Existence of Two‐Dimensional Physical Gels even at Zero Surface Pressure at the Air/Water Interface: Rheology of Self‐Assembled Domains of Small Molecules

Films of mesoscopic domains self‐assembled from fluorocarbon/hydrocarbon diblock copolymers (FnHm) at the air/water interface were found to display highly elastic behavior. We determined the interfacial viscoelasticity of domain‐patterned FnHm Langmuir monolayers by applying periodic shear stresses. Remarkably, we found the formation of two‐dimensional gels even at zero surface pressure. These monolayers are predominantly elastic, which is unprecedented for surfactants, exhibiting gelation only at high surface pressures. Systematic variation of the hydrocarbon (n=8; m=14, 16, 18, 20) and fluorocarbon (n=8, 10, 12; m=16) block lengths demonstrated that subtle changes in the block length ratio significantly alter the mechanics of two‐dimensional gels across one order of magnitude. These findings open perspectives for the fabrication of two‐dimensional gels with tuneable viscoelasticity via self‐assembly of mesoscale, low‐molecular‐weight materials. Gelbildung organischer Monoschichten: Hochelastische zweidimensionale Gele können bei einem Oberflächendruck von 0 mN m−1 aus mesoskopischen Oberflächendomänen von Fluorkohlenstoff/Kohlenwasserstoff‐Diblockcopolymeren (FnHm) erhalten werden. Die Grenzflächenviskoelastizität der FnHm‐Monoschichten wurde durch Anwendung periodischer Scherspannung bestimmt.