Pyrolysis field desorption mass spectrometry of polymers: II. Pyrolysis field ionization and field desorption mass spectrometry of aliphatic and aromatic poly(4,4′-dipiperidylamides)

The first combined use of field ionization and field desorption mass spectrometry for the identification of pyrolysis produtcs and the characterization of technical polymers is reported.Pyrolysis with a specially designed inlet probe at temperature between 600 and 700°C generates gaseous products which can be ionized in a high electric field. The field ions are electrically recorded by low-resolution mass spectrometry and give a detailed insight into the pyrolysis mechanisms and the structure of the monomer unit. Mass shifts and changes in the relative abundances of significant ions allow one to determined the diamine and acid components in a homologous series of twelve polymers. Distinct differences in the thermal cleavages of aliphatic and aromatic poly (4,4′-dipiperidylamides) are observed.Direct submicro-pyrolysis of the polymers adsorbed on the surface of high-temperature-activated tungsten wires also shows clear differences for polymers with aliphatic and aromatic moieties. Electrical registration and integrating ion recording on photoplates under high mass resolution conditions yield sequences of singly and multiply charged ions which allow the detection of thermally produced, high-molecular-weight fragments >2000 mass units) of the synthetic polymers. A basic rule for the interpretation of pyrolysis-field desorption mass spectra of heteroatom-linked polymers is proposed and the characteristic features of ion formation are discussed.