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The coexistence of two phases in concentrated dispersions of monodispersed platelike particles is reported. Small-angle neutron diffraction has been used to identify a highly ordered phase which coexists at equilibrium with a less ordered, less dense phase. The interparticle interactions were varied by adjusting the salt concentration, and this influenced the concentration at which the phase transition occurred. Columnar or layer structures which could account for the observed diffraction pattern from the ordered phase are discussed.

The structure of dispersions of sterically stabilised poly(methyl methacrylate)(PMMA) particles under flow conditions are presented. Data have been obtained with a light scattering apparatus in which the sample can be sheared. The colloidal dispersions were prepared from particles with a significant density difference to the suspending medium which gives rise to sedimentation. The scattering patterns indicate fluid-like structures coexisting with ordered arrays of particles. The ordered phase, which has a higher number density than the fluid, is found to undergo significant structural changes under steady shear. Diffraction from ordered and disordered layers of particles in finite-sized stacks is discussed. Quantitative interpretation of the scattering patterns in terms of particle arrangements are presented. The sedimentation gives rise to density and velocity gradient variations across the sample with slip regions. Such important effects would go undetected in rheological measurements, leading to misinterpretation of the rheological behaviour.

The layering of ionic liquids close to flat, charged interfaces has been identified previously through theoretical and some experimental measurements. Here we present evidence for oscillations in ion density (‘layering’) in a long chain ionic liquid (1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide) near the interface with mica using two complementary approaches. Neutron reflection at the ionic liquid-mica interface is used to detect structure at a single interface, and surface force balance (SFB) measurements carried out with the same ionic liquid reveal oscillatory density in the liquid confined between two mica sheets. Our findings imply the interfacial structure is not induced by confinement alone. Structural forces between two mica surfaces extend to approximately twice the distance of the density oscillations measured at a single interface and have similar period in both cases.

The combination of differential scanning calorimetry and incoherent elastic neutron scattering has been used to demonstrate the formation of solid layers adsorbed onto graphite from pure alkanes an...

The complexation behaviour of duplex linear DNA (negatively charged) with amidine functionalised sub-micron latex spheres (positively charged) was studied using dynamic light scattering (DLS) and a PALS interferrometric zeta potential sizer. Four types of DNA-sphere complex were investigated as a function of component concentration by combining amidine functionalised polystyrene microspheres with radii of 10.5 nm and 60 nm, and herring DNA of lengths of 35 nm and 85 nm. At low DNA concentrations (c(DNA)), the undercharged complexes showed a small increase in measured hydrodynamic radius (R(h)) and a decrease in zeta potential with increasing c(DNA). Within a critical DNA concentration range R(h) was seen to peak sharply, and the zeta potentials were approximately 0 mV, corresponding to the formation of unstable neutral complexes. Immediately above this concentration region the measured R(h) values became comparable with those at low c(DNA), and the zeta potential became negative, indicating the formation of stable overcharged complexes. The small and large spheres formed multi-sphere and single sphere overcharged aggregates respectively, which is thought to be determined by the relative magnitude of the chain persistence length (approximately 50 nm) and the sphere radius, switching on or off the DNA bridging interaction.

We report a dynamical-mechanical study of stress relaxation at small deformation in a natural (polyisoprene) rubber well above its glass transition temperature Tg. We find that an almost complete relaxation of stress takes place over very long periods of time, even though the elastic network integrity is fully retained. The relaxation rate and the long-time equilibrium modulus are sensitive functions of temperature which do not follow time-temperature superposition. Many characteristic features of non-ergodic ageing response are apparent at both short and very long times. We interpret the observed behaviour in terms of the properties of rubber crosslinks, capable of isomerisation under stress, and relate the results to recent models of soft glassy rheology., Latex 2e (EPJ style), 5 EPS figures

© 2016 The Authors The behaviour and molecular structure of three organic additives adsorbed from oil onto a copper surface rich in copper (II) oxide is presented. The variation in the ability of these three agents to prevent corrosion of the copper oxide surface by exposure to sulphur is also included. A combination of visible observations, X-ray photoelectron spectroscopy (XPS) and neutron reflection (NR) are used to characterise both the adsorbed layer and underlying copper oxide. The model additives are chosen to represent ‘effective’, ‘intermediate’ and ‘ineffective’ inhibitors for copper.