NIR reflective surfaces based on organic coatings

Poor attention has been paid so far to the 50% of NIR radiation flux (750-2500 nm), coming from direct, diffused and reflected sun radiation, which contributes to increase the temperature in urban areas. To reduce the increasing demand for energy consumption for air conditioning or to produce cool fabrics, there is a need for NIR reflective pigments and coatings formulation since reflecting the sun’s radiation minimizes the amount of energy absorbed by the surface (1). To date, NIR reflectivity is obtained with the use of inorganic pigments such as expensive metal oxides and complexes (2). The key to obtaining innovative cool pigments is instead the production of NIR reflective organic molecules to avoid the inconveniences related to costs, environmental impacts, while maintaining the efficiency and color provided by the current inorganic pigments. This work aims at the preparation of organic coatings containing designed perylene- and naphthalene-bis imides properly functionalized with peripheral moieties able to confer the desired color and NIR reflectivity according to the π-π stacking behavior of the extended conjugated nuclei (3). Notably, different pigment formulations are prepared from commercially available resin dispersions in water and the NIR reflective features of the derived coatings are discussed in terms of the utilized pigments, additives and their content, and compared with those of commercially available inorganic benchmarks.