CHARACTERIZATION OF BRANCHED ALKYL END-GROUPS OF POLY(METHYL METHACRYLATE) BY PYROLYSIS-GAS CHROMATOGRAPHY

Branched alkyl end groups of poly(methyl methacrylate) (PMMA) polymeri zed radically with 2,2'-aiobis(2,4,4-trimethylpentane) as an initiator were characterized by pyrolysis-gas chromatography (Py-GC). On the re sulting pyrogram at 540 degrees C, characteristic products formed from the end group moiety due to the initiator, such as isobutane, isobute ne, and so on, were clearly separated from those from the main chain. Then number-average molecular weight (M(n)) of PMMA was determined by the ratio of the relative intensity of these peaks due to the end grou p and the main chain. After simple correction using a reference PMMA s ample having different end groups, M(n) values estimated by Py-GC agre ed well with those obtained by size exclusion chromatography. Furtherm ore, determination of end groups well supported the assumption that di sproportionation was dominant in termination in this polymerization sy stem of MMA.