Z-RAFT star polymerization of styrene: Comprehensive characterization using size-exclusion chromatography
Z-RAFT star polymerization of styrene: Comprehensive characterization using size-exclusion chromatography
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DOI：
10.1016/j.polymer.2008.09.048
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发表时间：
2008-11-10
期刊：
影响因子：
4.6
通讯作者：
Vana, Philipp
中科院分区：
文献类型：
--
作者：
Boschmann, Daniel;Edam, Rob;Vana, Philipp
本文详细研究了苯乙烯在80 ℃下的可逆加成-断裂链转移（RAFT）本体聚合反应，其中活性RAFT基团通过稳定化Z-基团与核相连。苯乙烯的这些Z-RAFT星星聚合显示出优异的分子量控制，直到非常高的单体转化率和大于200 kDa的星星尺寸。发现施加高达2600巴的高压显著增加了活性星星聚合物的相对量。即使在非常高的单体转化率和大的星星分子，阻碍RAFT过程的增长臂的屏蔽效应可以确定。通过使用线性和星形RAFT试剂的混合物，使用常规校准的SEC设置以高精度测定星星聚合物的绝对分子量。当使用苯乙基作为离去R-基团时，形成了与理论预测完全匹配的定义明确的星星聚合物。然而，当使用苄基作为离去基团时，观察到单体转化率对星星聚合物拓扑结构的显著影响，并且不能获得具有预期臂数的纯星星聚合物。(c)2008爱思唯尔有限公司保留所有权利。
Reversible addition-fragmentation chain transfer (RAFT) polymerizations of styrene in bulk at 80 degrees C using tri-, tetra-, and hexafunctional trithiocarbonates, in which the active RAFT groups are linked to the core via the stabilizing Z-group, were studied in detail. These Z-RAFT star polymerizations of styrene showed excellent molecular weight control up to very high monomer conversions and star sizes of more than 200 kDa. The application of high pressure up to 2600 bar was found to significantly increase the relative amount of living star polymer. Not even at very high monomer conversions and for large star molecules, a shielding effect of growing arms hampering the RAFT process could be identified. Absolute molecular weights of star polymers using a conventionally calibrated SEC setup were determined with high precision by using a mixture of linear and star-shaped RAFT agents. When using phenylethyl as the leaving R-group, well-defined star polymers that perfectly match the theoretical predictions were formed. However, when using benzyl as the leaving group, a pronounced impact of monomer conversion on the star polymer topology was observed and pure star polymers with the expected number of arms could not be obtained. (c) 2008 Elsevier Ltd. All rights reserved.