The atom transfer radical polymerization (ATRP) of styrene was investigated using the popular alkyne-functional initiator prop-2-yn-1-yl 2-bromo-2-methylpropanoate (PBiB). The polymerization kinetics and evolution of molecular weight as a function of monomer conversion were systematically studied with PBiB and similar initiators with protecting groups at the reactive propargylic and terminal acetylenic sites. These studies were compared to control studies using the nonfunctional initiator ethyl 2-bromoisobutyrate. As confirmed by NMR analysis of a model reaction, the terminal alkynes undergo oxidative alkyne–alkyne coupling under ATRP conditions, resulting in polymers with bimodal molecular weight distributions. This side reaction is significant because it diminishes the orthogonality of ATRP/copper-catalyzed azide–alkyne cycloaddition procedures as well as the control of ATRP.

中文翻译：

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丙基-2-炔-1-基2-溴-2-甲基丙酸酯：鉴定和抑制常用的末端炔烃功能ATRP引发剂的副反应

使用流行的炔烃官能引发剂2-溴-2-甲基丙酸丙-2-炔-1-基丙酯（PBiB）研究了苯乙烯的原子转移自由基聚合（ATRP）。用PBiB和类似的在反应性炔丙基和炔基末端带有保护基的引发剂，系统地研究了聚合动力学和分子量随单体转化率的变化。将这些研究与使用非功能性引发剂2-溴异丁酸乙酯的对照研究进行了比较。如模型反应的NMR分析所证实的，末端炔烃在ATRP条件下会经历氧化炔烃-炔烃偶联反应，从而产生具有双峰分子量分布的聚合物。