Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry: determining Mark-Houwink-Sakurada parameters and analyzing the breadth of polymer molecular weight distributions

Polystyrene, poly(methyl methacrylate), and poly(ethylene glycol) standards were characterized via matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. This study develops two new contributions to the rapidly growing body of data appearing in recent literature. First, MALDI was found to be an optimum absolute molecular weight technique accompanying viscosity measurements for determining Mark-Houwink-Sakurada parameters. Second, since MALDI provides the mass spectra of polymer molecules without fragmentation, a new method of describing the breadth of the distribution of polymer standards is presented. The ratio of the distribution breadth at half-height to the molecular weight of the monomer unit, polymer spread, is shown to more clearly represent the molecular weight distribution than the customary ratio, M_w/M_n.