Behavior of Ionic Conduction in Poly(methyl methacrylate) under a High Electric Field

Electrical conduction of poly (methyl methacrylate) (PMMA) is considered to be ionic from low to very high fields near breakdown. Support for the ionic mechanism can be supplied from the compensation law, and from the temperature dependence of the electrical conductivity and the breakdown field. In high electric fields above the ohmic region, it was observed that the apparent activation energy decreased with increasing electric field. A simplified equation for the activation energy was derived in which the dependence of the electric field on ionic jump energy and ionic dissociation energy was taken into consideration. The ionic jump distance between equilibrium positions computed from the equation was 10 to 20 A and was in good agreement with periodic structure of PMMA.