Supramolecular assembled nanostructure containing cubic silsesquioxane in aqueous solution.

Micellization and aggregation behavior of amphiphilic cubic silsesquioxane-poly(ethylene oxide) (CSSQ-PEO) in aqueous solution was studied by Dynamic and Static Light Scattering (DLS and SLS), and Transmission Electron Microscopy (TEM). The effects of CSSQ-PEO concentration and temperature on particle size were also investigated. Above the critical aggregation concentration (CAC), a combination of unassociated single micelle and micellar aggregates is observed up to a certain level of CSSQ-PEO concentration as determined by DLS and TEM studies. The size of unassociated single micelles are found to be independent of CSSQ-PEO concentration while that of the micellar aggregates become larger at higher concentration due to the aggregation growth. Both studies revealed that a small CSSQ core is surrounded by PEO corona and found self-assembled nanostructure of CSSQ-PEO in aqueous solution. The molecular weight of micellar aggregates (Mw,agg), radius of gyration (Rg), and apparent aggregation number (Nagg) were evaluated by SLS measurement. The decrease in the particle size (described by hydrodynamic diameter: Dh) upon increasing temperature was observed because of the diminishing hydrophilicity of PEO. Surprisingly, Rg is also decreased at higher temperature assuming the dissociation of micellar aggregates by repulsive forces due to the crowding effect. The encapsulation property of CSSQ-PEO to model drug has also been studied. Our preliminary results from DLS and TEM studies showed the formation of CSSQ-PEO nanospheres containing drug in aqueous solution. The size of the drug loaded CSSQ-PEO nanospheres are found to be larger (250-300 nm) than that of the core-corona CSSQ-PEO micellar aggregates (approximatly 180 nm) in dilute aqueous solution.