MEASURING OXIDE RATIOS IN MIXED-OXIDE POLYOLS BY SOLVERE LIQUID CHROMATOGRAPHY DETECTOR

Importance of the topic

Accurate determination of co-monomer ratios in mixed-oxide polyols is critical for quality control and performance optimization in polymer manufacturing. Conventional methods such as NMR and FTIR can be resource-intensive and may not provide molecular weight-resolved composition data. The Solvere LC detector offers a simplified, mass-sensitive approach capable of quantifying carbon content across a polymer's molecular weight distribution.

Objectives and study overview

This study evaluated the feasibility of using gel permeation chromatography (GPC) paired with refractive index (RI) and Solvere detectors to measure relative carbon content in polyols composed of varying ratios of short-chain and long-chain oxides. The aim was to establish a linear correlation between the detector response ratio and the actual carbon fraction determined by CHN analysis.

Methodology and instrumentation

Polyol samples were dissolved in THF at 0.2 g/20 mL. GPC separations were performed on an Agilent 1260 system with a PLgel MiniMix-D column, using THF at 0.4 mL/min. Parallel detection included:

• Agilent variable wavelength detector at 270 nm
• Agilent refractive index detector
• Solvere LC detector interfaced via Agilent 35900E A/D

Solvere signals were baseline-corrected and scaled to match RI magnitude. Retention times were aligned to compensate for Solvere flow path delay. Absolute peak areas were extracted and plotted as the Solvere/RI ratio.

Main results and discussion

Overlay chromatograms show that as the proportion of long-chain oxide increases, the Solvere/RI peak area ratio rises accordingly. A linear relationship (R² = 0.87) was found between this ratio and the CHN-measured carbon fraction across 14 polyol samples. Excluding three statistical outliers improved the correlation to R² = 0.94. These findings demonstrate the detector’s potential for predicting carbon content directly from chromatographic data.

Benefits and practical applications

The Solvere detector provides:

• Rapid, chromatography-resolved composition analysis without external calibration
• Simultaneous molecular weight distribution and carbon content profiling
• Reduced analysis time and resource requirements compared to NMR and FTIR

This approach supports quality control and formulation optimization in polymer and polyol production.

Future trends and possibilities

Further work should explore:

• Validation with larger sample sets and replicates
• Extension to other co-monomer systems with fixed heteroatom content
• Integration of advanced data processing for automated composition mapping
• Coupling with additional detectors for multi-property analysis

Such developments could enhance in-line monitoring and feed-forward control in industrial settings.

Conclusion

The Solvere LC detector combined with GPC separation offers a viable, efficient method for measuring carbon-based co-monomer ratios in mixed-oxide polyols. The demonstrated linear response to carbon fraction enables simultaneous assessment of molecular weight and composition, streamlining polymer analysis workflows.

References

1. Erskine S., Fosdick S., Fan J., Hawkes A., Saunders T., Jones A. Measuring Oxide Ratios in Mixed-Oxide Polyols by Solvere Liquid Chromatography Detector, Application Note, Dow Chemical and Activated Research Company