Biomedical Engineering Reference
In-Depth Information
a) PEG-PAA-PS
O
O
Br
O
n
m
*
p
COO H
COOH
Ph
Ph
c) PEO-
b
-P D M A
b) PS-PAA
O
*
*
O
*
n
m
*
n
m
O
O
COOH
O
N
d) CPM PC
CH
3
CH
3
O
Br
C
CH
2
C
C
O
CH
2
O
n
12
CH
3
C
O
O
CH
2
CH
2
O
O
P
O
CH
2
CH
2
N+(CH
3
)
3
O
Figure 1.5
Chemical structure of block copolymers: (a) PEG-PAA-PS, (b) PS-PAA, (c)
PEO-
b
-PDMA, and (d) CPMPC.
This cross-linking method was previously successfully attempted with
poly(styrene)-block-poly(acrylic acid) (PS-PAA) (Fig. 1.5b) and produced
complexes soluble and stable for weeks in both hydrophilic and hydrophobic
solvents.
29
In both cases, the encapsulation of the SWCNTs preceded the
cross-linking process; the SWCNTs and the polymer were initially mixed in a
solvent that solvates all the polymer blocks but that does not induce micellar
formation, and water was then added dropwise to the CNT-polymer mixture
Non-covalent modiication of CNTs is also achieved by zwitterionic
interaction between the carboxylic groups present on the surface of oxidised
nanotubes and a polycationic polymer; this type of interaction is pH
dependent, and such a characteristic could have important applications in
drug delivery and CNT puriication.
30
Zwitterionic interactions between the double-hydrophilic block copolymer
poly(ethylene oxide)-
b
-poly[3-(
N
,
N
-dimethylamino-ethyl) methacrylate]
(PEO-
b
-PDMA) and oxidised SWCNTs were conirmed by
1
H-NMR, where the
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