The effect of defects on the electronic structure of long chain ferroelectric polymers

The apparent molecular density of states from combined photoemission and inverse photoemission spectroscopies is compared to the bulk conductivity and frequency dependent dielectric measurements for a variety of ferroelectric polymer poly(vinylidene fluoride) (PVDF) copolymers and terpolymers. While some extra chemical groups introduced into the PVDF long chains increase the measured conductivities at room temperature and can cause significant changes in the dielectric properties, few changes are observed in the overall experimental molecular density of states. The exception appears to be the very short polymer chains. The significance of this comparison is that profound changes can occur in the overall dielectric and transport properties of this class of polymers and copolymers through molecular "dopant addition," without altering the overall density of states of the dominant PVDF polymer host.