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Article Excerpt
Chair: Douglas Masterson, University of Southern Mississippi
Vice-chair: Ken Lee, Jackson State University
THURSDAY MORNING
Mahogany
O3.01
9:00 ECL QUENCHING BEHAVIOR OF RU(BPY)32+/TPRA SYSTEM BY CL- AT AU ELECTRODE: DIRECT EVIDENCE OBTAINED FROM EQCM
Shijun Wang, Wujian Miao
University of Southern Mississippi
Electrogenerated chemiluminescence (ECL) is a process of light generation from electrochemical reactions. For example, light emission can be observed at an electrode placed in contact with an aqueous solution containing luminophore Ru(bpy)32+ (ruthenium (II) tris(2,2'-bipyridine) and an ECL coreactant tripropylamine (TPrA) upon anodic potential scanning. A number of factors such as the nature of the working electrode and the components of the electrolyte could affect the ECL intensity that is often proportional to the luminophore concentrations. Understanding of such effects is important in designing an ECL system that possesses highly reproducible and efficient ECL signals. We report here the influence of chloride ions on ECL at Au electrode for Ru(bpy)32+/TPrA system. Chloride ions commonly exist in biological systems, e.g., in phosphate buffer saline solutions. Direct evidence obtained from electrochemical quartz crystal microbalance (EQCM) experiments will be presented in support our proposed ECL quenching mechanism that involves the electrochemical formation of AuI/III-Cl-complexes. Our data also suggest that caution must be taken when one uses a saturated calomel electrode (SCE) combined with an Au working electrode for ECL studies, since SCE contains high concentrations of chloride ions which could penetrate the porous tip of the electrode to the ECL system. Financial support from NSF-MRSEC grant (NSF-DMR 0213883) is gratefully acknowledged.
O3.02
9:15 DETECTION OF CHEMICAL NERVE AGENT SIMULANTS: PROGRESS TOWARDS QCM SENSORS
Karl Wallace
University of Southern Mississippi
Quartz crystal microbalance (QCM) is a sensing tool that used for the detection of toxic chemicals. The change in frequency of the quartz crystal is attributed to the change in mass of the quartz crystal (QC). It is well known that sulfur containing functional groups can act as "anchors" to gold surfaces to form self-assembled-monoayers. The work presented here describes the synthesis of a family of dithiol monomers that contain a reactive functional group, which will bind directly to the stimulant. These monomers then form SAMs onto a gold surface, on a QC platform. The same family of monomers have also been tethered to gold to form nanospheres. The synthesis and characterization of both the monomers, SAMs and the gold nanoparticles, and our initial results using QCM as a sensor towards chemical nerve agent stimulants, will be discussed.
O3.03
9:30 APPROACHES TO THE SYNTHESIS OF A TITANANTHRACENE
Jahnavi Chatterjee (1), Neil Allison (1)
(1) Mississippi University for Women, (2) University of Arkansas
The goal of this project was to synthesize the transition metallaaromatic compound titananthracene in order to study the fundamental concept of aromaticity and how it applies to this class of metallacycles. Previous unsuccessful attempts have been made to synthesize titananthracene by the removal of a hydride or proton from titanadibenzocyclohexa-2,5-diene. This research focused on replacing a hydrogen at the saturated C(4) position of titanadibenzocyclohexa-2,5-diene with a TMS group. Removal of the TMS group with fluoride is expected to form a titananthracene. The first three steps of the proposed synthetic reaction scheme have been successfully carried out.
O3.04
9:45 VEGETABLE OIL MACROMONOMER-BASED LATEXES AND WATERBORNE INDUSTRIAL COATINGS
Yvette Abadie, James Rawlins
The University of Southern Mississippi
Vegetable oil-based macromonomers (VOMMs) are a series of vegetable oil derivatives functionalized for facile incorporation into emulsion polymers via random copolymerization with conventional monomers. VOMMs enable good film coalescence and reduce the volatile organic compound (VOC) levels by replacing coalescing solvents in waterborne coatings. Moreover, VOMMs crosslink after application via auto-oxidation. Soybean oil-based VOMMs were synthesized and incorporated into industrial emulsion polymer models at varying VOMM concentrations. The polymers were formulated as waterborne industrial coatings using hexamethoxymethylolmelamine as the crosslinker and evaluated versus a commercial latex at varying latex to crosslinker ratios. Post application crosslinking and material response to deformation was evaluated via dynamic mechanical analysis. The coatings specific properties were measured by comparing data from differential scanning calorimetry, infrared spectroscopy, and ASTM tests. The data confirm that higher VOMM levels improve coating performance mainly quantified through improved solvent and impact resistance, and flexibility testing.
O3.05
10:00 FRONTAL POLYMERIZATION WITH ENCAPSULATED INITIATORS PREPARED BY SEVERAL METHODS
Christopher Bounds, John Pojman
The University of Southern Mississippi
We studied frontal polymerization with initiators microencapsulated by several techniques. Microcapsules were produced containing benzoyl peroxide, triethylenetetramine, and N,N-dimethyl-p-toluidine using different encapsulation processes with sizes ranging from >400 microns to <100 microns. These microcapsules were subjected to validity and function testing. If the parameters were feasible, frontal polymerization processes were applied to an acrylate or a thiol-ene system containing these microcapsules. It was determined that stability and the size of the microcapsules were important issues in regards to the preparation of a front of polymerization using these microcapsules. When the size of the microcapsules is too large the front velocity is very slow, and in some cases, large microcapsules caused low polymer conversion.
10:15 Break
O3.06
10:30 MASS SPECTROMETRY BASED ASSAY FOR THE ENZYMATIC HYDROLYSIS OF PSEUDOPROCHIRAL MALONATE DIESTERS
Dale Rosado Jr., Cassie Nabors, Douglas Masterson
University of Southern Mississippi
Enzymes (i.e. Pig Liver Esterase) have been proven to be extremely efficient in hydrolyzing derivitized malonate diesters with high selectivity for the R or S enantiomer and with high chemical yield. To date, no assay exists where different conditions for these hydrolyses can be monitored in a rapid and efficient manner. Our group has developed a Mass Spectrometry based assay that allows for quick and efficient monitoring of the selectivity of various enzymes under various conditions. This assay uses pseudo-prochiral (H5, D5) malonate diesters, which need only be enantiomerically enriched, which is hydrolyzed under a variety of conditions and monitored by LDI-TOF or ESI-MS. The peak intensities and areas from the mass spectra were then used to determine an observed ratio of enantiomers, which can then be corrected to give the actual ratio. Chiral HPLC was then used to verify the accuracy of the assay.
O3.07
10:45 PREPARATION AND CHARACTERIZATION OF TRIS(2,2'-BIPYRIDYL)RUTHENIUM(II)-LOADED MICROCAPSULES AS ELECTROGENERATED CHEMILUMINESCENT LABLES FOR BIOMOLECULES DETECTION Tommie L. Pittman* and Wujian Miao, University of Southern Mississippi, Hattiesburg, MS 39406
Tommie Pittman, Wujian Miao
University of Southern Mississippi
Polymerized liposome-based microcapsules loaded with water soluble tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)32+) as electrogenerated chemiluminescent (ECL) labels for ultrasensitive biomolecule detection is reported. Ru(bpy)32+-loaded liposomes with a biological importance surface functional group, biotin, were prepared on the basis of our recently reported technique. The liposomes were produced from phospholipid molecules such as DSPC and DSPE-PEG(2000)Biotin after solubilization in chloroform along with the addition of 50 mM Ru(bpy)3C12 prepared in 10 mM Tris buffer. Water (containing Ru(bpy)32+)-in-oil emulsion was then formed by vortexing the mixture. The resulting emulsion was layered on 0.1 M Tris buffer. The liposomal solution was transferred to warm water bath and the organic phase (chloroform) was removed by using argon and subsequent addition of low concentrations of styrene monomer and photoinitiator species before proceeding to gently agitation to form Ru(bpy)3C12 multilamellar vesicles. A micro-extruder with suitable pore-sized polycarbonate membranes was then used to produce monodisperse unilamellar vesicles while allowing the styrene monomer and photoinitiator species to penetrate through the outside lipid layer and remain in the hydrophobic zone of the liposome. Photo-polymerization process was carried out and Ru(bpy)32+-loaded microcapsules with a layer of polystyrene was produced. The characterization of polymerized ECL labels was carried out with scanning electron microscopy, optical microscopy, and light scattering techniques. The detection of DNA and protein with above prepared microcapsules using ECL will be discussed.
O3.08
11:00 FRONT TEMPERATURE AND FRONT VELOCITY AS A FUNCTION OF BENZOYL PEROXIDE CONCENTRATION, TRITHIOL CONCENTRATION AND FILLER LOADING IN THE FRONTAL POLYMERIZATION OF A TRIACRYLATE
Veronika Viner, John Pojman
The University of Southern Mississippi
Frontal polymerization is a localized reaction that propagates from the coupling of the Arrhenius dependence of the kinetics of an exothermic polymerization and the diffusion of thermal energy. The front temperature with multifunctional acrylates, can be as high as 250 [degrees]C. Such high temperatures result in smoking and the release of volatile compound that prevent the use indoors. We studied how the front temperature and front velocity were affected by the addition of fillers, a trithiol, a plasticizer, and benzoyl peroxide. For the monomer we used trimethylol proprane triacrylate. Different types of filler (Poly-gloss 90 and Cabosil) were tested. As filler loading was increased, the front temperature decreased until the propagating front was quenched. As the % plasticizer and % trithiol were increased, the front temperature and front velocity decreased. As BPO concentration was increased, the front temperature and front velocity increased along with more smoke being produced.
O3.09
11:15 EXO-AND ENANTIOSELECTIVE DIELS ALDER REACTIONS: PYRAZOLIDINONE AUXILIARIES ARE ABLE TO OVERRIDE SECONDARY ORBITAL INTERACTIONS
Mukund Sibi (1), Jessica Shackleford (2), Levi Stanley (1), Xiaoping Nie (1), Frances Bouret (1)
(1) North Dakota State University, (2) University of Southern Mississippi
Due to secondary orbital interactions, the majority of Diels-Alder reactions are highly endo-selective. Despite this general rule, past research shows that there are certain methods for switching the major product of certain Diels-Alder reactions from the endo product...
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