-
221st
ACS National Meeting
-
April 1 - April 5, 2001
-
San Diego, California
-
-
Barron
Research Group Abstracts
-
- Reversible binding of a Lewis base
to a gallium aryloxide polymer: An example of a molecular sensor.
-
- Laura G. van Poppel,a Simon G.
Bott,b Andrew R. Barron.a*
- aDepartment of Chemistry,
Rice University, Houston, TX 77005 and bDepartment of Chemistry,
University of Houston, Houston, TX 77204
-
- The oligomeric species [{(tBu)2Ga}(µ-OC6H4O)]n
has been formed from the reaction of tri-tert butyl gallium with hydroquinone
in a noncoordinating solvent. Dissolution of [{(tBu)2Ga}(µ-OC6H4O)]n
in pyridine gives the monomer [(tBu)2Ga(py)2]2(µ-OC6H4)
which has been characterized by single crystal X-ray diffraction. In the solid
state, [(tBu)2Ga(py)2]2(µ-OC6H4)
loses 2 equivalents of pyridine at 125°C, reforming the oligomeric species.
This process is reversible and is accompanied by a change in color from yellow
to colorless. The characterization of this Lewis acid/base interaction will
be presented
-
-
- STRENGTHENING CERAMIC BODIES BY INFILTRATION AND SURFACE
REPAIR UTILIZING CARBOXYLATE-ALUMOXANES
-
- Kimberly A. DeFriend-Varela and Andrew R. Barron,
Department of Chemistry, Rice University, Houston, TX 77005
-
- We have investigated the use of carboxylate-substituted
alumina nanoparticles (carboxylate-alumoxanes) as ceramic precursors to provide
surface repair to machined ceramic surfaces. We have also developed a method
to form an equivalent to a CMCFC'c, ceramic matrix ceramic fiber composites,
at a low cost, by infiltrating a porous ceramic with the alumoxanes. The effects
of solution concentration, number of coatings, and increased strength have
been determined. ESEM, AFM, elemental mapping, micro-hardness testing, and
3 point bend test results will be presented.
-
-
Cement hydration inhibition: In situ creation of composite structures
-
- Maximilienn Bishop1, and Simon
G. Bott2, Andrew R. Barron1. (1) Department of
Chemistry, Rice University, 6100 main Street, Houston, TX 77005, Fax: 713-348-5619,
arb@rice.edu, (2) Department of Chemistry, University of Houston
-
- The effects of organophosphonates retarders
on the hydration of the main components of Portland Cement and the formation
of ettringite have been investigated in order to gain insight into the different
mechanisms of hydration inhibition. It was found that the organophosphonate
initially accelerates the hydration of the aluminate phase and the formation
of ettringite, then halts the reactions completely for several hours. In addition,
nitrilotris(methylene)triphosphonic acid enhances the dissolution of calcium
oxide and subsequently precipitates a layered calcium phosphonate polymer.
The structure of this material and the dissolution-precipitation mechanism
are discussed with regard to cement hydration inhibition. The formation of
an in-situ composite structures is discussed.
-
-
- Molecular coupling layers formed by reactions with
self-assembled carboxylate monolayers grown on the native oxide of aluminum
-
- Christopher L. Edwards, Cullen T. Vogelson, Andrea
Keys, and Andrew R. Barron, Department of Chemistry, Rice University, Houston,
TX 77005
-
- In order to produce molecular coupling layers, epoxy
resins cross-linked with self-assembled monolayers (SAMs) grown on the native
oxide of aluminum have been investigated. Initially, SAMs have been formed
by the attachment of carboxylic acids RCO2H [R=C17H35, CH3, C6H4-3-Br,
C6H4-4-OH, C6H4-4-SH, and C(NH2)(CH2)4NH2] to the native oxides of aluminum
thin films on silicon substrates. In order to investigate the cross-linking
reaction between carboxylate monolayers and an epoxide, grown monolayers of
p-hydroxybenzoate and lysine were reacted with a mono-epoxy resin, 1,2-epoxy-3-phenoxypropane.
The SAM systems have been characterized by Grazing Angle Specular Reflectance
FTIR, XPS, EDX analysis, and contact angle measurements. In addition to these
surface materials, aluminum oxide surfaces supporting either lysine or p-hydroxybenzoate
monolayers were reacted in pairs with a di-epoxide (DER 332) to form an adhesive
layer between the two surfaces. This epoxy-SAM interaction is shown to form
a "molecular glue" type interface which has been characterized by SEM and
contact angle. Finally, aluminum oxide surfaces supporting p-thiobenzoate
monolayers were reacted with gold surfaces.
-
-
- POSTER
-
- The effect of organic admixtures on the hydration
and surface chemistry of tricalcium aluminate and tricalcium silicate.
- M. Bishop, S.G. Bott, and A.R. Barron*,
Rice University, Houston, Texas 77005.
-
- The desire for precise control of the hydration and setting
of Portland Cement has inspired research into the mechanisms of cement hydration
inhibition. The effects of several organic additives on the hydration of tricalcium
aluminate and tricalcium silicate, two of the main components of Portland
Cement, were investigated. Use of an organophosphonate retarder lead to the
development of a calcium phosphonate model compound which is thought to bind
to the surface of tricalcium aluminate and [the mineral] ettringite.
The interactions of the calcium phosphonate with the surface of ettringite
and tricalcium aluminate and their relationship to cement hydration inhibition
will be discussed.
-
- Aluminum and gallium chloride stabilized arene-mercury
complexes
-
- Alexander S. Borovik1, and Simon G. Bott2,
Andrew R. Barron1. (1) Department of Chemistry, Rice
University, Houston, TX 77005, Fax: 713-348-5619, arb@rice.edu, (2) Department
of Chemistry, University of Houston
-
- Novel Lewis acid-base mercury (II) complexes featuring
strong coordination of arenes toward mercury have been prepared by the reaction
of mercury dichloride with two equivalents of the trichlorides of aluminum
and gallium in a variety of aromatic solvents. These new compounds were found
to be extremely efficient activators of C-H bonds. The catalytic proton-deuterium
exchange and the olefin addition to the aromatic ring will be discussed. Toluene,
ethylbenzene, o-xylene, trimethylbenzene complexes were characterized by X-ray
crystallography.
-
-
- Return to
Barron Home Page