Study of Charge and Polarization Distribution in Polymers.
Final rept. 1 Jul 82-30 Jun 85,
NATIONAL BUREAU OF STANDARDS GAITHERSBURG MD
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It has been established that space charge effects are important in determining the polarization distribution of ferroelectric polymers when these are poled under conditions of significant, though still extremely small, conductivity. Asymmetric distributions are observed and these are indicative not only of space charge present during poling but also of polarity-dependent barrier effects at the metallic electrode-polymer interfaces. Among the polymers surveyed in this contract which gave simple asymmetric polarization profiles, PVF2 and PVF2-TE showed a tendency to pole most strongly in the regions near the poling anode indicating accumulation of negative charge during poling, while PVF and Nulon 11 tend to pole most strongly near the poling cathode, indicating accumulation of positive charge. The difference among samples in the sign of the change accumulated during poling suggests that a basic relation exists between charging behavior and bulk or surface polymer structure however, additional work is required to establish the nature of such a relation. Under conditions of negligible conductivity, the observation of nonuniform sample properties are suspected to be of morphological origin or due to pre-existing polarization of unknown origin. However, it appears that under these conditions, the polarization distributions are nominally symmetric. Studies of electron-beam irradiated PVC have revealed interesting, new information-storage properties of this material. Keywords Piezoelectric polymers, Pyroelectric polymers.
- Electricity and Magnetism