MASS-SPECTROSCOPY AND SEC OF SRM-1487, A LOW-MOLECULAR-WEIGHT POLY(METHYL METHACRYLATE) STANDARD

Matrix Assisted Laser Desorption Ionization (MALDI) Time of Flight (TO F) Mass Spectrometry (MS) was used to study the molecular weight distr ibution (MWD) and the number of alpha-methyl styrene (alpha-MeSty) rep eat units in SRM 1487, a narrow MWD poly(methyl methacrylate) (PMMA) s tandard reference material of about 6300 g/mol, which was initiated wi th alpha-MeSty. It was found that each PMMA polymer chain had from zer o to seven alpha-MeStys per chain. The MWD of the polymer chains conta ining a fixed number of alpha-MeStys was obtained. The MWD, M-w, and t he average number of alpha-MeSty at a given molecular weight from MALD I TOF NS compare well with those obtained from more traditional method s such as ultracentrifugation and Size Exclusion Chromatography (SEC). The implications of the number of alpha-MeStys per chain is discussed in terms of the chemistry of anionic polymerization. (C) 1997 John Wi ley & Sons, Inc.