Analysis of block copolymer by field desorption (FD) using JMS-T100GC “AccuTOF GC”

Significance of the topic

Field desorption mass spectrometry provides direct characterization of block copolymers by minimizing fragmentation and offering high sensitivity to polymer repeat units. Accurate compositional and molecular weight distribution data are essential for quality control and research in polymer science.

Objectives and Overview

This study applied field desorption mass spectrometry to a commercial poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) triblock copolymer using a time-of-flight detector, aiming to perform a detailed group-type analysis of the polymer structure.

Methodology and Instrumentation

A 50 mg/mL solution of the copolymer in tetrahydrofuran was used. Field desorption parameters included a cathode potential of –10 kV and an emitter current ramped to 40 mA. Spectra were acquired over m/z 35–1600 with a 1 s scan interval.

• Mass spectrometer JMS-T100GC AccuTOF GC in field desorption mode
• Cathode potential –10 kV
• Emitter current ramp 0 to 40 mA
• Mass range m/z 35–1600, 1 s spectral interval

Results and Discussion

The FD mass spectrum showed a base peak at m/z 1005.7 and a series of peaks spaced by 58 Da, corresponding to the addition of C3H6O (propylene oxide) units. Group-type analysis assigned combinations of C3H6O and C2H4O (ethylene oxide) repeats to signals between m/z 920 and 1020. Distribution analysis revealed PO repeat numbers from 12 to 17 and EO repeats from 0 to 10. Calculated molecular weights were a number average (Mn) of 1053.2, weight average (Mw) of 1077.1, Z average (Mz) of 1100.9 and a polydispersity index (PDI) of 1.03, indicating a narrow molecular weight distribution.

Benefits and Practical Applications

The integration of field desorption MS with dedicated group-type analysis software enables rapid determination of block copolymer composition and molecular weight metrics with minimal sample preparation. This approach supports quality control in polymer manufacturing and structure-property research.

Future Trends and Possibilities

Emerging emitter designs and coupling of field desorption with separation techniques may extend analysis to more complex polymer architectures. Advancements in high-resolution time-of-flight detection and machine learning for spectral interpretation are expected to further enhance analytical performance.

Conclusion

Field desorption mass spectrometry on the JMS-T100GC AccuTOF GC, combined with group-type analysis software, offers a fast, sensitive, and reproducible method for compositional profiling and molecular weight distribution of block copolymers.

Reference

• JEOL Ltd MS Data Sheet No 040 and No 110 Mass Spectrometry Application Group 2008