Fluoride ion encapsulated polyhedral oligomeric silsesquioxane: A novel filler for polymer nanocomposites with enhanced dielectric constant and reduced dielectric loss

Polymer dielectrics have been considered as an ideal choice for preparation of advanced power and electronic systems as their good comprehensive performances. However, it remains a challenge to obtain polymer dielectrics with high dielectric constant (epsilon(r)), low dielectric loss (tan delta) and high temperature capability. Although adding high permittivity inorganic nanofillers has become a promising approach to improve the epsilon(r) of polymers, it usually causes the adverse increment tan delta. Herein, we demonstrate that fluoride ion encapsulated polyhedral oligomeric silsesquioxane (POSS@F-) can be regarded as a novel filler to enhance the epsilon(r )and reduce the tan 5 of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) simultaneously. Compared with the pristine PPO, the epsilon(r) of PPO/POSS@F- composite can be enhanced from 2.81 to 5.31, while its tan delta is still relatively low (0.0011 at 1 kHz). Meanwhile, the breakdown strength of PPO can also be slightly reinforced from 334.9 kV/mm to 394.0 kV/mm. Owing to the good thermal properties of PPO and POSS@F-, these composites exhibit good dielectric properties and improved dimension stability at high temperature. We believe that these results are particularly important for the preparation of advanced dielectric materials for desirable applications.