Dual regulation of flexible chain segments and dynamic covalent bonds for a self-healable copolyimide

Abstract

Polyimide (PI) is an indispensable material in the field of electrical insulation devices owing to its high mechanical strength, high insulating properties and excellent thermal stability. However, the rigid structure not only gives PI these excellent properties but also makes it difficult for PI to self-heal, be recycled, and reused. Herein, a self-healable PI (SHPI) film is developed by the synergistic combination of dynamic disulfide bonds and flexible polysiloxane molecules (PDMS). Two functional monomers are introduced into the PI matrix through simple copolymerization, which confers excellent self-healing and recycling abilities. Furthermore, the SHPI retains high thermal stability with thermal decomposition temperature at 5 wt% weight reduction (T_d5%) = 427 °C and good breakdown strength (E₀ ∼ 318 MV m⁻¹). Moreover, carbon fiber (CF) reinforced composite films (CFRCs) by combining SHPI with CFs are also produced, and they exhibit excellent mechanical strength and load-bearing capacity. The CFs can be reused multiple times with a recycling efficiency of nearly 100%. The SHPI is expected to have widespread use and popularity in the field of electrical insulation as an excellent recyclable insulation material.