Chemistry Reference
In-Depth Information
CH
3
CH
2
CH
CH
2
C
CH
2
CH
O
O
O
n
m
n
NH
NH
O
(CH
2
)
3
CH
3
H
3
C
CH
3
H
3
C
CH
3
PNIPAAm
P(NIPAAm-
co
-BMA)
100
80
60
40
Heat
20
Cool
0
0
10
20
30
40
Temperature (°C)
Figure 20.1
Chemical structures and temperature-dependent optical transmittance change of PNIPAAm
copolymers aqueous solution (0.5 w/v
%
) with various BMA compositions: PNIPAAm (LCST 32°C,
Δ
); BMA1
%
(LCST 30°C,
◊
); BMA3
%
(LCST 25°C,
t
); BMA5
%
(LCST 20°C,
ó
).
the pH of the buffer solution [19]. Kim
et al
. also reported on the pH sensitivity of the LCST of a
copolymer containing diethylaminoethyl methacrylate (DEAEMA) [20]. In addition, Kobayashi
et al
.
made an examination of the effect of the charge density for a temperature change by measuring p
K
a
and the zeta-potential. Regarding the p
K
a of the copolymer of NIPAAm, BMA and
N,N
-
dimethylaminopropylacrylamide (DMAPAAm) at high temperature, dehydration of the NIPAAm
isopropyl groups occurs, as well as an enhanced deprotonation of the amino group. The surface charge
densities as well as the hydrophobic functional group were shown to be altered by changing the
temperature. These polymers responded to both the temperature and the pH. Control of the surface charge
density becomes possible with a structural change of the copolymer by changing the temperature. These
facts show that control of different interactions was expected by hydrophobic and electrostatic interactions,
by changing only the temperature.
We have been investigating PNIPAAm and related temperature-responsive polymers used to generate a
thermally responsible stationary phase. Our major activity in this area has been to modify a temperature-
responsive polymer to a packing-material surface, including a terminally, cross-linked and high density
polymer brush.
