Chemistry Reference
In-Depth Information
Table 4.
Results of Fenton's reagent test of various sulfonated polyimide membranes at room temperature
Membrane
Thickness
[µm]
τ
1
*
[h]
τ
2
*
[h]
NTDA-ODADSA/ODA(1/1)
29
20
24
NTDA-ODADS/BAPB(1/1)
37
29
32
NTDA-ODADS/BAPF(1/1)
40
29
32
NTDA-ODADS/BAPHF(1/1)
26
24
29
NTDA-BAPFDS/ODA(4/1)
58
17
21
NTDA-BAPFDS/ODA(1/1)
23
18
22
NTDA-BAPFDS/BAPB(4/3)
31
22
26
NTDA-BAPFDS/BAPPS(2/1)
26
21
26
NTDA-BAPBDS
19
13
25
NTDA-BDSA/ODA(1/1)
21
13
20
NTDA-BDSA/BAPF(1/1)
34
23
26
NTDA-BDSA/BAPHF(1/1)
25
18
20
τ
2
refer to the time elapsed when the membranes became slightly brittle and started to
dissolve in the solution, respectively.
*
τ
1
and
4. CONCLUSIONS
1. Three kinds of sulfonated diamine monomers ODADS, BAPFDS, and
BAPBDS were successfully synthesized by direct sulfonation of the parent
diamines. Various sulfonated polyimides were prepared from NTDA,
ODADS, BAPFDS, BAPBDS, and non-sulfonated diamines.
2. At relative humidities below 100%, the proton conductivities of the sulfonated
polyimide membranes are generally lower than that of Nafion 117 in water,
most of the sulfonated polyimides showed similar or higher proton
conductivities than Nafion 117.
3. Water stability of the sulfonated polyimide membranes is greatly affected by
the flexibility of polymer chains, i.e., a flexible chain structure results in good
water stability. ODADS-based polyimide membranes displayed similar proton
conductivities but much better water stability than the corresponding BDSA-
based ones because of the more flexible structure of the former.
4. Besides the flexibility and the IEC, the basicity of the sulfonated diamine
moieties also has a great effect on water stability of the polyimide mem-
branes. BAPFDS-based polyimide membranes displayed much better water
stability than the corresponding BDSA-based ones with similar IEC because
for the former the unfavorable effect due to the rigid structure was offset by
the favorable effect due to the high basicity of BAPFDS.
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