Bottom-Up Self-Assembly of Nanofibers in the Surfactant Mixture of CTAB and Pluronics

Bottom-up self-assembly of nanofibers in a chemical method is presented using the surfactant mixture of cetyltrimethylammonium bromide (CTAB) and Pluronics as the anisotropic micellar templates. Fully fluorinated perfluorooctanoic acids with highly hydrophobic C-F chains are necessary for inducing exceptionally long fibers.. Ag(I) provides robustness of the materials by the complexation with ethylene oxides in Pluronic copolymers, and the distribution of Ag is broadly observed on the surface of nanofibers. Fluorocarbons reside in the PPO(polypropylene oxide) blocks in Pluronic polymers and accordingly in inverse micelle structures, they are placed in the surrounding regions of nanofibers. Nanofibers with relatively high aspect ratios were obtained when Pluronic copolymers with low number average molecular weights (M_n) such as L-31 (M_n ~ 1100) and L-64 (M_n ~ 2900) were used. Heterogeneous catalytic activities of these nanofibers were monitored in the reduction reactions of 4-nitrophenol, and the nanorods prepared from the inverse micelles of Pluronic 31R1 show the best catalytic performances with a rate constant of 0.00235 s^-1. The roles of fluorine or C-F groups in perfluorooctanoic acids are believed to be the disruption of hydrogen bonding between water and PEO groups, and the phase separation of nanofibers from the aqueous environment by the dehydration of hydrophobic cores.