Engineering of Small-Molecule Gels Based on the Thermodynamics and Kinetics of Fiber Formation - Soft Fibrillar Materials: Fabrication and Applications - page 98

(a) (d)

140

(g)

y = 2.68x + 2.81
y = 0.69x + 3.29

120

100

80

60

40

20

(b) (e)

0

0 50 100 150 200

t , s

4

(h)

No additive
With additive

3.5

3

(c) (f)

2.5

2

1.5

1

0.5
0 20

30 40 50

T , ° C

a function of time at 40 ◦ C (the slopes of
the lines correspond to fiber growth rate),
and (h) and the influence of PMMMA on
the growth rate of GP-1/PG fibers. The scale
bars in (a-f) represent 100 μ m. (d,f,g, and
h) are reprinted with permission from Ref.
[33], Copyright

Figure 2.10 Micrographs illustrating the ef-
fects of supersaturation (a-c) and a copoly-
mer (PMMMA) additive (d-f) on fiber net-
work formation. (a-c) GP-1 fiber networks
formed in PG at 25, 40, and 50 ◦ C, respec-
tively; (d-f) GP-1 fiber networks formed
in PG at 40 ◦ C with 0.02, 0.04, and 0.06%
PMMMA, respectively, (g) fiber length as

© 2009, American Chemical

Society.

be reduced. Therefore, suitable additives can also be used to control the nucleation
kinetics and thus to modify the topological structure of the fiber networks.
Figure 2.10a-c displays the spherulitic fiber networks of GP-1 formed in propy-
lene glycol. The supersaturation of the systems were controlled by fixing the gelator
concentrations while changing temperature. The primary nucleation rate (number
density of spherulites) of the system decreases with an increase in temperature,
leading to the formation of larger spherulites. The temperature-controlled nucle-
ation and fiber network formation has also been reported for other gel systems,
such as those formed by the gelation of n -alkanes by 5R-cholestan-3 -yl N -(2-

naphthyl)carbamate [18a]. Similar results were obtained. Changing the size of

β