We have developed a molecular model to describe the structural changes and potential collapse of weak polyelectrolyte layers end-tethered to planar surfaces and spherical nanoparticles as a function of pH and divalent ion concentration. In particular, we describe the structural changes of polymer-coated nanoparticles end-tethered to copolymers of poly(acrylic acid) (pAA) and poly arcrylamido-2-methylpropane sulfonate (pAMPS) in the presence of Ca²⁺ ions. We find that end-grafted poly(acrylic acid) layers will collapse in aqueous solutions containing sufficient amounts of Ca²⁺ ions, while polymers and copolymers with sufficient AMPS monomers will not collapse. The collapse of end-tethered pAA is due to the formation of calcium bridges between two acrylic acid monomers and one calcium ion. On the other hand pAMPS layers do not collapse due to the lack of calcium bridges. The collapse of pAA layers is strongly dependent on the pH as well as divalent and monovalent salt concentrations of the environment. The collapse is also strongly influenced by the curvature of the tethering surface.

中文翻译：

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竞争性钙离子与末端连接的弱聚电解质结合†

我们已经开发了一种分子模型来描述作为末端pH值和二价离子浓度的函数的，被束缚在平面表面和球形纳米颗粒上的弱聚电解质层的结构变化和潜在的塌陷。特别是，我们描述了在Ca ²⁺离子存在的情况下，末端连接到聚丙烯酸（pAA）和聚弧酰氨基-2-甲基丙烷磺酸盐（pAMPS）共聚物的聚合物涂层纳米颗粒的结构变化。我们发现，末端接枝的聚（丙烯酸）层会在含有足够量的Ca ^2+的水溶液中坍塌离子，而具有足够的AMPS单体的聚合物和共聚物则不会崩解。末端连接的pAA的崩溃是由于两种丙烯酸单体和一种钙离子之间形成钙桥所致。另一方面，由于缺乏钙桥，pAMPS层不会塌陷。pAA层的破裂在很大程度上取决于pH值以及环境中的二价和单价盐浓度。塌陷也受到束缚表面的曲率的强烈影响。