Chemistry Reference
In-Depth Information
Fig. 5
Supermolecular liquid-crystalline materials consisting of only one unit that has
mesogenic tendencies
ity spacer units tend to support anticlinic properties, whereas even parity
spacers support synclinic properties.
There have also been a number of examples reported of supermolecular
materials composed of different mesogenic units. For example, Yelamaggad
et al. [48, 49] reported a supermolecular material,
8
,thatwascomposedof
three different mesogenic groups linked together in a linear fashion, see
Fig. 6. This material possesses a chiral steroidal unit, a linear biphenyl moi-
ety and a photoactive azobenzene unit, and remarkably it exhibits unusual
frustrated chiral mesophases.
Fig. 6
A trimesogen that possesses three different mesogenic units, and which exhibits
frustrated liquid crystal phases
Laterally appended mesogens have been investigated for a number of sys-
tems. For example Fig. 7 shows a comparative family of laterally appended
dimeric systems which were investigated systematically by Mehl et al. [50-
53]. A three-ring (A) and a four-ring (B) monomer were synthesized with
the potential to be linked together through a silyloxy uniting moiety. The
synthetic programme yielded the symmetrical
9
(AA) and
10
(BB) bimeso-
gens, and the
11
(AB) dimesogen. For completion, the silyloxy terminated,
laterally-substituted monomers were also prepared,
12
and
13
.TheAAand
Search WWH ::
Custom Search