Direct Radical Polymerization of Vinyl Ethers: Reversible Addition-Fragmentation Chain Transfer Polymerization of Hydroxy-Functional Vinyl Ethers
Direct Radical Polymerization of Vinyl Ethers: Reversible Addition-Fragmentation Chain Transfer Polymerization of Hydroxy-Functional Vinyl Ethers
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DOI：
10.1021/acs.macromol.6b00145
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发表时间：
2016-03-08
期刊：
影响因子：
5.5
通讯作者：
Maeda, Yasushi
中科院分区：
文献类型：
--
作者：
Sugihara, Shinji;Kawamoto, Yuki;Maeda, Yasushi
报道了前所未有的乙烯基醚可控自由基聚合（CRP）的可逆加成裂解链转移（RAFT）聚合。为了克服乙烯基醚直接自由基聚合的挑战，对2-羟乙基乙烯醚（HEVE）等商品羟基官能团乙烯基醚进行自由基聚合，得到不含聚缩醛的乙烯基聚合物。在使用非酸性偶氮引发剂如二甲基2,2'-偶氮（2-甲基丙酸）进行本体聚合的情况下，传统的自由基乙烯基聚合发生在足够高的数平均分子量下。以相应的HEVE单体为原料制备聚HEVE， M-n = 26 400，收率高，>= 75%。所得到的聚合物与使用受保护单体的活性阳离子聚合所制备的聚合物几乎相同，除了sterfc规则（自由基聚合和阳离子聚合的中位二元分别为51%和67%）。此外，氰甲甲基（苯基）氨基硫代酸酯被发现是一种有效的RAFT剂，使羟基官能团乙烯醚的CRP成为可能。在聚合条件下，制备了聚（HEVE）大分子链转移剂（macrocta）。RAFT聚合的动力学研究表明，分子量呈线性增加，单体转化率高达50%，多分散性相对较低（M-w/M-n < 1.38）。此外，用得到的聚（HEVE）宏观cta进行了扩链实验，包括与醋酸乙烯酯和n -乙烯基吡啶酮的嵌段共聚，以证实聚（HEVE）的“活性”。
Unprecedented controlled radical vinyl polymerization (CRP) of vinyl ethers using reversible addition fragmentation chain transfer (RAFT) polymerization is reported. In order to overcome the challenge of direct radical polymerization of vinyl ethers, commercial hydroxy-functional vinyl ethers such as 2-hydroxyethyl vinyl ether (HEVE) were subjected to free radical polyinerization, generating vinyl polymers without polyacetals obtained by self-polyaddition polymerization. In the case of bulk polymerization using a nonacidic azo-initiator such as dimethyl 2,2'-azobis(2-methylpropionate), conventional free radical vinyl polymerization occurred with sufficiently high number-average molecular weight. For example, poly(HEVE) was-produced,from the corresponding HEVE monomer with M-n = 26 400 in high yield, >= 75%. The resulting polymer was nearly identical to the polymer prepared by living cationic polymerization using the protected monomers except for the sterfc-regularity (meso dyads are 51% and 67% for radical and cationic polymerizations, respectively). Furthermore, cyanomethyl methyl(phenyl)carbamodithioate was found to be an efficient RAFT agent, enabling the CRP of hydroxy-functional vinyl ethers. Under the polymerization conditions, poly(HEVE) macromolecular chain transfer agent (macro-CTA) was prepared. The kinetic studies of RAFT polymerization showed a linear increase of the molecular weight, with up to 50% monomer conversion and relatively low polydispersities (M-w/M-n < 1.38). In addition, chain extension experiments including block copolymerization with vinyl acetate and N-vinylpyrrolidone were demonstrated using the resulting poly(HEVE) macro-CTA to confirm the "livingness" of the poly(HEVE).