Kresheck, Gordon C.
M.S. (Master of Science)
Department of Chemistry
Micelles; Surface active agents; Phospholipids
Mixed micelles of sodium dodecyl sulfate (SDS)- dimyristoylphosphatidylcholine (DMPC) (mole fraction of sodium dodecyl sulfate equal to 0.95, 0.90, and 0.85), sodium dodecyl sulfate-dipalmitoylphosphatidylcholine (DPPC) (mole fraction of sodium dodecyl sulfate equal to 0.95, 0.90, and 0.85), and dodecyltrimethylammonium bromide (DTAB)-dipalmitoylphosphatidyl-choline (mole fraction of dodecyltrimethylammonium bromide equal to 0.98, 0.90, and 0.85) were characterized by titration calorimetry, ion selective electrodes (ISE), ultrafiltration, and dye solubility studies. The apparent critical micelle concentration (cmc) (from titration calorimetry) of SDS-DMPC (sodium dodecyl sulfate-dimyristoylphosphatidylcholine) and SDS-DPPC (sodium dodecyl sulfate-dipalmitoylphospha- tidylcholine) mixed micelles decreased as the mole fraction of detergent decreased. The heat of micellization for all types of mixed micellization was exothermic. For both SDS-DMPC and SDS-DPPC mixed micelles, the heat of micellization became more exothermic as the concentration of phospholipid increased. However, no trend was observed (heat of micellization) for DTAB-DPPC mixed micelles. The heat of dilution for SDS-DPPC mixed micelles became more endothermic as the concentration of phospholipid increased. The cmc of SDS and SDS-DPPC mixed micelles (mole fraction of SDS equal to 0.95) by sodium ion selective electrode was found to be the same (7.8 mM). The cmc of DTAB-DPPC mixed micelles (mole fraction of DTAB equal to 0.98) and DTAB by bromide ion selective electrode (ISE) was found to be 19.0 and 15.0 mM, respectively. The degree of counterion association in DTAB micelles was found from the ultrafiltration experiments to be 83% at the cmc. Dye solubility studies were undertaken to determine the cmc and to relate to the size of mixed micelles. The cmc values obtained from this study (both for SDS-DPPC and DTAB-DPPC mixed micelles) were significantly lower than those obtained by other methods. For SDS micelles containing methyl yellow, a dye, the absorbance was directly proportional to the concentration of SDS up to 60 mM and the absorbance was directly proportional to the concentration of SDS up to 40 mM. For SDS-DPPC mixed micelles, the absorbance increased as the concentration of DTAB increased.
Bodani, Umesh C., "The characterization of mixed micelles formed by mixtures of ionic surfactants and phospholipids" (1989). Graduate Research Theses & Dissertations. 5354.
xii, 101 pages
Northern Illinois University
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