Lulevich Valentin V, Vinogradova Olga I
Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany.
Langmuir. 2004 Mar 30;20(7):2874-8. doi: 10.1021/la049934h.
By using a combination of atomic force and confocal microscopy, we explore the effect of pH and salt on the stiffness of polyelectrolyte microcapsules with shells composed of strong polyanions and weak polycations. The stiffness of the capsules was found to be largest in water. It decreases slightly with added salt and gets much smaller both in acidic and in alkaline solutions. The moderate softening of the capsules in electrolyte solutions indicates that even high salt concentration does not significantly dissociate polyelectrolytes in the multilayer. The dramatic softening of the capsules at high pH probably reflects a decrease in the charge density of a polycation, which leads to a reduction in the number of ionic cross-links. In contrast, low stiffness of the capsules in acidic solutions seems to be connected mostly with the enhanced permeability of the multilayer shell.
通过结合使用原子力显微镜和共聚焦显微镜，我们探究了pH值和盐对具有由强聚阴离子和弱聚阳离子组成的壳层的聚电解质微胶囊刚度的影响。发现微胶囊在水中的刚度最大。随着盐的添加，其刚度略有下降，而在酸性和碱性溶液中则变得小得多。微胶囊在电解质溶液中的适度软化表明，即使高盐浓度也不会使多层中的聚电解质显著解离。在高pH值下微胶囊的显著软化可能反映了聚阳离子电荷密度的降低，这导致离子交联数量的减少。相比之下，微胶囊在酸性溶液中的低刚度似乎主要与多层壳层通透性的增强有关。
