标题： pH依赖的聚合物膜在液-液界面通过氢键组装的界面流变学 显示英文标题

标题： pH-dependent interfacial rheology of polymer membranes assembled at liquid-liquid interfaces using hydrogen bonds

摘要： 聚合物通过非共价相互作用在液体界面的自组装已成为一种有前景的技术，可用于可逆地制备自修复膜。 除了组装过程外，控制这些膜的机械性能也至关重要。 在这里，我们测量了使用氢键在液-油界面组装的PMAA-PPO（聚甲基丙烯酸-聚丙二醇）聚合物膜的界面流变特性。 改变pH值可以使PMAA链的电离程度发生变化，从而影响它们与PPO建立氢键的能力。 界面层的频率扫描显示，在低频下的粘性区域和高频下的弹性区域之间存在交叉。 在所研究的pH范围内，实验进行一小时后，交叉弹性模量减少了一半，这可以归因于随着pH增加，层厚度的减小。 此外，我们发现交叉频率随PMAA的电离程度呈指数变化。 为了解释这些观察结果，我们提出一个简单的模型，其中短链的PPO作为非共价交联剂，连接多个PMAA链。 解离速率以及因此交叉频率由每条PPO链参与氢键的PO单元数量控制。 显示英文摘要

摘要： Self-assembly of polymers at liquid interfaces using non-covalent interactions has emerged as a promising technique to reversibly produce self-healing membranes. Besides the assembly process, it is also crucial to control the mechanical properties of these membranes. Here, we measure the interfacial rheological properties of PMAA-PPO (polymethacrylic acidpolypropylene oxide) polymer membranes assembled using hydrogen bonds at liquid-oil interfaces. Varying the pH enables us to modify the degree of ionization of the PMAA chains, and hence their ability to establish hydrogen interactions with PPO. Frequency sweeps of the interfacial layers show a crossover between a viscous regime at low frequencies and an elastic regime at high frequencies. The crossover elastic modulus decreases by half after one hour of the experiment over the pH range investigated, which can be accounted for by a decrease of the layer thickness as pH increases. Furthermore we find that the crossover frequency varies exponentially with the degree of ionization of PMAA. To account for these observations, we propose a simple picture where the short PPO chains behave as non-covalent cross-linkers that bridge several PMAA chains. The dissociation rate and hence the crossover frequency are controlled by the number of PO units per PPO chain involved in the hydrogen bonds.