CHARACTERIZATION OF POLYESTERS BY AGILENT 1260 INFINITY MULTI-DETECTOR GPC/SEC SYSTEM

Importance of Topic

Polyesters such as polyethylene terephthalate (PET) rank among the most versatile industrial polymers, finding use in textiles, packaging films and bottles. Their performance characteristics depend strongly on molecular weight and distribution. Accurate sizing of PET by gel permeation chromatography (GPC) is essential for quality control, product development and research into polymer structure–property relationships.

Objectives and Study Overview

This work demonstrates a robust GPC/SEC method for PET using the Agilent 1260 Infinity multi-detector system. The main goals were to overcome challenges in dissolving high-molecular-weight PET, to avoid high-temperature solvents, and to generate absolute molecular weights via light scattering independent of column calibration.

Methodology and Instrumentation

Sample preparation involved dissolving PET in hexafluoroisopropanol (HFIP) before dilution in chloroform. Analysis parameters included:

• Agilent 1260 Infinity Quaternary Pump, 1.0 mL/min flow
• Autosampler, 100 µL injection
• Column compartment at 30 °C with two PL Gel Mixed B columns
• Detectors: multi-detector suite with viscometer, light scattering and refractive index
• Eluent: 100 % chloroform

Column calibration was performed using polystyrene EasiVial standards to generate a 12-point curve.

Main Results and Discussion

Triple detection yielded the following average molecular weights for the PET sample: Mn ≈ 33 100, Mw ≈ 44 544, Mz ≈ 57 456 and dispersity ≈ 1.3. The light scattering detector provided absolute Mw independent of calibration. The Mark–Houwink plot showed a linear relationship (slope ≈ 0.75), indicating random coil conformation in a good solvent. Molecular weight distribution traces confirmed narrow polydispersity and uniform polymer architecture.

Benefits and Practical Applications

This approach offers:

• Reliable molecular weight determination without high-temperature solvents
• Reduced solvent costs by using HFIP only for dissolution
• Absolute measurement via light scattering, enhancing confidence in results
• Compatibility with routine QC and R&D workflows in polymer labs

Future Trends and Opportunities

Anticipated advances include:

• Integration of multi-angle light scattering for improved accuracy
• Automated online sample preparation to streamline PET analysis
• Expansion to copolyesters and recycled polymers
• Coupling with advanced data analytics for predictive polymer performance

Conclusion

The described protocol combining HFIP dissolution and chloroform analysis on the Agilent 1260 Infinity GPC system yields precise polymer size characterization. Triple detection, especially light scattering, ensures absolute molecular weight data, supporting reliable QC and materials research.

References

Agilent Technologies, Inc. 2016. Characterization of Polyesters by Agilent 1260 Infinity Multi-Detector GPC/SEC System. Document 5991-7039EN.