Stabilizing charged species in nonpolar solvents is difficult due to their low relative permittivity (Er); therefore, surfactants that form inverse micelles are often used as charge control additives (CCAs). In this Thesis, the structural and electrokinetic properties of surfactants and surfactant-charged colloids in nonpolar solvents were studied. The aggregation of surfactants was studied using high-resolution small-angle neutron scattering (SANS) measurements. Critical micelle concentrations (CMCs) for inverse micelle formation were measured for an anionic and a nonionic surfactant, and the transition was different for the two types. However, variations to the surfactant counterion and the solvent did not influence the CMC. Contrast-variation SANS (CV-SANS) was used to study the interaction of surfactant with polymer latexes. The surfactant did not strongly interact with the steric stabilizer polymer and, rather, was located throughout the entire latex. Such a distribution of surfactant differs from other model colloids in nonaqueous solvents where the surfactant is assumed to be adsorbed at the core-solvent interface. Molecular variations to the surfactant structure resulted in differences to the charge of particles. Modifying the surfactant tail groups resulted in more effective CCAs. Triple-chain surfactants were more effective, and this may be due to the larger number of inverse micelles. Changing the surfactant counterion resulted in instability of the particles. This may be due to decreased particle charge and increased electrolyte screening. The results presented in this Thesis provide much-needed structural information and systematic variations to the field of charging in nonpolar solvents. Determining the chemical interactions between surfactants and solvents or colloids is important for understanding how surfactants form inverse micelles, stabilize particles, and generate charge.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:683919 |
| Date | January 2015 |
| Creators | Smith, Gregory N. |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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