Rare earth cerium oxide (ceria) nanoparticles are stabilized using end-functional phosphonated-PEG oligomers. The complexation process and structure of the resulting hybrid core-shell singlet nanocolloids are described, characterized, and modeled using light and neutron scattering data. The adsorption mechanism is nonstoichiometric, yielding the number of adsorbed chains per particle N(ads) = 270 at saturation. Adsorption isotherms show a high affinity of the phosphonate head for the ceria surface (adsorption energy DeltaG(ads) approximately -16kT) suggesting an electrostatic driving force for the complexation. The ease, efficiency, and integrity of the complexation is highlighted by the formation of nanometric sized cerium oxide particles covered with a well anchored PEG layer, maintaining the characteristics of the original sol. This solvating brushlike layer is sufficient to solubilize the particles and greatly expand the stability range of the original sol (

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. For five different systems of nanocolloids and polymers, we first demonstrated that the electrostatic complexation resulted in the formation of stable core-shell aggregates in the 100 nm range. 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, presumably through complexation of the polyelectrolyte blocks by the surface charges. The cluster stability was monitored by systematic light scattering measurements. 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. Combining the efficient adsorption and strong stability of the CeO2-based core-shell hybrids on various substrates, it is finally suggested that these systems could be used appropriately for coating and anti-biofouling applications. I -IntroductionDevelopment of functional molecular architectures is one of the final goals of modern chemistry, biology and physics. For the design of artificially intelligent devices, fabrication and control of materials at nanometer scale with chemical and physical attributes has been attracting much attention in the last decade. In particular, the complexation of polymers and nanoparticles is opening pathways for engineering novel hybrid structures combining the advantageous properties of both the organic and inorganic moieties [1][2][3]. The first challenge of the present paper was the design of nano-objects with new functionalities and resulting from the association between nanocolloids and polymers. The nanocolloids put under scrutiny were of two kinds: surfactant micelles and inorganic cerium oxide nanoparticles. As for polymers, polyelectrolyte-neutral block copolymers also called double-hydrophilic copolymer...

Experimental evidence is given for the mechanism of film formation from industrial waterborne latices using Inverse‐Micro‐Raman‐Spectroscopy (IMRS). In the vertical direction of the film drying is gas‐side controlled, indicated by uniform water concentration profiles. In the horizontal direction inhomogeneous drying resulting from a horizontal mass flux toward the edge of the film and the formation of a drying front are observed. The completeness of film formation is tested by so‐called IMRS redispersion experiments. For hard latices (Texperiment ≃ Tmff) particle deformation is incomplete and the final coating—although transparent and optically clear—is a porous structure with a network of surfactant material located at the particle interfaces. The use of a film‐forming aid lowers the polymer's minimum film formation temperature (Tmff) and facilitates particle deformation and polymer interdiffusion. The result is a nonporous film structure where individual particles and a network of surfactant material are no longer observed. IMRS redispersion experiments are compared with pictures of the final coating surface obtained from atomic force microscopy (AFM). © 2007 American Institute of Chemical Engineers AIChE J, 2007

Water-soluble clusters made from 7-nm inorganic nanoparticles have been investigated by small-angle neutron scattering. The internal structure factor of the clusters was derived and exhibited a universal behavior as evidenced by a correlation hole at intermediate wave vectors. Reverse Monte Carlo calculations were performed to adjust the data and provided an accurate description of the clusters in terms of interparticle distance and volume fraction. Additional parameters influencing the microstructure were also investigated, including the nature and thickness of the nanoparticle adlayer.

We report the presence of a correlation between the bulk and interfacial properties of electrostatic coacervate complexes. Complexes were obtained by co-assembly between cationic-neutral diblocks and oppositely charged surfactant micelles or 7 nm cerium oxide nanoparticles. Light scattering and reflectometry measurements revealed that the hybrid nanoparticle aggregates were more stable both through dilution and rinsing (from either a polystyrene or a silica surfaces) than their surfactant counterparts. These findings were attributed to a marked difference in critical association concentration between the two systems and to the frozen state of the hybrid structures.The design of functional molecular architectures and materials has attracted much attention during the last decade. In particular, the controlled association of polymers and nanoparticles using covalent [1][2][3] and noncovalent [4][5][6] binding has appeared as a promising way to combine organic and inorganic moieties at a nanoscospic level. The development of hybrid nanostructures was also stimulated by industrial and biomedical applications, especially by applications in the realm of coating technologies. In order to modify the surface properties of materials, inorganic nanoparticles with unique physical features (such as magnetic, fluorescent, UV-absorbent, high dielectric constant or catalytic properties) are actually crucial ingredients. In association with macromolecules, these nanoparticles could be also used for coatings with improved stability and performances (wetting, antibiofouling).In 2004, Cohen Stuart and coworkers have shown that electrostatic complexes made from oppositely charged polyelectrolytes could be effectively adsorbed on hydrophilic and hydrophobic surfaces [7][8][9]. Experiments were conducted at the liquid-solid interfaces on electrostatic core-shell complexes resulting from the selfassembly of an anionic-neutral copolymer and a short cationic homopolymer. On silica and polystyrene substrates, it was found that the cores of the aggregates adsorbed on the surface whereas the shell formed a brush on the top of it. These authors also confirmed the stability of the deposited layer upon rinsing and its repellent effect with respect to proteins [7]. The approach followed in the present communication aimed to extend these measurements to two new types of electrostatic systems, namely to organic and hybrids coacervate complexes. Here, we show the existence of a correlation between the bulk and adsorption properties of surfactant/copolymer (organic) and nanoparticle/copolymer (hybrid) complexes. Using Stagnation Point Adsorption Reflectometry (SPAR), organic and hybrid complexes were found to adsorb readily on hydrophilic and hydrophobic substrates. However, upon rinsing the organic complexes were shown to disassemble and finally desorb from the solid surface, whereas the hybrids remained. These findings were interpreted in terms of a critical association concentration which is much higher for organic systems than for the hybrids.Fo...