last update: March 28, 2001
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STC-ERSP Program Details Principal Investigator: J. M. DeSimone Project Title: Synthesis of Cationic Silicone-based Surfactants/Nanoporous Materials (Former Prog #35) Research Plan Connectivity Outreach Components Requested Budget Allocation - Year 1 Plans for Additional Funding Research Plan Overall objectives DeSimone proposes to design surfactant molecules that have solvent-density-dependent association properties and exhibit both a critical micelle density and a critical micelle concentration (CMC). By utilizing an understanding of the phase equilibria of various molecular segments as a function of composition, molecular weight and topology, we will synthesize A-B diblock copolymers in which both block segments are soluble in CO2 at high densities (molecules exist as unimers only) but only one block is soluble at lower densities (molecules associated into micelles). Light scattering will also be used to study their general solution properties. Relation to overall objectives of the Center The ability to design surfactants for interfaces between CO2 and liquids or solids offers new opportunities in materials science, protein/polymer chemistry, separation science and environmental science. Little is known about the static or dynamic interfacial properties between liquid or supercritical CO2 and solid surfaces, water, or organic phases, with or without surfactants. A key objective will be to determine how to balance the "CO2-philic" and "CO2-phobic" (anchor) segments of a surfactant to achieve the desired degree of adsorption at a given interface. A rigorous fundamental understanding of the relationship between interfacial properties and surfactant structure is a prerequisite to the rational design and synthesis of surfactants for CO2. Approach and timelines Years 1-2: Develop living anionic polymerization protocols to enable the synthesis of block copolymers containing fluorooctyl methacrylate blocks (CO2-philic segment) covalently attached to t-butyl methacrylate blocks (CO2-phobic segment). Synthesize a series of block copolymers with varying block lengths. Characterize the solution properties of these materials. Attempt the hydrolysis of the t-butyl groups to transform to a hydrophilic acid-containing segment. Years 2-3: Develop living anionic polymerization protocols to enable the synthesis of siloxane-containing polymers (CO2-philic segment) that have quaternized ammonium end groups (CO2-phobic segment that is hydrophilic). Synthesize a series of these polymers with varying MWs and counter ions. Characterize the solution properties of these materials. Years 2-5: Extend protocols to new materials based on findings in early studies and use these amphiphiles in collaboration with others for further solution characterization. Make new samples to include deuterated analogs for SNAS/NMR analysis. Thrust area of this proposal Thrust Area C: Rate Processes Connectivity Collaborators, multi-institutional, multi-disciplinary components These surfactants will be analyzed in partnership with numerous groups. The dynamic equilibrium of molecules that exhibit such a unimer-to-micelle transition will be studied as a function of density using a variety of techniques. Rubinstein and DeSimone (UNC-CH) will use static and dynamic light scattering and Fulton (PNNL) and Wignall (ORNL) will use small X-ray scattering (both static and time-resolved), to understand the structure of these solutions. Wignall (ORNL) and Cochran (ORNL) will use small angle neutron scattering with deuterium labeled block copolymers to elucidate micelle structure and size. Forbes (UNC-CH) will use time-resolved electron paramagnetic resonance spectroscopy (TREPR) to study free radical polymerization initiator decomposition kinetics to characterize the micellar environment (e.g. viscosity) and to determine the rates at which the initiator diffuses in and out of the core. Charles Johnson (UNC-CH) will focus on the use of pulsed field gradient NMR (PFG-NMR) to study dynamics of solutions of block copolymers in CO2. Samulski (UNC-CH) also proposes to extend newly developed NMR methods for quantifying residual proton dipolar interactions in entangled melts to 19F NMR studies of aggregated fluoropolymers in CO2. Wallen (UNC-CH) proposes to use amide 1H exchange as a menas of determining protein and enzyme stability in the D2O core of reverse micelles dissolved in a CO2 continuous phase. Carbonell (NCSU) will use free meniscus techniques to create films of liquid CO2 solutions and from measurements of film thickness in a free-drainage geometry, they will determine the interfacial tension using the methods developed by Tallmadge. Johnston (UT-Austin) will measure the static and dynamic interfacial tension of such solutions using high-pressure pendant drop tensiometer. Related work The researchers in Thrust Area B (Molecular Thermodynamics and Computer Simulations) will be developing models that will facilitate the rational design of new surfactants and will assist in understanding the self-assembly processes. The researchers in Thrust Area C (Rate Processes) will be using these surfactants in the study of novel separations that use surfactants and will investigate the utility of surfactants in modifying forming processes. The researchers in Thrust Area D (Chemistry and Catalysis) will be using these surfactants to stabilize polymeric colloids and to emulsify extremophilic enzymes in CO2. Sharing of resources (students, supplies, equipment, etc.) The student responsible for this project will be sharing the resultant molecules with other groups for analysis and will be integrally involved in the further understanding of the solution properties of these molecules. This student will be working closely with the PIs outlined above. Outreach Components Suggested K-12 Outreach Ideas DeSimone and the student funded through this project would be available in teacher workshops to present topics such as "What do soaps do anyway?" and to describe opportunities for the use of surfactants in CO2 including cleaning studies. Requested Budget Allocation Personnel salaries
Plans for Additional Funding 1) NIH: Use of oligopeptide-containing surfactants for separations with Carbonell/Kelly in Spring 2000 2) DOE: Use of surfactant-modified CO2 for breaking emulsions found in petroleum refineries with Carbonell/Kirkpatrick in Spring 2000 Return to top. |
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