A Monte Carlo study of the statistics of loop and bridge formation between colloidal particles, and in particular micelles, by telechelic polymers is presented. The experimental fact that the hydrophobic outer blocks of a triblock copolymer tend to stick into micelles in aqueous solution is mimicked by counting only polymer chains with both ends on the surface of the micelles. The long inner hydrophilic block is generated by a random walk procedure. It is excluded from the volume of the micelles, and it can form either a loop, with both stickers on the same micelle, or a bridge, with the stickers on two different micelles. In this paper, the pair potential is determined between two micelles as a function of distance and chain-to-micelle size ratio, for ideal and self-avoiding chains. In the latter case, the effect of many chains has also been explored

A method was developed to prepare asymmetric end-capped poly(ethylene oxide)s (PEOs), containing an alkyl group on one chain end and a perfluoroalkyl group on the other one (C18H37-PEO-C2H4-C8F17 and C18H37-PEO-C10H20-C8F17). These new telechelic associative polymers (APs) were synthesized by anionic polymerization of ethylene oxide initiated by an alkoxide (C18H37-O-K+) followed by esterification. The rheological behavior of asymmetric and analogous symmetric APs in aqueous solutions has been investigated as a function of polymer concentration (C), hydrophobic end-cap and surfactant used to homogenize the system: sodium dodecyl sulfate (SDS) or lithium perfluorooctyl sulfonate (LiFOS). A steep increase of the static viscosity η, attributed to the formation of a multiconnected network, is observed for C ≈ 1 wt %. Semidilute solutions present a Maxwellian rheological behavior with only one relaxation time τ associated with the least hydrophobic end group. The viscoelastic response is modified by the interactions between hydrophobic end groups and surfactant inside mixed aggregates.

Hybrid gold-polymer nanoparticles are obtained by self-assembly of amphiphilic copolymers (Pluronics) in solutions containing preformed gold nanoparticles (diameter ca. 12 nm). Dynamic light scattering, TEM, cryo-TEM, and small-angle neutron scattering experiments with contrast variation are used to characterize the structure of the gold-polymer particles. Five Pluronics (F127, F68, F88, F108, P84) with different molecular weights and hydrophilic/hydrophobic balances are investigated. Gold nanoparticles are individually embedded within globules of polymer, even under conditions for which Pluronics micelles do not form in solution. The hybrid particles are several tens of nanometers in size (larger than micelles of the corresponding Pluronics), and the size can be tuned by changing the temperature.

Model microemulsion networks of oil droplets stabilized by non ionic surfactant and telechelic polymer C18-PEO(10k)-C18 have been studied for two droplet-to-polymer size ratios. The rheological properties of the networks have been measured as a function of network connectivity and can be described in terms of simple percolation laws. The network structure has been characterised by Small Angle Neutron Scattering. A Reverse Monte Carlo approach is used to demonstrate the interplay of attraction and repulsion induced by the copolymer. These model networks are then used as matrix for the incorporation of silica nanoparticles (R=10nm), individual dispersion being checked by scattering. A strong impact on the rheological properties is found for silica volume fractions up to 9%.

Model self-assembled networks of telechelic polymer C18-PEO(35k)-C18 in water have been studied. The rheology of such transient networks has been investigated as a function of polymer concentration, and a typical percolation law has been observed. The network structure has been characterised by Small Angle Neutron Scattering in D2O, where the interactions between micelles formed by the hydrophobic C18-stickers of the polymer give rise to a peak in the scattered intensity. These model networks have then been used as a matrix for the incorporation of silica nanoparticles (R=10nm), and we have checked individual dispersion by scattering using contrast variation. The rheological response of the networks is considerably modified by the presence of the silica nanoparticles, and in particular an interesting dependence of the relaxation time on silica concentration has been found. The analogy in reinforcement behaviour of such a self-assembled, viscoelastic, and aqueous system with model experiments of elastomers filled with nanoparticles is discussed by comparison to a silica-latex system.