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Surfactants and Polymers: Synthesis, Properties and Applications

Grant number: 00/00222-3
Support type:Research Projects - Thematic Grants
Duration: June 01, 2000 - November 30, 2006
Field of knowledge:Physical Sciences and Mathematics - Chemistry
Principal Investigator:Omar Abou El Seoud
Grantee:Omar Abou El Seoud
Home Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated scholarship(s):05/50894-1 - Applications of surfactants: the relevance of the interfacial water properties, BP.DD

Abstract

We are interested in investigating some aspects of the chemistry of surfactant solutions and polymers, including amphiphilic polymers. With regard to surfactant solutions both in water, and in organic solvents (reverse aggregates) we are interested in the following: (i) physico-chemical properties of aqueous micelles; (ii) properties of water in the interfacial regions of aqueous and reverse aggregates; (iii) micellar effects on chemical reactivity. Four surfactant series whose hydrophilic/hydrophobic moieties are systematically changed will be synthesized. The effects of the surfactant structure on the following properties of aqueous micelles will be studied: critical micelle concentration; degree of dissociation of the surfactant counter-ion; micellar aggregation number and hydrodynamic radius; equilibrium constant for micelle formation; and the chemical shifts of the monomer and micelle. These properties will be determined by surface tension, conductivity, light scattering, fluorescence, and NMR. Several solvate chromic probes will be employed in order to determine the effects of surfactant structure on the microscopic polarity of water in their interfacial regions. Another property of interest is the structure of interfacial water of both aqueous and reverse aggregates. H2O-D20 mixtures will be used as a solvent for aqueous micelles, or will be dissolved in reverse aggregates. Curve deconvolution of the vod band of solubilized HOD will be used in order to determine the structure of the water solubilized by reverse aggregates. NMR will be used to probe the structure of interfacial water of both aqueous and reverse aggregates. The use of this technique is based on analysis of the dependence of the chemical shift of the H, O-D, O mixture on its deuterium content. pH-Independent hydrolyses of N-acylimidazoles and phenyl esters of activated acids will be studied in the presence of aqueous and reverse micelles. These substrates act as kinetic probes for the properties of interfacial water, micellar effects on reaction rates, on activation parameters, and on Hammett p values will be analyzed in terms of the micellar medium and electrostatic effects. Cellulose and chitin/chitosan will be studied. We are interested in derivatization of cellulose under homogeneous solution conditions. This process is more advantageous than the (industrial) heterogeneous process, albeit more expensive. (AU)