Research Interests
My research interests are focused
in the relatively new area of organogels. Some of the
projects we are currently investigating are:
Synthesis of Biphenyl-Cholesterol Derivatives: The Effect
of the Spacer Length on their Gelation Ability.
Among the types of gelators found by different investigators thus far are single molecules or two component systems. The introduction of two components increases the aggregation ability and the formation of super gels--gels formed at concentrations lower than 1% (w/w). We have synthesized several biphenyl fatty acids and connect them to cholesterol compounds by an ester link. We are interested in finding out what effect, if any, the length of the connecting chain has on the gelation ability of these compounds.
The stability
of these gels and the relationship between structure/scaffold/gelation is analyzed by studying the phase transition
temperatures and absorption and emission behavior.
Study of Biphenyl-Cholesterol
Gels: Chirality Influence on C-3 in the Cholesterol
Moiety.
The purpose of this project is to understand the effect of stereochemistry on the structure of some biphenyl-cholesterol derivatives and their gelation ability in several organic solvents. For this purpose, we have synthesized four biphenyl derivatives connected by an ester linkage to the C-3 of a cholesterol moiety. Cholesterol in its natural configuration contains the hydroxyl group positioned in an S-configuration. We have synthesized two biphenyl-cholesterol compounds with an S-configuration at C3 and two other with and R-configuration. In two of the compounds the biphenyl is connected directly to the cholesterol. In the other two compounds, there are eight methylene units in between the two components. By molecular modeling simulations, we observe different packing arrangements for these compounds. By emission, absorption and circular dichroism spectroscopy, we investigate the nature of the aggregates formed.
Synthesis and Gelation
Studies of a Dicholesterol-Biphenyl Derivative
The formation of a gel depends on the relationship of the gelator’s structure and the nature of the solvent involved in gelation among other factors. One important aspect of the structure is the ability to self assembly. Fibrous aggregates of low-molecular weight compounds formed by noncovalent interactions are responsible for such aggregation. It is well known that aromatic compounds can form aggregates due to the p-p interaction of the benzene rings, also certain cholesterol derivatives can form stable gels due to the helical stacking of the cholesterol units. We envision a more powerful gelator consisting of an aromatic part connected by a methylene chain to two cholesterol moities. By having three driving forces leading to self assembly this compound could be a super gelator, i.e., a compound capable to form gels at less than 0.5% (w/w) concentration. We propose the total synthesis of dicholesteryl-4,4’-biphenoxyoctanoate, the gelation studies and photophysical characterization of this compound in gels, isotropic state and in dilute solutions.
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Former and present Research Students
Dan Galka- ACS
meeting, San Francisco, March 2006
Magdalene
Assimon
Sara Villani
Spencer Varney
