Determination of Molecular Weight and Composition of a Perfluorinated Polymer from Fragment Intensities in Time-of-Flight Secondary Ion Mass Spectrometry

Abstract

Analysis of submicrogram quantities of a perfluorinated polyether (PFPE) homopolymer on different surfaces has been done by finding empirical, quantitative relationships between the Intensities of specific peaks in the high mass fragmentation spectra of tirne-of-flight secondary ion mass spectrometry (TOF-SIMS) and the composition of the PFPE and the number average molecular weight of the polymer samples. These relationships are explained in terms of a direct proportionality of the appropriate high mass fragment ion yields to these different properties of the PFPE material. Since both the positive- and negative-ion, high mass fragments of the PFPE are formed without any observable cationizatlon from the substrate species, these quantitative relationships are found to be relatively Independent of the substrate used to support the liquid PFPE films. This study represents one of the first attempts to make quantitative use of the high mass fragment ion intensities In SIMS studies of polymers. This is an important advance for the general case of quantitative analysis of polymers of up to 10000 amu on nonspecific substrates and H complements the powerful, but less general, technique of cationized molecular Ion SIMS, which requires special sample treatment and/or special substrates. © 1990, American Chemical Society. All rights reserved.