Studying a new type of surfactant aggregate ("Spherulites") as chemical microreactors. A first example: Copper ion entrapping and particle synthesis

We report the first example of a chemical reaction in a new type of surfact ant aggregates called "spherulites" or "onions". Spherulites are spherical microdomains (200-1000 nm)of lamellar phase. They are prepared by means of shear of a lamellar phase under controlled conditions. Spherulites can be c onsidered as surfactant vesicles with a dense multilamellar structure. Chem ical reduction of copper(II) ions encapsulated into spherulites by hydrazin e demonstrates the possibility of using this new surfactant assembly as che mical microreactors. We describe the process of encapsulation of copper(II) ions into spherulites. The use of a ligand-like surfactant proved to be ef ficient in preventing the leakage of these ions despite spherulite permeabi lity to small hydrosoluble molecules. Encapsulation ratios up to 80% are ob tained. When hydrazine is added to an aqueous suspension of Cu(II)-containi ng spherulites, hydrazine diffuses into the spherulites and chemical reduct ion of the entrapped ions occurs. The formation of small Cu2O particles (10 -30 nm) is observed throughout the multilayered structure of the spherulite s. The suspension of nanoparticles embedded in the surfactant structure is stable, and the nanoparticles can be recovered by destruction of the spheru lites.