APPLICATION OF SIZE-EXCLUSION CHROMATOGRAPHY MATRIX-ASSISTED-LASER-DESORPTION IONIZATION TIME-OF-FLIGHT TO THE DETERMINATION OF MOLECULAR MASSES IN POLYDISPERSE POLYMERS/

The determination of molecular mass (MM) data for polydisperse polymer s by size exclusion chromatography matrix assisted laser desorptinn/io nization time-of-flight (SEC/MALDI-TOF) involves the fractionation of samples through an analytical SEC. Selected fractions are then analyse d by MALDI-TOF and the mass spectra of these nearly monodisperse sampl es allow the determination of M-n and M-w averages. To test the reliab ility of the molecular mass estimates by the SEC/MALDI-TOF method, a s ample of polymethylmethacrylate (PMMA), two samples of polydimethylsil oxane (PDMS), and four samples of copolyesters, all polydisperse, were analysed. The results show that the molecular mass values of PMMA fra ctions obtained by MALDI-TOF are coincident with those obtained using the SEC calibration plots obtained with anionic PMMA standards. In the case of the two polydimethylsiloxanes (PDMS1 and PDMS2: linear and cy clic, respectively), two slightly differing SEC calibration plots were obtained, reflecting the different structures of the polymer chains o f the two samples. The SEC traces of four copolyesters were obtained i n tetrahydrofuran and CHCl3. Data on MM, MM distribution solvent effec ts and copolymer composition are reported. (C) 1998 John Wiley & Sons, Ltd.