PULSED-LASER POLYMERIZATION MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS-SPECTROMETRY - AN APPROACH TOWARD FREE-RADICAL PROPAGATION RATE COEFFICIENTS OF ULTIMATE ACCURACY/

Free-radical polymerizations of styrene (S) and methyl methacrylate (M MA) in bulk were induced at 25 and 60 degrees C using a pulsed ultravi olet excimer laser. Molecular weight distributions (MWDs) of the polym er products produced were measured by both size exclusion chromatograp hy and matrix-assisted laser desorption/ionization mass spectrometry a nd compared with one another. Propagation rate coefficients k, were de termined from these MWDs taking into account impacts of varying termin ation rates and varying pulse periods as well as errors resulting from instrumental broadening. Values of k(p)(25 degrees C, S) = 96.5 L mol (-1) s(-1), k(p)(60 degrees C, S)= 364 L mol(-1) s(-1), k(p)(25 degree s C, MMA) = 372 L mol(-1) s(-1), and k(p)(60 degrees C, MMA) = 962 L m ol(-1) s(-1) are finally suggested.