For decades, the materials that store electrical energy in flexible capacitors have been caught in a fundamental tension: improve one property, and another fails — a constraint that has quietly limited the ambitions of engineers designing electronics for extreme environments. A research team has now dissolved that tension at the molecular level, engineering polyetherimide copolymers whose hydrogen bonding networks allow polarization and thermal stability to reinforce rather than undermine each other, achieving remarkable energy storage performance at 200 degrees Celsius. The advance suggests t