Marshmallow-like Macroporous Silicone Monoliths as Reflective Standards and High Solar-Reflective Materials

Abstract

The growing need to expand outdoor remote sensing using drones and robots and to mitigate the urban heat island effect has led to an increasing demand for highly reflective materials suitable for outdoor use. I have successfully developed flexible macroporous silicone monoliths that exhibit high diffuse reflectance due to Mie scattering caused by the skeletal structure. The porous silicone materials were prepared by a two-step acetic acid−triethanolamine catalyzed surfactantfree sol−gel process using tetra-, tri-, and difunctional silicon alkoxides as co-precursors. In the optimal sample, the material exhibited a total reflectance of more than 97.5% in the 400−1100 nm wavelength. This range corresponds to the light detection range of silicon diodes. The optical property suggests potential applications for the silicone monoliths as simple optical calibration targets (reflective standard), providing a viable alternative to conventional materials such as porous polytetrafluoroethylene or barium sulfate. In addition, high reflectance of the material surfaces across the solar spectrum results in a significant reduction of increased surface temperature when exposed to direct sunlight. With its combination of reflectivity, water repellency, UV resistance, low thermal conductivity, and mid-infrared radiation properties, the macroporous silicone monolith offers promising potential for outdoor thermal management applications.