Tatani, Aikaterini (2021) Occlusion of oil droplets within inorganic host crystals for laundry applications. MPhil thesis, University of Sheffield.
Abstract
Well-defined spherical diblock copolymer nanoparticles were synthesised by reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerisation of 2-ethylhexyl methacrylate using a water-soluble poly(methacrylic acid) precursor as a steric stabiliser. These nanoparticles are homogenised with a model oil (methyl myristate) under high shear with subsequent high pressure microfluidisation leading to the formation of oil-in-water nanoemulsions. The relative low glass transition temperature of the hydrophobic poly(2-ethylhexyl methacrylate) block leads to in situ dissociation of the nanoparticles, with the resulting strongly amphiphilic block copolymer chains acting as a polymeric surfactant for the oil droplets. This wholly aqueous route to nanoemulsions represents a useful improvement on a recent report that utilised RAFT dispersion polymerisation of lauryl methacrylate in methanol (Y. Ning et al., Chem. Sci. 2019, 10, 8964-8972). The model oil was then replaced with various hydrophobic multicomponent fragrances supplied by the industrial sponsor of this project (Procter & Gamble). The poly(methacrylic acid) block confers anionic character on the oil droplets, which enables their occlusion within calcium carbonate (calcite) crystals prepared in situ by the ammonia diffusion method at pH 9. Given the environmentally benign nature of the inorganic host matrix, such oil-loaded crystals offer a potential new biocompatible matrix for fragrance encapsulation/release in laundry applications. Systematic variation of the mean degree of polymerisation of the hydrophobic block indicated that poly(methacrylic acid)138-poly(2-ethylhexyl methacrylate)45 gave the best emulsifier
performance for the production of stable nanoemulsions in which the oil phase comprised a multi-component fragrance. Scanning electron microscopy studies of oilloaded calcite crystals confirmed the successful occlusion of micron-sized droplets. Thermogravimetric analysis indicated a maximum oil loading of 8.3% by mass for optimised formulations.
Metadata
Supervisors: | Armes, Steven P. |
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Awarding institution: | University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Chemistry (Sheffield) |
Depositing User: | Miss Aikaterini Tatani |
Date Deposited: | 18 Aug 2021 15:24 |
Last Modified: | 05 Aug 2022 00:31 |
Open Archives Initiative ID (OAI ID): | oai:etheses.whiterose.ac.uk:29310 |
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