Liquid Crystalline Assembly of Rod–Coil Molecules - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 95

tendency of the rod block to form orientational order. The incorporation of
different rod-like segments such as helical rods, low molar mass mesogenic
rods, and conjugated rods as a part of the main chain in rod-coil molecular
architecture has already proven to be an effective way to manipulate supramo-
lecular structures in nanoscale dimensions. Depending on the relative volume
fraction of rigid and flexible segments, and the chemical structure of these seg-
ments, rod-coil copolymers and their low molar mass homologs self-assemble
into a variety of supramolecular structures through the combination of shape
complimentarity and microphase separation of rod and coil segments as an
organizing force. The supramolecular structures assembled by rod segments
in rod-coil systems include sheets, cylinders, finite nanostructures, and even
perforated sheets that organize into 1D, 2D, and 3D superlattices, respectively.
It should be noted that self-assembly can be used to prepare well-defined
macromolecular nanoobjects that are not possible to prepare by conventional
synthetic methodologies, when the rod-coil copolymers self-assemble into
discrete supramolecular structures. In this respect, many synthetic strategies
have been developed that allow the incorporation of functional rod segments
into well-defined rod-coil architectures for specific properties. Electron trans-
fer, second harmonic generation, and piezoelectricity have been reported for
supramolecular structures of rod-coil copolymers containing conjugated rods
or highly polar end groups [108-110]. Many more rod-coil systems are ex-
pected to be developed soon for possible applications as diverse as molecular
materials for nanotechnology, supramolecular reactors, periodic porous mate-
rials, transport membranes, and biomimic materials.
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