Identification and determination of cross-linkers in cross linked poly(vinylpyrrolidone) by pyrolysis-gas chromatography mass spectrometry

Pyrolysis-GC and pyrolysis-GC/MS were used to identify and quantify specific nitrogen-containing cross-linker compounds incorporated into the structures of commercially available cross-linked poly(vinylpyrrolidone) polymers which appear to be identical by FT-IR spectroscopy. The pyrolyzer regenerates and volatilizes specific cross-linkers which can be distinguished from other pyrolysate compounds by either peak retention time or mass spectral response. Individual compounds studied included 3-ethylidene-1-vinyl-2-pyrrolidone, 3,3'-ethylidenebis(1-vinyl-2-pyrrolidone), and N,N'-divinylimidazolidone. In general, the level of specific cross-linkers in various commercial products ranged from 1.8 to 2.5% w/w. The effect of pyrolysis temperature upon this level varied with the cross-linkers studied. The cross-linker content obtained by this technique correlated with the swell volume data for a specific series of cross-linked poly-(vinylpyrrolidone) samples made with a single cross-linker and having similar particle size distributions. The pyrolysis methodology cannot distinguish the level of crosslinker which is incorporated as a pendant functionality from that portion which is incorporated through both vinyl groups.