii L. Kovrigin, J. Patrick Loria
Enzyme Dynamics Along The Reaction Coordinate: Critical Role Of A Conserved Residue, Evgenii L. Kovrigin, J. Patrick Loria
Chemistry Faculty Research and Publications
Conformational flexibility of the enzyme architecture is essential for biological function. These structural transitions often encompass significant portions of the enzyme molecule. Here, we present a detailed study of functionally relevant RNase A dynamics in the wild type and a D121A mutant form by NMR spin-relaxation techniques. In the wild-type enzyme, the dynamic properties are largely conserved in the apo, enzyme−substrate, and enzyme−product complexes. In comparison, mutation of aspartic acid 121 to alanine disrupts the timing of active-site dynamics, the product-release step, and global conformational changes, indicating that D121 plays a significant role in coordinating the dynamic events in RNase …
Fire Properties Of Styrenic Polymer–Clay Nanocomposites Based On An Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Fire Properties Of Styrenic Polymer–Clay Nanocomposites Based On An Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Chemistry Faculty Research and Publications
An oligomerically-modified clay has been used to fabricate nanocomposites with styrenic polymers, such as polystyrene, high-impacted polystyrene, poly(styrene-co-acrylonitrile) and acrylonitrile–butadiene–styrene by melt blending. The clay dispersion was evaluated by X-ray diffraction and bright field transmission electron microscopy. All of the nanocomposites have a mixed delaminated/intercalated structure. The fire properties of nanocomposites were evaluated by cone calorimetry and the mechanical properties were also evaluated.
Ligand-Promoted Solvent-Dependent Ionization And Conformational Equilibria Of Re(Co)3Br[Ch2(S-Tim)2] (Tim = 1-Methylthioimidazolyl). Crystal Structures Of Re(Co)3Br[Ch2(S-Tim)2] And {Re(Co)3(Ch3Cn)[Ch2(S-Tim)2]}(Pf6), Rosalice M. Silva, Brendan J. Liddle, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Ligand-Promoted Solvent-Dependent Ionization And Conformational Equilibria Of Re(Co)3Br[Ch2(S-Tim)2] (Tim = 1-Methylthioimidazolyl). Crystal Structures Of Re(Co)3Br[Ch2(S-Tim)2] And {Re(Co)3(Ch3Cn)[Ch2(S-Tim)2]}(Pf6), Rosalice M. Silva, Brendan J. Liddle, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Chemistry Faculty Research and Publications
The compounds Re(CO)3Br[CH2(S-tim)2] (1) and {Re(CO)3(CH3CN)[CH2(S-tim)2]}(PF6) (2), where tim is 1-methylthioimidazolyl, were prepared in high yields and characterized both in the solid state and in solution. The solid-state structures show that the ligand acts in a chelating binding mode where the eight-member chelate ring adopts twist-boat conformations in both compounds. A comparison of both solid-state IR data for CO stretching frequencies and the solution-phase voltammetric measurements for the Re1+/2+ couples between 1, 2, …
Polystyrene Nanocomposites Based On An Oligomerically-Modified Clay Containing Maleic Anhydride, Xiaoxia Zheng, David D. Jiang, Charles A. Wilkie
Polystyrene Nanocomposites Based On An Oligomerically-Modified Clay Containing Maleic Anhydride, Xiaoxia Zheng, David D. Jiang, Charles A. Wilkie
Chemistry Faculty Research and Publications
An oligomerically-modified clay containing maleic anhydride was used to prepare polystyrene-clay nanocomposites by melt blending and the effect of this modified clay on the thermal stability and fire performance was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed immiscible/intercalated/delaminated morphology. The maleic anhydride modified clay improved the compatibility between the clay and the polystyrene.
Thermal And Flame Properties Of Polyethylene And Polypropylene Nanocomposites Based On An Oligomerically–Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Thermal And Flame Properties Of Polyethylene And Polypropylene Nanocomposites Based On An Oligomerically–Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Chemistry Faculty Research and Publications
An oligomerically-modified clay was made using a surfactant which is the ammonium salt of an oligomer. The newly modified clay contains 37.5% inorganic clay and 62.5% oligomer. Polyethylene and polypropylene nanocomposites were made by melt blending the polymer with the oligomerically-modified clay in a Brabender mixer at various clay loadings. The structure of the nanocomposites was characterized by X-ray diffraction and transmission electron microscopy. Mechanical testing showed that the polyethylene nanocomposites had an enhanced Young's modulus and slightly decreased elongation, while the changes for polypropylene nanocomposites are small compared with the virgin polymers. The thermal stability and flame properties were …
The Redox Couple Of The Cytochrome C Cyanide Complex: The Contribution Of Heme Iron Ligation To The Structural Stability, Chemical Reactivity, And Physiological Behavior Of Horse Cytochrome C, Abel Schejter, Michael D. Ryan, Erica R. Blizzard, Chongyao Zhang, Emanuel Margoliash, Benjamin A. Feinberg
The Redox Couple Of The Cytochrome C Cyanide Complex: The Contribution Of Heme Iron Ligation To The Structural Stability, Chemical Reactivity, And Physiological Behavior Of Horse Cytochrome C, Abel Schejter, Michael D. Ryan, Erica R. Blizzard, Chongyao Zhang, Emanuel Margoliash, Benjamin A. Feinberg
Chemistry Faculty Research and Publications
Contrary to most heme proteins, ferrous cytochrome c does not bind ligands such as cyanide and CO. In order to quantify this observation, the redox potential of the ferric/ferrous cytochrome c–cyanide redox couple was determined for the first time by cyclic voltammetry. Its E0′ was −240 mV versus SHE, equivalent to −23.2 kJ/mol. The entropy of reaction for the reduction of the cyanide complex was also determined. From a thermodynamic cycle that included this new value for the cyt c cyanide complex E0′, the binding constant of cyanide to the reduced protein was estimated to …
Janus Scorpionates: Supramolecular Tectons For The Directed Assembly Of Hard−Soft Alkali Metallopolymer Chains, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Janus Scorpionates: Supramolecular Tectons For The Directed Assembly Of Hard−Soft Alkali Metallopolymer Chains, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Chemistry Faculty Research and Publications
A new scorpionate ligand [HB(mtda)3-] containing mercaptothiadiazolyl (mtda) heterocyclic rings with both hard nitrogen donors and soft sulfur donors has been prepared. This new ligand, the Janus scorpionate, is a hybrid of a tris(pyrazolyl)borate and a tris(mercaptoimidazolyl)borate. The differential hard/soft character of the dissimilar donor groups in this bridging ligand was exploited for the controlled solid-state organization of homometallic and heterometallic alkali metal coordination polymers. Remarkably, in the case of sodium, coordination polymers with both acentric (with NaS3N3H kernels) and centric (with alternating NaN6 and NaS6H2 kernels) chains are …
Simultaneous Ejection Of Six Electrons At A Constant Potential By Hexakis(4-Ferrocenylphenyl)Benzene, Vincent J. Chebny, Dwairath Dhar, Sergey V. Lindeman, Rajendra Rathore
Simultaneous Ejection Of Six Electrons At A Constant Potential By Hexakis(4-Ferrocenylphenyl)Benzene, Vincent J. Chebny, Dwairath Dhar, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
A simple synthesis of a dendritic hexaferrocenyl electron donor (5) is described in which six ferrocene moieties are connected at the vertices of the propeller of the hexaphenylbenzene core. The molecular structure of 5 is confirmed by X-ray crystallography. An electrochemical analysis along with redox titrations (which are tantamount to coulometry) confirmed that it ejects six electrons at a single potential.
A Practical Synthesis Of Bridged Diarylacetylenes, Ruchi Shukla, Daniel M. Brody, Sergey V. Lindeman, Rajendra Rathore
A Practical Synthesis Of Bridged Diarylacetylenes, Ruchi Shukla, Daniel M. Brody, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
An efficient and practical synthesis of bridged diarylacetylenes in multigram quantities has been successfully carried out using high-yielding (classical) synthetic methods and readily available starting materials. The structural analysis of the representative bridged diarylacetylenes by X-ray crystallography strongly suggests that conformations, bending of the linear triple bond, and the angle between the mean planes of aromatic rings in various bridged diarylacetylenes are governed by the p−π conjugation among the aromatic rings and the ethereal groups. Furthermore, the synthetic scheme also allows the preparation of (appropriately) bromo-substituted bridged diarylacetylenes which hold potential for their future usage for the preparation of polymeric …
Highly Cooperative Tetrametallic Ruthenium-Μ-Oxo-Μ-Hydroxo Catalyst For The Alcohol Oxidation Reaction, Chae S. Yi, Tonya N. Zeczycki, Ilia A. Guzei
Highly Cooperative Tetrametallic Ruthenium-Μ-Oxo-Μ-Hydroxo Catalyst For The Alcohol Oxidation Reaction, Chae S. Yi, Tonya N. Zeczycki, Ilia A. Guzei
Chemistry Faculty Research and Publications
The tetrametallic ruthenium-oxo-hydroxo-hydride complex {[(PCy3)(CO)RuH]4(μ4-O)(μ3-OH)(μ2-OH)} (1) was synthesized in two steps from the monomeric complex (PCy3)(CO)RuHCl (2). The tetrameric complex 1 was found to be a highly effective catalyst for the transfer dehydrogenation of alcohols. Complex 1 showed a different catalytic activity pattern toward primary and secondary benzyl alcohols, as indicated by the Hammett correlation for the oxidation reaction of p-X-C6H4CH2OH (ρ = −0.45) and p-X-C6H4CH(OH)CH3 (ρ = +0.22) (X = …
Synthetic Studies Directed Toward The Proposed Structure For Heteroscyphic Acid A, Subhabrata Chaudhury, Shukun Li, William A. Donaldson
Synthetic Studies Directed Toward The Proposed Structure For Heteroscyphic Acid A, Subhabrata Chaudhury, Shukun Li, William A. Donaldson
Chemistry Faculty Research and Publications
A route to the carbon skeleton of the proposed structure for heteroscyphic acid A was developed utilizing a Mn(III)/Cu(II) mediated oxidative free-radical cyclization and nucleophilic addition to (3-methylpentadienyl)iron(1+) cation.
Combined X-Ray Diffraction And Diffuse Reflectance Analysis Of Nanocrystalline Mixed Sn(Ii) And Sn(Iv) Oxide Powders, Hongmei Deng, Jeanne Hossenlopp
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 …
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
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 …
Electrochemical Attachment Of Motile Bacterial Cells To Gold, Sergey Rozhok, Richard C. Holz
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 …
Molecular Discrimination Of Type-I Over Type-Ii Methionyl Aminopeptidases, Krzysztof Swierczek, Alicja J. Copik, Sabina I. Swierczek, Richard C. Holz
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 …
A Short Synthesis Of The Common Dihydropyran Segment Of The Antifungal Agents Ambruticin And Jerangolid A, Julie Lukesh, William A. Donaldson
A Short Synthesis Of The Common Dihydropyran Segment Of The Antifungal Agents Ambruticin And Jerangolid A, Julie Lukesh, William A. 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.
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
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 …
Expandable Graphite/Polyamide-6 Nanocomposites, Fawn Marie Uhl, Qiang Yao, Hiroyoshi Nakajima, Evangelos Manias, Charles A. Wilkie
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.
Fire Retardancy Of Vinyl Ester Nanocomposites: Synergy With Phosphorus-Based Fire Retardants, Grace Chigwada, Panchatapa Jash, David D. Jiang, Charles A. Wilkie
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 …
Synergy Between Nanocomposite Formation And Low Levels Of Bromine On Fire Retardancy In Polystyrenes, Grace Chigwada, Panchatapa Jash, David D. Jiang, Charles A. Wilkie
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 …
Effects Of Surfactants On The Thermal And Fire Properties Of Poly(Methyl Methacrylate)/Clay Nanocomposites, Panchatapa Jash, Charles A. Wilkie
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 …
An Introduction To The Use Of Fillers And Nanocomposites In Fire Retardancy, Charles A. Wilkie
An Introduction To The Use Of Fillers And Nanocomposites In Fire Retardancy, Charles A. Wilkie
Chemistry Faculty Research and Publications
No abstract provided.
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
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.
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
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 …
Synthesis Of Cyclopropanes Via Organoiron Methodology: Preparation And Rearrangement Of Divinylcyclopropanes, Nathaniel J. Wallock, William A. Donaldson
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.