Healing Materials for Harsh Space Environments: Intrinsic Self-Healing Copolyimides for Lunar Exploration

Future lunar exploration missions pose critical challenges to the use of polymeric materials because of severe mechanical abrasion induced by the lunar regolith dust. Lunar regolith is adhesive, sharp, and highly abrasive, particularly when interacting with exposed equipment. As a result, material surfaces can undergo mechanical damage, which may progressively degrade system performance and ultimately lead to mission failure. Polyimides (PIs) are high-performance polymers widely used in space applications thanks to their excellent thermo-mechanical stability, low outgassing, and chemical resistance. PIs are widely employed in different systems, from satellites in low Earth orbit (LEO) to components for future lunar missions. For LEO applications, PIs are commonly utilized as multilayer insulating systems, as a component of flexible solar arrays, deployable and inflatable structures, as wellas in solar propulsion sails for deep space missions. However, conventional fully aromatic PIs possess rigid backbones that limit polymer chain mobility, preventing intrinsic self-healing and making them susceptible to progressive surface damage under abrasive lunar conditions. In this work, a class of semi-aromatic branched copolyimides (coPIs) with intrinsic self-healing is developed and investigated for potential application in the lunar environment. The coPIs are synthesized by reacting aromatic and aliphatic monomers at different stoichiometric ratios. The aromatic content improves the thermal stability, while the aliphatic content allows the self-healing. The aim of this work is to find a balance between resistance and stability to harsh conditions (UV exposure, extreme thermal cycling, ultra-low vacuum) and the material’s self-healing ability. Chemical structures are confirmed by Fourier transform infrared (FTIR) spectroscopy, while thermo-mechanical properties and self-healing ability and efficiency are systematically investigated via dynamic mechanical analysis (DMA) and confocal microscopy under specific conditions to assess their suitability for lunar applications. Semiaromatic coPIs exhibit efficient intrinsic, thermally activated self-healing via chain interdiffusion and supramolecular interactions. Overall, semi-aromatic branched coPIs combine mechanical robustness, low density, and intrinsic self-repair, making them promising materials for long-duration lunar missions.