CO₂‑Responsive Microemulsions Based on Reactive Ionic Liquids

We demonstrate that the nanodomains within a ternary system consisting of oil, surfactant, and a new reactive ionic liquid can be tuned reversibly upon exposure to and removal of CO₂ under mild conditions of temperature and pressure. The equilibrium microstructures of these domains have been characterized by small-angle neutron scattering and demonstrate that control over emulsion morphology (and therefore physicochemical properties such as viscosity) and the breaking of emulsions can be achieved without the need for irreversible changes in system composition or significant energy input

Spatially Resolved Concentration and Segmental Flow Alignment in a Shear-Banding Solution of Polymer-Like Micelles

We measure the spatially resolved microstructure and concentration in the plane of flow for a viscoelastic solution of polymer-like micelles comprised of mass fraction 6.0% (volume fraction 6.6%) solution of 2:1 molar ratio cetylpyridinium chloride/sodium salicylate in 0.5 mol/L NaCl/D₂O through the shear banding transition. Spatially resolved flow small-angle neutron scattering measurements in the velocity–velocity gradient (1–2) plane of flow establish the local microstructure, and scanning narrow-aperture flow ultrasmall-angle neutron scattering (SNAFUSANS) measurements indicate no flow-induced concentration gradients within measurement accuracy. These results show shear banding in this solution is not associated with an isotropic–nematic transition and are fundamentally important for validating models of shear-banding complex fluids. Improvements in the SNAFUSANS method are also documented

Structure of flocs of latex particles formed by addition of protein from Moringa seeds

Proteins extracted from the seeds of Moringa trees are effective flocculents for particles dispersed in water and are attractive as a natural and sustainable product for use in water purification. Studies with a model system consisting of polystyrene latex particles have shown that the protein adsorbs to the surface and causes flocculation as unusually dense aggregates. Small-angle neutron scattering that exploits contrast matching of deuterated latex particles dispersed in D2O to highlight bound protein has shown that the adsorbed amount reaches about 3 mg m(-2). The particles form very compact flocs that are characterized by fractal dimensions that approach the theoretical maximum of 3. Ultra small-angle neutron scattering allows these flocs to be characterized for a range of particle and protein concentrations. Proteins from two species of Moringa trees were investigated. The protein from Moringa stenopetala seeds gave rise to slightly lower fractal dimensions compared to Moringa oleifera, but still much larger than values observed for conventional ionic or polymeric flocculents that are in the range 1.75-2.3. Compact flocs are desirable for efficient separation of impurities and dewatering of sludge as well as other applications. A trend of increasing fractal dimension with particle concentration was observed when M. stenopetala seed protein was used and this resembles the behaviour predicted in Brownian dynamics simulation of flocculation

Structure of Two-Compartment Hydrogels from Thermoresponsive ABC Triblock Terpolymers

Aqueous dispersions of a poly­(ethylene-<i>alt</i>-propylene)-<i>b</i>-poly­(ethylene oxide)-<i>b</i>-poly­(<i>N</i>-isopropyl­acrylamide) (PON) triblock terpolymer with block molecular weights of 3 000–25 000–10 000 and polymer concentrations ranging from 1 to 5 wt % were investigated at several temperatures from 25 to 55 °C using cryogenic scanning electron microscopy (cryo-SEM), cryogenic transmission electron microscopy (cryo-TEM), and small-angle neutron scattering (SANS). The cryo-SEM and cryo-TEM micrographs revealed that PON triblock terpolymer self-assembled into spherical micelles with PEP cores and PEO–PNIPAm coronae at room temperature and subsequently formed a two-compartment micellar network consisting of distinct spherical PEP and PNIPAm cores upon heating above the critical gelation temperature (42 °C). The formation of two discrete spherical PEP and PNIPAm hydrophobic domains was supported by detailed SANS analysis of the PON triblock samples in D₂O, as the resulting intensity profiles can be successfully fitted using a scattering equation based on the two-compartment network structure. The two-compartment structure was further confirmed using contrast-matching SANS experiments on a PON_d7 triblock sample with similar block molecular weights and a partially deuterated PNIPAm block. An important result of the SANS profiles in the gel state was the emergence of two distinct scattering peaks, which could be accounted for by considering spatial correlations between PEP and PNIPAm micellar cores. This study confirms the hypothesis that the formation of two-compartment networks in ABC terpolymer hydrogels results in better gelation properties, in comparison to other physically associated hydrogels, and can further guide the design and development of advanced hydrogel systems with enhanced performance

Structure of flocs of latex particles formed by addition of protein from Moringa seeds

Proteins extracted from the seeds of Moringa trees are effective flocculents for particles dispersed in water and are attractive as a natural and sustainable product for use in water purification. Studies with a model system consisting of polystyrene latex particles have shown that the protein adsorbs to the surface and causes flocculation as unusually dense aggregates. Small-angle neutron scattering that exploits contrast matching of deuterated latex particles dispersed in D2O to highlight bound protein has shown that the adsorbed amount reaches about 3 mg m(-2). The particles form very compact flocs that are characterized by fractal dimensions that approach the theoretical maximum of 3. Ultra small-angle neutron scattering allows these flocs to be characterized for a range of particle and protein concentrations. Proteins from two species of Moringa trees were investigated. The protein from Moringa stenopetala seeds gave rise to slightly lower fractal dimensions compared to Moringa oleifera, but still much larger than values observed for conventional ionic or polymeric flocculents that are in the range 1.75-2.3. Compact flocs are desirable for efficient separation of impurities and dewatering of sludge as well as other applications. A trend of increasing fractal dimension with particle concentration was observed when M. stenopetala seed protein was used and this resembles the behaviour predicted in Brownian dynamics simulation of flocculation