Interactions between polyacrylonitrile and solvents: density functional theory study and two-dimensional infrared...

Area of Science:

• Polymer Science and Engineering
• Materials Chemistry
• Computational Chemistry

Background:

• Polyacrylonitrile (PAN) is a polar, semicrystalline polymer typically processed from solutions.
• Solvent selection critically impacts the structure and properties of processed PAN materials.
• Understanding PAN-solvent interactions is key for optimizing polymer processing.

Purpose of the Study:

• To elucidate the interaction mechanisms between polyacrylonitrile (PAN) and various solvents.
• To theoretically and experimentally determine the binding affinities and interaction orders.
• To provide insights for selecting appropriate solvents for PAN processing.

Main Methods:

• Theoretical calculations using Density Functional Theory (DFT) to model PAN-solvent complexes.
• Experimental characterization via Fourier Transform Infrared (FTIR) spectroscopy.
• Advanced analysis using two-dimensional Infrared (2D-IR) correlation spectroscopy.

Main Results:

• DFT calculations confirmed dipole-dipole interactions forming PAN-solvent complexes with antiparallel alignment.
• Calculated binding energies indicated a preferential interaction order: DMSO2 > DMSO > EC > PC > DMF > DMAc.
• FTIR and 2D-IR analyses revealed red shifts in vibrational frequencies and distinct interaction dynamics depending on the solvent (DMSO vs. EC/DMF).

Conclusions:

• The study successfully combined theoretical and experimental approaches to characterize PAN-solvent interactions.
• Identified specific solvent interaction preferences and dynamics, offering guidance for solvent selection.
• The findings are valuable for optimizing the processing of PAN and other polar polymers.