Pyrolysis field desorption mass spectrometry of polymers. III. Aliphatic polyamides

Pyrolysis field desorption mass spectrometry has been performed from various polyamides such as nylon 6, 8, 12, and nylon 66. The pyrolytic behaviour of these compounds depends strongly on the solvent and the temperature program employed. Using formic acid as solvent strong thermal fragmentation is observed, while with 1,1,1,3,3,3‐hexafluoro‐2‐propanol almost exclusively molecular ions or cationized molecules of the monomer building block M are produced. With increasing temperature larger clusters of polymeric subunits (Mn + Na)+ are generated, but thermal fragmentation on the emitter surface also increases. The cationized molecules dominate all spectra. They are found from M3 to M5 or M15 depending on the chain length of the polymer subunit. With increasing temperature, the base peak of the spectrum is shifted to the higher mass end and small signals up to m/z 2000 and above are recorded. Thermal products are mainly formed by water elimination (−18 mu), loss of the acid amide group (−44 mu) after rearrangement and from longer polyamides by loss of the methylene groups (− 42 or 56 mu) by cis‐elimination. These thermal fragmentations of the polymeric substances on the emitter surface can be controlled by appropriate emitter heating and correlate directly with the common chemical knowledge of these materials in the liquid or solid phase. Together with the options of integrating recording, high mass resolution and direct isotope determination, the combination of pyrolysis and field desorption mass spectrometry offers a unique tool for characterization of building blocks and high mass sequences in synthetic polymers. Pyrolyse‐Felddesorptions‐Massenspektrometrie ist zur Untersuchung verschiedener Polyamide wie Nylon 6,8,12 und Nylon 66 verwendet worden. Das pyrolytische Verhalten dieser Verbindungen hängt stark vom Lösungsmittel und vom Temperatur‐programm ab. Ameisensäure als Lösungsmittel ruft starke thermische Fragmentierung hervor, während mit 1,1,1,3,3,3‐Hexafluoro‐2‐propanol fast ausschließlich Molekülionen oder kationisierte Moleküle gebildet werden. Mit zunehmender Temperatur entstehen größere Cluster der polymeren Untereinheit (Mn + Na)+, aber gleichzeitig nimmt die thermische Fragmentierung auf der Emitteroberfläche zu. Die kationisierten Moleküle sind in allen Spektren dominant. Sie werden von M3 bis M5 oder M15 gebildet, je nach Kettenlange der polymeren Untereinheit. Mit zunehmender Temperatur verschiebt sich der Basispeak des Spektrums zu höheren