Polyelectrolyte Gel Surfactant Complexes

Polyelectrolyte gel-surfactant complexes (PGSCs) are highly ordered systems which were extensively studied by theorists and experimentalists [15-18]. In these systems, surfactant molecules self-assemble and their ordering even exceeds the ordering of surfactant in the solutions [19]. As PGSCs contain a number of ions in well-ordered surfactant areas inside a weakly cross-linked gel, their replacement with ions of interest (transition metal ions) should offer the possibility of metal nanoparticle formation in a nanostructured medium. As found, metal ion uptake takes place when metal ions are oppositely charged toward polyelectrolyte charged groups [20-22]. In doing so, the incorporated metal compounds form clusters which are located between charged groups of a polymer chain and surfactant head groups. These clusters behave as nuclei for metal nanoparticle formation during reduction. If a fast reducing agent is used (NaBH4), particles grow completely in an ordered environment. Moreover, as reported in [22], although particle growth decreases the degree of crystalline ordering in PGSCs, the ordering around growing particles even increases, which results in additional control over particle growth and a very narrow particle size distribution (Fig. 2). If reduction is carried out with a sluggish reducing agent (N2H4 x H2O), small clusters and ions migrate in unstructured areas of the gel where uncontrolled particle growth occurs. This results in large particles with a very broad particle size distribution. PE gels without internal nanostructure are also unable to control the particle growth.

Figure 2. Volume distribution functions for the PDADMACl/sodium dodecylbenzosulphonate (SDBS) gel containing H2PtCl6 evaluated from anomalous small angle X-ray scattering (ASAXS) difference curves. (1): compound clusters; (2) and (3): Pt nanoparticles reduced with NaBH4 and N2H4 • H2O, respectively. The distributions are normalized to a maximum value of unity. Reprinted with permission from [22], D. I. Svergun et al., J. Phys. Chem. B 104, 5242 (2000). © 2000, American Chemical Society.

Figure 2. Volume distribution functions for the PDADMACl/sodium dodecylbenzosulphonate (SDBS) gel containing H2PtCl6 evaluated from anomalous small angle X-ray scattering (ASAXS) difference curves. (1): compound clusters; (2) and (3): Pt nanoparticles reduced with NaBH4 and N2H4 • H2O, respectively. The distributions are normalized to a maximum value of unity. Reprinted with permission from [22], D. I. Svergun et al., J. Phys. Chem. B 104, 5242 (2000). © 2000, American Chemical Society.

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