Ferroelectricity, a bistable ordering of electrical dipoles in a material, is widely used in sensors, actuators, nonlinear optics, and data storage. Traditional ferroelectrics are ceramic based. Ferroelectric polymers are inexpensive lead-free materials that offer unique features such as the freedom of design enabled by chemistry, the facile solution-based low-temperature processing, and mechanical flexibility. Among engineering polymers, odd nylons are ferroelectric. Since the discovery of ferroelectricity in polymers, nearly half a century ago, a solution-processed ferroelectric nylon thin film has not been demonstrated because of the strong tendency of nylon chains to form hydrogen bonds. We show the solution processing of transparent ferroelectric thin film capacitors of odd nylons. The demonstration of ferroelectricity, as well as the way to obtain thin films, makes odd nylons attractive for applications in flexible devices, soft robotics, biomedical devices, and electronic textiles.

Ferroelectric tunnel junctions (FTJs) are ideal resistance‐switching devices due to their deterministic behavior and operation at low voltages. However, FTJs have remained mostly as a scientific curiosity due to three critical issues: lack of rectification in their current‐voltage characteristic, small tunneling electroresistance (TER) effect, and absence of a straightforward lithography‐based device fabrication method that would allow for their mass production. Co‐planar FTJs that are fabricated using wafer‐scale adhesion lithography technique are demonstrated, and a bi‐stable rectifying behavior with colossal TER approaching 106% at room temperature is exhibited. The FTJs are based on poly(vinylidenefluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)], and employ asymmetric co‐planar metallic electrodes separated by <20 nm. The tunneling nature of the charge transport is corroborated using Simmons direct tunneling model. The present work is the first demonstration of functional FTJs manufactured via a scalable lithography‐based nano‐patterning technique and could pave the way to new and exciting memory device concepts.

Polymeric nanocomposite thin films of magnetic nanoparticles blended with the ferroelectric polymer poly-(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) are promising candidates for multiferroic applications. To date, only thick-film multiferroic nanocomposites have been reported. Fabrication of nanocomposite thin films along with the study of the ferroic properties with magnetic nanoparticle loading is crucial for the realization of functional devices. However, systematic studies, and in particular the dynamic of ferroelectric polarization switching and a solid understanding of the microstructure formation in thin films, are still missing. Here, we present solution-processed P(VDF-TrFE):magnetic nanoparticle thin films for multiferroic applications, wherein the ferroic properties, polarization switching dynamic, and the microstructure formation are studied as a function of nanoparticle loading. Our results demonstrate that as the nanoparticle loading increases, the ferroelectric polarization of the nanocomposite decreases and the saturation magnetization increases. Moreover, the presence of the nanoparticles substantially increases the polarization switching time and shifts the switching mechanism to one-dimensional growth. The P(VDF-TrFE):magnetic nanoparticle solution phase separates upon film casting. The crystalline regions of P(VDF-TrFE) are pure. The amorphous regions accommodate the nanoparticles. The phase separation leads to agglomerated nanoparticles at higher loadings, and eventually stratified vertical phases occur. The insight gained from the study of thin-film microstructure would help to optimize the performance of the nanocomposite for multiferroic applications and can be used for better understanding of the polymer:nanoparticle nanocomposites for energy storage and memory applications.

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