Self-Assembly Structures of Nonionic Surfactants at Graphite/Solution Interfaces

The interfacial self-assembly structures of a series of poly(oxyethylene) n-dodecyl ether (C12En) nonionic surfactants on graphite has been imagedby atomic forcemicroscopyusing only the steric stabilization force as the contrast mechanism. Aggregates are arranged in parallel stripes perpendicular to the underlying graphite symmetry axes for C12E5-C12E10. These are interpreted as hemicylindrical micelles, consistent with previous studies of ionic surfactants adsorbed on graphite. C12E23 shows a featureless layer and C12E3 forms an anchored lamellar phase growing normal to the graphite surface. We relate the interfacial structures to those formed in bulk solution and show that the initially adsorbed molecules template the interfacial aggregates, modifying their self-assembly behavior.