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Title: Study of the molecular behaviour of ionic liquid colloidal suspension using rheometry and NMR
Author: Smith, Catherine Franklin
ISNI:       0000 0004 6063 0768
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2017
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In this thesis, a systematic investigation has been carried out to study the effect of cations and anions on the interactions and aggregation of silica nanoparticles in ionic liquid colloidal suspensions. Suspensions of hydrophobic and hydrophilic silica nanoparticles in four ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate, [C\(_2\)mim][BF\(_4\)], 1-butyl-3-methylimidazolium tetrafluoroborate, [C\(_4\)mim][BF\(_4\)], 1-ethyl-3-methylimidazolium bis(trifluoromethylsufonyl)imide, [C\(_2\)mim][NTf\(_2\)], and 1-butyl-3-methylimidazolium bis(trifluoromethylsufonyl)imide, [C\(_4\)mim][NTf\(_2\)], have been studied. Shear thinning rheology was observed in all systems. Suspensions of [C\(_2\)mim][BF\(_4\)] and [C\(_4\)mim][BF\(_4\)] showed shear thickening behaviour at high hydrophilic silica nanoparticle concentrations. Magnetic resonance velocity imaging experiments were performed to study the local rheology of the suspensions, which compared well with the bulk rheology, but indicated shear banding in suspensions of [C\(_4\)mim][NTf\(_2\)] with hydrophilic nanoparticles. No hydrogen bonding, between either cation or anion with silica nanoparticles, was observed by IR spectroscopy. With increasing silica concentration, a decrease in the NMR \(T\)\(1\) relaxation time of protons on the imidazolium ring, of the cation, was observed for all ionic liquids indicating it is the cation that interacts with the nanoparticles. For all ionic liquid suspensions investigated, clusters of nanoparticles were observed by dynamic light scattering. However, for suspensions of hydrophilic silica in [C\(_4\)mim][NTf\(_2\)] and hydrophobic silica in [C4mim][BF4], high proportions of single nanoparticles were also present. These data have been interpreted in terms of the formation of colloidal gels and glasses.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TP Chemical technology