Biomedical Engineering Reference
In-Depth Information
...
...
NH
CH
(CH
2
)
4
NH
CO
(CH
2
)
8
CO
NH
CH
CO
O
D
O
CO
CH
2
CH(CH
3
)
2
CO
NH
H
3
C
CH
3
4-amino-TEMPO
N
O
.
H
3
C
CH
3
Scheme 5.9
Functional
co
- PEA containing covalently attached 4 - amino - TEMPO.
HS
CH
2
COOH
~
(
92%)
SCH
2
COOH
PEA
CH
2
OH
HS
CH
2
~
90%)
(
CH
2
OH
SCH
2
NH
2
CH
2
CH
2
COOH
~
(
28%)
NH
CH
2
CH
2
COOH
Figure 5.12
Chemical transformations of fumaric acid based UPEA.
The covalent attachment of mono-ethanolamine to these polymers increases
their hydrophilicity and water solubility (depending on mole portion of lysine
residue in the polymers backbones). The obtained polyols can be used for further
transformations, for example, to obtain chemically and photochemically active
polymers by attaching unsaturated acids like acrylic, methacrylic, etc. [63, 64].
UPEAs, containing active double bonds of fumaric acid's residue can be func-
tionalized by their interaction under mild conditions with thiol- and amino-
compounds [19] as is shown in Figure 5.12.
As one can conclude, the thio-compounds are far more active in these
transformations.
The epoxy -PEAs given in Figure 5.10 contain activated (by two adjacent electron-
withdrawing carbonyl groups) oxirane cycles and interact under mild conditions
(DMA, 20-60 °C) with various compounds of both nucleophilic and electrophilic
nature [20] .
Due to the high activity of epoxy-PEAs, they can be considered as “ready for use”
carriers - in contrast to polyacids above, because they interact with 4-amino-
TEMPO in DMA solution at 60 °C without using condensing agent, as shown in
Scheme 5.10 .
Both UPEAs and epoxy-PEAs are also subjected to chemical, thermal and pho-
tochemical curing that allows one to regulate their properties, for example, to
increase mechanical characteristics and decrease biodegradation rate.
