Abstract
Materials that have high dielectric constants, high energy densities and minimum dielectric losses are highly desirable for use in capacitor devices. In this sense, polymers and polymer blends have several advantages over inorganic and composite materials, such as their flexibilities, high breakdown strengths, and low dielectric losses. Moreover, the dielectric performance of a polymer depends strongly on its electronic, atomic, dipolar, ionic, and interfacial polarizations. For these reasons, chemical modification and the introduction of specific functional groups (e.g., F, CN and R−S(=O)2−R´) would improve the dielectric properties, e.g., by varying the dipolar polarization. These functional groups have been demonstrated to have large dipole moments. In this way, a high orientational polarization in the polymer can be achieved. However, the decrease in the polarization due to dielectric dissipation and the frequency dependency of the polarization are challenging tasks to date. Polymers with high glass transition temperatures (Tg) that contain permanent dipoles can help to reduce dielectric losses due to conduction phenomena related to ionic mechanisms. Additionally, sub-Tg transitions (e.g., γ and β relaxations) attributed to the free rotational motions of the dipolar entities would increase the polarization of the material, resulting in polymers with high dielectric constants and, hopefully, dielectric losses that are as low as possible. Thus, polymer materials with high glass transition temperatures and considerable contributions from the dipolar polarization mechanisms of sub-Tg transitions are known as “dipolar glass polymers”. Considering this, the main aspects of this combined strategy and the future prospects of these types of material were discussed.
Highlights
The development of innovative materials with outstanding dielectric properties has attracted much attention due to their potential applications in energy storage, digital memory devices, Polymers 2019, 11, 317; doi:10.3390/polym11020317 www.mdpi.com/journal/polymersPolymers 2019, 11, 317 pulsed power systems, and signal processing
These results indicate that the dipole density is, notably, involved in the increase in the dielectric constant. Based on these outstanding physical properties, these polymers have been identified as promising dielectric materials for energy storage applications [12]. Another interesting prospect emerges from the use of elastomer dielectric materials, which explores the oxidation of the thioether groups present in polysiloxanes
Dipolar glass polymers have emerged as promising versatile materials for a wide variety of energy
Summary
The development of innovative materials with outstanding dielectric properties has attracted much attention due to their potential applications in energy storage, digital memory devices, Polymers 2019, 11, 317; doi:10.3390/polym11020317 www.mdpi.com/journal/polymers. The main reason for the synergistic combination of polymers and nanosized particles lies in the low dielectric permittivities (~2–3 at frequencies of 1 MHz) that tend to be exhibited by conventional polymers that are fabricated on a large scale, such as poly(ethylene), poly(styrene), and poly(propylene) This clearly limits the possible application of these types of polymers in capacitors or energy storage devices. Polymers containing nanostructured because of the polarizability thiophene domains have exhibited high permittivities and relatively low dielectric losses. This has which would enhance the dielectric propertiesmultiple of the polymer material. A variety of π-conjugated thiophene oligomer-containing polymers have been high dielectric constants and low dielectric losses in the 100 Hz–4 MHz range of frequencies. Ademonstrated variety of π-conjugated thiophene oligomer-containing have been storage demonstrated to be potentially applicable as technological materials for energy storage capacitors
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