High-temperature semicrystalline/amorphous polymer blends exhibiting enhanced dielectric constant with high breakdown strength

High-temperature polymers with high dielectric constant (K) and breakdown strength are of great interest in many electronic and electric devices and systems. Blending different polymers is a general and highly scalable strategy to improve polymer performance. We investigate two types of semicrystalline polyimide (PI) with different chemical structures blended with amorphous polymer poly (1,4-phenylene ether sulfone) (PES). They formed immiscible polymer blends and exhibited distinctively semicrystalline/amorphous behaviors. The blends of 4,4’-biphthalic anhydride (BPDA)-typed PI with PES form semicrystalline polymer phases and the blend at 50/50 wt% composition exhibits an increased dielectric constant while maintaining the high breakdown field of the neat PI(BPDA) at E_b of 600 MV/m. In contrast, blends of pyromellitic dianhydride (PMDA)-typed PI and PES, which form amorphous phases, show a dielectric increase but a large reduction in E_b. Computational simulations indicate that PI(BPDA) assumes a preferred orientation on PES, which expedites crystallization, while overlaying PI(PMDA) on PES results in more disorder and larger voids. Our finding that the PI(BPDA)/PES blends at 50/50 wt% composition generates enhancement in K without negatively affecting E_b is the first in polymer blends. The results suggest that strategically designing high-temperature polymer blends and exploiting the crystallites within the polymer matrix can achieve an enhanced dielectric constant while maintaining a high breakdown strength. This approach is highly scalable and low cost, thus paving the way for developing practical and high-performance dielectric polymers with high energy density and broad operating temperatures.