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Superhydrophobic Hierarchically Assembled Films of Diblock Copolymer Hollow Nanospheres and Nanotubes
Reported
are the formation of rough particulate films from cross-linked diblock
copolymer vesicles and nanotubes and the wetting properties of the
resultant films. The diblock copolymers used were F<sub>66</sub>M<sub>200</sub> and F<sub>95</sub>A<sub>135</sub>, where the subscripts
denote the repeat unit numbers, whereas M, A, and F denote polyÂ(2-cinnamoyloxyethyl
methacrylate), polyÂ(2-cinnamoyloxyethyl acrylate), and polyÂ(2,2,2-trifluoroethyl
methacrylate), respectively. The precursory polymers to F<sub>66</sub>M<sub>200</sub> and F<sub>95</sub>A<sub>135</sub> were prepared by
atom transfer radical polymerization. In 2,2,2-trifluoroethyl methacrylate
(FEMA), a selective solvent for F, vesicles and tubular micelles were
prepared from F<sub>66</sub>M<sub>200</sub> and F<sub>95</sub>A<sub>135</sub>, respectively. Photo-cross-linking the M and A blocks of
these aggregates yielded hollow nanospheres and nanotubes bearing
F coronal chains. These particles were dispersed into CH<sub>2</sub>Cl<sub>2</sub>/methanol, where CH<sub>2</sub>Cl<sub>2</sub> was a
good solvent for both blocks and methanol was a poor solvent for F.
Casting CH<sub>2</sub>Cl<sub>2</sub>/methanol dispersions of these
particles yielded films consisting of hierarchically assembled diblock
copolymer nanoparticles. For example, the hollow nanospheres fused
into microspheres bearing nanobumps after being cast from CH<sub>2</sub>Cl<sub>2</sub>/methanol at methanol volume fractions of 30 and 50%.
The roughness of these films increased as the methanol volume fraction
increased. The films that were cast at high methanol contents were
superhydrophobic, possessing water contact angles of ∼160°
and water sliding angles of ∼3°