Gas separation membrane comprising crosslinked thermally rearranged poly(benzoxazole-co-imide) and preparation method thereof

A polymer membrane comprising a crosslinked thermally rearranged poly(benzoxazole-co-imide) having a repeating unit represented by the following Chemical Formula 1:

• wherein, in Chemical Formula 1, Ar is an aromatic cyclic group selected from substituted or non-substituted tetravalent C6-C24 arylene groups and substituted or non-substituted tetravalent C4-C24 heterocyclic groups, wherein the aromatic cyclic group is present alone;
• two or more of the aromatic cyclic groups form a condensed ring together;
• two or more of the aromatic cyclic groups are linked to each other via O, S, CO, SO2, Si(CH3)2, (CH2)p (1≦P≦10), (CF2)q (1≦q≦10), C(CH3)2, C(CF3)2 or CO—NH,
• Q is a single bond;
• or O, S, CO, SO2, Si(CH3)2, (CH2)p (1≦P≦10), (CF2)q (1≦q≦10), C(CH3)2, C(CF3)2, CO—NH, C(CH3)(CF3), or a substituted or non-substituted phenylene group, and
• each of x and y represents a molar fraction in the repeating unit, wherein 0.8≦x≦0.95, 0.05≦y≦0.2 and x+y=1.