POLYMER MOLECULAR-WEIGHT DISTRIBUTION - RESULTS FROM MATRIX-ASSISTED LASER-DESORPTION IONIZATION COMPARED WITH THOSE FROM GEL-PERMEATION CHROMATOGRAPHY

A sample of poly(methyl methacrylate) (PMMA), of which the molecular w eight was known from light-scattering measurements, was subjected to g el-permeation-chromatographic analysis, and the resulting Weight versu s log molecular weight (MW) plot was converted by suitable computation to a Number versus linear MW plot. This could then be compared direct ly with the matrix-assisted laser desorption ionization MW distributio n results obtained for the same sample. The MW distributions obtained by the two methods were significantly different. Two explanations for the discrepancy are offered.