# Fabrication of Microphase-Separated Tröger’s Base Polymer Membranes for Oxygen Enrichment

## TL;DR

Researchers created a new type of polymer membrane that can efficiently separate oxygen from other gases by using a special structure called microphase separation.

## Contribution

The study introduces a novel method to enhance gas separation performance by grafting hydrophobic chains onto Tröger’s base polymers, creating microphase-separated channels.

## Key findings

- Quaternized Tröger’s base membranes showed improved oxygen permeability due to microphase-separated channels.
- The QTB-C4-70% membrane exhibited the highest oxygen permeability among tested samples.
- Oxygen permeability decreased slightly with pressure but increased with temperature, indicating good pressure stability.

## Abstract

Tröger’s base (TB) polymers have received increasing attention as a novel class of polymers with intrinsic microporosity, particularly for applications in gas separation. In this study, TB was quaternized with hydrophobic long chains to create a microphase-separated structure to enhance gas separation performance. On one hand, the tertiary amine structure of TB enabled facile grafting modification through the Menshutkin reaction. On the other hand, microphase-separated channels were created in the quaternized Tröger’s base (QTB) membrane due to the polarity differences between the hydrophilicity of the quaternary ammonium groups and hydrophobicity of iodoalkanes, providing channels for gas transport within the membrane and thereby improving permeability selectivity. The successful synthesis of QTB membranes was confirmed by FTIR and 1H NMR spectroscopy, while AFM and SAXS analyses validated the microphase-separated morphology. To investigate the impact of microphase separation on oxygen permeability and selectivity, different iodoalkanes and various concentrations of iodobutane were grafted onto the TB backbone. Among the prepared membranes, QTB-C4-70% membrane exhibited the highest in O2 permeability. Gas separation performance under different O2 pressures and temperatures revealed that O2 permeability decreased slightly with increasing pressure, indicating good pressure stability of the membrane. With increasing temperature, the permeability increased while the selectivity decreased. These findings demonstrated that microphase-separated QTB membranes offer a viable strategy for creating effective materials for gas separation.