Impulsive stimulated thermal scattering studies of thermally induced cure in thin films of PMDA/ODA

We use a noncontact laser based method to monitor in real time the viscoelastic and thermal properties of thin (micron) polyamic acid films of PMDA/ODA as thermally induced imidization proceeds. Our measurements indicate that the most rapid thermal and viscoelastic changes coincide with or occur at slightly higher temperatures than the peak imidization rate as determined using a variety of other more conventional analytical techniques. The thermal and viscoelastic properties continue to change at temperatures beyond which imidization is largely completed, but within uncertainties cease to change at temperatures greater than 350°C.