Solid Forms of Bio-Based Monomer Salts for Polyamide 512 and Their Effect on Polymer Properties

Area of Science:

• Materials Science
• Polymer Chemistry
• Crystallography

Background:

• Polyamide properties depend on polymerization and feedstock.
• Nylon salt solid forms critically influence final material characteristics.
• Long-chain bio-nylon 512 is the focus of this study.

Purpose of the Study:

• To investigate the solid forms of nylon 512 salt.
• To control and regulate these solid forms using phase transformations.
• To determine the effect of different solid forms on polyamide properties.

Main Methods:

• Extensive experimental screening for solid forms.
• Single-crystal X-ray diffraction and Hirshfeld surface analysis.
• Solid-state transformations (SSTs) and solution-mediated phase transformations (SMPTs).
• Direct solid-state polymerization (DSSP) and property characterization.

Main Results:

• Nylon 512 salt identified in two crystal forms (anhydrate, dihydrate) and four morphologies (needle, plate, rod, block).
• Formation of solid forms is influenced by water activity, temperature, solvent, and ultrasonic fields.
• Polyamides from anhydrate salt showed higher melting points (204.22 °C) and elastic modulus (3.366 GPa) than those from dihydrate salt.

Conclusions:

• Solid forms of nylon 512 salt can be regulated via SSTs and SMPTs.
• The crystal form and morphology of the nylon salt significantly affect the resulting polyamide's structure, melting point, and mechanical properties.
• Optimizing salt solid forms offers a pathway to tailor bio-nylon 512 performance.