New Highly Elastic Ferroelectric Materials Containing Poly(vinylidene fluoride) are Released

Poly(vinylidene fluoride), referred to as PVDF, is a thermoplastic fluoropolymer. It can be synthesized by the polymerization of 1,1-vinylidene fluoride. It has excellent properties such as anti-aging, chemical resistance, weather resistance, and ultraviolet radiation resistance.

Ferroelectric material is a functional material, which usually refers to a crystal material that has spontaneous polarization within a certain temperature range and the polarization direction can be flipped or redirected with changes in the external electric field. The core of ferroelectric material is spontaneous polarization. Special crystal point groups endow ferroelectric materials with many properties, enabling them to have many applications in data storage and processing, sensing and energy conversion, as well as nonlinear optics and optoelectronic devices. However, the elastic recovery that a crystal can produce when subjected to stress is extremely small, usually less than 2%. This is why traditional ferroelectric materials are mostly brittle (inorganic) or plastic (organic).

The rapid development of wearable devices, flexible electronics and intelligent sensing has put forward increasingly higher requirements for the materials used. Materials used in electronic devices can be divided into conductors, semiconductors and insulating materials according to their conductivity. Conductors and semiconductors are currently flexible. Ferroelectric materials, as one of the most versatile functional materials among insulating materials, have not yet achieved elasticity, which greatly limits the application of ferroelectric materials in fields such as flexible electronics. The ferroelectricity of ferroelectric materials mainly comes from its crystalline region, but the crystal itself has almost no elasticity, so it is difficult to combine ferroelectricity and elasticity in the same material.

Organic ferroelectric materials include organic small molecule ferroelectric materials and polymer ferroelectric materials represented by PVDF (Poly(vinylidene fluoride)). The ferroelectricity of ferroelectric polymers mainly comes from the dipoles formed from one side to the other by atoms or groups with large differences in polarity on both sides of the molecular chain. Ferroelectric polymers are characterized by high flexibility, ease of fabrication into complex shapes, mechanical robustness, and polar activity. Ferroelectricity in polymers was discovered in Poly(vinylidene fluoride) in the 1970s and is a platform for efficient cross-coupling between electrical, mechanical and thermal energy. Therefore, ferroelectric polymers that possess both ferroelectricity and flexibility may be the best candidates for ferroelectric elastification.

Some researchers have made an elastic ferroelectric material and proposed a method of elasticizing ferroelectric materials. Elasticity is achieved by precisely controlling the cross-linking density, while reducing the impact of structural changes on the crystallization properties of the material. It is a pioneering effort to endow elasticity and ferroelectricity to the same material at the same time.

The researchers proposed the concept of elastic ferroelectric materials and established a network structure in ferroelectric polymers. Select poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE), 55/45 mol%) as the reaction matrix material, and polyethylene oxide diamine (PEG-diamine) with soft and long chains is selected as the cross-linking agent material, and low cross-linking density (1%~2%) is used to impart elasticity to the linear ferroelectric polymer material while maintaining crystallinity. Research shows that the crystalline phase of cross-linked ferroelectric films is dominated by the β phase, and the crystals are evenly dispersed in the polymer cross-linked network. When stressed, the network-like structure can evenly disperse external forces and withstand more stress. Crystallized areas are protected from damage. Experimental results show that the cross-linked ferroelectric film still has a good ferroelectric response under 70% strain, with a residual polarization of about 4.5 μC/cm2 and can remain stable during the stretching process, greatly improving reliability and service life. , expanding the scope of use. Researchers use simple chemical reactions to achieve a good match between ferroelectricity and elasticity, providing a new idea for the elasticity of ferroelectric materials. At the same time, the application of the prepared elastic ferroelectric materials in wearable electronic devices, energy conversion and storage, and dielectric drive will be explored.