Smart organic–inorganic nanohybrid stars based on star-shaped poly(acrylic acid) and functional silsesquioxane nanoparticles

pH- and salinity-responsive organic–inorganic nanohybrid stars based on poly(acrylic acid) (PAA) stars and N,N-di(2,3-dihydroxypropyl)3-aminopropylfunctional silsesquioxane nanoparticles are readily formed by mixing of aqueous solutions of the components. The interaction between stars of two different arm lengths, (PAA100)21, (PAA200)24, with water-soluble silsesquioxane nanoparticles is studied according to changes in pH and salt concentration. The original size of the stars is conserved during complexation according to dynamic light scattering (DLS) measurements and light scattering (LS) titration experiments, which exclude star–star aggregation or crosslinking during the interaction. The proposed interaction mechanism is based on hydrogen-bonding and Coulomb interactions. Cryogenic transmission electron microscopy measurements demonstrate the formation of nanohybrid stars. Small-angle neutron scattering experiments enable a quantitative determination of the fraction of bound nanoparticles and indicate an equilibrium between free and bound nanoparticles.