Mortise-and-tenon molecular chains enable polymeric hexagonal crystallinity with superior high-temperature capacitor performance.

High-symmetry crystalline materials exhibit superior physical properties. However, polymers lack high-symmetry crystals due to their long-chain characteristics. Herein, we report that all-trans poly(adamantane-norbornene-imide) can form high-symmetry hexagonal crystal, exhibiting superior electrical insulation properties and capacitor performances at an elevated temperature of 250°C, characterized by a high breakdown voltage of 802 megavolts per meter, and a notable discharged energy density of 7.29 joules per cubic centimeter, which surpasses all previously reported polymers. We propose that the mortise-and-tenon interlocking between adamantane side groups in polymer chains enables perfectly symmetrical alignment of polymer molecular chains, thereby addressing the challenge of forming high-symmetry crystals in polymers. We anticipate that the mortise-and-tenon interlocking mechanism of polymer chains will lead to the development of more polymers with high-symmetry crystal and superior physical properties.