last update: March 28, 2001
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STC-ERSP Program Details Principal Investigator: Malcolm D. E. Forbes Project Title: Application of EPR to Measure Kinetics of Polymerizations in CO2 (Formere Prog #15) Research Plan Connectivity Outreach Components Requested Budget Allocation - Year 1 Plans for Additional Funding Research Plan Overall objectives There are three major objectives of this research: 1) Construction of a flow system for CO2/water emulsion polymerizations for EPR measurement of free radical concentrations, 2) Study of chain dynamics of main chain polymeric free radicals produced from photolysis of FOA and FOMA at 248 nm, particularly in block copolymer structures, and 3) the study of radical pair dynamics in different regions (inner and outer layers) of micelles in CO2, with particular emphasis on radical rotational correlation times and micellar escape rates. Relation to overall objectives of the Center The general use of CO2/water emulsions for free radical polymer synthesis would be a big step forward in green chemistry. While in principle this has been shown to work, we would like to understand the fundamental rate processes of these emulsion polymerizations to help determine the optimal conditions for such reactions. Construction of an apparatus to measure steady-state free radical concentrations, similar to that developed at Rohm and Haas Company, will help us understand the kinetics and also the structure of such emulsions. Additionally, we want to take advantage of our recent discoveries in acrylate and methacrylate photodegradation by studying the UV decomposition of FOA and FOMA polymers in CO2. The time-resolved EPR spectra of main chain radicals observed in these experiments should tell us much about the difference in macromolecular chain dynamics between CO2 and conventional solvents, and about their UV-light stability at these wavelengths. Information about their possible use as photoresists at even shorter wavelengths (193 nm) will be obtained. Finally, the disposition and mobility of free radicals in CO2 micellar structures is important for understanding molecular partitioning at CO2-philic/ CO2-phobic interfaces. Time-resolved EPR is an ideal technique for such studies. Approach and Year 1-Year 5 timelines Years 1-2: Construct flow system for both steady-state and time-resolved EPR experiments in CO2/water emulsions. This will require complete re-engineering of the current flow system, which at present can accommodate only low-dielectric samples such as pure CO2. The new system will stress ease of use as well as facile temperature and pressure variation. Reconstruction of the microwave end of the spectrometer for enhanced sensitivity will also take place at this time, with the inclusion of a GaAsFET microwave amplifier on the signal return arm of the bridge. Years 2-3: Perform EPR experiments on water/ CO2 emulsions similar to those of Dave Westmoreland at Rohm and Haas Company, to measure free radical concentrations under steady-state conditions. Also at this time begin time-resolved studies of FOA and FOMA degradation in CO2,including block copolymers. Years 2-5: Computer modeling of results, especially molecular modeling of chain dynamics studies and spin physics calculations of radical mobilities in different regions of CO2 micelles. Based on early results, design new systems to optimize free radical polymerization reactions in CO2/water emulsion, and optimize block structures for any desired radical mobility in micellar structures in CO2. Thrust area of this proposal Thrust Area C: Rate Processes, Diffusion/Mass Transfer Studies Connectivity Collaborators, multi-institutional, multi-disciplinary components DeSimone (UNC-CH) will be the primary source of new materials for these studies, in particular in supplying block copolymers of varying block size and overall molecular weight. It will be very useful to interact with Johnson and Samulski (UNC-CH) in that NMR and EPR often generate complementary data with regard to the time scales of dynamic effects and magnitudes of magnetic interactions that it is possible to measure. Interaction with Rubinstein (UNC-CH) will be of paramount importance when computer simulation of the dynamics becomes necessary. Wallen's (UNC-CH) work on enzymes could be extend to spin-labeled proteins for dynamic EPR studies. Related work in other thrust areas The researchers in Thrust Area B (Molecular Thermodynamics and Computer Simulations) will be developing models for understanding the self-assembly processes and the dynamics of the resulting micelles and FOA and FOMA polymers. The researchers in Thrust Area C (Rate Processes) will be studying similar dynamic aspects of these soaps and polymers in the study of novel separations. The connection between NMR and EPR measurements is obvious. The researchers in Thrust Area D (Chemistry and Catalysis), who will be using CO2 soluble surfactants to stabilize polymeric colloids and to emulsify extremophilic enzymes in CO2, will be interested to learn about the fundamentals of their dynamics. Sharing of resources (students, supplies, equipment, etc.) The researcher responsible for this project will collaborate with any other P.I. interested in studying free radicals in CO2, and will interact with other students and postdocs synthesizing new block copolymer structures that may make novel micelles in CO2. In addition, the construction aspects of the flow system make it highly likely that contact with the chemical engineers will be important. Outreach components Suggested K-12 Outreach Ideas We would be interested in accepting a Project SEED high school student from the ACS in year 2 or 3 of this work. Requested Budget Allocation Personnel salaries
Plans for Additional Funding Funding agencies/programs and planned dates of submission: NSF Division of Materials Research: Study of Macromolecular Chain Dynamics Using Time-Resolved EPR Spectroscopy Return to top. |
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