This award provides partial support for the University of Oklahoma to acquire a tensile rheometer for the measurement of polymer viscoelastic properties. This instrument, termed a dynamic mechanical thermal analyzer (DMTA), measures storage and loss moduli for polymers ranging from stiff glasses to very flexible rubbers and viscous melts. Both the requency of oscillation and the measurement temperature can be varied, which enables the construction of master curves using time-temperature superposition. This instrument can also perform stress relaxation experiments permitting the determination of relaxation times. A special option will be purchased to measure the dichroic and birefringent properties simultaniously with the rheological properties. Birefringence measures segmental orientation, while dichroism measures orientation of microdomains, such as spherulites, in the specimen. Hence we will be able to directly correlate segmental orientation with relaxation times, WLF shift constants, or activation energies.
This instrument will significantly improve the current research programs of four investigators in two different departments (Chemistry and Chemical Engineering) and will also be used to initiate research in a new area. Faculty in Chemical Engineering are interested in the effect of fillers on polymer morphology. Room temperature relaxation times have been correlated with crystallite orientation after stretching at elevated temperatures in reticulate doped composites. This instrument will accurately determine relaxation times and also allow the measurement of relaxation times at different temperatures. Studies are also underway on a unique coating method that improves polymer-filler adhesion in composites. This instrument will help identify the optimal coating for a given polymer. Faculty in Chemical Engineering are conducting studies of fundamental processes associated with producing both melt-spun and melt-blown fibers. With this instrument, they will be able to more fully characterize the fibers to better understand the relationship between processing and properties. The optical attachment will be used to correlate rheological properties with segmental orientation of polymer chains. Faculty in Chemistry are presently investigating mechanisms of ionic conduction in polymer/salt electrolytes. The most extensive studies have involved poly(ethylene oxide)/lithium systems. The DMTA will be used to measure changes in mechanical and relaxation behavior and these changes will be correlated with changes in salt speciation determined by various spectroscopies. Other faculty currently synthesize novel intrinsically electrically conducting polymer films. Physical properties are important to end use but samples are either only available as thin films (<200 u) or the use of interest is as thin films and evaluation in that form would be desirable. Finally, it is planned to initiate studies to measure rheological properties using the DMTA while simultaneously measuring the orientation behavior of polymer crystallites using synchrotron radiation. %%% ***
