Synthesis of imidazolium-mediated Poly(benzoxazole) Ionene and composites with ionic liquids as advanced gas separation membranes

Thermally rearranged (TR) polymers and ionic polymers are two material classes which have been employed in leading gas separation membranes. This work introduces a novel approach of combining the benzoxazole functionality associated with TR polymers with tailorable cationic groups, yielding a new type of imidazolium-mediated poly(benzoxazole) ionene polymer, Im-PBO-Ionene with the aim of enhanced CO2 separation performance. The structural changes exhibited from the Coulombic interactions between the ionene backbone and the free ionic liquid (IL) resulted in enhanced gas separation performance, shown in fundamental characterizations, observed through increased diffusivities and more notably, retained high selectivities and 3x or 5x respective increases in CO2 permeability upon the addition of 1 or 2 equivalents of IL per polymer repeat unit. These new high-performance ionenes demonstrate the versatility of ionene design and potential of the ionene + IL material platform for gas separation membranes with versatile incorporation of sophisticated functional and structural features.

Automated summary

This study introduces a novel approach to enhance CO2 separation performance by combining the benzoxazole functionality with tailorable cationic groups, resulting in a new type of imidazolium-mediated poly(benzoxazole) ionene polymer. The structural changes from Coulombic interactions between the ionene backbone and free ionic liquid contribute to enhanced gas separation performance, showing increased diffusivities, high selectivities, and significant increases in CO2 permeability. These new high-performance ionenes demonstrate the versatility of ionene design and potential of the ionene + IL material platform for gas separation membranes with sophisticated functional and structural features.