A novel diamine monomer containing a Tröger's base (TB) structure

2

8-diamino-4

10-dimethyl-6

12 -hydrogen-5

11 methylene dibenzo [1

5] diazo octane (TBDA)

was designed and synthesized. This monomer was then copolymerized with 4

4'- (hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 2

2'-bis (3-amino-4-hydroxyl-phenyl) hexafluoropropane (APAF) to synthesize a series of polyimides (HPI) containing ortho-hydroxyamide units. The HPI membranes underwent thermal rearrangement (TR) at high temperatures to yield poly(benzoxazole-co-imide) (PBO-PI) gas separation membranes by the thermal rearrangement containing the TB structure and the thermally rearranged benzoxazole units. The results demonstrated that the synergistic effect of the inherent microporosity of TB moieties and thermal rearrangement inhibited the dense packing of molecular chains

providing the membrane with a rich free volume

thus imparting excellent gas separation properties. The gas permeation coefficients of the 6FTB1-TR membrane containing 10 mol% of TBDA and thermally rearranged at 430 °C demonstrated excellent gas separation performance with CO2

CH4

O2

and N2 permeation coefficients of 267.6

7.0

57.2

and 12.5 Barrer

respectively

with the ideal selectivities of α(CO2/CH4) and α(O2/N2) were 38.2 and 4.6

respectively. Moreover

the glass transition temperature (Tg) exceeded 400 °C

demonstrating excellent thermal stability. This study provides new insights into the design and development of novel high-performance gas separation membranes.