Breath Figure in Reactive Vapor: A New Route to Nanopore Array

A breath figure (BF)-inspired method for preparing ordered porous films has attracted more and more attention because of its simplicity, low cost, and easy implementation. However, it remains a challenge to use this method to fabricate nanoscale porous structures without designed polymer architecture and auxiliary. Herein, we first report a facile method to fabricate BF arrays with nanopores (nanoBFAs) in reactive vapor. Depending on the chemical reaction between the formic acid (FA) droplet template and the polyvinylpyridine (PVP) segments in copolymer, we successfully create nanoBFAs by casting a PVP-containing copolymer solution in CS₂ in FA vapor. The condensed FA droplets can be instantly fixed by the PVP composition, and thus the growth and the aggregation of adjacent droplets are effectively restricted. Eventually, nanoBFAs are achieved in wide range solution concentration. In addition, binary porous structures with both nano- and microscale topology can be formed by using a FA/water mixed vapor with a one-step BF process. The produced nanoBFA films exhibit excellent antireflection performance with 0.5% reflectance, which is well-preserved even after hydrophobic treatment. This modified BF technique not only facilitates the elucidation of BFA formation mechanism but also opens a new way of fabricating nanoporous structures, which may have potential applications in electronic and optical devices.