Silica Coating of Single-Walled Carbon Nanotubes
Elizabeth Whitsitt and Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX 77005
Liquid phase deposition (LPD) of silicon dioxide using fluorosilicic acid solutions saturated with silicon dioxide has been documented in the literature and patented for selected applications in industry. Utilizing this method, we have been able to coat materials, with selectively functionalized surfaces, at low temperatures in aqueous solvent. Single-walled carbon nanotubes (SWNTs) have recently been made water soluble by encasing them in a surfactant micelle. This allows us to use LPD to coat individual and small ropes of SWNTs. Characterization of this novel material was performed with scanning and transmission electron microscopies, and ATR-FTIR , Raman, and UV/Vis spectroscopies.
Preparation of template derived Li ion separator membrane
Jianzhong Yang and Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX 77005
A big obstacle of developing hybrid fuel cell vehicles has been the high costs of existing battery system. Li-ion battery was promising as a possible solution for its high specific energy and cycle life. However, the further development of Li-ion technology was limited by current expensive separator material. To overcome this problem, a template derived separator membrane system was investigated. Three different types of polymer membranes, polyurethane, polymethy acrylate and polystyrene were prepared and tested. The membrane impregnated with Alumoxane material was found to possess higher wettabilty and conductivity.
Soft-Lithographic Patterned Features in Carboxylate-Alumoxane Based Ceramics
J. Ryan Loscutova and Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX 77005
Microfabrication of MEMS structures through the use of soft-lithographic techniques has been a promising method for producing micrometer and sub-micrometer scale features with high aspect ratios. We have explored the utility of soft lithography in generating features in alumina ceramics derived from various carboxylate-alumoxane precursors. These techniques are employed to form a polydimethylsiloxane mold containing the imprinted patterns, in which the desired alumoxane precursor is poured, to produce an imprinted preceramic film. Alumoxanes of differing organic substituents are blended to alter the properties of shrinkage, hardness, pore size, drying times, and gross curvature. Metals such as yttrium and calcium can be doped into the alumoxane precursors, to alter these same properties. The effects of blending on image fidelity and shrinkage are examined after firing to alumina. SEM images of the ceramic bodies confirm the aspect qualities and amounts of shrinkage of the imprinted features.
Synthesis and Characterization of Novel Aluminum-Bipyridyl Complexes
Douglas C. Ogrin(a), Laura van Poppel(a), Simon Bott(b), and Andrew R. Barron(a),
(a)Department of Chemistry, Rice University, Houston, Texas 77005, (b)Department of Chemistry, University of Houston, Houston, Texas 77204
As the interest in molecular devices grows, the use of different metal centers and bridging ligands is being investigated. Our research has mainly focused on synthesizing novel aluminum complexes with bifunctional pyridyl ligands. NMR, X-ray crystallography, IR, and MS have been used to characterize these complexes. Of interest is an equilibrium that develops between a fully complexed, partial complexed, and unassociated ligand. This was first observed in the reaction of di-tert-butyl aluminum phenoxide and bipyridine. 1H NMR and IR have been used to monitor this equilibrium. We are presently investigating whether this is an isolated event or a common occurrence among other related complexes. Hence, additional complexes have been synthesized in which the Lewis acidity of the aluminum center and the distance between the aluminum centers has been altered.
The Effect of Additives in Calcium Carbonate Crystallization
Robin Anderson, Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX 77005
Many additives have been utilized in the past to control various aspects of calcium carbonate crystallization, from organics that can form self-assembling monolayers mimicking biomineralization to others that determine crystal size, shape or morphology. This research focuses on the effect that the addition of hydroxybuckminsterfullerenes (fullerols) has on the calcium carbonate crystal formation. Studies of the effect of pH and of various temperatures on morphology and phase have been made. The resulting precipitates have been characterized by ESEM and XRD. This investigation may lead to new calcium carbonate materials with applications for filters.
BONE MATERIALS USING CARBOXYLATE ALUMOXANES
Naureen Shahid(1), Antonios G. Mikos(2), Andrew R. Barron(1), Department of Chemistry(1), Department of Bioengineering(2), Rice University, 6100 Main Street, Houston, TX, 77005
Liquid poly(propylene fumarate) (PPF) when reacted with liquid poly(propylene fumarate)-diacrylate (PPF-DA) forms a solid biodegradable bone cement PPF/PPF-DA. This has been used in tissue engineering as it can be made to cross-link during orthopedic surgery. This cement is reliable for areas that are not subjected to high loads, such as, rib bones. However, this cement is not reliable in areas, that need to support high loads and stress such as the femur. We have shown that polymer matrices containing lysine - alumoxane have increased tensile and short beam shear strengths; where as, matrices containing p-hydroxybenzonato alumoxane have increased torsional strength. This study describes the syntheses of the alumoxane containing strong cements and shows how the presence of alumoxanes have increased the strength of biodegradable poly(propylene fumarate) - based polymers.
SELECTIVE CHEMICAL FUNCTIONALIZATION OF CARBON NANOTUBES
Ramon Colorado, Jr., Elizabeth A. Whitsitt, and Andrew R. Barron, Department of Chemistry, Rice University, 6100 Main Street, Houston, TX 77005
Recent efforts have focused on the chemical derivatization of carbon nanotubes to improve their solubility and processibility. However, the methods developed thus far only target either the nanotube ends or the entire nanotube sidewall and thus offer limited selectivity in functionalization. We have developed a method for selective chemical functionalization of carbon nanotubes that involves (1) coating the nanotubes with silica, (2) selectively etching the coated nanotubes to expose regions of bare nanotubes, (3) conducting chemical reactions on the exposed regions, and (4) removing the remaining silica coating to yield the selectively functionalized nanotubes. Characterization of these materials using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and UV-Vis spectroscopy will be presented.
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