In this report, a dipolar glass polymer, poly(2-(methylsulfonyl)ethyl methacrylate) (PMSEMA), was synthesized by free radical polymerization of the corresponding methacrylate monomer. Due to the large dipole moment (4.25 D) and small size of the side-chain sulfone groups, PMSEMA exhibited a strong γ transition at a temperature as low as -110 °C at 1 Hz, about 220 °C below its glass transition temperature around 109 °C. Because of this strong γ dipole relaxation, the glassy PMSEMA sample exhibited a high dielectric constant of 11.4 and a low dissipation factor (tan δ) of 0.02 at 25 °C and 1 Hz. From an electric displacement-electric field (D-E) loop study, PMSEMA demonstrated a high discharge energy density of 4.54 J/cm(3) at 283 MV/m, nearly 3 times that of an analogue polymer, poly(methyl methacrylate) (PMMA). However, the hysteresis loss was only 1/3-1/2 of that for PMMA. This study suggests that dipolar glass polymers with large dipole moments and small-sized dipolar side groups are promising candidates for high energy density and low loss dielectric applications.

Over the past decades, it has been commonly considered that ferroelectricity is closely related to the polar crystalline structure of odd-numbered nylons, and even-numbered nylons should not exhibit ferroelectricity due to their nonpolar crystalline structures. In this work, we ask a fundamental question: Are odd-numbered nylons with polar crystalline structures prerequisites for ferroelectricity? Here, ferroelectric properties are reported for mesomorphic even-numbered nylons (nylons-12 and -6) quickly quenched from the melt, using electric displacement–electric field (D–E) hysteresis loop measurements. From X-ray diffraction and infrared studies, the structure of the mesophases in the quenched samples was considered to contain multiple twists in the chain conformation, resulting in enlarged interchain distance and dangling/weak hydrogen bonds. Upon high field electric poling, the mesophase structure enables dipolar switching of the dangling/weak hydrogen bonds, forming electric-field-induced ferroelectric domains with twisted chain conformations in the crystal. The domain sizes in even-numbered nylons should be smaller than those in odd-numbered nylons, and thus D–E hysteresis loops should be slimmer. This study shows that odd-numbered nylons and polar crystalline structures are not prerequisites for ferroelectricity in nylons. Instead, mesophases with enlarged interchain spacing and disordered hydrogen bonds are the key to ferroelectricity. The knowledge obtained from this study will help us design new nylons and nylon copolymers with defective crystalline structures for enhanced ferroelectric properties.

A new class of high-temperature dipolar polymers based on sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) (SO -PPO) was synthesized by post-polymer functionalization. Owing to the efficient rotation of highly polar methylsulfonyl side groups below the glass transition temperature (T ≈220 °C), the dipolar polarization of these SO -PPOs was enhanced, and thus the dielectric constant was high. Consequently, the discharge energy density reached up to 22 J cm . Owing to its high T , the SO -PPO sample also exhibited a low dielectric loss. For example, the dissipation factor (tan δ) was 0.003, and the discharge efficiency at 800 MV m was 92 %. Therefore, these dipolar glass polymers are promising for high-temperature, high-energy-density, and low-loss electrical energy storage applications.

Novel ferroelectric properties, such as slim double and single hysteresis loop (DHL and SHL) behaviors, are attractive for high energy density and low loss dielectric applications. In this study, temperature-dependent ferroelectric behavior was studied for mesomorphic even-numbered nylons (i.e., nylon-12 and nylon-6) using electric displacement− electric field (D−E) loop measurements. Upon raising the temperature from room temperature to 100 °C, the D−E loops became increasingly narrower, finally leading to slim DHLs with significantly enhanced apparent dielectric constants (i.e., ∼30 and ∼60) and small remanent polarizations (i.e., 3.5 and 8.2 mC/m 2 ) for quenched and stretched nylon-12 and nylon-6, respectively. Combining wide-angle X-ray diffraction and infrared studies, changes in the mesophases and orientation of hydrogen-bonded amide groups after electric poling were used to unravel the structure−ferroelectric property relationship for the even-numbered nylons. At 100 °C, the quenched and stretched nylon-12 and nylon-6 films exhibited a paraelectric mesophase with twisted chain conformation and disordered hydrogen bonds. Upon high field poling (>100 MV/m), transient nanodomains could be generated with additional twists in the main chain. The observed DHL behavior was attributed to the electric-fieldinduced reversible transitions between the paraelectric (less twisted chains) and ferroelectric (more twisted chains) states in the mesomorphic crystals of even-numbered nylons. The knowledge gained from this study can inspire potential applications of nnylons for electric energy storage, e.g., high temperature and high energy density multilayer polymer film capacitors.

An ew class of high-temperature dipolar polymers based on sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) (SO 2 -PPO) was synthesized by post-polymer functionalization. Owing to the efficient rotation of highly polar methylsulfonyl side groups below the glass transition temperature (T g % 220 8 8C), the dipolar polarization of these SO 2 -PPOs was enhanced, and thus the dielectric constant was high. Consequently,the discharge energy density reached up to 22 Jcm À3 . Owing to its high T g ,t he SO 2 -PPO 25 sample also exhibited alow dielectric loss.F or example,the dissipation factor (tan d) was 0.003, and the dischargee fficiency at 800 MV m À1 was 92 %. Therefore,t hese dipolar glass polymers are promising for high-temperature,h igh-energy-density,a nd low-loss electrical energy storage applications.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.