Keywords: electroactive fluorinated polymers
Summary:Since the discovery of piezoelectric and pyroelectric properties of polyvinylidene fluoride (PVDF), polymers based on vinylidene fluoride (VDF) have attracted research interest due to their application in the fields of sensors, actuators, medical imaging, IR detectors, underwater acoustic transducers and emerging organic electronics. The piezoelectric, pyroelectric, and ferroelectric properties of VDF-based resins as well as their transition behavior were extensively studied during the 70s and 80s. However, the application of the PVDF homopolymer was limited because it does not crystallize directly into its ferroelectric β-phase. In order to obtain a ferroelectric material, PVDF thick films have to be mechanically stretched and then poled under a high electric field. This fabrication process restricted the development of PVDF-based electroactive devices. On the other hand, PVDF copolymers, such as poly(vinylidene fluoride/trifluoroethylene) P(VDF-TrFE), directly form a ferroelectric crystalline structure from solution or melt. Thin copolymers ferroelectric films can then be easily processed as inks via printing techniques and poled using a moderate voltage. Recently, a new class of polymers has been developed and commercialized: the relaxor ferroelectric polymers. These printable terpolymers are based on P(VDF-TrFE) with a third monomer, either chlorofluoroethylene (CFE) or chlorotrifluoroethylene (CTFE), which alters the crystalline structure to result in a relaxor ferroelectric. Compared to the normal ferroelectric polymers, such as P(VDF-TrFE), these materials exhibit a narrow electrical hysteresis curve, good mechanical properties, a high dielectric constant at ambient temperature and large deformations under an applied electric field. We present here an overview of the new developments of fluorinated electroactive polymers in the fast developing fields of printed and flexible electronics. A focus is given on our recent work on electroactive polymers for haptic applications as well as a novel approach to computer chip cooling using a polymeric electrocaloric effect.