last update: July 05, 2000
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STC-ERSP Program Details
Principal Investigator: Steve Webber (co PI: Keith Johnston) Project Title: Dynamics and Structure of Colloids in CO2 (#5) Phone/Fax: 512-471-3633 E-mail: cmsew@utxdp.dp.utexas.edu Research Plan Connectivity Outreach Components Additional Comments Requested Budget Allocation - Year 1 Plans for Additional Funding Research Plan Overall objectives The stabilization of microemulsions and latexes with surfactants will be measured by dynamic light scattering as a function of solvent density. The structure of these colloids will be characterized from nanometer to micron-sized dimensions. The thickness of polymer steric layers on colloidal particles will be measured by dynamic light scattering as a function of solvent quality to understand steric stabilization mechanisms. We will also determine the critical flocculation density where colloids become unstable in CO2 and relate this to the solvation and structure of the stabilizing chains. Fluorescence spectroscopy will be used to determine the dynamics (small molecule or polymer exchange rates) and thermodynamics (e.g. partition coefficients) for colloids including micelles, microemulsions, inorganic suspensions and latexes. Relation to overall objectives of the Center A sound fundamental understanding of the relationship between colloid stability and surfactant structure is of vital importance for the rational design and synthesis of surfactants, especially given the unusual solvent properties of CO2. The behavior of stabilizing chains at interfaces will be compared with complementary studies of chains in bulk solution. Approach and Year 1-Year 5 timelines Years 1-2: Study the thickness of PDMS polymer layers on colloids by dynamic light scattering. Study exchange rates for microemulsions with fluorescence probe-quencher techniques. These experiments will be used to estimate the diffusion constant of a small molecule or polymer that is exiting an aqueous microemulsion droplet. Years 2-5: Include other polymers such as perfluoropolyethers and polyfluoroacrylates for studies of layer thickness. Determine critical flocculation densities for various types of stabilizing chains. Vary surfactant structures for microemulsions. Perform fluorescence probe quencher experiments for polymer latexes to study diffusion. Thrust area of this proposal Thrust Area A: Interfacial and Colloid Science in Compressible Media Connectivity Collaborators, multi-institutional, multi-disciplinary components DeSimone is synthesizing a variety of interesting surfactant structures.Johnson is utilizing pfg- nmr methods to study solvent/solute penetration into solids and diffusion coefficients of small molecules in polymers. Dynamic studies of microemulsions by nmr and fluorescence techniques are highly complementary. Carbonell and Roberts are using chromatographic techniques to study diffusion. The studies of formation and stabilization of micelles (DeSimone et al., Area A), microemulsions (Webber, Area A; Kelly and Carbonell, Area C), and latexes (DeSimone, Area D) will benefit from an understanding of steric stabilization. The dynamics of microemulsions is important in the work of Tumas, Area D, in catalytic processes, to understand the water-CO2 interface and in cleaning(Carbonell, Area C). The theoretical studies of Rossky and Johnston of the water and CO2 interface will complement these experimental studies. Related work in other thrust areas Listed in above section Sharing of resources (students, supplies, equipment, etc.) The students will be shared between Webber and Johnston and the studies may be interfaced with those of other groups as listed in collaborators section. Outreach Components Suggested K-12 Outreach Ideas Webber and the student will be available in teacher workshops to demonstrate experiments to illustrate interfacial properties and to explain how surfactants can be developed for CO2. Additional Comments Please contact me if you have systems you would like to study. Requested Budget Allocation - Year 1 Personnel salaries
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