Abstract Sharply thermo- and pH-responsive pentablock terpolymer with a core-shell-corona structure was prepared by RAFT polymerization of N-isopropylacrylamide and methacrylic acid monomers using PEG-based benzoate-type of RAFT agent. The PEG-based RAFT agent could be easily synthesized by dihydroxyl-capped PEG with 4-cyano-4-(thiobenzoyl) sulfanylpentanoic acids, using esterification reaction. This pentablock terpolymer was characterized by 1H NMR, FT-IR, and GPC. The PDI was obtained by GPC, indicating that the molecular weight distribution was narrow and the polymerization was well controlled. The thermo- and pH-responsive micellization of the pentablock terpolymer in aqueous solution was investigated using fluorescence spectroscopy technique, UV–vis transmittance, and TEM. The LCST of pentablock terpolymer increased (over 50 °C) compared to the NIPAM homopolymer (~32 °C), due to the incorporation of the hydrophilic PEG and PMA blocks in pentablock terpolymer (PNIPAM block as the core, PEG the block and the hydrophilic PMA block as the shell and the corona). Also, pH-dependent phase transition behavior shows at a pH value of about ~5.8, according to pKa of MAA. Thus, in acidic solution at room temperature, the pentablock terpolymer self-assembled to form core–shell–corona micelles, with the hydrophobic PMA block as the core, the PNIPAM block and the hydrophilic PEG block as the shell and the corona, respectively.

中文翻译：

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RAFT自由基聚合合成对温度和PH值敏感的PMA-b-PNIPAM-b-PEG-b-PNIPAM-b-PMA及其在水溶液中的分裂胶束化


摘要 采用PEG基苯甲酸酯型RAFT试剂，通过N-异丙基丙烯酰胺和甲基丙烯酸单体的RAFT聚合制备了具有核-壳-电晕结构的热响应性和pH响应性五嵌段三元共聚物。基于PEG的RAFT剂可以通过二羟基封端的PEG与4-氰基-4-(硫代苯甲酰基)磺基戊酸通过酯化反应轻松合成。这种五嵌段三元共聚物通过 1H NMR、FT-IR 和 GPC 进行了表征。通过GPC得到PDI，表明分子量分布窄，聚合反应控制良好。使用荧光光谱技术、紫外可见光透射率和 TEM 研究了五嵌段三元共聚物在水溶液中的热响应性和 pH 响应性胶束化。与 NIPAM 均聚物 (~32 °C) 相比，五嵌段三元共聚物的 LCST 有所增加（超过 50 °C），这是由于五嵌段三元共聚物中加入了亲水性 PEG 和 PMA 嵌段（PNIPAM 嵌段为核心，PEG 为嵌段，亲水性 PMA 嵌段（如壳和冠）。此外，根据 MA​​A 的 pKa，pH 依赖性相变行为在 pH 值约为 5.8 时表现出来。因此，在室温下的酸性溶液中，五嵌段三元共聚物自组装形成核-壳-冠胶束，其中疏水性PMA嵌段为核，PNIPAM嵌段和亲水性PEG嵌段分别为壳和冠。