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state is able to dynamically respond to external fields and form periodic de-
fects. Depending on the evaporation of solvent, they showed that hierarchical
morphology was induced in a rod-coil block copolymer film.
When the rod blocks contained reactive side groups with a composition
having a large coil-to-rod volume ratio (PIC 23K, PS 200K), prism-like mi-
celle nanoobjects could be synthesized via self-assembly of rod-coil diblock
copolymers [57]. The PIC domain was cross-linked thermally via condensa-
tion of triethoxysilyl side groups and the rod directors remain parallel to each
other due to the liquid crystalline order. Thermal cross-linking of the rod
blocks only took place within each micellar nanodomain because the high
molecular weight PS blocks could completely separate from each other. The
TEM images indeed showed prism-like nanoobjects, which suggests a tilted
bilayer structure consisting of 300 aggregates of the rod-coil block copoly-
mer, as shown in Fig. 6. The result presents a novel method for forming
anisotropic organic particles with potential multifacial surface characteris-
tics.
De Boer et al. reported on the synthesis of a donor-acceptor, rod-coil di-
block copolymer with the objective of enhancing the photovoltaic efficiency
of the poly(phenylenevinylene)-C
60
system by incorporation of both com-
ponents in a rod-coil molecular architecture that self-assembled through
microphase separation [58]. These rod-coil copolymers showed nematic li-
quid crystalline phase and exhibit thermotropic transition at two regions. The
first transition is attributed to the melting of the side chains, and the second
higher one is an isotropic transition. Consequently, the diblock copolymers
possess complex and rich phase behavior due to the combination of a meso-
genic rod-like block and the adjacent coil-like block. The morphology of the
polymer in bulk can play an important role in determining the photovoltaic
cells, which the combination of a poly(
p
-phenylenevinylene)-type polymer as
the donor material and C
60
as acceptor has effectively utilized.
Fig. 6
Semectic ordering
of the
anisotropic nanoobjects
formed from PIC(23K)/
PS(200K). Reprinted with permission from [57].
©
2004 American Chemical Society
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