High-Temperature Polymers With Record-High Breakdown Strength Enabled By Rationally Designed Chain-Packing Behavior In Blends

Polymers with high dielectric breakdown strength (E-b) over a broad temperature range are vital for many applications. The presence of weak points, such as voids and free volume, severely limit the E-b of many high-temperature polymers. Here, we present a general strategy to reduce these weak points by exploiting interchain electrostatic forces in polymer blends. We show that the strong interchain electrostatic interaction between two high-temperature polymers in blends of polyimide (PI) with poly(ether imide) (PEI) yields an extended polymer chain conformation, resulting in dense chain packing and a corresponding decrease in weak spots in the polymers. This leads to a greater than 65% enhancement of E-b at room temperature and 35% enhancement at 200 degrees C. In conjunction with results from blends of Pl/poly(1,4-phenylene ether-sulfone) (PSU) and blends of PEI/PSU, we show that this previously unexplored molecular engineering strategy is efficient and straightforward in minimizing weak points in dielectric polymers.