Unraveling the Spontaneous Zwitterionic Copolymerization Mechanism of Cyclic Imino Ethers and Acrylic Acid
Unraveling the Spontaneous Zwitterionic Copolymerization Mechanism of Cyclic Imino Ethers and Acrylic Acid
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DOI：
10.1021/acs.macromol.7b02608
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发表时间：
2018-01-23
期刊：
影响因子：
5.5
通讯作者：
Kempe, Kristian
中科院分区：
文献类型：
--
作者：
Steinkoenig, Jan;de Jongh, Patrick A. J. M.;Kempe, Kristian
报道了一种高分辨电喷雾电离质谱仪(HR-ESI-MS)，利用共聚过程中积累的特征物种和串联质谱学(MS/MS)，深入研究了环亚胺基醚(即2-甲基-2-恶唑啉(MeOx)、2-乙基-2-恶唑啉(EtOx)或2-乙基-2-恶嗪(EtOz))与丙烯酸(AA)之间的自发两性离子共聚合机理。我们通过筛选环亚胺醚和丙烯酸的不同进料比例(例如，MeOx：AA=1：1；MeOx：AA=2：1；以及MeOx：AA=1：2)，展示了在α，omega-端基团形成中的偏好。关键的是，建立了一条基于AA-MeOx-AA二聚体的校正曲线，允许半定量地测定不同进料比例的丙烯酸的端基比例。MS/MS实验证实了上述交替共聚物的形成。从MeOx到EtOx再到EtOz，与理想交替组成的偏差被发现减小。(半定量)HR-ESI-MS和MS/MS测量结果首次如此精确地提出了两性离子(交替)自发共聚的聚合机理，表明了最佳的单体比例和配对。
We report a high-resolution electrospray ionization mass spectrometric (HR ESI-MS) access route leading to in-depth insights into the spontaneous zwitterionic copolymerization mechanism between cyclic imino ethers (i.e., 2-methyl-2-oxazoline (MeOx), 2-ethyl-2-oxazoline (EtOx), or 2-ethyl-2-oxazine (EtOz)) with acrylic acid (AA), exploiting the characteristic species accumulating during the copolymerization as well as tandem mass spectrometry (MS/MS). We demonstrate preferences in alpha,omega-end group formation by screening various feed ratios of cyclic imino ethers and acrylic acid (e.g., MeOx:AA = 1:1; MeOx:AA = 2:1; and MeOx:AA = 1:2). Critically, a calibration curve-based on AA-MeOx-AA dimer-was established allowing for the semiquantitative determination of the end-group ratios with different feed ratios of acrylic acid. The formation of previously suggested alternating copolymers was confirmed by MS/MS experiments. Deviations from an ideal alternating composition were found to decrease from MeOx to EtOx to EtOz. The results of (semiquantitative) HR ESI-MS and MS/MS measurements suggest, for the first time presented in such precision, a polymerization mechanism for the spontaneous zwitterionic (alternating) copolymerization indicating optimal monomer ratios and pairings.