Universités Aix-Marseille I, II et III-CNRS, UMR 6264: Laboratoire Chimie Provence, Spectrométries Appliquées à la Chimie Structurale, F-13397 Marseille, France.
Anal Chim Acta. 2009 Nov 3;654(1):49-58. doi: 10.1016/j.aca.2009.06.044. Epub 2009 Jun 24.
Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have been combined to achieve the complete microstructural characterization of a poly(methacrylic acid)-poly(methyl methacrylate) (PMAA-PMMA) copolymer synthesized by nitroxide-mediated polymerization. Various PMAA-PMMA species could be identified which mainly differ in terms of terminaisons. 1H and 13C NMR experiments revealed the structure of the end-groups as well as the proportion of each co-monomer in the copolymers. These end-group masses were further confirmed from m/z values of doubly charged copolymer anions detected in the single stage mass spectrum. In contrast, copolymer composition derived from MS data was not consistent with NMR results, obviously due to strong mass bias well known to occur during electrospray ionization of these polymeric species. Tandem mass spectrometry could reveal the random nature of the copolymer based on typical dissociation reactions, i.e., water elimination occurred from any two contiguous MAA units while MAA-MMA pairs gave rise to the loss of a methanol molecule. Polymer backbone cleavages were also observed to occur and gave low abundance fragment ions which allowed the structure of the initiating end-group to be confirmed.
质谱 (MS) 和核磁共振 (NMR) 已被结合使用，以实现通过氮氧自由基介导聚合合成的聚（甲基丙烯酸）-聚（甲基丙烯酸甲酯）（PMAA-PMMA）共聚物的完全微观结构表征。可以鉴定出各种 PMAA-PMMA 物种，它们主要在端基方面有所不同。1H 和 13C NMR 实验揭示了端基的结构以及共聚物中每种共聚单体的比例。这些端基质量进一步通过在单级质谱中检测到的双电荷共聚物阴离子的 m/z 值得到证实。相比之下，来自 MS 数据的共聚物组成与 NMR 结果不一致，这显然是由于在这些聚合物物种的电喷雾电离过程中存在众所周知的强烈质量偏差。串联质谱可以基于典型的解离反应揭示共聚物的随机性质，即水从任何两个相邻的 MAA 单元中消除，而 MAA-MMA 对则导致甲醇分子的损失。还观察到聚合物主链的断裂，并产生低丰度的片段离子，这允许确认引发端基的结构。
