Interaction of Polystyrene-block-poly(ethylene oxide) Micelles with Cationic Surfactant in Aqueous Solutions. Metal Colloid Formation in Hybrid Systems

Abstract

The interaction of the amphiphilic block copolymer, polystyrene-block-poly(ethylene oxide) (PS-b-PEO), with cationic surfactant, cetylpyridinium chloride (CPC), in aqueous media was studied by static light scattering and analytical ultracentrifugation. Three well-defined populations of hybrid structures corresponding to micelles, micellar clusters, and supermicellar aggregates were found to exist in the PS-b-PEO/CPC aqueous solutions at a block copolymer concentration of 10 g/L. The relative ratio of each type of structure and their parameters strongly depend on the CPC concentration, mobility of the polystyrene micellar core, and chemical composition of the dispersing media. Ion exchange of the surfactant counterions in the hybrid PS-b-PEO/CPC system by PtCl6 2-and PdCl4 2-ions resulted in saturation of the micellar structures with noble metal ions. The subsequent reduction of the metal-containing PS-b-PEO/CPC/MXn species with NaBH4 and molecular hydrogen resulted in the formation of metal nanoparticles mainly located in the block copolymer micelles.

The Hybrids of Polystyrene-block-Poly(ethylene Oxide) Micelles and Sodium Dodecyl Sulfate in Aqueous Solutions: Interaction with Rh Ions and Rh Nanoparticle Formation

“…Our idea was to extend the possibility of using amphiphilic block copolymers in water as a reliable stabilizing medium for metal nanoparticle formation by charging the micelle cores with surfactant molecules. This approach was described recently in our preceding paper for polystyrene-block-poly(ethylene oxide) (PS-b-PEO) block copolymer micelles interacting with cetylpyridinium chloride (CPC) (28). We have assumed that, if ionic surfactants are added to the aqueous micellar solutions of amphiphilic diblock copolymers (e.g., PS-b-PEO), the surfactants will penetrate inside the hydrophobic micellar cores of block copolymers.…”

Nanostructured Polymeric Nanoreactors for Metal Nanoparticle Formation

“…These systems display exceptional stability (for years), if metal salt loading does not exceed 1.24 ¥ 10 -2 M. Hydrogen reduction results in metal nanoparticle formation both in micelles and micellar clusters so colloidal solutions are stable at metal salt concentration below 3.36 ¥ l0 -3 M (Figure 4.12). Unlike many other systems [30,40], here the nanoparticle size does not depend on the reducing agent type, but depends on the metal type [45][46][47]. We surmise that strong interaction of surfactant head groups with growing nanoparticles along with hydrophobic interactions with the PS core control the nanoparticle size.…”

“…If the micelle corona is not functionalized, then nanoparticle stabilization is only governed by hydrophobic interactions with the hydrophobic micelle core, and the stability of the soluble metal-polymer nanocomposites will be inferior [44]. To improve stabilization in the micelle coronas, we suggested using hybrid SOLUBLE POLYMER NANOSTRUCTURES micelles consisting of PS-b-PEO and cationic or anionic surfactants [45][46][47]. We assumed that when surfactant is loaded in an aqueous solution containing block copolymer micelles, the favorable path for surfactant molecules will be penetration into the hydrophobic micelle cores.…”

“…Combination of dynamic light scattering (DLS), sedimentation in an ultracentrifuge (UC), and 1 H NMR spectroscopy allowed us to prove comicellization of block copolymer macromolecules and cationic or anionic surfactants. Ion exchange of the surfactant counterions in the PS-b-PEO/CPC system for PtCl 6 2-or PdCl 4 2-ions followed by reduction of metal-containing hybrid micellar systems (PS-b-PEO/CPC/MX n ) with NaBH 4 or H 2 yields nanoparticles, the morphology and stability of which depend on the metal compound loading and the type of the reducing agent [45]. NaBH 4 reduction leads to decomposition of micellar clusters and formation of micelles with embedded nanoparticles (Figure 4.11).…”

Structural analysis and shape-dependent catalytic activity of Au, Pt and Au/Pt nanoparticles

“…However, the chemical routes that allow us to obtain monodispersed metallic nanoparticles with controlled size are still limited. The morphology and stability of the nanoparticles depend on the precursors, their concentration, and the type of the reducing agent [13].…”