“Grafting to”D route to high-k and low-loss PS@BaTiO<inf>3</inf> nanocomposites for energy storage applications

Abstract

Polystyrene@BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (PS@BT) nanomposites with high dielectric constant and low dielectric loss were prepared by using the grafting to strategy. In this method, PS macromolecules with different molecular weights were first prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and then the PS macromolecules were grafted onto the surfaces of BT nanoparticles by using a so-called thiolene click reaction. Transmission electron microscopy (TEM) was used to confirm the successful fabrication of the core-shell structured PS@BT nanocomposites. Frequency dependent dielectric constant and dielectric loss tangent were measured at room temperature by a broadband dielectric spectroscopy. The room temperature electric displacement-electric field (D-E) loops were measured by a ferroelectric polarization tester and the power energy storage of the nanocomposites was calculated accordingly. Our results showed that, regardless of the molecular weight, all the nanocomposites exhibit significantly enhanced dielectric constant but low dielectric loss tangent. In addition, it is found that the molecular weight of the polymer chains play an important role in determining the dielectric loss tangent of the nanocomposites, particularly at low frequencies, whereas only resulting in marginal difference in dielectric constant and energy density of the nanocomposites. Compared with other methods such as the “grafting from” route, the unique feature of this approach is that we can control the molecular weight of the polymer shell (i.e., polymer matrix) and tune the dielectric loss by tailoring the molecular weight of the polymer shell.