Superhydrophobic and breathable resorcinol-formaldehyde Xerogels

A new macroporous, waterproof and breathable material has been synthetized. The synthesis of these materials consists in a modified version of the classical resorcinol-formaldehyde (RF) xerogels synthesis. This new process includes a further treatment, after the gelation-curing-drying process, with methanol at 240 °C in order to passivate the hydrophilic phenolic groups of the surface of the RF xerogel. It was found that the treatment time strongly depends on the pore size of the xerogels. After reaching a threshold time, the hydrophilic materials become superhydrophobic. It is postulated that the exohedral inner surface of the porous xerogels, different from most porous materials, is responsible for this behavior. Although the materials exhibit a superhydrophobic behavior against liquid water and maintain its waterproofness for a long period of time, they are able to adsorb/desorb water vapor, which makes them also breathable.