Flexible honeycomb films

Micro-porous polymer films with self-assembled honeycomb morphology produced by the 'breath figure' (BF)([1]) technique have distinct advantages over other lithographic techniques: there is no need for expensive equipment, and it is a simple and cheap process that can control pore sizes through varying casting conditions.([2]) These ordered porous films have potential applications particularly in biotechnology industries.([3]) Similar films have been made from a variety of polymers, for example, star polymers,([4]) and core cross-linked star (CCS) polymers.([5])The BF process involves the evaporation of a volatile solvent from a polymer solution in the presence of atmospheric humidity.([1]) The cooled solution surface (evaporative cooling) induces condensation of water droplets. These droplets self-assemble into an ordered array, and are stabilized by a precipitating polymer layer. After complete evaporation, a honeycomb-like scaffold remains.The porous films prepared by the BF technique are often prepared from polymers with a high glass transition temperature T-g, and hence brittle films are prepared, leading to high degree of cracking. If this process is to lead to commercial products, a new strategy is needed-the utilization of soft, visco-elastic polymer precursors.