Relaxation Dynamics and Underlying Mechanism of a Thermally Reversible Gel from Symmetric Triblock Copolymer
Relaxation Dynamics and Underlying Mechanism of a Thermally Reversible Gel from Symmetric Triblock Copolymer
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DOI：
10.1021/acs.macromol.9b01856
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发表时间：
2019-11
期刊：
影响因子：
5.5
通讯作者：
Y. Ye;Kunpeng Cui;T. Indei;Tasuku Nakajima;D. Hourdet;T. Kurokawa;J. Gong
中科院分区：
文献类型：
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作者：
Y. Ye;Kunpeng Cui;T. Indei;Tasuku Nakajima;D. Hourdet;T. Kurokawa;J. Gong
我们报道了一种在二甲基甲酰胺（DMF）溶剂中由聚甲基丙烯酸丁酯-b-聚甲基丙烯酸-b-聚甲基丙烯酸丁酯（PBMA-b-PMAA-b-PBMA）三嵌段共聚物组成的新型热响应体系。该体系通过冷却低于临界温度Tc表现出溶胶-凝胶转变。这些凝胶的网络弛豫时间正好落在典型的流变实验窗口内，使我们能够结合线性流变学、时间分辨小角x射线散射（SAXS）和温度升高的核磁共振（NMR）测量来研究弛豫动力学和潜在的机制。时间-温度叠加（TTS）和时间-浓度叠加（TCS）在该体系中得到很好的体现。温度低于和高于Tc时的弛豫动力学有很大不同，分别给出两个不同的活化能E1a和E2a。E1a与聚合物浓度无关，与端段胶束形成有关，而与端段胶束形成有关。
We report a novel thermally responsive system from poly(butyl methacrylate)-b-poly(methacrylic acid)-b-poly(butyl methacrylate) (PBMA-b-PMAA-b-PBMA) triblock copolymer in dimethylformamide (DMF) solvent. This system shows a sol–gel transition by cooling below a critical temperature Tc. The network relaxation times of these gels rightly fall in the typical rheological experiment window, permitting us to investigate the relaxation dynamics and underlying mechanism, with a combination of linear rheology, time-resolved small-angle X-ray scattering (SAXS), and temperature-elevated nuclear magnetic resonance (NMR) measurements. Both time–temperature superposition (TTS) and time–concentration superposition (TCS) are well held in this system. The relaxation dynamics at temperatures below and above Tc are quite different, giving two different activation energies E1a and E2a, respectively. The E1a, being polymer concentration independent, is related to micelle formation of end-blocks, while the concentration depend...