High-Molecular-Weight Polymer Analysis by Laser Microprobe Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

The frequency-quadrupled output of a Nd:YAG laser (266 nm) is focused to a spot of about 10 micrometers diameter and used to ablate eight industrially important polymers of known composition within a Fourier transform ion cyclotron resonance mass spectrometer (FTICR). The spectra usually show distinct and dramatic differences compared with those obtained with conventional laser microprobes based on a time-of-flight approach. Although rearrangement products are more prevalent than structural ions, the spectra are directly distinguishable by qualitative inspection. Spectra are consistent with two simple mechanisms for formation of rearrangement products: carbon clustering and condensation of stable subunits. High-mass C clusters resembling the “fullerenes,” including a particularly prominent C 60 peak, are observed for poly(phenylene sulfide). Other polymers show low- and intermediate-mass C cluster distributions in positive-ion spectra. Odd-mass ion series which are consistent with the formula HA m B n + , where A and B are molecular fragments or atoms, are observed. Negative-ion spectra generally show more structural information than corresponding positive-ion spectra.