Transparent Self-Cleaning Coatings Repellent to Ultralow Surface Tension Liquids in Extreme Environments

Abstract

Self-cleaning coatings have been garnering significant attention for their ability to reduce surface pollution by repelling liquids. However, creating transparent self-cleaning coatings that effectively repel ultralow surface tension liquids in harsh environments, like extremely high or low temperature environments, remains a challenge. Here, a transparent omniphobic coating (PMAPOSS-co-PFMA) is reported to achieve the repellency of droplets with surface tensions down to 15.5 mN·m-1(n-pentane), even at temperatures up to 160°C and down to -70°C. The coating is engineered by grafting fluoropolymer with fluoroalkyl side chains onto the rigid polyhedral oligomeric silsesquioxane framework. The fluoroalkyl side chains tend to crystallize on the coating's surface, resulting in its low surface tension (measured at 9.39 mN·m-1). The incorporation of the robust POSS significantly enhances the coating's chemical, mechanical, and thermal stability. Moreover, with low roughness (Ra = 1nm), the coating has a light transmittance of 90.5%, surpassing untreated glass by 3.2%. Heated at 80°C, the migration of the long-fluorinated polymer chains within the PMAPOSS-co-PFMA coating enables its self-healing properties upon damage. These results provide a new perspective to develop versatile self-cleaning omniphobic coatings suitable for practical applications in extreme environments, such as asphalt transport pipes operating in high-temperature conditions.

Keywords: transparency, ultralow surface tension, self-healing, high and low temperature resistance