Biomedical Engineering Reference
In-Depth Information
dispersible, oleylamine has to be replaced with a hydrophilic amine, which some-
times makes the product unstable. In comparison, C18AA is a phase transfer agent
for Au nanoparticles between an organic solvent and water [49]. It forms a lamellar
structure in apolar solvents and selectively adsorbs specifically onto the Au surface,
directing the growth of gold nanostructures. The gold nanowires formed are water
dispersible.
5.4
Controlled Formation of Organic and Composite Structures
While fabrication of inorganic nanostructures in gels has been a focus, some
organic or inorganic/organic composite structures were also successfully prepared
in gels. In fact, the three-dimensional network formed by the supramolecular
assembly of a gelator is itself a self-supporting porous material [50]. Depend-
ing on the properties of the gelator, these materials can find applications in
many fields, such as tissue engineering. Alternatively, this porous network can be
imprinted into other materials with desired properties. Macroporous polymethyl-
methacrylate (PMMA) was prepared in a gel formed by Fe(NO
3
)
3
ยท
9H
2
Oand1,
3, 5-benzenetricarboxylic acid (with a molar ratio of 3 : 2) in ethanol [51]. UV
polymerization of the precursor methylmethacrylate added in the gel containing
azoisobutyronitrile produces PMMA in the gel. Upon removing the gel network
with hydrochloric acid, a macroporous PMMA imprinting the gel network formed.
Using a small-molecule organogel as reverse template, porous divinylbenzene
polymer films with submicrometer channels were also fabricated (Figure 5.7) [52].
nm
nm
(a)
3250
(b)
3000
2750
2500
2250
2000
1750
1500
1250
1000
750
500
250
0
3000
2000
1000
0
0
1000
2000
3000
nm
1000
2000
3000
nm
Figure 5.7
AFM images of a divinylbenzene polymer film before (a) and after (b) removal
of gel fibers. Channels are clearly shown in (b).
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