last update: March 28, 2001
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STC-ERSP Program Details Principal Investigator: Edward T. Samulski Project Title: Optical microscopy and NMR characterization of surfactants in CO2 (#32) Phone/Fax: 919-962-1561/919-962-2388 E-mail: et@unc.edu Research Plan Connectivity Outreach Components Requested Budget Allocation - Year 1 Research Plan Overall objectives Samulski plans to construct a microscope and associated optical cells that will enable one to characterize self-assembly of surfactants in CO2. The qualitative microscopy findings will be reinforced with quantitative studies of surfactant-CO2 interaction with high-pressure NMR. The latter know-how is already present in the Samulski group; the acquisition of the 600Mhz spectrometer dedicated to CO2-related work will facilitate experiments that require higher sensitivity (S/N) as well as larger chemical shift dispersion. The ultimate goal is to understand molecular dynamics and the nature of solute-solvent interactions in CO2. In particular, we want to ascertain whether or not the behavior of concentrated surfactant solutions in CO2 parallel that found in conventional solvents (water), i.e., can liquid crystalline phases and biological assemblies (cells, virus particles, etc.) be processed in this unusual solvent? Relation to overall objectives of the Center The microscopic details of CO2-solute interactions ultimately will determine the scope of the utility of CO2 in applications ranging from cleaning to biotechnological processing. There currently are conflicting interpretations of experimental data associated with the solvating power of CO2. For example, is the unusual solubility of fluoropolymers in CO2 driven by specific solute-solvent interaction? We will examine fluorocarbon-based surfactants synthesized in the Center in order to extract structure-(solvent)-properties so that new microscopic findings can be rapidly fed back into the surfactant design and synthesis effort. Approach and Year 1-Year 5 timelines Years 1-2: Develop a versatile high-pressure/variable-temperature optical cell that can be used with polarizing microscopy to monitor phase transitions in surfactant-CO2 systems. Initial studies will commence with the modification of extant light-scattering cell designs. The 600 Mhz specifications are complete and the instrument will be out for bids by 10 February; we anticipate delivery of the spectrometer in early summer 2000. Testing of high-pressure NMR cells for CO2-polymer plasticization studies is underway and a quntitation protocol for extracting molecular dynamics with be finalized. Years 2-3: Model Center surfactants will be characterized; cmc, liquid-crystal forming propensity will be studied (as a function of temperature and CO2 density) to extract correlations with surfactant molecular architecture. Detailed NMR studies of model solutes (e.g., 2-D exchange spectroscopy and J-coupling studies in perfluorinated alkanes in CO2) will help delineate evidence for solute-solvent interactions. Years 2-5: Refine experimental protocols and thereby formulate surfactant design rules with microscopy and NMR findings on structure-property relations. Thrust area of this proposal Thrust area A: Interfacial and Colloid Science in Compressible Media Connectivity Collaborators, multi-institutional, multi-disciplinary components The microscopy cell design will draw on expertise in Carbonell's (NCSU) and Rubinstein's (UNC-CH) rheo-optical and light-scattering work, respectively. We are extending the utility of Wallen's (UNC-CH) PEEK, high-pressure NMR cells for studies of CO2 plasticization in fluorine containing polymers synthesized by DeSimone (UNC-CH). Data on solute-CO2 solvent interactions will naturally feed into theory and modeling efforts at UNC, NCSU and UT-Austin. The NMR studies of relaxation, J-couplings and chemical shifts due to specific CO2-surfactant interactions complements studies by Johnson (UNC-CH). Related work in other thrust areas Hard data on solute-solvent interactions can be factored into modeling in Thrust Area B (Molecular Thermodynamics and Computer Simulations). Findings should impact surfactant engineering efforts in this thrust area (A) and in Thrust Area D (Chemistry and Catalysis). Sharing of resources (students, supplies, equipment, etc.) A joint postdoc (with Wallen and Johnson) will insure that the NMR researchers remain in intimate contact. A joint student (with DeSimone) will constitute the interface with the surfactant design effort and a joint student (with Carbonell) will facilitate extensions to biotech processing applications. The high-pressure optical microscope facility will be generally available to all researches in the Center. Outreach Components Samulski is currently teaching a Chemical Sciences course to a middle school class (grades 5-9) and will exploit heuristic Center findings with this platform. Requested Budget Allocation - Year 1 Personnel salaries
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