last update: March 28, 2001
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STC-ERSP Program Details Principal Investigator: C. S. Johnson, Jr. Project Title: Dynamics of Surfactants in CO2 by Means of Pulsed Field Gradient NMR (#1) Phone/Fax: (919)966-5229/(919)962-2388 E-mail: charles_johnson@unc.edu Research Plan Connectivity Outreach Components Requested Budget Allocation - Year 1 Plans for Additional Funding Research Plan Overall objectives Johnson proposes to study the dynamics of self-assembly of surfactants in CO2 by means of NMR diffusion and relaxation measurements. The aim will be to determine sizes of micelles and microemulsion droplets, solubilization efficiencies, and exchange rates for unimers and entrapped solutes as functions of CO2 density, concentration, and temperature. The resulting knowledge will aid in the design of surfactants for use in solubilizing and transporting compounds and for sequestering solvents for reactions and spectroscopic studies. Relation to overall objectives of the Center Characterization of the interactions of surfactants in CO2 is essential for testing molecular design ideas. The balance between CO2-philic and either hydro or lipophilic components must be adjusted to achieve the optimum compounds for applications in cleaning, promoting chemical reactions, and providing specific environments for molecules under study. Approach and Year 1-Year 5 timelines Years 1-2: Implement diffusion measurements on 500 MHz and 600 MHz spectro-meters and evaluate various NMR cell designs. Assess the advantages of toroid cavities for diffusion measurements. Initiate comparison of NMR and light scattering (static and dynamic) for the characterization of self-assembly of (block co-polymer) surfactants in CO2. Begin studies of exchange rates of unimers and entrapped solutes between microemulsion droplets and with the bulk solution particularly for systems with entrapped water with hydrophilic solutes. Years 2-3: Continue studies of exchange in microemulsions and begin studies of the mobility of entrapped solutes through relaxation and diffusion studies. Begin studies of the interaction between entrapped solutes and between entrapped solutes and surfactants by means of NOE experiments. Years 3-5: Extend diffusion, relaxation, and NOE methods developed in years 1-3 to new systems developed at the Center. Thrust area of this proposal Thrust area A: Interfacial and Colloid Science in Compressible Media Connectivity Collaborators, multi-institutional, multi-disciplinary components The DeSimone group will provide advice about surfactant systems of interest and will provide some of the materials for studies described here. The NMR studies will be correlated with the light scattering studies of Rubinstein and Samulski to compare advantages and deficiencies and to obtain complementary information. Also, Wallen will perform spectroscopic studies on entrapped solutes. Diffusion and relaxation NMR measurements will be performed on the same systems in an attempt to better understand the restricted environment in microemulsion droplets. The NOE and relaxation studies will overlap with molecular simulations performed by Berkowitz. Related work in other thrust areas Thrust Area B (Molecular and Computer Simulations) will work toward an understanding of interactions between unimers and the self-assembly process. Thrust Area D (Chemistry and Catalysis) will also be concerned with the emulsification of solutes in aqueous cavities. Sharing of resources (students, supplies, equipment, etc.) The Diffusion NMR project will share materials with other groups and will provide advice about NMR capabilities and requirements for sample handling. The major equipment will be the shared 600 MHz NMR spectrometer as well as the shared 400 MHz wide bore and 500 MHz NMR spectrometers. Outreach Components Suggested K-12 Outreach Ideas Johnson and students supported through this project will be available for workshops to explain principles of NMR and light scattering, e.g. "What is a Spin Echo and Why Do We Care" and "Why is the Sky Blue and Soap Solutions are Cloudy"? Requested Budget Allocation - Year 1 Personnel salaries
Plans for Additional Funding Funding agencies/programs and planned dates of submission: Uncertain. Study of PTAN-b-PVAc in CO2 and the development of high pressure toroid cavity detectors has just been funded by NSF (1999-2002). Return to top. |
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