Molecular Gels and their Fibrillar Networks - Soft Fibrillar Materials: Fabrication and Applications - page 27

low gelator concentrations and high incubation temperatures, the morphology
is changed completely, from spherulitic to rod-like (NB, lower left panel in
Figure 1.23). Transformations from spherulitic to rod-like s have been

observed in other organogel systems, with gelators with much simpler different
structures, as well [4].
Even more dramatic changes in the microstructures of the aggregates were
observed for the dipeptide LMOG , di-phenylalanine (l- Phe -l- Phe ), in different
toluene/ethanol mixtures [86]. The fibrillar network of the gels became micro
flower-like crystallites as the ethanol content of the liquid increased (Figure 1.24)
and the samples were no longer gels at

SAFIN

> 40% ethanol.

(a) (b)

10 μ m 10 μ m

(c) (d)

500 μ m 100 μ m

(e) (f)

500 μ m 200 μ m

(g) (h)

500 μ m 100 μ m

Figure 1.24 Scanning electron micrographs of samples of L - Phe - L - Phe formed at different
toluene/ethanol contents: (a) 100/0; (b) 90/10; (c,d) 75/25; (e) 60/40; (f) 30/70; and (g,h)
0/100. Reprinted with permission from Ref. [86]. Copyright 2010 Wiley.