Dynamic co-assembly behaviors of polyoxometalates and giant surfactants in dual solvents

Abstract

Inorganic-organic hybridization is a widely used method to develop new functional materials involving polyoxometalates (POMs), affording them with unique synergistic physical and chemical properties. As one of the core topics in hybrid materials, the study of their assembly structures is critical for the optimization of their performances.In the present work, dynamic co-assembly behaviors of several giant surfactants XPOSS-PS (X, POSS and PS denote different polar groups, polyhedral oligomeric silsesquioxane and polystyrene, respectively) and Keggin-type silicotungstic acid H4SiW12O40 (H4SiW for short) were investigated. We designed and synthesized three series of giant surfactants that possess heads bearing cationic (NPOSS-PS, N for ammonium group), neutral (DPOSS-PS, D for dihydroxyl group) and anionic charges (APOSS-PS, A for carboxylic acid group), respectively. The different charge types of POSS heads lead to different electrostatic interactions with the anionic POM clusters, resulting in different co-assembly structures in dual mixed solvents. Moreover, we found the POM's loading content and PS chain length are another two important factors that can determine the morphology of co-assembly structures. This work expands the scope of co-assembled structures of POM-based hybrid materials, and provides a platform for the study of the basic physical principles of their co-assembly behaviors.

Keywords

• Polyoxometalates
• Giant surfactants
• Co-assembly
• Onion-like spheres
• Pupa-like ellipsoids