Dipolar Glass Polymers Containing Polarizable Groups as Dielectric Materials for Energy Storage Applications. A Minireview

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.

Studies of the effect of temperature on charge accumulation in PVDF-PMMA double-layered thin films based on depolarization current measurements

“…The space charge polarization is characterized by a peak at its glass transition temperature and dipolar polarization is due to the motion of the side group of polymers at low temperatures. 33 The low temperature in PVDF is related to the local motions of the frozen in main chains in the amorphous region of semi-crystalline polymer and the high-temperature peak is associated with molecular motions in amorphous-crystalline boundaries. 34,35 In air-gap TSDC, the charge carriers are not in the position to join with the image charges at the adjoining electrode due to blocking of the electrode by the adjacent air-gap.…”

High-Performance Triboelectric Devices via Dielectric Polarization: A Review

“…On the other hand, the dipole moment can be modified by introducing polar single molecules [58], such as -CN, -NO 2 , and -SO 2 -, or polar polymers [59][60][61], including polystyrene, poly(2-hydroxyethyl methacrylate), and poly(dopamine methacrylamide), which allow the rotation of dipoles in the free volume of polymers, thereby leading to an improvement in the dielectric constant. Dipolar polarization has been recently utilized to increase the dielectric Fig.…”

“…On the other hand, the dipole moment can be modified by introducing polar single molecules [ 58 ], such as –CN, –NO 2 , and –SO 2 –, or polar polymers [ 59 – 61 ], including polystyrene, poly(2-hydroxyethyl methacrylate), and poly(dopamine methacrylamide), which allow the rotation of dipoles in the free volume of polymers, thereby leading to an improvement in the dielectric constant. Dipolar polarization has been recently utilized to increase the dielectric constant of triboelectric materials by attaching polar groups with large dipole moments to the side chain of polymers [ 22 ]; Lee et al demonstrated that the PVDF-graft copolymer remarkably increased the triboelectric output performance (Fig.…”

“… In addition to dielectric polymer nanocomposites, modifying polymer chain structures can enhance the dielectric properties because of the dipolar polarization through the improved dipole moments. Until now, polymeric materials with high dielectric constants have been synthesized by grafting polarizable components [ 58 , 60 ] or by engineering nanostructures [ 61 , 62 , 75 , 76 ], which increases the dielectric constant by dipolar polarization. Polymer-based dielectric materials are good candidates for use as triboelectric materials because of their physical properties, such as flexibility and solution-processability, which facilitate the development of printable triboelectric devices for next-generation wearable applications.…”

Molecular Weight Enables Fine-Tuning the Thermal and Dielectric Properties of Polymethacrylates Bearing Sulfonyl and Nitrile Groups as Dipolar Entities

“…This mechanism stands out over the others by achieving a high polarized state while keeping a relatively low dissipation behavior, since other mechanisms capable of reaching high polarizations (e.g., ionic and interfacial), usually depend on the presence of ionic species, whose diffusion increases the dissipative character of the material, in addition to affecting its much-needed insulating property [1,12,13]. To date, there is a significant number of reports that summarize and explain the physics and chemistry behind this class of materials, allowing to improve their understanding [12][13][14][15][16][17][18].…”