Soap-free emulsion polymerization of styrene using poly(methacrylic acid) macro-RAFT agent
Soap-free emulsion polymerization of styrene using poly(methacrylic acid) macro-RAFT agent
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DOI：
10.1016/j.polymer.2008.10.014
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发表时间：
2008-12
期刊：
影响因子：
4.6
通讯作者：
Yeonhwa Wi;K. Lee;B. Lee;S. Choe
中科院分区：
文献类型：
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作者：
Yeonhwa Wi;K. Lee;B. Lee;S. Choe
使用 4-甲基丙烯酸二硫代苯甲酸酯作为 RAFT 试剂，通过本体聚合合成了一种结构明确的聚（甲基丙烯酸）（PMAA）大分子 RAFT 试剂，并成功用作苯乙烯无皂乳液聚合中的反应性乳化剂，形成稳定的乳液。由原位胶束形成制备的两亲性嵌段共聚物含有亲水性 PMAA 嵌段和疏水性 PS 嵌段，在成核步骤中通过苯乙烯单体转移反应至 PMAA 大分子 RAFT 剂中的二硫酯官能团。使用 FTIR 和 NMR 确认了用 PMAA 大分子 RAFT 试剂合成的 PS 的化学结构。另外，通过ESCA测定，确认了粒子表面存在大分子RAFT剂。提出的反应机理是，稳定的球形颗粒是通过小颗粒的聚集而增大的，也是由微小的小颗粒之间的化学或物理键合产生的。结果表明，PMAA大分子RAFT剂用作乳化剂，原位形成PS颗粒和嵌段共聚物[P(S-b-MAA)]。
A well-defined poly(methacrylic acid) (PMAA) macro-RAFT agent has been synthesized by the bulk polymerization using 4-toluic acid dithiobenzoate as a RAFT agent and successfully employed as a reactive emulsifier in the soap-free emulsion polymerization of styrene, leading to a formation of stable latex. The amphiphilic block copolymer, prepared from the in situ micelle formation, contains a hydrophilic PMAA block and a hydrophobic PS block, via styrene monomer transfer reaction to the dithioester function in PMAA macro-RAFT agent during the nucleation step. The chemical structure of the synthesized PS with the PMAA macro-RAFT agent was confirmed using FTIR and NMR. In addition, it was confirmed that the macro-RAFT agent is present on the particle surface via the ESCA measurement. The reaction mechanism was proposed that the stable spherical particles enlarged by the aggregation of small particles, which were also produced by the chemical or physical bonding between the tiny small particles. The results indicate that the PMAA macro-RAFT agent is used as emulsifier for the formation of PS particles and block copolymer [P(S-b-MAA)] in situ.