Optical surfaces coated with a thin layer to improve Light transmission are ubiquitous in everyday optical applications as well as in industrial and scientific instruments. Discovered first in 1817 by Fraunhofer, the coating of Lenses became standard practice in the 1930s. In spite of intensive research, broadband antireflection coatings are still limited by the Lack of materials with Low refractive indices. A method based on the phase separation of a macromolecular Liquid to generate nanoporous polymer films is demonstrated that creates surfaces with high optical transmission.