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Fig. 18
Chemical structures of monomers and polymers used by Lin et al. to access side
chain and network SLCPs
mers leading to reduced stability (a lower clearing temperature) of the LC
phase and formation of LC phases at lower temperatures. This nicely demon-
strates the importance of carefully designing the nature of the supramolecular
motif in such side chain SLCPs. SLCP networks formed using these same
materials were also investigated. A series of supramolecular polymers (
41
)
with different mole fractions of benzoic acid units were used to compare
the blend of the two complementary polymers (
37
and
39
)withacopoly-
mer which contains both binding motifs. It was found that the copolymer
41
forms LC materials with a much wider mole fraction of benzoic acid
derivatives than the blends of
37
and
39
(0.42-0.89 vs 0.4-0.55), which is
consistent with the formation of more homogenous structures in the copoly-
mers. In general, for both systems the higher the crosslinked density (i.e.,
the closer to a 1 : 1 molar ratio of benzoic acid:stilbazole) the more sta-
ble the LC phase is, although it should be noted that higher isotropization
temperatures are observed with an increase in the ratio of benzoic acid moi-
eties. This is presumably a consequence of the ability of the benzoic acid
units to form hydrogen bonding homo-complexes via carboxylic acid dimers.
The same groups went on to investigate related SLCP networks in which
the benzoic acid containing polymer was “crosslinked” with a bis(pyridyl)
small molecule, demonstrating that these complexes also formed smectic
phases [106].
An example of side-chain SLCPs whose mesogen consists of part of the
main-chain as well as the side chain (Fig. 3h) has been reported by Kato
et al. [107]. In this case the hydrogen bond mesogenic motif utilized was
a benzoic acid (as part of the small molecule side chain
42
) with a 2,6-diamino-
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