title: Surface ordering of a perfluorinated, self-assembled, dendrimer on a water subphase.
abstract: We have investigated the surface ordering of a synthetic, asymmetric, fan-shaped dendrimer containing a carboxyl core and perfluorinated tails which was obtained by the esterification of the intermediary. X-ray diffraction patterns and transmission electron microscopy (TEM) images show the molecules self-assemble into a hexagonal, cylindrical mesophase. Surface pressure-area isotherms and Brewster angle microscopy measurements show the molecule forms a stable monolayer at the air-water interface with a single phase transition. As a condensed monolayer, the perfluorinated tails are well-packed with hexagonal symmetry with (10) spacing of approximately 0.5 nm from molecular-scale atomic force microscopy (AFM) images. Such dense molecular-scale packing has not been observed in other dendritic molecules thus far. Compared to the case of conventional dendritic molecules with alkyl tails, these molecules occupy a much smaller molecular area due to the strong microphase separation between the carboxylic core and perfluorinated tails at the air-water interface. After monolayer collapse, the irregular islands with terrace morphology are observed in contrast with conventional alkyl-terminated self-assembled dendritic molecules where irregular islands do not appear. The interfacial and internal structure of every terrace shows planar columnar morphology from AFM and TEM imaging. From these results, we discuss the stability of perfluorinated, self-assembled dendrimers on water, as well as how to generate planar morphology on a hydrophilic surface.
authors.affiliation: Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 Korea.
authors.forename: Su Rim
authors.initials: SR
authors.lastname: Lee
authors.forename: Dong Ki
authors.initials: DK
authors.lastname: Yoon
authors.forename: Sang-Hyun
authors.initials: SH
authors.lastname: Park
authors.forename: Eun Ho
authors.initials: EH
authors.lastname: Lee
authors.forename: Yun Ho
authors.initials: YH
authors.lastname: Kim
authors.forename: Patrick
authors.initials: P
authors.lastname: Stenger
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Zasadzinski
authors.forename: Hee-Tae
authors.initials: HT
authors.lastname: Jung