Date of Award
Doctor of Philosophy (PhD)
Isiah M. Warner
The research presented in this dissertation involves the comparison and characterization of polymeric and monomeric amino acid based surfactants for the enantiomeric separation of chiral compounds. Comparison of the performance of these two kinds of surfactants in EKC suggest that polymers are better chiral pseudostationary phases (CPSP) than the monomers for enantiomeric separation of neutral and cationic analytes, at least for the examined in this dissertation. However, the anionic enantiomers of 1,1'-binaphthyl-2-2 '-dihydrogen phosphate (BNP) were better separated using monomeric CPSPs. The depth of penetration of binaphthyl derivatives into the micellar core of chiral dipeptide surfactants (CDS) was examined using various techniques. The results indicate that enantiomers of BNP interact preferentially with the C-terminal amino acid of monomeric CDS, whereas these enantiomers interact with both chiral centers (C- and N-terminal) of polymeric CDS. In this dissertation, steady state fluorescence anisotropy and pulse field gradient NMR techniques are used to study the chiral interactions of binaphthyl derivatives with these amino acid based surfactants. The results indicate that the anisotropy and diffusion coefficients of various enantiomers are different when complexed to poly sodium undecanoyl leucyl-leucinate. Interestingly, the enantiomer that binds stronger to the CPSP, as evidenced by EKC experiments, has higher anisotropy values and lower diffusion coefficients. The results of this study suggest that these two techniques can be used to gain further insight into chiral recognition. The physical properties of CDS are examined in Chapters 4 and 5 of this dissertation. The polymeric CDS examined in this dissertation always have lower aggregation numbers than their monomeric counterparts. As can be deduced from the aggregation numbers, regardless of the size of the polar head, polymeric CDS most likely adopt a spherical shape in solution, while the shape of monomeric CDS depend on the size of the polar head group. In addition, polymeric CDS have a higher effective charge, and are less polar than the monomers. Furthermore, polymeric surfactants have a lower solubilization capacity for neutral organic probes compared to the monomer. This in turn results in faster mass transfer in EKC experiments when polymeric surfactants are used as a CPSP. Finally, the chiral separations of a variety of analytes are examined using polymeric surfactants. Some of the factors examined were number and position of chiral centers, dipeptide amino acid order, and steric effects.
Billiot, Fereshteh Haddadian, "Chiral Recognition Using Polymeric and Monomeric Amino Acid Based Surfactants." (2000). LSU Historical Dissertations and Theses. 7317.