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The selection of appropriate solvents into which inorganic and organic sub-micron particles can be dispersed is important for product manufacturability and performance. Molecular-level interactions determine solvent suitability but are difficult to measure; existing experimental approaches require slow/expensive tests of dispersion stability. Solvent relaxation NMR measurements are shown to be a fast indicator of solvent suitability, with sensitivity to the solvent-particle intermolecular forces making it a reliable proxy for stability measurements. A structured approach to relaxation measurements with a selection of both good and poor solvents yields the Hansen Solubility Parameters (HSP) for the particle surface. Suitable solvents can be selected from a database of HSP values, and solvents can be blended to match the particle interface. The application of the approach is illustrated using a range of surface modified zinc oxide and aluminum oxide particles, with similarities and differences between the particle surfaces becoming evident through the analysis.

Solvent relaxation NMR has been used to estimate the surface areas and wettability of various types of nanostructured carbon materials in a range of solvents including water, ethanol, and tetrahydrofuran. We illustrate the application of the technique through several short case studies using samples including nanocarbon blacks, graphene oxide, nanographites, and porous graphenes. The technique is shown to give a good measure of surface area, correlating well with conventional surface area estimates obtained by nitrogen adsorption, transmission electron microscopy, or light scattering for the non-porous samples. NMR relaxation has advantages in terms of speed of analysis and being able to use concentrated, wet, and opaque samples. For samples that are porous, two distinct surface areas can be estimated assuming the two environments ('inner' and 'outer') have the same surface chemistry, and that there is a slow exchange of solvent molecules between them. Furthermore, we show that differences in wettability and dispersability between samples dispersed in water, ethanol, and cyclopentanone can be observed, along with changes to the surface chemistry of the interface.

Methacrylate-terminated poly(dimethylsiloxane)s in both linear and star architectures have been produced through a time-efficient 1 pot, 2 stage reaction which involved hydrosilylation of small molecule silanes with allyl methacrylate and subsequent equilibration of the product with octamethylcyclotetrasiloxane (D4) in the presence of an acid catalyst. This synthetic route required only one work-up procedure and the products were comparable to those produced by 2 step processes typically reported in literature. All methacrylate-terminated products were approximately double the molar masses anticipated based on reagent loadings. This is thought to be due to redistribution of siloxane bonds in the presence of the platinum hydrosilylation catalyst accompanied by a loss of silicon from the reaction by evaporation of dimethylsilane. It is believed that this is the first report of such siloxane equilibration occurring at room temperature.

Small-angle neutron scattering has been used to investigate the structure of copolymers at the liquid/liquid interface. The results are compared with theoretical predictions from the self-consistent field theory of Scheutjens and Fleer extended to include three components and a penetrable interface. Both poly(ethylene oxide)/poly(propylene oxide) block oopolymers and poly(vinyl alcohol-co-acetate) random copolymers have been used as non-ionic surfactants. The emulsions were prepared by using an aerosol method and by a more conventional high speed mixing process.

Small-angle neutron scattering has been used to investigate the structure of copolymers at the liquid/liquid interface. The results are compared with theoretical predictions from the self-consistent field theory of Scheutjens and Fleer extended to include three components and a penetrable interface. Both poly(ethylene oxide)/poly(propylene oxide) block oopolymers and poly(vinyl alcohol-co-acetate) random copolymers have been used as non-ionic surfactants. The emulsions were prepared by using an aerosol method and by a more conventional high speed mixing process.

The weak polyelectrolyte sodium polyacrylate, NaPA, and the neutral poly(vinyl pyrrolidone), PVP, were combined and the effects of complexation both in solution and at the nanoparticle interface were studied under basic pH conditions. Using a combination of SANS and PCS, we demonstrate that attractive inter-polymer interactions occur between PVP and NaPA in solution (for polymers with molecular weights equal to 40. K and 60. K respectively); typically, no attractive interactions between PVP and NaPA are reported above a critical pH of 4-5. Polymer interactions in the bulk are observed between the larger molecular weight polymers studied. The mass ratios of polymer also affect the interactions in the bulk, indicating that polymer interactions are influenced by the charges present in the system. The addition of NaPA to a silica dispersion with PVP previously adsorbed to the particles is shown to led to polymer desorption and the destabilisation of the system leading to particle aggregation or even flocculation. SANS data show that the interparticle potential changes from being repulsive with bare silica or PVP-coated silica to attractive on addition of NaPA. The molecular weight of PVP is seen to affect the amount of polymer desorbed, whereas the molecular weight of NaPA had an effect on the aggregation of particles. © 2014 Elsevier B.V.