Membrane Gas Separation

8.2
Experimental 
8.2.1
Materials 
TAPOB was synthesized by reduction of 1,3,5 - tris(4 - nitrophenoxy)benzene with palla-
dium carbon and hydrazine in methanol [14] . 6FDA was kindly supplied from Daikin 
Industries, Ltd. Pyromellitic dianhydride (PMDA) and 4,4 
′
- oxidiphthalic anhydride 
(ODPA) were obtained from Daicel Chemical Industries, Ltd. and Manac Incorporated, 
respectively. TMOS, MTMS, 3 
- 
aminopropyltrimethoxysilane (APTrMOS), and
N,N -
dimethylacetamide (DMAc) were purchased from Aldrich. Chemical structures of mono-
mers and alkoxysilanes are shown in Figure 8.2 .
8.2.2
Polymerization 
3 mmol of dianhydride (6FDA, PMDA, and ODPA) was dissolved in 40 mL of DMAc in 
a 100 mL three - neck fl ask under N 
2
fl ow at room temperature. To this solution, 1.6 mmol 
of TAPOB in 20 mL of DMAc was added dropwise through a syringe with stirring for 
3 h. After that 0.4 mmol of APTrMOS was added in the reaction mixture with stirring for 
1 h to afford hyperbranched polyamic acid.
8.2.3
Membrane Formation 
The HBPI – silica hybrid membranes were prepared by thermal imidization and sol – gel 
reaction with two kinds of alkoxysilanes, TMOS and/or MTMS. Appropriate amounts of 
TMOS and/or MTMS and ion exchange water were added in the DMAc solution of the 
hyperbranched polyamic acids. For TMOS/MTMS combined system, TMOS and MTMS 
were added to achieve equivalent weight fraction of silica components arising from 
TMOS and MTMS. The mixed solutions were stirred for 24 h and cast on PET fi lms and 

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146
Membrane Gas Separation
dried at 85 ° C for 3 h. The prepared membranes were peeled off and subsequently imidized 
at 100 ° C for 1 h, 200 ° C for 1 h, and 300 ° C for 1 h in a heating oven under N 
2
fl ow. The 
thickness of the HBPI – silica hybrid membranes was about 30
μ
m. A schematic diagram 
for the hybrid membrane preparation is shown in Scheme 8.1 .