  We report on the formation and the structural properties of supermicellar
aggregates also called electrostatic complexes, made from mineral nanoparticles
and polyelectrolyte-neutral block copolymers in aqueous solutions. The mineral
particles put under scrutiny are ultra-fine and positively charged yttrium
hydroxyacetate nanoparticles. Combining light, neutron and x-ray scattering
experiments, we have characterized the sizes and the aggregation numbers of the
organic-inorganic complexes. We have found that the hybrid aggregates have
typical sizes in the range 100 nm and exhibit a remarkable colloidal stability
with respect to ionic strength and concentration variations. Solid films with
thicknesses up to several hundreds of micrometers were cast from solutions,
resulting in a bulk polymer matrix in which nanoparticle clusters are dispersed
and immobilized. It was found in addition that the structure of the complexes
remains practically unchanged during film casting.
