RAFT polymerization of acrylonitrile and preparation of block copolymers using 2-cyanoethyl dithiobenzoate as the transfer agent
RAFT polymerization of acrylonitrile and preparation of block copolymers using 2-cyanoethyl dithiobenzoate as the transfer agent
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DOI：
10.1021/ma034942a
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发表时间：
2003-11-18
期刊：
影响因子：
5.5
通讯作者：
Matyjaszewski, K
中科院分区：
文献类型：
--
作者：
Tang, CB;Kowalewski, T;Matyjaszewski, K
过去十年见证了受控/活性自由基聚合 (CRP) 领域的重大发展，1-4 它使人们能够合成具有受控摩尔质量、窄分子量分布以及明确的结构和功能的聚合物。 5-8 详细研究了几种 CRP 工艺，包括使用过渡金属络合物的原子转移自由基聚合 (ATRP)、使用硝基氧的 9-11 硝基氧介导的聚合 (NMP)、12 和使用二硫酯的可逆加成断裂链转移 (RAFT)。 4, 13 CRP 与多种单体相容，包括丙烯酸酯、甲基丙烯酸酯和苯乙烯。丙烯腈（AN）是一种具有挑战性的单体，因为它的高反应活性和聚丙烯腈（PAN）的溶解度差。然而，PAN 有多种重要应用，例如碳纤维的制备，14 这促使人们以受控方式合成聚丙烯腈 (PAN)。我们的小组 15-17 已经报道了通过 ATRP 合成明确的 PAN。此外，我们还研究了含有 AN 和丙烯酸正丁酯 (n-BA) 的嵌段共聚物的合成，该共聚物具有明确的结构，17 直接需要通过热解制备纳米结构碳阵列。 18 Hawker 和同事 19 以及我们小组 17 报告了使用 NMP 控制 PAN 的合成。我们组还制备了具有明确结构的AN和n-BA嵌段共聚物。 17 RAFT法制备PAN尚未见报道。 RAFT 涉及活性物质和休眠物质之间的可逆加成-断裂链转移，并通过添加合适的二硫酯转移剂 (1) 进行，该转移剂具有选择的适当 Z 和 R 基团以提供有效的转移过程。 20-22 我们首次尝试在 AN 聚合中使用二硫代苯甲酸枯基酯 (CDB, 2)，但未能很好地控制聚合（表 1 中的条目 3 和 4）。本文介绍了一种新型二硫酯，二硫代苯甲酸2-氰基乙酯（CED，3）作为RAFT试剂，可以制备窄分子量分布的PAN及其嵌段共聚物。
The past decade has witnessed significant developments in the field of controlled/living radical polymerization (CRP), 1-4 which enables one to synthesize polymers with controlled molar mass, narrow molecular weight distribution, and well-defined architectures and functionalities. 5-8 Several CRP processes were investigated in detail, including atom transfer radical polymerization (ATRP) using transition metal complexes, 9-11 nitroxide-mediated polymerization (NMP) using nitroxides, 12 and reversible addition-fragmentation chain transfer (RAFT) using dithioesters. 4, 13 CRP is compatible with a wide range of monomers including acrylates, methacrylates, and styrene. Acrylonitrile (AN) is a challenging monomer because of its high reactivity and the poor solubility of polyacrylonitrile (PAN). Nevertheless, PAN is used in several important applications, such as the preparation of carbon fibers, 14 which motivates one to synthesize polyacrylonitrile (PAN) in a controlled way. Our group15-17 already reported the synthesis of well-defined PAN by ATRP. Furthermore, we investigated the synthesis of block copolymers containing AN and n-butyl acrylate (n-BA) with well-defined structures, 17 which were needed directly to prepare nanostructured carbon arrays by pyrolysis. 18 Hawker and coworkers, 19 and our group, 17 reported controlled synthesis of PAN using NMP. Block copolymers of AN and n-BA were also prepared with well-defined structures by our group. 17The preparation of PAN by RAFT has not yet been reported. RAFT involves a reversible addition-fragmentation chain transfer between an active and a dormant species and is performed by adding a suitable dithioester transfer agent (1), which has the appropriate Z and R groups selected to provide an effective transfer process. 20-22 Our first attempts to use cumyl dithiobenzoate (CDB, 2) in AN polymerizations did not control the polymerization well (entries 3 and 4, Table 1). In this paper a new dithioester, 2-cyanoethyl dithiobenzoate (CED, 3), is introduced as a RAFT agent, allowing preparation of PAN and its block copolymers with narrow molecular weight distribution.