Room temperature synthesis, characterization and enhanced gas transport properties of novel poly(oxindolylidene arylene)s with dibenzothiophene, dibenzothiophene-S-oxide and dibenzothiophene-S,S-dioxide fragments in the main chain

Aromatic sulfur-containing polymers poly(arylene ether sulfone)s and poly(arylene sulfide sulfone)s are widely used in membrane-based gas- and liquid separations and purification technologies. In this work, we report a facile, robust, room temperature synthesis of a series of novel, solution processable aromatic polymers containing dibenzothiophene, dibenzothiophene-S-oxide, and dibenzothiophene-S,S-dioxide fragments in the main chain, alternating with bulky, torsion resistant oxindolylidene groups. The NMR studies of the polymers obtained revealed ladderized, rigid kink-structured backbones. This combination provides membranes with higher permeability and selectivity with gas pairs CO2/CH4, H2/CH4 and H2/N2, close to or even surpassing the 2008 Robeson’s trade-off line, that compare favorably with polysulfones and poly(ether sulfone)s reported in the literature that lie below the 1991 upper bond. Polymer P2-SO2 containing dibenzothiophene-S,S-dioxide fragments showed impressive CO2 and H2 permeabilities (243. 3 and 315.1 Barrer, respectively); on the other hand, P1-SO containing dibenzothiophene-S-oxide exhibited remarkable H2/CH4 and H2/N2 selectivity (127.26 and 99.34, respectively). This work offers a novel and facile route to fabricate various polysulfones and polysulfoxides with reversible-tunable gas separation properties inspired by the concept of rigid kink-structured backbones that shift their gas transport properties towards higher permeability and higher selectivity.