Advanced Ferroelectric and Related Electromechanical Polymers

This talk will cover two classes of electroactive polymers under development recent at Penn State. One is the modified poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) polymer and the other is the high dielectric constant all-organic composite. Recently, making use of the defect structure modification in P(VDF-TrFE) based polymers, we converted normal ferroelectric P(VDF-TrFE) into relaxor ferroelectric polymer. This new class of polymer exhibits very high electrostrictive strain (~7%) with high elastic energy density (~1 J/cm), attractive for actuators and electromechanical transducers. In addition, it also possesses a high room temperature dielectric constant (~60) which opens up possibilities for high performance polymer based dielectric devices. This talk will discuss those features and the approaches taken to modify the P(VDF-TrFE) based polymers, i.e., the high-energy electron irradiation and terpolymer approaches. One of the challenges in further improving the performance of electroactive polymers driven by external field is how to significantly raise the dielectric constant. Although the modified PVDF based polymer exhibits the highest room temperature dielectric constant (60 versus below 10), it is still far below those in the inorganic materials. This talk will present experimental results showing the potential of using delocalized electrons in conjugated bonds to achieve ultrahigh dielectric response in polymer-like materials or conductive polymers, where an all-organic composite with a dielectric constant near 1000 can be achieved. As a result, a strain of near 2% with an elastic energy density higher than 0.1 J/cm can be induced under a field of 13 V/μm.