[Characterization of insoluble polyamide-6,T by MALDI-TOF MS]

Five different sample solvents (trifluoroacetic acid, tetrahydrofuran, formic acid, acetonitrile, 60% acetonitrile /5% trifluoroacetic acid) and two kinds of sample preparation methods were chosen for characterizing the structure, mole mass and mass distribution of insoluble polymer of polyamide-6, T (PA6T) by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). It was shown that the spectra with wide mole mass and high signal-to-noise (S/N) ratio were obtained, when using 60% acetonitrile /5% trifluoroacetic acid as solvent, and solvent sample preparation with one step droplet method was better than non-solvent sample preparation. The main chain structure of PA6T polymerized in ionic liquid was analyzed, which was linear without the presence of cyclic polymer. Three structures of end groups were obtained, carboxyl group or amino group at both ends or carboxyl group at one end and amino group at the other. The mean mole mass and mass distribution were obtained by MALDI-TOF MS and size-exclude chromatography (SEC). It was shown that the mean mole mass by MALDI-TOF MS is lower than that by SEC and the mass distribution was narrower than that by SEC method, which resulted from the default of low mass fraction when calculated by exploring data and high mass fraction hardly detected for the difficulty of ionization. MALDI-TOF MS is a suitable method for the characterization of the structure and mole mass of insoluble poly(aromatic amide).