An in situ measurement technique that isolates the mobility of charge carriers is described and analyzed. The technique allows significant improvement over conductivity measurements to monitor changes in the physical properties and state of a material as it cures. This is essential in systems where Ni, the number of charge carriers, cannot be assumed constant such as during cure of epoxies, urethanes and polyimides.;Currently, there is an assumption made in the literature that the number of charge carriers present in a curing material is constant when conductivity is used as an in situ measurement technique to monitor changes in mobility. Ion mobility, time of flight (ITOF) measurements, which are described here, are an appropriate technique to isolate and measure particle mobility due to changes in the state of the material. The ITOF technique, coupled with the measurement of sigma, the ionic conductivity, allows one to measure separately changes in the mobility and the number of charge carriers due to curing or changes in temperature. This is possible since conductivity is the product of the number of charge carriers and their mobility. Length of pulse, strength of applied field, sensor geometry, and temperature/viscosity are examined to determine optimum parameters of measurement for both a simple non-curing system, and more complex, hydrogen-bonded epoxy.;The second focus of this thesis is our recently developed single stage in situ synthesis of hybrid membranes comprised of nanometer-sized metal and metal oxide particles in polyimides. The major goal is development of polymer based structural materials designed to achieve exceptional performance properties regarding gas permeability and gas separation selectivity, particularly in regard to their thickness, modulus, and strength to weight ratio. We investigate hybrid inorganic-polyimide films where the nanoparticle inorganic phases are of two types: (1) nanometer-sized rare earth (lanthanum, gadolinium and holmium) oxide molecular clusters and (2) nanometer-sized palladium and silver metal clusters. For the polymeric phase we used aromatic poly(amic acid)s-polyimides because of their strength and chemical and thermal stability.
| Identifer | oai:union.ndltd.org:wm.edu/oai:scholarworks.wm.edu:etd-3221 |
| Date | 01 January 2003 |
| Creators | Warner, Julia D. |
| Publisher | W&M ScholarWorks |
| Source Sets | William and Mary |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Dissertations, Theses, and Masters Projects |
| Rights | © The Author |
Page generated in 0.0018 seconds