  We report the co-assembly and adsorption properties of coacervate complexes
made from polyelectrolyte-neutral block copolymers and oppositely charged
nanocolloids. The nanocolloids put under scrutiny were ionic surfactant
micelles and highly charged 7 nm cerium oxide (CeO2) nanoparticles. Static and
dynamic light scattering was used to investigate the microstructure and
stability of the organic and hybrid complexes. The microstructure of the
CeO2-based complexes was resolved using cryogenic transmission electronic
microscopy (Cryo-TEM), and it revealed that the cores were clusters made from
densely packed nanoparticles. In the concentration range of interest, c = 10-4
- 1 wt. %, the surfactant-based complexes were shown to exhibit a critical
association concentration (cac) whereas the nanoparticle-polymer hybrids did
not. The adsorption properties of the same complexes were investigated above
the cac by stagnation point adsorption reflectometry. The adsorbed amount was
measured as a function of time for polymers and complexes using anionically
charged silica and hydrophobic poly(styrene) substrates. It was found that all
complexes adsorbed readily on both types of substrates up to a level of 1 - 2
mg m-2 at stationary state. Upon rinsing however, the adsorbed layer was
removed for the surfactant-based systems, but not for the cerium oxide
clusters. As for the solution properties, these finding were interpreted in
terms of a critical association concentrations which are very different for
organic and hybrid complexes.
