Construction of micro/macro‐scale Janus polypeptoid‐based two‐dimensional structures at the air–water interface

Abstract Janus two‐dimensional (2D) polymeric materials present asymmetric dual surfaces that enable a variety of applications of biosensors, catalysts, drug delivery, etc. This work reports the evaporation‐induced interfacial self‐assembly of amphiphilic block copolymer poly(ethylene glycol)‐ b ‐poly(N‐(2‐phenylethyl) glycine) (PEG‐ b ‐PNPE) at the air–water interface. The PEG‐ b ‐PNPE was initially assembled into a monolayer with a uniform thickness of ~2.5 ± 0.1 nm, which was mechanically compressed into a bilayer structure by Langmuir–Blodgett (LB) technology as surface pressure is exceeding the critical collapse pressure. Both monolayer and bilayer nanostructure span over hundreds of microns in both dimensions. The surface contact angle of the sample was measured by dynamic/static optical contact angle/interface tensiometer, which showed asymmetric wettability on the air side and the water side. The evolution from a monolayer to a bilayer was further tracked by an atomic force microscope. By the evaporation‐induced interfacial self‐assembly at the air–water interface, we also prepared macroscopic Janus films with a diameter of ~3.5 mm. The obtained micro/macro‐scale 2D materials have potential applications in nanoscience and biomedicine.