DETERMINATION OF BLOCK LENGTH DISTRIBUTIONS OF POLY(OXYPROPYLENE) ANDPOLY(OXYETHYLENE) BLOCK-COPOLYMERS BY MALDI-FTICR MASS-SPECTROMETRY

Matrix-assisted laser desorption/ionization (MALDI) was performed on a n external ion source Fourier transform ion cyclotron resonance mass s pectrometer (FTICR-MS) to analyze the block length distributions of tr iblock polymers of poly(oxypropylene) and poly(oxyethylene). The first series of results presented demonstrate that the apparent molecular w eight distributions are distorted. This distortion is induced by the f light-time-induced mass discrimination inherent in the experimental te chnique, the variation of isotopic patterns over the measured mass ran ge, and the overlap of peaks in the spectrum, Subsequently, a method f or the treatment of molecular weight distributions measured by MALDI o n an external ion source FI?CR-MS is developed to yield the actual mol ecular weight distribution and, from that, the individual block length distributions. For the first time, detailed and accurate molecular we ight data were obtained on a complex sample using this methodology, wh ich independently validates the data provided by the manufacturer. The experimentally verified random coupling hypothesis proves the validit y of the methodology.