Water-Induced Conformational Transitions and Complex Formation in Concentrated Polyacrylonitrile-Dimethyl Sulfoxide...

Area of Science:

• Polymer science and engineering
• Materials science
• Physical chemistry

Background:

• High-performance fiber technologies rely on understanding molecular interactions between solvents and polymers.
• Polyacrylonitrile (PAN) is a precursor for advanced fibers, particularly carbon fibers.
• The role of solvent composition, specifically water content in dimethyl sulfoxide (DMSO), on PAN solution properties is not fully understood.

Purpose of the Study:

• To elucidate the fundamental role of dimethyl sulfoxide-water interactions in polyacrylonitrile (PAN) solutions.
• To correlate molecular-level solvation phenomena with macroscopic rheological behavior and fiber properties.
• To establish a link between molecular solvation, processability, and the mechanical performance of PAN fibers.

Main Methods:

• Combination of vibrational spectroscopy (Infrared spectroscopy) and quantum-chemical modeling.
• Rheological analysis to assess viscoelastic properties.
• Controlled stretching experiments under varying humidity conditions.

Main Results:

• Infrared spectroscopy identified distinct hydrogen bonding signatures between solvent-solvent and solvent-polymer components.
• Quantum-chemical calculations rationalized these spectral signatures and correlated them with rheological behavior.
• The study revealed how water content influences PAN solution viscoelasticity and fiber drawability.
• Nanoscale solvent structuring was directly linked to tunable mechanical performance in PAN fibers.

Conclusions:

• Molecular solvation, specifically dimethyl sulfoxide-water interactions, significantly impacts PAN solution processability.
• The findings provide a molecular-level understanding of how solvent composition affects fiber properties.
• This research opens avenues for designing advanced precursors for high-performance fibers, including carbon fibers.