Molecular interactions of polyimides with single-walled carbon nanotubes

Abstract

Morphology control at the nanoscale is crucial for the application of polymer–nanomaterial hybrid composites. Phase separation of the constituents should be avoided when nanocomposites are prepared. In this work, highly dispersed single-walled carbon nanotubes (SWNTs) in polyimides are explored. We synthesized a variety of polyimides (PIs) based on 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and studied the resulting dispersion of single-walled carbon nanotubes (SWNTs) in N,N-dimethylacetamide (DMAc) solution of the PI. We found that the molecular structure plays an important role in dispersing SWNTs in PIs, and particularly biphenyl groups without ortho substituents are critical for dispersion in common organic solvents. SWNT dispersion in PI membranes rendered the membrane electrically conductive without causing phase separation. SWNT dispersion itself did not alter the permeability of CO₂. We also found that the resistance across the membrane increased with response only to the CO₂ flux. The polyimide–SWNT nanocomposites may find use in CO₂ sensors, CO₂ separation membranes, and antistatic coatings especially under high temperatures.