APC Analysis of Polyamides in HFIP as an Alternative to High Temperature GPC

Importance of the Topic

Polyamides such as Nylon 6,6 are vital engineering polymers valued for their thermal and chemical resistance. Characterizing their molecular weight distribution is essential for quality control and performance prediction. Traditional high-temperature GPC methods rely on harsh solvents and elevated temperatures, leading to long run times, high solvent consumption, and increased hazardous waste.

Objectives and Study Overview

This application note evaluates the Waters ACQUITY Advanced Polymer Chromatography (APC) System using hexafluoro-2-propanol (HFIP) as a mobile phase. The goals are to reduce analysis time, lower solvent use, and maintain high resolution for polyamide molecular weight determination, presenting a sustainable alternative to conventional high-temperature GPC.

Methodology

Samples of various polyamides were dissolved at 1 mg/mL in HFIP overnight. The APC System operated isocratically at 0.45 mL/min with HFIP containing 0.1 % sodium trifluoroacetate. A temperature of 50 °C was applied to a five-column ACQUITY APC XT setup (45 Å to 900 Å particle pore sizes). Refractive index detection at 50 °C and Empower 3 software managed data acquisition and processing.

Instrumentation

• ACQUITY Advanced Polymer Chromatography System with Isocratic Solvent Manager
• Refractive Index Detector (ACQUITY UPLC RI)
• Empower 3 Chromatography Data System, FR5

Main Results and Discussion

PMMA calibration standards produced a 5th-order calibration curve with R² = 0.9985. The optimized 15-minute run achieved comparable resolution to a traditional 45-minute GPC, using under 7 mL of HFIP per injection versus over 22 mL. Shorter columns shifted high molecular weight points slightly off the linear range but did not compromise analysis of typical polyamide samples.

Benefits and Practical Applications

• Threefold faster analysis increases sample throughput.
• Substantially reduced toxic solvent consumption lowers operational costs and hazardous waste.
• High-pressure, low-dispersion APC retains resolution with viscous HFIP.
• Applicable to laboratories seeking greener, cost-effective polymer characterization.

Future Trends and Applications

Expanding HFIP-based APC to other resistant polymers, integrating automated sample preparation, and exploring alternative salt additives may further improve resolution and sustainability. Advances in column materials and detector technologies could enable even faster, more sensitive polymer separations.

Conclusion

The Waters ACQUITY APC System using HFIP offers a rapid, sustainable alternative to high-temperature GPC for polyamide molecular weight analysis, delivering high resolution with reduced solvent usage and analysis time.

Reference

• Palmer RJ. Polyamides, Plastics. In: Encyclopedia of Polymer Science and Technology. Wiley; 2001.
• Wudy K, Drummer D. Aging Effects of Polyamide 12 in Selective Laser Sintering: Molecular Weight Distribution and Thermal Properties. Additive Manufacturing. 2018;25.
• Chen A-L, Wei K-L, Jeng R-J, Lin J-J, Dai S. Well-Defined Polyamide Synthesis from Diisocyanates and Diacids Involving Hindered Carbodiimide Intermediates. Macromolecules. 2010;44.
• Trinite D, Gough J. Fast, High-Resolution Analysis of Polydimethylsiloxanes in Toluene with Advanced Polymer Chromatography Coupled to Refractive Index Detection. Waters Application Note. 2022.