Chemistry Reference
In-Depth Information
E
§
·
1
1
a
¨
©
¸
¹
ln
a
T
R
T
T
0
where
E
a
is the activation energy,
R
is the ideal gas constant and the temperature T is
given in Kelvin. The reference temperature T
0
was chosen to be 31°C. The activation
energy depends on the cation-anion interactions and can be interpreted as the average
energy barrier that must be overcome for ions within the ionic liquid to move past each
other.
[67]
The activation energies for compounds
6
-
14
are in the range of 77-109 kJ/mol,
see Table 6 on the next page.
In summary, compounds
6-10+12
(Q
7
-based) and
13-14
(Q
8
-based) show qualitative
differences in their rheological behavior. This is suggested to be due to the differences
in cation alkyl chain length and in consequence, due to the cation-anion distances and
interactions. For the Q
7
-based POM-ILs
5-10,
viscoelastic behavior over a wide range of
deformation was observed. In contrast, Q
8
-based compounds
11-12
are less viscous and
their internal structure is only stable at low deformations. At higher deformation rates,
deviation from Maxwell fluid behavior, most likely associated with significant changes of
the internal fluid structure, was observed.
Compound no. Activation energy E
a
[kJ/mol]
6
94±0.3
7
109±0.7
8
98±0.6
9
140±0.3
10
96±0.3
12
76.3±0.2
13
81±0.6
14
81±0.2
Table 6
The activation energy
E
a
of the compounds No. 6-14
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