The surface molecular orientation of a liquid crystalline (LC) layer made up of semifluorinated (SF) single side groups [−CO−(CH2)
x
-
1−(CF2)
y
F] (single SF groups) attached to polyisoprene
homopolymer or the isoprene block of a styrene−isoprene diblock copolymer was determined by analyzing
the partial electron yield C-edge NEXAFS signal. The results show that the surfaces of thin SF polymer
films are covered with a uniform layer, consisting of the SF−LC groups whose average −CF2− tilt angle
with the surface normal lies in the range 29−46°. This is in direct contrast to the bulk, where the directors
of the SF−LC mesogens are aligned parallel to the polystyrene/SF−polyisoprene interface of the block
copolymers. This average tilt angle increases with increasing the length of the −(CH2)
x
-
1− group (x
increases) but decreases with increasing the length of the −(CF2)
y
− part of the molecule (y increases) at
constant x.
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