Mechanism of Z-RAFT Star Polymerization
Mechanism of Z-RAFT Star Polymerization
复制标题
Z-RAFT星形聚合机理
DOI：
10.1021/bk-2009-1024.ch014
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
P. Vana
中科院分区：
文献类型：
--
作者：
D. Boschmann;M. Mänz;M. G. Fröhlich;G. Zifferer;P. Vana
苯乙烯和几种丙烯酸酯的Z-RAFT星星聚合使用多功能星形RAFT试剂，其中多达六个控制二硫酯部分通过其Z-基团不可逆地连接到核，其特征在于在实验和模拟方面的深入其机制。详细介绍了通过常规校准SEC获得星星聚合物的绝对摩尔质量的方法，以及通过NMR使用全氘代单体跟踪臂生长的初始化的方法。这些研究揭示了预平衡的重要影响，即，在星星聚合物拓扑结构上离去基团的选择。在主平衡中发生的屏蔽效应的蒙特卡罗模拟表明，空间拥挤在很大程度上不影响该过程。在丙烯酸酯的Z-RAFT星星聚合反应中，由于分子间的链转移，出现了意想不到的星-星星偶联。最后，提出了一种基于倍半硅氧烷核的新型八角形Z-RAFT试剂。
Z-RAFT star polymerizations of styrene and several acrylates using multifunctional star-shaped RAFT agents, in which up to six controlling dithioester-moieties are irreversibly linked to the core via their Z-group, were characterized in-depth both experimentally and by simulations with respect to their mechanism. Methods for obtaining absolute molar masses of star polymers via conventionally calibrated SEC and for tracing the initialization of arm growth via NMR using fully deuterated monomer are detailed. These studies revealed a significant impact of the pre-equilibrium, i.e., the choice of the leaving group, on the star polymer topology. Monte Carlo simulations of the shielding effect occurring in the main equilibrium indicated that steric congestion is not affecting the process to a major extent. Unexpected star-star coupling in Z-RAFT star polymerization of acrylates was identified as a result of intermolecular chain transfer to polymer. Finally, a novel octagonal Z-RAFT agent that bases on a silsesquioxane core is presented.