MALDI-TOF MASS-SPECTROMETRY IN THE STUDY OF STATISTICAL COPOLYMERIZATIONS AND ITS APPLICATION IN EXAMINING THE FREE-RADICAL COPOLYMERIZATION OF METHYL-METHACRYLATE AND N-BUTYL METHACRYLATE

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry nas used to obtain bivariate distributions of compo sition and chain length for a series of copolymers of methyl methacryl ate (MMA) and n-butyl methacrylate (BMA) produced by free radical cata lytic chain transfer polymerization. The relationship between the biva riate distributions of copolymers and the kinetics of the copolymeriza tion reactions from which they were formed was derived using the termi nal copolymerization model. This relationship was used with the mass s pectra from the MMA/BMA copolymerizations studied to estimate kinetic parameters which describe the polymerizations. For this copolymerizati on the reactivity ratios, (catalytic) chain transfer coefficients, and initiator selectivity were determined to be r(MMA) = 1.09, r(BMA) = 0 .77, C-S,C-MMA = 17 900, C-S,C-BMA = 6150, and S-MMA = 0.535, respecti vely The reactivity ratios for these polymerizations were also determi ned from H-1 NMR to be r(MMA) = 0.75 and r(BMA) = 0.98, using an error -in-variables model (EVM) treatment. The parameters determined from th e mass spectra were compared with both the NMR values and literature v alues, where available, and general agreement is shown.