Department of Chemistry, Knight Chemical Laboratory, The University of Akron, Akron, OH, 44325-3601, USA.
Department of Chemistry, Tulane University, New Orleans, LA, 70118, USA.
J Am Soc Mass Spectrom. 2019 Oct;30(10):1981-1991. doi: 10.1007/s13361-019-02260-0. Epub 2019 Jul 30.
Tandem mass spectrometry (MS) has been employed to elucidate the topology and branching architecture of star-branched polyethers. The polymers were ionized by matrix-assisted laser desorption/ionization (MALDI) to positive ions and dissociated after leaving the ion source via laser-induced fragmentation. The bond scissions caused under MALDI-MS conditions occur preferentially near the core-branch joining points due to energetically favorable homolytic and heterolytic bond cleavages near the core and release of steric strain and/or reduction of crowding. This unique fragmentation mode detaches complete arms from the core generating fragment ion series at the expected molecular weight of each branch. The number of fragment ion distributions observed combined with their mass-to-charge ratios permit conclusive determination of the degree of branching and the corresponding branch lengths, as demonstrated for differently branched homo- and mikto-arm polyether stars synthesized via azide-alkyne click chemistry. The results of this study underscore the utility of MS for the characterization of branching architecture and branch lengths of (co) polymers with two or more linear chains attached to a functionalized central core.
串联质谱（MS）已被用于阐明星型支化聚醚的拓扑结构和支化结构。聚合物通过基质辅助激光解吸/电离（MALDI）被离子化为正离子，并在离开离子源后通过激光诱导碎裂而解离。由于在核心和支链连接处附近的有利的均裂和异裂键断裂以及空间应变的释放和/或拥挤度的降低，MALDI-MS 条件下的键断裂优先发生。这种独特的碎裂模式会从核心上完全分离出完整的臂，在每个支链的预期分子量处产生碎片离子系列。观察到的碎片离子分布的数量及其质荷比允许对支化度和相应的支化长度进行明确的确定，如通过叠氮化物-炔点击化学合成的不同支化的同型和混合臂聚醚星所证明的那样。这项研究的结果强调了 MS 用于（共）聚合物的支化结构和支化长度的表征的实用性，这些聚合物具有两个或更多个线性链连接到功能化的中心核心上。
