Molecular Dynamics of Physical Aging Processes in Polymer Glasses
Final rept. Jan 1990-Dec 1992
CASE WESTERN RESERVE UNIV CLEVELAND OH
Pagination or Media Count:
We have used the positron as a microscopic probe to clarify the connection between the microscopic properties e.g., free volume distributions and macroscopic properties pressure, volume, and temperature relations of polymers in the glassy state. Measurements of the positron lifetime distribution in the polymer as a function of temperature, aging, and applied strain have shown that positrons are sensitive to the distribution of free volume elements. However, we have also found that refinements in data analysis are necessary, and that we are far from obtaining an unambiguous free-volume distribution from the current results. Theoretical models are being tested to see if they are consistent with the results. We have also generated simulated positron lifetime distributions to test the validity of our curve-fitting methods, and we have discovered that these methods break down when the instrumental resolution curve exceeds approximately 250 nanoseconds, in width.
- Polymer Chemistry
- Atomic and Molecular Physics and Spectroscopy
- Nuclear Physics and Elementary Particle Physics