Temporally Stable Supramolecular Polymeric Salts Enabling High-Performance 3D All-Aromatic Polyimide Lattices

Area of Science:

• Polymer Chemistry
• Materials Science
• Additive Manufacturing

Background:

• Vat photopolymerization (VP) additive manufacturing (AM) is limited by the thermal performance of available aliphatic thermoset materials.
• Photoactive polyimide (PI) precursors, termed polysalts, were synthesized using ring-opening dianhydrides and acrylate nucleophiles.

Purpose of the Study:

• To address the instability of previously developed polysalts (e.g., ODA polysalts) caused by aza-Michael addition.
• To develop novel, stable polysalt solutions for high-resolution 3D printing of polyimides.

Main Methods:

• Synthesis of polysalts using sulfone-containing diamines (e.g., DDS) to prevent aza-Michael addition.
• In situ FTIR spectroscopy, solution, and photo-rheological measurements to analyze stability.
• Vat photopolymerization additive manufacturing to create 3D structures.

Main Results:

• Identified and resolved a time-dependent instability in ODA polysalts via aza-Michael addition.
• Developed stable DDS polysalt solutions enabling reproducible printing of polyimide organogel intermediates.
• Successfully 3D printed intricate, high-resolution all-aromatic polyimide structures, including the first beam latticed architecture.
• Demonstrated multi-material printing capability using alternating polysalt compositions.

Conclusions:

• Replacing electron-donating diamines with electron-withdrawing sulfone-containing monomers (DDS) creates stable, photocurable polyimide polysalts.
• This breakthrough enables advanced 3D printing of high-performance, all-aromatic polyimide components with complex geometries.
• The polysalt platform offers versatility for multi-material additive manufacturing applications.