Recently, the teams of Caihong Xu/Zongbo Zhang and Jian Jiang from the Institute of Chemistry, Chinese Academy of Sciences made important progress in the field of ultrathin, hard, flexible, and transparent coatings for extreme environments. To meet the growing demand for deployable spacecraft, flexible optical systems, and lightweight protective materials, the researchers proposed a cooperative hydrolysis-condensation strategy based on organopolysilazane (OPZ) and bis[3-(trimethoxysilyl)propyl]amine (BTMSPA). Through this strategy, an ultrathin transparent protective network dominated by ladder-like polysilsesquioxane (LPSQ) was constructed on polymer film surfaces. With a thickness of about 2 μm, the coating combines high hardness, excellent flexibility, high transparency, and outstanding resistance to simulated space environments, offering a new materials design approach for flexible aerospace devices, space optical materials, and advanced protective coatings.

With the rapid development of deployable spacecraft, next-generation flexible optical systems, and lightweight functional devices, polymer films have become important substrates for flexible optical components and space-deployable structures due to their light weight, high transparency, rollability, and deformability. However, polymer films usually suffer from low surface hardness, poor wear resistance, and limited resistance to radiation and atomic oxygen. Under extreme space conditions such as vacuum ultraviolet irradiation, high-energy radiation, thermal cycling, and atomic oxygen erosion, their performance can easily deteriorate. Therefore, achieving high hardness, flexibility, transparency, and environmental stability simultaneously in an ultrathin coating remains a major challenge in the field of protective coatings.

To address this challenge, the research team developed a cooperative hydrolysis-condensation strategy using OPZ and BTMSPA. In this system, the secondary amine groups in BTMSPA provide a weakly alkaline environment, promoting the hydrolysis of OPZ to generate silanols. The silanols then undergo co-condensation with OPZ-derived structures, guiding the formation of an ordered network dominated by LPSQ. Compared with a BTMSPA-only system, which tends to undergo rapid and disordered crosslinking, this cooperative system suppresses premature network densification and directs the coating network toward a gradually expanding ladder-like structure. As a result, the material achieves a molecular-level balance between hardness and flexibility.

According to public reports, the ultrathin transparent coating has a thickness of about 2 μm, a hardness of up to 0.73 GPa, an elastic recovery rate of about 80%, a transmittance of 94.1%, and an adhesion rating of 5B. It also maintains excellent stability in simulated space environment tests, including thermal cycling, gamma-ray irradiation, ultraviolet irradiation, atomic oxygen exposure, and lunar dust testing. In particular, the mass loss after atomic oxygen testing was only 7.5%, and the lunar dust removal efficiency reached 95.2%. The related research was recently published in Advanced Materials under the title “Ladder-Like Polysilsesquioxane Enable Space-Durable Ultrathin Hard-Yet-Flexible Transparent Coatings,” with the DOI 10.1002/adma.73354. The co-first authors are Yuny u Liu and Dingyu Hou, and the corresponding authors are Researcher Zongbo Zhang and Researcher Jian Jiang.

The core value of this study lies in its combination of reaction kinetics control and network topology design. By constructing an inorganic-dominated coating network, the researchers achieved high hardness, toughness, and transparency even at an ultrathin thickness. This work helps overcome the long-standing contradiction between traditional transparent hard coatings, which are often hard but brittle, and polymer coatings, which are flexible but less wear-resistant. It provides a general method for preparing ultrathin hard-yet-flexible coatings for extreme environments.

From an industrial application perspective, the significance of this achievement goes beyond the development of a high-performance transparent coating. More importantly, it presents a scalable materials design concept: by using the cooperative reaction between OPZ and the functional silane monomer BTMSPA, an ordered siloxane ladder-like network can be built under relatively mild conditions, enabling a balance among hardness, flexibility, transparency, and resistance to extreme environments. In the future, such materials may find applications in flexible solar arrays, deployable optical windows, flexible displays, protective films, radiation-resistant aerospace components, and high-end transparent wear-resistant coatings. For the organosilicon, polysilazane, silane coupling agent, and specialty coating raw material industries, this study also highlights the potential value of silicon-based functional materials such as OPZ and BTMSPA in advanced protective coating applications.

Source: Public research updates from the Institute of Chemistry, Chinese Academy of Sciences, and related Advanced Materials publication reports.