Poly(vinylidene fluoride)-based dielectric materials are prospective candidates for high power density electric storage applications because of their ferroelectric nature, high dielectric breakdown strength and superior processability. However, obtaining a polar phase with relaxor-like behavior in poly(vinylidene fluoride), as required for high energy storage density, is a major challenge. To date, this has been achieved using complex and expensive synthesis of copolymers and terpolymers or via irradiation with high-energy electron-beam or γ-ray radiations. Herein, a facile process of pressing-and-folding is proposed to produce β-poly(vinylidene fluoride) (β-phase content: ~98%) with relaxor-like behavior observed in poly(vinylidene fluoride) with high molecular weight > 534 kg mol⁻¹, without the need of any hazardous gases, solvents, electrical or chemical treatments. An ultra-high energy density (35 J cm⁻³) with a high efficiency (74%) is achieved in a pressed-and-folded poly(vinylidene fluoride) (670-700 kg mol⁻¹), which is higher than that of other reported polymer-based dielectric capacitors to the best of our knowledge.

Optical transparency is an important property for a material, especially in certain fields like packaging, glazing, and displays. Existing commercial transparent polymeric materials are mostly amorphous. Semicrystalline polymers have often‐superior chemical resistance and mechanical properties particularly at elevated temperatures or after solid‐state drawing but they appear opaque or white in most cases. This review describes the present state‐of‐the‐art of methodologies of fabricating optically transparent materials from semicrystalline polymers. A distinction is made between isotropic, biaxially stretched, and uniaxially stretched semicrystalline polymers. Furthermore, some functionalities of transparent nanocomposites based on semicrystalline polymers are also discussed. This review aims to provide guidelines regarding the principles of manufacturing transparent high‐performance semicrystalline polymers and their nanocomposites for potential applications in fields like packaging, building, and construction, aerospace, automotive, and opto‐electronics.

The typical limitations of ferroelectric polymers like poly(vinylidene fluoride) (PVDF) – low crystallinity and indirect ferroelectric β-phase crystallization – and poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) – high materials and processing costs and a low Curie point – are tackled by a simple and industrially viable melt blending approach. Despite the immiscible nature of PVDF and PVDF-TrFE, strong interactions exist between the two polymers, which substantially affect the morphology and texture of the blends as well as their dielectric and ferroelectric properties. Surprisingly, minor amounts of PVDF-TrFE lead to a significant increase in the β-phase content and preferred orientation of PVDF, well beyond the rule-of-mixtures. Moreover, the blends exhibit maximum increases in the dielectric constant of 80% and 30%, respectively, compared with pure PVDF and PVDF-TrFE. The ferroelectric remnant polarization increases from 0.040 to 0.077 C m⁻², while the coercive field decreases from 75 to 32 kV mm⁻¹ with increasing PVDF-TrFE content from 0 to 40 wt%. The enhancement of properties is explained by the strong interactions at the interfaces between PVDF and PVDF-TrFE, which also suppress the Curie transition of PVDF-TrFE, providing a potentially increased working temperature range for blended films, which is important in applications like non-volatile energy storage devices, ferroelectric field-effect transistors and touch sensors.

In this study, thermoplastic polyurethane (TPU) fibres containing multi-walled carbon nanotubes (MWNTs) and fabricated via an extrusion process were demonstrated to possess a tuneable level of electrical conductivity. A simple approach based on the time–temperature superposition applied to the electrical conductivity of carbon nanotube (CNT) percolating in a thermoplastic polyurethane (TPU) melt was also developed to predict the conductivity of the nanocomposite fibres. The observation of Arrhenius dependence of zero-shear viscosity and the assumption of simple inverse proportionality between the variation of conductivity, due to network formation, and viscosity allow a universal plot of time variation of conductivity to be composed, which is able to predict the conductivity of the extruded fibres. The same TPU/CNT fibres were also demonstrated to possess good strain sensing abilities, which makes them good candidates for applications in smart textiles.

The electric polarization of ferroelectric polymers with tailored structures was studied using the terahertz time-domain spectroscopy technique combined with impedance analysis.