364
M. Funahashi
Fig. 18.4 Molecular structures of LC perylene bisimide derivatives bearing oligosiloxane chains
and their phase transition temperatures. Col hd , Col ho , and Col ro denote a columnar hexagonal
disordered, columnar hexagonal ordered, and columnar rectangular ordered phase, respectively
shown in Fig. 18.4. Compounds 4–6 exhibit columnar phases over wide temperature
ranges including room temperature and do not crystallize even when they are cooled
to −100 °C [24–26].
Figure 18.5a shows X-ray diffraction patterns of compounds 4 and 5. In columnar
phases, the lattice constants were shorter than the molecular lengths, suggesting interdigitation of the oligosiloxane moieties. Interestingly, oligosiloxane chains stabilize
the columnar structures because of nanosegregation in spite of the bulkiness of the
oligosiloxane chains, compared to that of alkyl chains. These compounds exhibit
ordered columnar phases in which the perylene bisimide cores stack periodically.
The intermolecular distance within the columnar aggregates is 3.4 Å, which is a
typical value for π –π stacking. Figure 18.5b displays a schematic illustration for
the columnar phase of these compounds. Crystal-like one-dimensional π-stacks are
surrounded by liquid-like mantle consisting of oligosiloxane moieties.
Fig. 18.5 a X-ray diffraction pattern of compounds 4 and 5 at room temperature, b schematic
illustration of the columnar phase
M. Funahashi
Fig. 18.4 Molecular structures of LC perylene bisimide derivatives bearing oligosiloxane chains
and their phase transition temperatures. Col hd , Col ho , and Col ro denote a columnar hexagonal
disordered, columnar hexagonal ordered, and columnar rectangular ordered phase, respectively
shown in Fig. 18.4. Compounds 4–6 exhibit columnar phases over wide temperature
ranges including room temperature and do not crystallize even when they are cooled
to −100 °C [24–26].
Figure 18.5a shows X-ray diffraction patterns of compounds 4 and 5. In columnar
phases, the lattice constants were shorter than the molecular lengths, suggesting interdigitation of the oligosiloxane moieties. Interestingly, oligosiloxane chains stabilize
the columnar structures because of nanosegregation in spite of the bulkiness of the
oligosiloxane chains, compared to that of alkyl chains. These compounds exhibit
ordered columnar phases in which the perylene bisimide cores stack periodically.
The intermolecular distance within the columnar aggregates is 3.4 Å, which is a
typical value for π –π stacking. Figure 18.5b displays a schematic illustration for
the columnar phase of these compounds. Crystal-like one-dimensional π-stacks are
surrounded by liquid-like mantle consisting of oligosiloxane moieties.
Fig. 18.5 a X-ray diffraction pattern of compounds 4 and 5 at room temperature, b schematic
illustration of the columnar phase