Towards suppressing loss tangent: Effect of polydopamine coating layers on dielectric properties of core-shell barium titanate filled polyvinylidene fluoride composites

Barium titanate (BT) particles coated with different thickness of polydopamine (PDA) layers were incorporated into polyvinylidene fluoride (PVDF) to investigate influence of PDA coating layers on dielectric properties of composites. It is found that PDA coating layers not only effectively improved the interfacial interaction between BT particles and matrix but also significantly affected dielectric properties. PVDF composites loaded with modified BT exhibits superior dielectric properties in comparison with unmodified BT. Interfacial polarization is substantially suppressed because the catechol groups of PDA are able to constrain the mobility of nomadic charge carriers and ionizable hydroxyl groups on surface of BT particles. As a result, dependency of dielectric constant on frequency attenuates and tan δ is lowered to below 0.050 (1 kHz). The effect of suppression on tan δ tends to be more prominent as the thickness of PDA coating layer increases. The tan δ derived from ionic relaxation polarization is also constrained due to the chelation of PDA catechol groups with migrated cations. The as-prepared composites possess high dielectric constant and ultralow tan δ, making them promising for the industrial application as embedded capacitors.