Investigation of new cooling paints actuated on hot days without electrical energy and labors

I New cooling paints were developed by exploiting the vaporization heat of water. These systems were constructed with N-isopropylacrylamide (NIPAAm) and butyl acrylate (BA). The homopolymer of NIPAAm is insoluble in water above ca. 32°C (hydrophobic), whereas it dissolves in water below the stated temperature (hydrophilic); therefore, application of the temperature responsive polymer on the outside of a house is difficult on cool and rainy days. By copolymerization of NIPAAm with a coating component of BA which is widely used for various commercial paints, water resistance was gained in this system. When the copolymer was applied to the wall of a model house, water molecules were adsorbed on the material from air during the night (below ca. 30°C) and the temperature of the room decreased if the outside temperature exceeded the temperature. The coating material could cool the room on hot days without using any electrical energy or labors, therefore this system can relieve the burden of energy consumption by air conditioners.