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Poly(ethylene oxide), poly(propylene oxide), and their copolymer (poly(EO-co-PO)) were analyzed by electrospray ionization-ion mobility spectrometry-mass spectrometry (ESI-IMS-MS). ESI produced multiply charged analytes of 2 to 5 Na + additions, and they were separately observed in a 2D map of m/z value vs. drift time. The collision cross-section of the analyte polymers was almost linearly proportional to (molecular weight) 0.644 , except for the analytes with 2Na + addition; a nonlinear relation called "folding" was significantly observed for the analytes with 2Na + addition. An increase in electrostatic repulsion, because of the increase in Na + addition, suppressed the folding of the polymer. Analyses of poly(EO-co-PO) with different EO compositions revealed that the copolymer with high EO composition tended to show folding. The separation of highly multiply charged poly(EO-co-PO)s with different EO contents by ESI-IMS-MS was successfully demonstrated.

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