Biomedical Engineering Reference
In-Depth Information
for micromolding
70
and photolithography.
71
Moreover, chitosan has
also been modified by a reaction with 4-vinylbenzoic acid. This
materialhasbeenusedtocreatetubularstructuresuponirradiation
withvisiblelight.
72
8.3.2
Photocurable Hydrogel from Synthetic Polymers
Anseth
et al
.
73
originally modified polyanhydrides with cross-
linkable methacrylate groups to produce polymer networks that
have controlled degradation and mechanics. There is an added
potential of network formation directly in the body. The gen-
eral structures for selected dimethacrylated anhydride monomers
are shown in Fig. 8.5. In general, the core of the molecule con-
sists of hydrophobic repeating units, such as sebacic acid, car-
boxyphenoxy propane, or carboxyphenoxy hexane. Other anhy-
dride monomers, including methacrylated tricarballylic acid and
methacrylated pyromellitylimidoalanine, have also been synthe-
sized to impart greater cross-linking density and a biologically
recognized component, respectively.
74
Photo-cross-linkable polyanhydrides have also been extensively
characterized with respect to reaction behavior and material prop-
erties. Even with mild initiation conditions (e.g., with 0.1 wt% ini-
tiator and 7 mW/cm
2
UV light, polymerization occurs within three
Figure 8.5.
Photo-cross-linkable polyanhydrides, typically synthesized
via the reaction of acids with methacrylate anhydride. Dimethacrylated
anhydride monomers, methacrylated sebacic acid (MSA), methacrylated
1,3-
bis
(
p
-carboxyphenoxy) propane (MCPP), and methacrylated 1,6-
bis
(
p
-
carboxyphenoxy) hexane (MCPH), as well as a general polymerization.
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