N‑Substituted Fluorinated Polybenzimidazoles: An Easy Post-Modification Strategy for Improved CO₂ Separation

Area of Science:

• Polymer Chemistry
• Materials Science

Background:

• Polybenzimidazoles (PBIs) are high-performance polymers with limited processability.
• Fluorinated PBIs (PBI-6F) offer a base for modifications.

Purpose of the Study:

• Synthesize and characterize N-substituted aromatic polybenzimidazoles (N-PBIs).
• Evaluate their processability, gas separation performance, and thermal stability.

Main Methods:

• Post-polymerization modification of PBI-6F with aliphatic amine-containing chains.
• Solubility testing in various organic solvents.
• Gas separation membrane performance evaluation (CO2/CH4).
• Thermal decomposition analysis and computational studies.

Main Results:

• N-PBIs exhibited enhanced solubility in common solvents like chloroform and THF.
• Amine-functionalized N-PBIs (PBI-DMEA, PBI-DMPA) showed improved CO2/CH4 permselectivity.
• Increased CO2 solubility parameter contributed to enhanced gas separation.
• Aliphatic amine presence led to significantly reduced decomposition temperatures.

Conclusions:

• N-substitution enhances PBI processability and CO2/CH4 separation.
• Balancing solubility and thermal stability is crucial for amine-functionalized PBIs.
• Computational analysis confirmed experimental observations on decomposition and transport properties.