last update: March 28, 2001
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STC-ERSP Program Details Principal Investigator: George W. Roberts (with Joseph M. DeSimone and Ruben G. Carbonell) Project Title: Continuous Step-Growth Polymerization in Supercritical Carbon Dioxide (#18) Phone/Fax: (919)515-7328/(919)515-3465 E-mail: groberts@eos.ncsu.edu Research Plan Connectivity Outreach Components Requested Budget Allocation - Year 1 Plans for Additional Funding Research Plan Overall objectives In collaboration with DeSimone and Carbonell, Roberts proposes to study the effect of supercritical carbon dioxide (scCO2) on the solid-state polymerization (SSP) of poly(bisphenol A carbonate), abbreviated here as PC. Three key parameters that affect the behavior of this reaction will be measured: the diffusion coefficient of phenol in PC; the equilibrium constant of the reaction, and; the kinetics of the SSP. These parameters will be determined as functions of temperature and the pressure of CO2. Fundamental models that explain the variation of each parameter with temperature and CO2 pressure then will be developed. These measurements and models are required in order to utilize existing mathematical models of SSP to define the conditions necessary to achieve PC of a sufficiently high molecular weight, and to evaluate the likely effect of operating in scCO2. Based on the results of these studies, a continuous laboratory reactor for SSP will be designed, constructed, and used to test the predictions of the SSP models, including the effect of scCO2. Relation to overall objectives of the Center Industrially, SSP of commodity polymers such as PC must be carried out continuously. However, SSP of this polymer is not practiced commercially at present. Continuous SSP in the presence of scCO2 is a promising approach to avoiding the hazards and pollution associated with the present commercial process, interfacial polymerization. Supercritical CO2 should increase the diffusion coefficient of phenol, a product of the SSP reaction, in the polymer, and it should also increase the intrinsic reaction kinetics by increasing chain-end mobility. However, a complex synthesis of information on chemical equilibrium, intraparticle mass transfer, interparticle mass transfer, and intrinsic chemical kinetics is required to evaluate to opportunities for continuous SSP, to define a feasible region of operation, and to define the optimum CO2 pressure. Approach and timelines Years 1-2: A chromatographic system for measurement of the diffusivity and solubility of phenol in PC, in the presence of various pressures of scCO2, will be constructed and debugged. A laboratory reactor to measure the kinetics and the equilibrium of the SSP of polycarbonate at various pressures of scCO2, will be constructed and debugged. The kinetics and equilibrium of the SSP in the absence of scCO2 will be characterized as a function of temperature, and the phenol diffusion coefficient in the absence of scCO2 will be measured as a function of temperature. Years 2-3: The kinetics and equilibrium of the SSP in the presence of scCO2 will be characterized as a function of temperature and CO2 pressure. Years 3-5: The knowledge gained in Years 1 - 3 will be used to construct a system for the continuous SSP of poly(bisphenol A carbonate), and to develop a predictive mathematical model of continuous SSP. 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 Professors Joseph M. DeSimone of UNC-CH and Ruben G. Carbonell of NCSU. It is directly connected to other projects: 1) Diffusion Coefficients in Polymers Using NMR, sponsored by Professor Charles S. Johnson of the Department of Chemistry, UNC-CH (Thrust Area C), and; 2) Polymer Motion By EPR, sponsored by Professor Malcom Forbes of the Department of Chemistry, UNC-CH (Thrust Area C). As the project develops, it is also 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 diffusivity of phenol, the equilibrium constant and the rate constant(s). Related work As noted above, this research is related to that being proposed in Thrust Area C by Professor Charles S. Johnson of the Department of Chemistry, UNC-CH and by Professor Malcom Forbes of the Department of Chemistry, UNC-CH. Sharing of resources (students, supplies, equipment, etc.) This project will require sharing of certain analytical equipment (UV-Vis, gas chromatograph) with other projects in the Partners I laboratory at NCSU. The project will also require use of the gel permeation chromatograph and the differential scanning calorimeter at UNC-CH. Outreach Components Suggested K-12 Outreach Ideas: The present commercial process for manufacturing PC is an outstanding example of the hazards and pollution that can be intrinsic to chemical processes. The proposed research demonstrates how creative process synthesis can address these problems. 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; 2) ARO: Environmentally-benign polycarbonate synthesis with DeSimone/Carbonell - Fall, 2000 Return to top. |
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