Suppressing the Long-Chain Branching in the Synthesis of Poly(styrene-b-butyl acrylate-b-styrene) in RAFT Emulsion Polymerization by Tuning the Interfacial Properties
Suppressing the Long-Chain Branching in the Synthesis of Poly(styrene-b-butyl acrylate-b-styrene) in RAFT Emulsion Polymerization by Tuning the Interfacial Properties
复制标题
通过调节界面性质抑制RAFT乳液聚合聚(苯乙烯-b-丙烯酸丁酯-b-苯乙烯)合成中的长链支化
DOI：
10.1002/pola.27578
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Luo Yingwu
中科院分区：
文献类型：
--
作者：
Guo Yunlong;Gao Xiang;Luo Yingwu
可逆加成-断裂链转移（RAFT）乳液聚合是合成嵌段共聚物乳液的重要技术。先前的研究表明，在使用两亲性低聚（丙烯酸-苯乙烯）macroRAFT作为表面活性剂和介体通过RAFT乳液聚合合成聚苯乙烯-B-聚（丙烯酸丁酯）-B-聚苯乙烯三嵌段共聚物中，分子量分布可以大大加宽至高于2的PDI。在本研究中，进行了深入调查，以减少PDI。发现在三嵌段嵌段共聚物的合成中可以形成长链分支，导致在最终产物的GPC曲线中出现较高分子量肩部。macroRAFT上的丙烯酸（AA）单元的较低中和度和较短的AA链将有助于抑制长链分支的形成，导致PDI约为1.5。结果表明，成功的抑制是由于促进自由基进入的结果，降低界面传输阻抗。研究还表明，在丙烯酸丁酯聚合过程中，苯乙烯的存在可以促进长支链的形成。© 2015威利期刊公司. J.波利姆科学，A部分：聚合物Chem.2015，53，1464-1473
Reversible addition‐fragmentation chain transfer (RAFT) emulsion polymerization is becoming an important technique to synthesize the latex of block copolymers. A previous study showed that in the synthesis of polystyrene‐b‐poly(butyl acrylate)‐b‐polystyrene triblock copolymer via RAFT emulsion polymerization using amphiphilic oligo(acrylic acid‐styrene) macroRAFT as surfactant and mediator, the molecular weight distribution could be much broadened to PDI higher than 2. In this study, an in‐depth investigation was performed to decrease PDI. It was found that long‐chain branches could be formed in the synthesis of triblock block copolymer, leading to the appearance of a higher molecular weight shoulder in the GPC curve of the final product. The lower neutralization degree of acrylic acid (AA) units on the macroRAFT and shorter AA chains would help to suppress the formation the long‐chain branches, leading to PDI around 1.5. It is evidenced that the successful suppression is due to the promotion of radical entry as a result of decreased interfacial transport impedance. It is also evidenced that the presence of styrene during the polymerization of butyl acrylate could promote the formation of long chain branches. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2015,53, 1464–1473