Co-Nonsolvency Effect in Solutions of Poly(methyl methacrylate)-b-poly(N-isopropylacrylamide) Diblock Copolymers in Water/Methanol Mixtures
Co-Nonsolvency Effect in Solutions of Poly(methyl methacrylate)-b-poly(N-isopropylacrylamide) Diblock Copolymers in Water/Methanol Mixtures
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DOI：
10.1021/acs.macromol.1c00512
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发表时间：
2021-06
期刊：
影响因子：
5.5
通讯作者：
Chia-Hsin Ko;Cristiane Henschel;Geethu P. Meledam;M. Schroer;Renjun Guo;Luka Gaetani;P. Müller‐Buschbaum-P.
中科院分区：
文献类型：
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作者：
Chia-Hsin Ko;Cristiane Henschel;Geethu P. Meledam;M. Schroer;Renjun Guo;Luka Gaetani;P. Müller‐Buschbaum-P.
研究了热响应性两亲二嵌段共聚物pmma21 -b- pnipam283在不同水/甲醇混合物中的自组装。它由一个短的疏水性聚（甲基丙烯酸甲酯）嵌段和一个长热响应性聚（n -异丙基丙烯酰胺）嵌段组成。加入甲醇作为共溶剂会使可溶于纯水和纯甲醇的PNIPAM块体由于所谓的共不溶性效应而崩溃。同时，甲醇的加入降低了PMMA块体与水的不相容性。采用比浊法和差示扫描量热法，建立了与溶剂组分相关的相图。动态光散射和基于同步辐射的小角度x射线散射在20°C下提供了依赖于溶剂成分的结构信息。在富水溶剂混合物中，形成自组装的球形核-壳胶束。溶剂组分通过两种方式调节胶束的内部结构：甲醇使PMMA胶束芯软化，同时使PNIPAM胶束壳收缩。在超过混相间隙的富甲醇溶剂混合物中，共聚物是分子溶解链。它们在共存线附近坍塌，随着甲醇含量的增加，它们变成随机线圈。我们认为胶束的内部形态和溶解链的构象在很大程度上取决于溶剂的组成，这是PNIPAM的共同非溶解效应叠加的结果，也是添加甲醇时PMMA的整体溶剂化增强的结果。
The self-assembly of the thermoresponsive amphiphilic diblock copolymer PMMA21-b-PNIPAM283is studied in different water/methanol mixtures. It consists of a short hydrophobic poly(methyl methacrylate) block and a long thermoresponsive poly(N-isopropylacrylamide) block. Adding methanol as a cosolvent causes the PNIPAM block, which is soluble in both pure water and pure methanol, to collapse due to the so-called co-nonsolvency effect. Meanwhile, the addition of methanol reduces the incompatibility of the PMMA block with water. By means of turbidimetry and differential scanning calorimetry, the solvent-composition-dependent phase diagram is constructed. Dynamic light scattering and synchrotron radiation-based small-angle X-ray scattering provide structural information at 20 °C in dependence on the solvent composition. In water-rich solvent mixtures, self-assembled spherical core–shell micelles are formed. The internal structure of the micelles is adjusted by the solvent compositions in two ways: methanol softens the PMMA micellar core, while it causes the shrinkage of the PNIPAM micellar shell. In methanol-rich solvent mixtures beyond the miscibility gap, the copolymers are molecularly dissolved chains. They are collapsed near the coexistence line, while they become random coils as the methanol content increases. We propose that the internal morphology of the micelles and the conformation of the dissolved chains depend strongly on the solvent composition, as a consequence of the superposed co-nonsolvency effect of PNIPAM and the overall enhanced solvation of PMMA when adding methanol.