Periodic surface topology of three-arm semifluorinated alkane monodendron diblock copolymers

Scanning force microscopy has been used to reveal the surface topology of t he smectic B phase of(styrene-isoprene) diblock copolymers that have semifl uorinated (SF) alkane mesogens attached as three-arm monodendrons to the is oprene backbone. On the largest length scales, the block copolymers microph ase separate into well-known diblock copolymer microstructures and evidence of these can been seen in the surface topology. However, there are periodi c surface structures, so-called domes (with periodicities of about 18.5 nm) , that arise solely from the arrangement of the SF mesogens at the polymer surface. These domes are intrinsically independent of the much larger morph ology of the block copolymer. Very long range (ca. micrometers) ordering of the domes is possible for lamellar block copolymer microstructures if the surfaces are prepared by very slow cooling from the isotropic to the smecti c B phase. We infer that the domes arise because of spontaneous surface cur vature resulting from mesogen crowding within the monodendrons.