Barron Research Group Abstracts

USE OF CARBOXYLATE ALUMOXANES IN BONE MATERIALS

Naureen Shahid, Jimmie D. Weaver, Kyung A. Son-Guidry, Andrew R. Barron
Department of Chemistry, Rice University, 6100 Main Street, Houston, TX, 77005

Poly(propylene fumarate) (PPF) is a biodegradable unsaturated polyester that has been used in tissue engineering, as it can be made to cross-link during orthopedic surgery, to form a solid biodegradable bone cement via an addition polymerization with N-vinyl pyrrolidione. This cement is reliable for areas which are not subjected to high loads, such as, the rib bones. However, this cement is not reliable for bones, such as the femur, that need to support high loads and stress. It has been shown earlier by this group that carbon fiber panels containing lysine alumoxane have increased tensile and short beam shear strengths, where as, panels 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 these two alumoxanes have increased the strength of biodegradable poly(propylene fumarate) - based polymers.

SILICA COATED FULLERENOLS

Elizabeth A. Whitsitt and Andrew R. Barron
Department of Chemistry, Rice University, 6100 Main Street, Houston, TX, 77005

Liquid phase deposition 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. Fullerenols, or polyhydroxylated fullenes, lend themselves well to this method. Characterization of this novel material was performed with scanning and transmission electron microscopies, and ATR-FTIR , Raman, and UV/Vis spectroscopies.

Synthesis and Characterization of Novel Aluminum-Bipyridyl Complexes

Douglas C. Ogrin and Dr. Andrew R. Barron
Department of Chemistry, Rice University, 6100 Main Street, Houston, TX, 77005

As the interest in molecular devices grows, the use of different metal centers and bridging ligands is being investigated. Our present research focuses on using aluminum complexes with bifunctional pyridyl ligands to synthesize unique Al-N complexes. NMR and X-ray crystallography have been used to characterize these complexes. Of interest, is an equilibrium that develops between a fully complexed, partial complexed, and free ligand. This was first seen in the reaction of di-tert-butyl aluminum phenoxide and bipyradine. This allows for insight into the communication between the two aluminum centers. Other areas of interest include the affect of the aluminum’s Lewis acidity on the overall complex and the maximum distance allowed between aluminum centers before the equilibrium is no longer seen.

Soft-Lithographic Patterned Features in Carboxylate-Alumoxane Based Ceramics

John Ryan Loscutova and Andrew R. Barron
Department of Chemistry, Rice University, 6100 Main Street, 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 sol-gel alumoxane precursor is poured, to produce an imprinted preceramic green body. Alumoxanes are blended in different ratios to alter the properties of shrinkage, hardness, pore size, drying times, and gross curvature. Metals such as lanthanum and calcium can be doped into the alumoxane precursors, to alter these same properties. Through the processes of replica molding and firing to alumina, the patterns undergo shrinkage, and acquire varying degrees of gross curvature without loss of image fidelity. SEM images of the ceramic bodies confirm the presence and aspect qualities of the imprinted features.

The Effect of Additives in Calcium Carbonate Crystalization

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 of the calcium carbonate crystal formation. One effect is that water-soluble fullerols provide many nucleating sites for calcium carbonate formation, resulting in smaller crystal size. This additive, others and various combinations have been investigated and may lead to new calcium carbonate materials with applications for, among others, filters.

Return to Barron Group Home Page