|M.Sc Student||Alona Lea Makarsky|
|Subject||Nanostructure of Novel Self-aggregative Block-copolymer and|
|Department||Department of Chemical Engineering||Supervisor||Professor Emeritus Talmon Yeshayahu|
|Full Thesis text|
The main objective of this work was to understand polymer/surfactant interaction, to investigate aqueous solutions of novel surfactants, and explore the influence of other surfactants on those novel surfactant systems.
The influence of hydrocarbon chain length of surfactants on the formation and inner structure of the cationic surfactant/anionic polymer complexes was explored. The phase behavior of a series of aqueous mixtures, containing positively charged surfactants with negatively charged polymer, was studied by transmission electron microscopy at cryogenic temperatures (cryo-TEM), a technique for direct visualization of the formed nanostructures. The solutions of alkyltrimethylammonium bromides, CxTABr, with five surfactant chain lengths C8, C10, C12, C14 and C16, and polyacrylic acid sodium salt (PAANa) with chain length of 153 repeating units were investigated. No any visible aggregates were produced by C8TAB/PAANa in water. Nanoparticles were found in the C10TAB/PAANa system. Clearly defined hexagonal phase was found in the C12/14/16TAB/PAANa systems. We also examined the effect of changing of the surfactant/polymer molar ratio on the formation and character of the complexes.
Aqueous solutions of a novel nonionic ABA-type silicone surfactant, (EO)15-(PDMS)15-(EO)15, a polymeric surfactant of 15 dimethylsiloxane (DMS) hydrophobic units and two hydrophilic blocks made by polyethylene oxide (EO)15, were investigated. Large multilamellar vesicles, small single-walled vesicles, threadlike micelles and spheroidal micelles were observed. The influence of adding a hydrocarbon surfactant on the self-aggregation behavior of silicone surfactant was checked. The threadlike micelles and vesicles were destroyed by the addition of sodium dodecyl sulfate (SDS). Vesicle-to-micelle transition was followed by cryo-TEM. Many complex structural changes and intermediates were imaged.
We also studied the effects of adding glycerol to the solvent. We found that the vesicles in dilute (EO)15-(PDMS)15-(EO)15 solutions are broken with increasing glycerol-to-water ratio. The effect of glycerol on the phase and aggregation behavior of the ABA-type silicone surfactant aqueous solution was explained by the vanishing of the attraction between the bilayers with increasing glycerol content.