Chemistry Reference
In-Depth Information
Temperature dependence of the frequency sweeps was studied for compounds
6
-
14
and are exemplified using compound
8
, see Figure 27. To create a master curve, time-
temperature superposition was carried out. With the temperature shift factor for the
storage modulus G' and the loss modulus
G''
taken to be unity, the vertical temperature
shift factor
a
T
was determined at low frequency from the complex viscosity.
K
*
:
a
T
K
*
(
T
)
K
*
(
T
)
,
[70, 71]
0
0
0
T
gives the temperature and
T
0
gives the reference temperature. The absolute value of
the complex viscosity was determined at 1 Hz as it is constant at the lowest frequencies
studied. It was observed that the dominant loss moduli collapse on a master curve,
suggesting Maxwell fluid behavior in the low frequency limit over the entire
measurement range.
10000000
1000000
31°C
34°C
37°C
40°C
100000
10000
1000
100
10
0.1
1
10
100
reduced frequency f
r
[Hz]
Figure 27
Master curve for (Q
7
)
5
[
D
-SiW
11
O
39
Fe(H
2
O)] (
8
) with the storage modulus (solid symbols) and loss
modulus (open symbols). The reference temperature is 34 °C.
The temperature dependence can be fitted with the Arrhenius function:
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