Simple fabrication of honeycomb- and pincushion- structured films containing thermoresponsive polymers and their surface wettability

A simple fabrication of honeycomb-and pincushion-structured films with thermoresponsive functionalities was investigated. Three types of poly(N-dodecylacrylamide-co-N-isopropylacrylamide), which have different copolymerization ratio between DAm and N-isopropylacrylamide (NIPAm), were synthesized by free-radical polymerization. The interfacial tension was strongly related to the stability of condensed water droplets in the polymer solution. Water droplets were embedded onto the solution surface when this tension was reduced. The interfacial tensions between chloroform solutions of polymer 1-3 and water were measured by using a typical pendant drop type interfacial tension meter. It was reported that PNIPAm shows its LCST at 32°C in water solution. On the other hand, the chloroform solution of polymer shows drastic transmittance decrease at 24°C when the visible light transmittance change was observed. The contact angle were higher on the honeycomb-structured films than on the flat film, but there was no discernible change in this angle with changing temperature.