Tiraferri Alberto, Maroni Plinio, Borkovec Michal
Department of Environment, Land, and Infrastructure Engineering, Polytechnic University of Turin, Torino, Italy.
Phys Chem Chem Phys. 2015 Apr 28;17(16):10348-52. doi: 10.1039/c5cp00910c.
The present study demonstrates that multivalent counterions trigger adsorption of polyelectrolytes on a like-charged substrate. In particular, adsorption of polystyrene sulfonate on silica is studied experimentally in NaCl, MgCl2, and LaCl3 solutions by optical reflectivity. While adsorption is negligible in the presence of Na(+), the polyelectrolyte adsorbs in the presence of Mg(2+) and La(3+). The adsorbed amount of the polyelectrolyte goes through a maximum as a function of the salt concentration. This maximum increases with increasing valence and shifts to lower salt concentrations. At low salt concentration, the adsorption is negligible. At intermediate salt level, ripening and multilayer formation leads to continuous growth of the adsorbed layer. At higher salt level, blocking and formation of a monolayer lead to saturation. These results are tentatively interpreted in terms of a charge reversal of the polyelectrolyte-metal complex. The molecular mass of the polyelectrolyte has an important effect on the adsorption behavior, whereby the tendency towards ripening becomes more pronounced at large molecular mass.
本研究表明，多价抗衡离子会引发聚电解质在带相同电荷的基底上的吸附。具体而言，通过光学反射率实验研究了在NaCl、MgCl2和LaCl3溶液中聚苯乙烯磺酸盐在二氧化硅上的吸附情况。在Na(+)存在时吸附可忽略不计，而在Mg(2+)和La(3+)存在时聚电解质会吸附。聚电解质的吸附量随盐浓度的变化呈现出一个最大值。该最大值随着价态的增加而增大，并向低盐浓度方向移动。在低盐浓度下，吸附可忽略不计。在中等盐浓度水平时，熟化和多层形成导致吸附层持续生长。在较高盐浓度水平时，阻塞和单层形成导致吸附饱和。这些结果初步解释为聚电解质 - 金属络合物的电荷反转。聚电解质的分子量对吸附行为有重要影响，在大分子质量时熟化趋势变得更加明显。
