Polyimides are a widely used class of high-temperature materials. They are used in microelectronics devices and packages as electrical insulators, and also find application in corrosion protection, α-particle barriers, and wire insulation for example. Polyimides (PI) are usually applied from either poly(amic acid) (PAA) or poly(amic ester) (PAE) solutions onto substrates and cured at elevated temperatures (up to 400°C) in inert ambients [1–9].