Membrane Gas Separation

6FDA - TAPOB
88.9
282
457
0
54
TMOS, 10 wt% SiO 
2
89.9
305
490
10
47
TMOS, 20 wt% SiO 
2
90.2
311
496
20
38
TMOS, 30 wt% SiO 
2
90.3
318
509
30
31
TMOS/MTMS, 10 
wt% SiO 
2
89.6
286
487
10
50
TMOS/MTMS, 20 
wt% SiO 
2
90.1
299
494
18
48
TMOS/MTMS, 30 
wt% SiO 
2
89.8
301
502
29
46
TMOS/MTMS, 40 
wt% SiO 
2
89.1
303
509
40
41
TMOS/MTMS, 50 
wt% SiO 
2
91.6
n.d.
4)
515
48
–
MTMS, 10 wt% SiO 
2
90.2
278
471
10
59
MTMS, 20 wt% SiO 
2
90.1
281
480
19
66
MTMS, 30 wt% SiO 
2
91.4
287
496
30
73
MTMS, 40 wt% SiO 
2
91.3
291
501
39
74
MTMS, 50 wt% SiO 
2
91.7
n.d.
4)
505
48
–
ODPA - TAPOB
85.8
272
470
0
52
TMOS, 10 wt% SiO 
2
87.0
276
494
10
45
TMOS, 20 wt% SiO 
2
87.5
289
504
20
38
TMOS, 30 wt% SiO 
2
88.2
291
506
30
32
TMOS/MTMS, 10 
wt% SiO 
2
86.6
272
484
12
49
TMOS/MTMS, 20 
wt% SiO 
2
88.3
279
491
21
47
TMOS/MTMS, 30 
wt% SiO 
2
90.5
281
501
31
41
MTMS, 10 wt% SiO 
2
86.1
259
474
11
54
MTMS, 20 wt% SiO 
2
87.5
263
484
21
61
MTMS, 30 wt% SiO 
2
89.8
267
496
30
64
PMDA - TAPOB
85.2
326
464
0
35
TMOS, 10 wt% SiO 
2
85.9
n.d.
4)
490
14
35
TMOS, 20 wt% SiO 
2
85.1
n.d.
4)
497
22
32
TMOS, 30 wt% SiO 
2
86.6
n.d.
4)
505
31
29
TMOS/MTMS, 10 
wt% SiO 
2
86.7
n.d.
4)
482
12
42
TMOS/MTMS, 20 
wt% SiO 
2
86.7
n.d.
4)
489
21
39
TMOS/MTMS, 30 
wt% SiO 
2
88.4
n.d.
4)
501
31
39
MTMS, 10 wt% SiO 
2
86.5
n.d.
4)
475
13
42
MTMS, 20 wt% SiO 
2
87.7
n.d.
4)
484
24
53
MTMS, 30 wt% SiO 
2
88.9
n.d.
4)
500
33
56
1) Optical transmittance at 600 nm.
2) Determined from the residual at 800 ° C.
3) CTE at 100 – 150 ° C.
4) Not detected.

---

150
Membrane Gas Separation
Figure 8.4 Glass transition temperature ( T
g
 ) (a) and 5% weight - loss temperature (
T
d
5
) 
(b) of 6FDA - TAPOB HBIP – silica hybrid membranes plotted against silica content
because of their good transparency, similar to corresponding pure HBPIs without silica. 
The high homogeneity is considered to be maintained not only by APTrMOS moiety 
which functions as covalent bond parts between organic and inorganic components but 
also by the characteristic hyperbranched structure of the molecular chains.
Thermal properties of the hybrid membranes were investigated by TG - DTA and TMA 
measurements. From T
g
curves it was again demonstrated that the prepared membranes 
are well imidized because no weight - losses attributed to dehydration by imidization are 
observed all through the measurements. Glass transition temperature ( T
g
) determined from 
DTA curves and 5% weight - loss temperature (
T
d
5
) of the hybrid membranes are summa-
rized in Table 8.1 in addition to the silica content determined from the residual at 800 ° C. 
It is confi rmed from the residual that all hybrid membranes contain appropriate amount 
of silica as expected. The T
g
and
T
d
5
values of the 6FDA - TAPOB HBPI – silica hybrid 
membranes are plotted against silica content in Figure 8.4 .
T
d
5
of the hybrid membranes 
increases with increasing silica content. This result indicates the increase in thermal 
stability of the HBPIs by hybridization with silica. The T
g
of the TMOS system consider-
ably increases with increasing silica content, suggesting the formation of robust three -
dimensional Si – O – Si network. However, for the MTMS system, the T
g
shows a minimum 
value at low silica content region, and the T
g
of the TMOS/MTMS combined system is 
lower than that of the TMOS system. This fact suggests that the introduction of MTMS 
leads to an insuffi cient formation of three - dimensional Si – O – Si network, which brings 
about less constraint of molecular chains in the hybrid membranes compared to the hybrid 
membranes prepared solely with TMOS.
Coeffi cients of thermal expansion (CTEs) from 100 to 150 ° C of the hybrid membranes 
are listed in Table 8.1 . The CTE of the TMOS system greatly decreases with increasing 
silica content, indicating the enhancement of thermal mechanical stability of the HBPIs 
by the formation of robust three - dimensional Si – O – Si network. In contrast, the CTE of 

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Physical and Gas Transport Properties
151
the MTMS system increases with increasing silica content. The increased CTE might be 
caused by a loose Si – O – Si network which induces an effective disruption of molecular 
chains packing and, as a result, provides a large amount of free volume elements [22] . 
The increased free volume decreases the hindrance of thermal expansion of molecular 
chains. The CTE of the TMOS/MTMS combined system shows the intermediate value 
between those of TMOS and MTMS systems.