Qingchun Yuan

Responsive core-shell latex particles as colloidosome microcapsule membranes.

Responsive core-shell latex particles are used to prepare colloidosome microcapsules using thermal annealing and internal cross linking of the shell, allowing the production of the microcapsules at high concentrations. The core-shell particles are composed of a polystyrene core and a shell of poly[2-(dimethylamino)ethyl methacrylate]-b-poly[methyl methacrylate] (PDMA-b-PMMA) chains adsorbed onto the core surface, providing steric stabilization. The PDMA component of the adsorbed polymer shell confers thermally responsive and pH-responsive characteristics to the latex particle, and it also provides glass transitions at temperatures lower than those of the core and reactive amine groups. These features facilitate the formation of stable Pickering emulsion droplets and the immobilization of the latex particle monolayer on these droplets to form colloidosome microcapsules. The immobilization is achieved through thermal annealing or cross linking of the shell under mild conditions feasible for large-scale economic production. We demonstrate here that it is possible to anneal the particle monolayer on the emulsion drop surface at 75-86 °C by using the lower glass-transition temperature of the shell compared to that of the polystyrene cores (∼108 °C). The colloidosome microcapsules that are formed have a rigid membrane basically composed of a densely packed monolayer of particles. Chemical cross linking has also been successfully achieved by confining a cross linker within the disperse droplet. This approach leads to the formation of single-layered stimulus-responsive soft colloidosome membranes and provides the advantage of working at very high emulsion concentrations because interdroplet cross linking is thus avoided. The porosity and mechanical strength of the microcapsules are also discussed here in terms of the observed structure of the latex particle monolayers forming the capsule membrane.

Desalination as a negative emissions technology

To limit global warming, governments and industries are engaged in reducing emissions of CO2. There is increasing evidence, however, that it may be necessary to go a step further by removing CO2 already emitted. For the purpose of Carbon Dioxide Removal (CDR), a number of Negative Emissions Technologies (NET) have been proposed. These generally make extensive usage of land, energy and water – if they are to be implemented at the large scales needed. It is therefore important to seek, investigate and compare alternative approaches to NET. Desalination plants, though normally seen as sources rather than sinks of CO2, could be modified to provide a new type of NET. In this study, we propose treating desalination reject brine by electrolysis to form Mg(OH)2 and thus absorb CO2 via the oceans. The energy and water penalties associated with the electrolysis are calculated as 1.8 GJ/tCO2 and 13.7 m3/tCO2 respectively, making it an interesting option in comparison with some other types of NET. However, NET-modification more than doubles the specific energy consumption of a reverse-osmosis desalination plant. It is concluded that NET-desalination has potential to contribute to CDR in arid countries (especially if solar energy is used) thus helping to meet Intended Nationally Determined Contributions (INDCs) following the COP21 summit.