Preparation method of polybenzoxazoles by thermal rearrangement, polybenzoxazoles prepared thereby, and gas separation membrane comprising the same

A method for preparing a benzoxazole-based polymer represented by Formula 1 comprising:

• preparing a poly(hydroxyamide) of Formula 2 by reacting a compound of Formula 4 with a compound of Formula 5, as depicted in Reaction Scheme 2 below:
• and
• thermally treating the poly(hydroxyamide) of Formula 2, as depicted in Reaction Scheme 1 below:
• wherein Ar is a bivalent C5-C24 arylene group or a bivalent C5-C24 heterocyclic ring, which is substituted or unsubstituted with at least one substituent selected from the group consisting of C1-C10 alkyl, C1-C10 alkoxy, C1-C10 haloalkyl and C1-C10 haloalkoxy, or two or more of which are fused together to form a condensation ring, or covalently bonded to each other via a functional group selected from the group consisting of O, S, C(═O), CH(OH), S(═O)2, Si(CH3)2, (CH2)p (in which 1≦p≦10), (CF2)q (in which 1≦q≦10), C(CH3)2, C(CF3)2 and C(═O)NH;
• Q is O, S, C(═O), CH(OH), S(═O)2, Si(CH3)2, (CH2)p (in which 1≦p≦10), (CF2)q (in which 1≦q≦10), C(CH3)2, C(CF3)2, C(═O)NH, C(CH3)(CF3), C1-C6 alkyl-substituted phenyl or C1-C6 haloalkyl-substituted phenyl in which Q is linked to opposite both phenyl rings in the position of m-m, m-p, p-m or p-p;
• n is an integer of 20 to 200;
• X is a halogen atom;
• and an acid acceptor is added during the reaction scheme 2.