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

WY Zhu and GC Rui and WC Lu and EL Briggs and J Bernholc and Q Zhang, NANO ENERGY, 128, 109898 (2024).

DOI: 10.1016/j.nanoen.2024.109898

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 Eb 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 Eb. 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 Eb 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 highperformance dielectric polymers with high energy density and broad operating temperatures.

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