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Microphase Separation and Gelation through Polymerization-Induced Self-Assembly Using Star Polyethylene Glycols
ACS Macro Letters ( IF 5.1 ) Pub Date : 2024-07-31 , DOI: 10.1021/acsmacrolett.4c00273
Riku Yamanaka 1 , Ayae Sugawara-Narutaki 1, 2 , Rintaro Takahashi 1
Affiliation  

Polymerization-induced self-assembly (PISA) during the synthesis of diblock copolymers has garnered considerable interest; however, architectures beyond diblock copolymers have scarcely been explored. Here, we studied PISA using 4- and 8-arm star polyethylene glycol (PEG), as well as 2-arm (linear) PEG, wherein each terminus of PEG was functionalized with a chain-transfer agent, holding a constant molar mass for each arm. Styrene was polymerized from each PEG terminus through reversible addition–fragmentation chain-transfer (RAFT) polymerization in an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6]), with a total solute concentration of 40 wt %. While the styrene monomer is soluble in [BMIM][PF6], polystyrene is not; thus, self-assembly and cross-linking (gelation) occur. Structural analysis by small-angle X-ray scattering revealed that a relatively ordered microphase-separated structure for PISA was observed. Two-arm PEG-PS formed hexagonally packed cylinders, whereas 4- and 8-arm PEG-PS exhibited hexagonal close-packed spheres and disordered spheres. The dynamics, studied by oscillatory rheology, were also influenced by the number of arms; the 4-arm star block copolymers showed the highest plateau modulus. This study demonstrates that the topology is an important factor in controlling the microphase-separated structure and mechanical properties when preparing gels through PISA.

中文翻译:


使用星形聚乙二醇通过聚合诱导自组装实现微相分离和凝胶化



二嵌段共聚物合成过程中的聚合诱导自组装(PISA)引起了人们极大的兴趣;然而,除二嵌段共聚物之外的结构几乎没有被探索过。在这里,我们使用 4 臂和 8 臂星形聚乙二醇 (PEG) 以及 2 臂(线性)PEG 研究了 PISA,其中 PEG 的每个末端都用链转移剂功能化,保持恒定的摩尔质量每只手臂。苯乙烯在离子液体(1-丁基-3-甲基咪唑鎓六氟磷酸盐,[BMIM][PF 6 ])中通过可逆加成断裂链转移(RAFT)聚合从每个 PEG 末端聚合,总溶质浓度为 40 wt %。虽然苯乙烯单体可溶于[BMIM][PF 6 ],但聚苯乙烯却不能;因此,发生自组装和交联(凝胶化)。小角 X 射线散射的结构分析表明,观察到 PISA 具有相对有序的微相分离结构。二臂PEG-PS形成六方堆积圆柱体,而四臂和八臂PEG-PS则呈现六方密堆积球体和无序球体。通过振荡流变学研究的动力学也受到臂数的影响。四臂星形嵌段共聚物表现出最高的平台模量。这项研究表明,在通过 PISA 制备凝胶时,拓扑结构是控制微相分离结构和力学性能的重要因素。
更新日期:2024-07-31
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