Hierarchically Superhydrophobic Stereo-Complex Poly (Lactic Acid) Aerogel for Daytime Radiative Cooling

摘要

Passive radiative cooling technology provides a sustainable way of coolingby the combination of emitting heat to the cold universe and reflecting solarlight without any energy input. However, the massive consumption of nondegradableradiative cooling materials causes resource waste and environmentalpollution. Meanwhile, the cooling efficiency can be easily affectedby dirt contamination in outdoor environments. Here, by the combinationof biomimetic hierarchical structure design and stereo-complex crystals, adegradable and superhydrophobic (152°) stereo-complex poly (lactic acid)aerogel with low thermal conductivity (37 mW m~（–1） K~（–1）), high compressionstrength (0.1 Mpa) and self-cleaning ability via a simple water-assisted thermallyinduced phase separation method is developed. The optimal aerogelhas a high sunlight reflection (89) and strong infrared emissivity (93) thatgets a temperature drop of 3.5 ℃ during the daytime and 5.8 ℃ during thenighttime. This aerogel opens an environmentally sustainable pathway toradiative cooling applications.