last update: March 28, 2001
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STC-ERSP Program Details Principal Investigator: George W. Roberts (with Joseph M. DeSimone) Project Title: Phase Equilibrium: Polymer/ Monomer/ Initiator/ Supercritical Carbon Dioxide Systems (Former Prog #19) Research Plan Connectivity Requested Budget Allocation - Year 1 Plans for Additional Funding Research Plan Overall objectives In collaboration with DeSimone, Roberts proposes to study the partitioning of various solutes between a supercritical fluid phase and a polymer phase, at conditions that are representative of continuous polymerization reactors with supercritical carbon dioxide (scCO2) as the reaction medium. The solubility of various reaction components, e.g., monomers, cosolvents, chain-transfer agents, and initiator mimics, will be measured in scCO2 at various pressures and temperatures. The solubility of these same components will then be measured in well-characterized polymers over the same range of temperature and CO2 pressure. Polymer swelling and sorption rates will also be measured. Using this data, partition coefficients between the fluid and the polymer will be calculated for each component, and fundamental models of the phase equilibrium for each component will be constructed. A knowledge of the equilibrium between the supercritical fluid and polymer phases is essential to understanding the mechanism of heterogeneous polymerizations such as precipitation polymerization, and also is essential to understanding the factors that control transport of the condensate molecule out of a polymer particle in solid-state polymerization (SSP). Initially, this project will focus on systems that arise in the continuous precipitation polymerization of vinylidene fluoride (VF2) in scCO2 to form poly(vinylidene fluoride) (PVDF). These systems include: CO2/VF2, CO2/VF2/PVDF, CO2/VF2/diethyl carbonate (DEC, a mimic of the initiator diethyl peroxydicarbonate), and CO2/VF2/PVDF/DEC. The research will then be extended to systems that are representative of various copolymers of VF2, and to systems that are representative of the SSP of poly(bisphenol A carbonate). Relation to overall objectives of the Center The continuous polymerization of various monomers in scCO2 is a cornerstone of the program of the NSF S&T Center. This project will provide long-range, fundamental support to the continuous polymerization program. Without the results generated by the proposed research, it will be impossible to mechanistically understand or to model the continuous, heterogeneous polymerizations of various monomers in scCO2. Approach and timelines Years 1-2: Systems for measuring phase equilibrium, polymer swelling, and sorption in polymers in the presence of various pressures of scCO2, will be constructed and debugged. Partition coefficients for CO2, VF2, and DEC in PVDF will be measured as a function of temperature and CO2 pressure. Various thermodynamic models, e.g. SAFT and Sanchez-Lacombe, will be evaluated for their ability to correlate this data. Years 2-3: Phase equilibrium, polymer swelling and sorption measurements will be carried out for various copolymers of PVDF and for poly(bisphenol A carbonate). Thermodynamic models will be refined. Years 3-5: Phase equilibrium, polymer swelling and sorption measurements will be carried out for other systems of interest for continuous polymerization, e.g., poly(acrylic acid) and styrene/butadiene rubber. Thermodynamic models will be further refined. Thrust area of this proposal Thrust Area C: Rate Processes Connectivity Collaborators, multi-institutional, multi-disciplinary components This project will be carried out in collaboration with Professor Joseph M. DeSimone of UNC-CH. As the project develops, it is likely to require support from researchers in Thrust Area B, in order to develop sound fundamental models of the effects of temperature and CO2 pressure on the phase equilibrium between various components in a supercritical fluid and in a polymer phase. Two of the models to be evaluated for this purpose are the Sanchez-Lacombe model, developed by Professor Isaac Sanchez of the University of Texas, and the SAFT model, developed by Professor Keith Gubbins of North Carolina State University. Both Professor Sanchez and Professor Gubbins will be participants in Thrust Area B. Related work The research of Professors Carol Hall, Isaac Sanchez, and Keith Gubbins in Thrust Area B will be related to this project. The proposed research also supports projects on continuous polymerization in Thrust Area C and in the Kenan Center for the Utilization of CO2 in Manufacturing. Sharing of resources (students, supplies, equipment, etc.) This project will require sharing of certain analytical equipment (UV-Vis, gas chromatograph, FTIR) with other projects in the Partners I laboratory at NCSU. Requested Budget Allocation Personnel Salaries
Plans for Additional Funding Funding Agencies/Programs and Planned Dates of Submission: 1) ARO/ONR (DURIP): Equipment proposal submitted 8/99 Return to top. |
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