Chemistry Reference
In-Depth Information
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Figure 1.6
Structure of a fluorinated gelator capable of gelling liquid CO
2
, and an
aliphatic amine turned into a gelator by a reversible reaction with CO
2
.
vancomycin, a well-known water-soluble antibiotic agent, into a potent
hydrogelator by appending it with the hydrophobic pyrene moiety. Interest-
ingly, the vancomycin hydrogels showed largely enhanced antibiotic activity
compared to vancomycin itself.
These examples clearly demonstrate that property-based design can be a
successful approach to develop new gelators with very different properties, by
starting from empirical relationships between gelator structure and macro-
scopically observable gelation behaviour. Because of the lack of insight on how
the macroscopic properties of gel formation are linked to the molecular
structure, the property-based design approach depended largely on trial and
error: only a few of the synthesised molecules showed the desired properties,
whereas the majority of the synthesised derivatives failed as gelator, often
without a satisfactory explanation. These failures emphasise once more that
gelation ability is very sensitive to the molecular structure. Nevertheless, these
negative results can also be very useful, because in combination with the suc-
cessful newly designed gelators they form a new structure-activity study, which
may lead to additional clues on the supramolecular arrangement within
these gels.
.
1.5.2 Library and Selection Approaches for the Discovery of
New Gelators
One possibility to accelerate the discovery of new gelator molecules and mo-
tives is to screen libraries of potential gelators, which consist of many different
compounds sharing a common property or structure. One of the first reports on
such an approach is by Shinkai and coworkers, who took the gelation prop-
erties of dibenziledene sorbitol as a starting point to prepare a library of po-
tential gelators from a set of different monosacharides by reacting them with
