Divalent鈥揂nion Salt Effects in Polyelectrolyte Multilayer Depositions

详细信息    查看全文

• 作者：Walter J. Dressick ; Kathryn J. Wahl ; Nabil D. Bassim ; Rhonda M. Stroud ; Dmitri Y. Petrovykh
• 刊名：Langmuir
• 出版年：2012
• 出版时间：November 13, 2012
• 年：2012
• 卷：28
• 期：45
• 页码：15831-15843
• 全文大小：753K
• 年卷期：v.28,no.45(November 13, 2012)
• ISSN：1520-5827

文摘

We systematically investigate the effects of divalent anions on the assembly of polyelectrolyte multilayers by fabricating polystyrene sulfonate (PSS)/polyallylamine hydrochloride (PAH) multilayer films from aqueous solutions containing SO₄^{2鈥?/sup>, HPO₄2鈥?/sup>, or organic dicarboxylate dianions. The chosen concentrations of these anions (i.e., 鈮?.05 M) allow us to isolate their effects on the assembly process from those of the polyelectrolyte solubility or solution ionic strength (maintained constant at 渭 = 1.00 M by added NaCl). Compared to a control film prepared from solutions containing only Cl鈥?/sup> anions, stratified multilayers deposited in the presence of dianions exhibit increased UV absorbance, thickness, and roughness. From the dependence of film properties on the solution concentration of SO₄2鈥?/sup> and number of polyelectrolyte layers deposited, we derive a generic model for the PSS/PAH multilayer formation that involves adsorption of PAH aggregates formed in solution via electrostatic interactions of PAH with bridging dianions. Experiments using HPO₄2鈥?/sup> and organic dicarboxylate species of varying structure indicate that the separation, rigidity, and angle between the discrete negatively charged sites in the dianion govern the formation of the PAH aggregates, and therefore also the properties of the multilayer film. A universal linear relationship between film UV absorbance and thickness is observed among all dianion types or concentrations, consistent with the model.}