High resolution mass spectrometric access to nitroxide containing polymers
High resolution mass spectrometric access to nitroxide containing polymers
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DOI：
10.1039/c7py01316g
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发表时间：
2017-09-21
影响因子：
4.6
通讯作者：
Barner-Kowollik, Christopher
中科院分区：
文献类型：
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作者：
Fischer, Tobias S.;Steinkoenig, Jan;Barner-Kowollik, Christopher
我们通过高分辨率电喷雾电离质谱（HR ESI MS）引入了一种含氮氧化物聚合物的质谱获取途径，这是一种聚合物类别，由于存在不成对的自旋，因此通过核磁共振技术进行分析非常具有挑战性。在由苯乙烯-stat-4-（氯甲基）苯乙烯(p（S-stat-CMS), 4800 >= Mn/g mol(-1) = 11 100）组成的统计共聚物中，聚合后修饰的4-羧基-2,2,6,6-四甲基哌啶-1 -氧（4-羧基- tempo）单元在聚合物链结构内的氮氧化物含量变化在11.3 ~ 29.1 mol%之间。通过仔细评估含氮聚合物的同位素模式，我们证明了在使用高达4.3 keV的喷雾电流和在负离子模式下使用氯离子附着技术的源内碰撞诱导解离能高达30 eV的软电离过程中，持久的硝基自由基保持了其结构完整性。有趣的是，高分子量的气相聚集体被鉴定为氮氧化物侧链功能化的增加量。为了进一步证明所引入的质谱方案的力量，通过原子转移自由基聚合（ATRP, Mn = 5600 g mol(-1), D = 1.05）合成了一个定义良好的苯乙烯基聚合物，该聚合物含有官能团，即端氰酸单元和汉密尔顿楔形部分，以及汉密尔顿楔形的次位自由氮氧化物。在一个高度明确的聚合物结构中，完整的持久性氮氧自由基在链端被其同位素模式明确地识别出来。
We introduce a mass spectrometric access route to nitroxide containing polymers via high resolution electrospray ionization mass spectrometry (HR ESI MS), a polymer class that is -due to the presence of unpaired spins-highly challenging to analyze via NMR techniques. The nitroxide content within the polymer chain structure was varied between 11.3 and 29.1 mol% in a statistical copolymer consisting of styrene-stat-4-(chloromethyl) styrene (p(S-stat-CMS), 4800 >= Mn/g mol(-1) = 11 100), where 4-carboxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4-carboxy-TEMPO) units were attached by post-polymerization modification. By carefully evaluating the isotopic pattern of the nitroxide containing polymers, we demonstrate that the persistent nitroxyl radical retains its structural integrity during the soft ionization process employing spray currents up to 4.3 keV and in-source collision induced dissociation energies up to 30 eV using chloride attachment technology in negative ion mode. Interestingly, high-molecular weight gas-phase aggregates are identified with increasing amounts of nitroxide side-chain functionalization. To further exemplify the power of the introduced mass spectrometric protocol, a well-defined styrene based polymer was synthesized via atom transfer radical polymerization (ATRP, Mn = 5600 g mol(-1), D = 1.05) containing functional groups, i.e. a terminal cyanuric acid unit and Hamilton Wedge moiety as well as a free nitroxide in the penultimate position to the Hamilton wedge. The intact persistent nitroxide radical at the chain end was unambiguously identified by its isotopic pattern in a highly defined polymer structure.