Molecular orientation of single and two-armed monodendron semifluorinated chains on "soft" and "hard" surfaces studied using NEXAFS

Citation
J. Genzer et al., Molecular orientation of single and two-armed monodendron semifluorinated chains on "soft" and "hard" surfaces studied using NEXAFS, MACROMOLEC, 33(16), 2000, pp. 6068-6077
Citations number
34
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
MACROMOLECULES
ISSN journal
00249297 → ACNP
Volume
33
Issue
16
Year of publication
2000
Pages
6068 - 6077
Database
ISI
SICI code
0024-9297(20000808)33:16<6068:MOOSAT>2.0.ZU;2-6
Abstract
Near-edge absorption fine structure (NEXAFS) measurements are used to probe the molecular orientation of semifluorinated (SF) mesogens, -(CH2)(x)(CF2) (y)F, which are attached to (i) the isoprene backbone of polyisoprene or a styrene-isoprene diblock copolymer ("soft" substrate), and (ii) a Au-covere d solid substrate via a thiol link ("hard" substrate). The SF groups on bot h surfaces are oriented and on average are tilted from the sample normal. T he tilt angle, [tau(F)-helix], of the fluorinated part of the SF group on e ach substrate is determined exclusively by the combination of x and y, incr easing with increasing x and with decreasing y. Moreover, [tau(F)-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 the architecture of the SF group (single vs 2-armed monodendron). Comparing the orientation of the SF groups on both substrates reveals that [tau(F)-helix ] is approximately 14 degrees higher on the "soft" substrate.