The synthesis and characterization of superhydrophobic polyimides and copolyimides are presented. These polymers have been designed through a suitable choice of dianhydride and diamine monomers and incorporation of a siloxane oligomer comonomer to produce materials for mitigation of lunar dust adhesion. Lunar dust represents a major obstacle to long-duration robotic and crewed missions as its strong adhesion and abrasive nature threaten the reliability of surface systems and habitats. The synthesized polyimides and copolyimides show inherently high-performance, lightweight, and heat resistance and, in addition, exhibit superhydrophobic properties with low surface energy and adhesion properties for lunar dust regolith. The synthetic strategy is based on the use of fluorinated dianhydride and/or diamine monomers that allow incorporation of trifluoromethyl side groups within the molecular structure of the homopolyimides and incorporation of siloxane functionalities through copolymerization of diamine and dianhydride monomers with amino-terminated polydimethylsiloxane oligomers of different molecular masses. The bulky −CF3 groups contribute to decreasing the surface energy of the outermost layers of the material, reducing adhesion properties, and enhancing its hydrophobicity. Moreover, the siloxane units act as surface migrating agents as they easily migrate from the interior of the material and segregate onto the surface contributing to a further increase in hydrophobicity and a decrease of adhesion properties. These properties have been demonstrated by the high values of the water contact angles exhibited by these materials up to a remarkable value of 120°, much higher than the value of 82° measured for a well-known commercial polyimide Kapton film, without compromising outstanding thermal and mechanical properties.
Stefano et al. (Tue,) studied this question.