Gil Alvaradejo Gabriela, Glassner Mathias, Hoogenboom Richard, Delaittre Guillaume
Institute of Toxicology and Genetics (ITG), Karlsruhe Institute of Technology (KIT) Hermann-von-Helmholtz-Platz 176344 Eggenstein-Leopoldshafen Germany
Macromolecular Architectures, Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT) 76128 Karlsruhe Germany.
RSC Adv. 2018 Mar 5;8(17):9471-9479. doi: 10.1039/c8ra00948a. eCollection 2018 Feb 28.
The synthesis of poly(2-ethyl-2-oxazoline)s with a maleimide group at the α chain end was carried out from new sulfonate ester initiators bearing a furan-protected maleimide group. The conditions of the polymerization were optimized for 50 °C using conventional heating (in contrast to microwave irradiation) to counteract the thermal lability of the cycloadduct introduced to protect the maleimide double bond. At this temperature, a tosylate variant was found to be unable to initiate the polymerization after several days. The controlled polymerization of 2-ethyl-2-oxazoline with a nosylate derivative was, however, successful as shown by kinetic experiments monitored by gas chromatography (GC) and size-exclusion chromatography (SEC). Poly(2-ethyl-oxazoline)s of various molar masses (4500 < < 12 000 g mol) with narrow dispersity ( < 1.2) were obtained. The stability of the protected maleimide functionality during the polymerization, its deprotection, and the reactivity of the deprotected end group by coupling with a model thiol molecule were proven by H NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS). Finally, the conjugation of maleimide-functionalized poly(2-oxazoline) to a model protein (bovine serum albumin) was demonstrated by gel electrophoresis and MALDI-ToF mass spectrometry.
以带有呋喃保护的马来酰亚胺基团的新型磺酸酯引发剂为原料，合成了α链端带有马来酰亚胺基团的聚（2-乙基-2-恶唑啉）。采用常规加热（与微波辐射相反）在50℃下对聚合条件进行了优化，以抵消为保护马来酰亚胺双键而引入的环加成物的热不稳定性。在此温度下，发现对甲苯磺酸酯变体在几天后无法引发聚合反应。然而，通过气相色谱（GC）和尺寸排阻色谱（SEC）监测的动力学实验表明，用对硝基苯磺酸酯衍生物对2-乙基-2-恶唑啉进行的可控聚合反应是成功的。获得了各种摩尔质量（4500＜ ＜12000 g/mol）且分散度窄（ ＜1.2）的聚（2-乙基恶唑啉）。通过核磁共振氢谱（H NMR）和电喷雾电离质谱（ESI-MS）证明了聚合过程中受保护的马来酰亚胺官能团的稳定性、其脱保护以及脱保护端基与模型硫醇分子偶联的反应活性。最后，通过凝胶电泳和基质辅助激光解吸电离飞行时间质谱（MALDI-ToF）证明了马来酰亚胺功能化聚（2-恶唑啉）与模型蛋白（牛血清白蛋白）的共轭作用。
