Characterizing Polymer Folding Patterns Using Ion Mobility Mass Spectrometry

Importance of the Topic

The three-dimensional arrangement of polymer chains plays a critical role in determining their physical behavior and performance in applications. Traditional methods such as GPC and NMR characterize average molecular weight and composition but do not provide information on chain conformation and folding. Ion Mobility Spectrometry–Mass Spectrometry (IMS-MS) offers rapid insight into polymer size, shape, and flexibility with minimal sample preparation.

Study Objectives and Overview

This study demonstrates how IMS-MS can differentiate and characterize polymer folding patterns in various copolymers and polylactides. It compares block and random copolymers of PEG and PPG, identifies folding thresholds in sodiated polylactide, and validates experimental findings with theoretical models.

Methodology and Instrumentation

Samples of PEG-r-PPG, PEG-b-PPG-b-PEG copolymers, and polylactide were prepared in acetonitrile/water solutions at defined concentrations. Analyses were performed on a Waters SYNAPT G2 HDMS system equipped with a Triwave IMS device and ToF analyzer. Key parameters included positive ESI, infusion at 10 µL/min, drift gas nitrogen, and controlled temperatures for desolvation and source.

Key Results and Discussion

Mobility plots revealed that block copolymers produce a linear correlation between m/z and drift time, whereas random copolymers display pronounced kinks due to diverse conformers. For polylactide, experimental collision cross section measurements showed that doubly sodiated ions fold between 12–16 monomer units and triply sodiated ions fold between 24–36 units. IMS-MS data from SYNAPT G2 HDMS corroborated these thresholds and further resolved multiple folding events for triply charged species.

Benefits and Practical Applications

• Rapid characterization of polymer architecture and flexibility
• Minimal consumable and sample requirements
• Enhanced differentiation of copolymer structures for QA/QC
• Potential to isolate conformers for targeted analysis

Future Trends and Opportunities

As polymer design grows more complex, regulatory and industrial demands for detailed structural information will increase. Advances may include integration of IMS-MS with computational modeling for predictive conformational analysis and expansion to novel polymer systems in pharmaceuticals, food contact materials, and advanced materials research.

Conclusion

IMS-MS on the SYNAPT G2 HDMS platform provides a powerful complement to conventional polymer analysis techniques by revealing three-dimensional folding patterns and conformational diversity. The approach is fast, sensitive, and requires minimal sample preparation, offering significant advantages for polymer research and quality control.

Reference

1. S Trimpin, D E Clemmer. Anal Chem 2008, 80, 9073-9083
2. J Gidden et al. J Am Chem Soc 2000, 122, 4692-4699
3. J De Winter et al. Chem Eur J 2011, 17, 9738-9745