ABSTRACTPorous polyimide (PI) materials containing lubricating oil have been widely used as bearing retainers in aerospace industry. High oil content and retention of porous bearing materials play an important role in assuring a successful mission of the spacecraft. Keeping both oil content and retention of bearing retainer materials high, however, is one of the bottlenecks to fulfill long lifetime missions. Chemical modification is expected to break this limitation by changing the surface properties. Inspired by this, here for the first time, the authors design a chemical method to improve silicon oil retention of porous PI samples. The results indicated that this modification could not only change the wettability of PI from hydrophilicity to hydrophobicity but also enhance the silicon oil retention from 52% to 87%. This strategy provides a novel approach to improve the oil retention of porous PI materials, which has the potential application in preparing bearing retainers with reliable, long‐term performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45106.