Counterions in Poly(allylamine hydrochloride) and Poly(styrene sulfonate) Layer-by-Layer Films

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• 作者：Joã ; o M. C. Louren&ccedil ; o ; Paulo Antó ; nio Ribeiro ; Ana Maria Botelho do Rego ; Francisco M. Braz Fernandes ; Augusto M. C. Moutinho ; and Maria Raposo
• 刊名：Langmuir
• 出版年：2004
• 出版时间：September 14, 2004
• 年：2004
• 卷：20
• 期：19
• 页码：8103 - 8109
• 全文大小：130K
• 年卷期：v.20,no.19(September 14, 2004)
• ISSN：1520-5827

文摘

The amount of counterions in layer-by-layer (LBL) films of poly(allylamine hydrochloride) (PAH) andpoly(styrene sulfonate) (PSS) has been determined with X-ray photoelectron spectroscopy (XPS) for filmsprepared from solutions with various NaCl concentrations. Sodium and chloride counterions are presentin LBL films produced from salt solutions, which are located at the surface and in the bulk of the films.The percentage of bulk counterions increases with the ionic strength of the polyelectrolyte before reachinga constant value. The bulk sodium/sulfur percentage ratios tend to 0.8 for samples washed with pure waterand for samples washed with NaCl aqueous solutions, while the bulk chlorine/nitrogen percentage ratiostend to 0.5 for the same samples. The ratio between the percentages of polyelectrolyte ionic groups liesclose to unity for all samples, indicating that counterions do not contribute to charge compensation in thepolyelectrolyte during the adsorption process. The presence of counterions in LBL films is explained byManning condensation near the polyelectrolyte ionic groups, leading to inter-polyelectrolyte ionic bondingsvia ionic networks. It is believed that condensation leads to the formation of NaCl crystallites in these LBLfilms, which was confirmed by X-ray diffraction measurements.