| Abstract
| - Near-edge absorption fine structure (NEXAFS) measurements are used to probe themolecular orientation of semifluorinated (SF) mesogens, −(CH2)x(CF2)yF, which are attached to (i) theisoprene backbone of polyisoprene or a styrene-isoprene diblock copolymer (“soft” substrate), and (ii) aAu-covered solid substrate via a thiol link (“hard” substrate). The SF groups on both surfaces are orientedand on average are tilted from the sample normal. The tilt angle, 〈τF-helix〉, of the fluorinated part of theSF group on each substrate is determined exclusively by the combination of x and y, increasing withincreasing x and with decreasing y. Moreover, 〈τF-helix〉 is found to be independent of the surface topology(flat surfaces vs surfaces covered with holes or islands of the copolymer), casting solvent, and thearchitecture of the SF group (single vs 2-armed monodendron). Comparing the orientation of the SFgroups on both substrates reveals that 〈τF-helix〉 is approximately 14° higher on the “soft” substrate.
|
