Laboratory of Physical Chemistry and Colloid Science, Wageningen University, PO Box 8038, 6700 EK Wageningen, The Netherlands.
J Colloid Interface Sci. 2011 Sep 15;361(2):407-22. doi: 10.1016/j.jcis.2011.05.080. Epub 2011 Jun 7.
When aqueous solutions of polycations and polyanions are mixed, polyelectrolyte complexes form. These are usually insoluble in water, so that they separate out as a new concentrated polymer phase, called a complex coacervate. The behavior of these complexes is reviewed, with emphasis on new measurements that shed light on their structural and mechanical properties, such as cohesive energy, interfacial tension, and viscoelasticity. It turns out that stoichiometric complexes can be considered in many respects as pseudo-neutral, weakly hydrophobic polymers, which are insoluble in water, but become progressively more soluble as salt is added. In fact, the solubility-enhancing effect of salt is quite analogous to that of temperature for polymers in apolar solvents. Since two-phase systems can be prepared in colloidal form, we also discuss several kinds of colloids or 'microphases' that can arise due to polyelectrolyte complexation, such as thin films, 'zipper' brushes, micelles, and micellar networks. A characteristic feature of these charge-driven two-phase systems is that two polymeric ingredients are needed, but that some deviation from strict stoichiometry is tolerated. This turns out to nicely explain how and when the layer-by-layer method works, how a 'leverage rule' applies to the density of the 'zipper brush', and why soluble complexes or micelles appear in a certain window of composition. As variations on the theme, we discuss micelles with metal ions in the core, due to incorporation of supramolecular coordination polyelectrolytes, and micellar networks, which form a new kind of physical gels with unusual properties.
当聚阳离子和聚阴离子的水溶液混合时，会形成聚电解质复合物。这些复合物通常不溶于水，因此会分离出来形成一种新的浓缩聚合物相，称为复杂共凝聚物。本文综述了这些复合物的行为，重点介绍了一些新的测量方法，这些方法揭示了它们的结构和力学性质，如内聚能、界面张力和粘弹性。事实证明，在许多方面，化学计量的复合物可以被视为伪中性的、弱疏水性聚合物，它们不溶于水，但随着盐的加入而逐渐变得更易溶解。实际上，盐的增溶效应与非极性溶剂中聚合物的温度效应非常相似。由于可以制备胶体形式的两相体系，我们还讨论了由于聚电解质复合而产生的几种胶体或“微相”，例如薄膜、“拉链”刷、胶束和胶束网络。这些电荷驱动的两相体系的一个特征是需要两种聚合物成分，但可以容忍一定程度的偏离严格化学计量。这很好地解释了层叠法如何以及何时起作用，杠杆规则如何适用于“拉链刷”的密度，以及为什么可溶性复合物或胶束会在特定的组成窗口中出现。作为主题的变体，我们讨论了由于超分子配位聚电解质的掺入而在核心中含有金属离子的胶束，以及形成具有特殊性质的新型物理凝胶的胶束网络。
