Dipole Glass Polymerwith High Dielectric ConstantBased on Side Chain Functionalized Poly(ether ether ketone)

A new dipolar glass polymer, sulfonylated poly(ether ether ketone) (PPLM–PEEK-SO₂), was designed and synthesized using the postfunctionalization of <i>o</i>-cresolphthalein units. The methyl sulfonyl group, as a side chain with a large dipole moment of 4.25 D, could well utilize the free volume (FV) provided by the rigid skeleton structure. This enhanced orientational polarization resulted in a high dielectric constant of 4.55 and a low loss of 0.0057 at 25 °C and 100 Hz for PPLM–PEEK-SO₂. In addition, PPLM–PEEK exhibited excellent discharge energy density, and the discharge efficiency (η) maintained about 97% at room temperature when the electric field increased from 50 to 500 MV/m. And even at 150 °C and 300 MV/m, it can also be as high as 95.42%, which is suitable for high-temperature energy storage. Moreover, PPLM–PEEK-SO₂ exhibited a higher energy storage density, such as 3.8 J/cm³ at 100 °C and 450 MV/m.