Controlled Chain Branching by RAFT-Based Radical Polymerization
Controlled Chain Branching by RAFT-Based Radical Polymerization
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DOI：
10.1021/ma025673b
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发表时间：
2003-05
期刊：
影响因子：
5.5
通讯作者：
Zhongmin Wang;Junpo He;Y. Tao;Liu Yang;Hongjin Jiang;Yuliang Yang
中科院分区：
文献类型：
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作者：
Zhongmin Wang;Junpo He;Y. Tao;Liu Yang;Hongjin Jiang;Yuliang Yang
苯乙烯自由基聚合是在一种可聚合的二硫酯——4-乙烯基二硫苯甲酸苄酯存在下进行的，它具有一个二硫酯基团和一个可聚合的双键。产物的多模态GPC曲线表明，聚合过程中形成了支化聚苯乙烯。支化聚苯乙烯在每个支点上含有一个二硫代苯甲酸酯C(dS)S片段，因此可以用胺解理来分析。解理后，GPC的轮廓变窄。随着单体转化率的增加，裂解产物的分子量呈线性增加，说明了聚合反应的活跃形式。通过同时在线测量粘度和光散射得到的溶液性质表明，与等分子量的线性聚苯乙烯相比，支化产物的粘度明显降低。采用红外光谱（FT-IR）对苯乙烯与4-乙烯基二硫苯甲酸苄酯的共聚行为进行了研究。结果表明，后者被均匀地掺入到聚苯乙烯链中。因此，根据原链的长度和窄分布，以及聚合物链上支化的程度和分布，合成了具有可控结构的支化聚苯乙烯。
Styrene radical polymerization was carried out in the presence of a polymerizable dithioester, benzyl 4-vinyldithiobenzoate, which possesses a dithioester group and a polymerizable double bond. Branched polystyrene was formed during the polymerization, as indicated by multimodal GPC curves of the products. The branched polystyrene contains a dithiobenzoate C(dS)S moiety at each branch point and thus can be analyzed by cleavage with amine. After cleavage, the GPC profiles became narrow. The molecular weight of the cleaved product increased linearly with monomer conversion, illustrating a living fashion of the polymerization. Solution property obtained by simultaneous online measurements of viscosity and light scattering indicates that the viscosity of the branched product decreased remarkably as compared to the linear polystyrene of equivalent molecular weight. The copolymerization behavior of styrene and benzyl 4-vinyldithiobenzoate was investigated by FT-IR monitoring during the polymerization. The results show that the latter was incorporated homogeneously into polystyrene chain. Therefore, branched polystyrene was synthesized with controlled architecture in the light of the length and narrow distribution of primary chains as well as the degree and the distribution of branching along the polymer chain.