No abstract

Solvent relaxation nuclear magnetic resonance has been widely used to study the interactions of polymers and surfactants with nanoparticles, an important area of research for use in a range of industrial formulations, especially with regards to competition effects between components. The ability of the solvent relaxation technique to distinguish between solvent molecules at the surface and those in the bulk solution has been used to obtain valuable information on the interfacial interactions and structure.We focus on systems containing combinations of polymer, surfactant and colloidal particles and illustrate how solvent relaxation measurements have addressed problems of stabilisation, flocculation and depletion in both academically and industrially relevant systems.

Polymerization-induced self-assembly (PISA) has become a widely used technique for the rational design of diblock copolymer nano-objects in concentrated aqueous solution. Depending on the specific PISA formulation, reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization typically provides straightforward access to either spheres, worms, or vesicles. In contrast, RAFT aqueous emulsion polymerization formulations often lead to just kinetically-trapped spheres. This limitation is currently not understood, and only a few empirical exceptions have been reported in the literature. In the present work, the effect of monomer solubility on copolymer morphology is explored for an aqueous PISA formulation. Using 2-hydroxybutyl methacrylate (aqueous solubility = 20 g dm–3 at 70 °C) instead of benzyl methacrylate (0.40 g dm–3 at 70 °C) for the core-forming block allows access to an unusual “monkey nut” copolymer morphology over a relatively narrow range of target degrees of polymerization when using a poly(methacrylic acid) RAFT agent at pH 5. These new anisotropic nanoparticles have been characterized by transmission electron microscopy, dynamic light scattering, aqueous electrophoresis, shear-induced polarized light imaging (SIPLI), and small-angle X-ray scattering.

Addition of excess sterically stabilized P2VP latex to a colloidal dispersion of P2VP-silica nanocomposite particles (with silica shells at full monolayer coverage) leads to the facile redistribution of the silica nanoparticles such that partial coverage of all the P2VP latex particles is achieved. This silica exchange, which is complete within 1 h at 20 degrees C as judged by small-angle x-ray scattering, is observed for nanocomposite particles prepared by heteroflocculation, but not for nanocomposite particles prepared by in situ copolymerization. These observations are expected to have important implications for the optimization of nanocomposite formulations in the coatings industry.