Micellar Aggregation and Thermogelation of Amphiphilic Random Copolymers in Water Hierarchically Dependent on Chain Length
Micellar Aggregation and Thermogelation of Amphiphilic Random Copolymers in Water Hierarchically Dependent on Chain Length
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DOI：
10.1016/j.eurpolymj.2022.111091
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发表时间：
2022-02
影响因子：
6
通讯作者：
Motoki Shibata;Takaya Terashima;T. Koga
中科院分区：
文献类型：
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作者：
Motoki Shibata;Takaya Terashima;T. Koga
详细研究了两亲性无规共聚物在水中的胶束聚集体和热响应凝胶化，重点关注聚合度 (DP) 对行为的影响。为此，我们设计了带有亲水性聚乙二醇和疏水性十二烷基的无规共聚物，其 DP 在 63 至 358 之间变化。疏水性单体的含量设置为 60 mol% 以促进热凝胶化。所有共聚物在水中形成多链聚集体，而尺寸分布取决于DP。由于具有较大 DP 的共聚物具有较小的组成分布，因此具有 145 或更高 DP 的共聚物在水中形成尺寸受控的聚集体。它们的浓缩溶液，高于聚集体的重叠浓度，在加热时完全胶凝，然后脱水收缩。相比之下，具有 63 DP 的短共聚物形成具有多峰尺寸分布的聚集体，并且浓缩溶液在加热时经历宏观相分离，随后富含聚合物的下层发生凝胶化。小角中子散射证实，适合热凝胶化的共聚物在稀水溶液中最初形成由多个胶束亚基组成的聚集体，而浓溶液的热凝胶化是通过加热时胶束亚基的物理堆积来驱动的。因此，我们发现，DP 不仅分层影响共聚物在水中自组装成尺寸受控的胶束聚集体，而且还影响浓溶液通过胶束间缔合的热凝胶化。
Micellar aggregates and thermoresponsive gelation of amphiphilic random copolymers in water were examined in detail, focused on effects of the degree of polymerization (DP) on the behavior. For this purpose, we designed random copolymers carrying hydrophilic poly(ethylene glycol) and hydrophobic dodecyl groups, where the DP was varied from 63 to 358. The content of the hydrophobic monomer was set to 60 mol% to facilitate thermogelation. All the copolymers formed multichain aggregates in water, while the size distribution depended on DP. Since copolymers with larger DP had less composition distribution, the copolymers with 145 or more of DP formed size-controlled aggregates in water. Their concentrated solutions, above the overlap concentration of the aggregates, gelled entirely upon heating, followed by syneresis. In contrast, the short copolymer with 63 of DP formed aggregates with multimodal size distribution, and the concentrated solution underwent macroscopic phase separation upon heating, followed by gelation of the polymer-rich lower layer. As confirmed by small-angle neutron scattering, the copolymer suitable for thermogelation originally formed aggregates consisting of multiple micelle subunits in the aqueous dilute solution, and the thermogelation of the concentrated solution was driven by the physical packing of the micelle subunits upon heating. Thus, we revealed that the DP hierarchically affected not only the self-assembly of the copolymers into size-controlled micellar aggregates in water but also the thermogelation of the concentrated solutions via intermicellar association.