Preparation and Characterization of Low-Molecular-Weight Polyacrylonitrile

Area of Science:

• Polymer Chemistry
• Materials Science
• Energetic Materials

Background:

• High-molecular-weight polyacrylonitrile (PAN) exhibits limitations in solubility and reactivity, hindering its use in advanced material applications.
• Developing low-molecular-weight PAN is crucial for overcoming these limitations and expanding its precursor potential.

Purpose of the Study:

• To synthesize low-molecular-weight polyacrylonitrile (PAN) via an environmentally friendly aqueous precipitation polymerization method.
• To characterize the structure, properties, and solubility of the synthesized low-molecular-weight PAN.
• To establish a method for rapid molecular weight determination of PAN.

Main Methods:

• Aqueous precipitation polymerization using ammonium persulfate as initiator and isopropanol as a chain transfer agent.
• Characterization techniques included FE-SEM, FT-IR, 1H NMR, TGA, DSC, and a visual melting point analyzer.
• Solubility studies and establishment of a linear regression for molecular weight estimation.

Main Results:

• Successfully synthesized low-molecular-weight PAN (Mη: 6.808 kDa) with improved solubility.
• Comprehensive analysis of PAN's morphology, chain structure, and thermal properties.
• First-time direct observation of state changes during PAN heating and established a linear regression for molecular weight determination via viscosity.

Conclusions:

• Low-molecular-weight PAN synthesized via CTA-controlled aqueous precipitation polymerization offers enhanced solubility and reactivity.
• This material holds significant potential as a precursor for tetrazole-based energetic materials.
• Viscosity measurements provide a simple and rapid method for determining PAN's molecular weight.