No description available.

No description available.

No description available.

Micellar surfactant solutions are highly complex systems containing aggregates of different shapes and sizes all in dynamic equilibrium. I have undertaken an investigation into the kinetic processes that occur in micellar surfactant solutions subjected to both bulk perturbations and close to expanding surfaces. Supporting information regarding the equilibrium properties of surfactant micelles has been acquired using several experimental techniques including small-angle neutron scattering (SANS) and pulsed field gradient spin echo (PFGSE) nmr. Bulk exchange kinetics between micelles and monomers in solution have been investigated using both numerical modelling and stopped-flow dilution experiments. My results show that conventional theories of monomer-micelle exchange kinetics apply only under very limited conditions. In order to understand how micellesolutions respond to large perturbations from equilibrium a different approach is required. I have hypothesised an alternative monomer-micelle exchange mechanism. This hypothesis has been tested using numerical modelling and comparison of theoretical predictions with the results of stopped-flow perturbation experiments. These experimental results are consistent with my hypothesis. In addition to bulk exchange kinetics, I have also undertaken a detailed experimental investigation of adsorption kinetics from micellar systems on the millisecond timescale. Again my results indicate that conventional theoretical approaches are incomplete and I suggest an alternative adsorption pathway that should be included in future theories of adsorption from micellar surfactant solutions

This research is focused on the effects of the multivalent counterions on the surface and solution properties of the anionic surfactants sodium oligoelhyiene glycol monoalkvl ether sui fates (sodium alkyl ether sulfate, SAES). The surface adsorption features at the air-water interface of sodium oligoethylene glycol monododecyl ether sulfates with different numbers of ethylene oxide groups (sodium lauryl ether sulfate, SLES) in the presence of trivalent counterion A13+, by the addition of AICI3. have been investigated by neutron reflectivity, NR, and surface tension, st. Tbe corresponding self-assembly structures in solutions have also been studied using small angle neutron scattering, SANS. The values of the critical micelle concentration (CMC) of SLES with one ethylene oxide, EO, group (SLES), with two EO groups (SLE,S) and with three EO groups (~LE3S) have been determined by ST measurements in Chapter 4. This chapter also includes initial NR measurements to assess the influence of the EO chain length on the surface packng of the SLES in the absence of any added counterions.

This thesis presents three experimental studies using model suspensions of dye-doped colloidal sepiolite clay rods. In all cases, dye molecules adsorbed onto the outer surfaces of the rods were removed by Soxhlet extraction, yielding dye-doped rods which were then sterically stabilised in toluene. The liquid crystalline phase behaviour of these rods was examined and was similar to that observed previously for undyed particles. The isotropic-nematic phase boundary was as expected for hard spherocylinders of the same aspect ratios; however the transition was broadened due to polydispersity of the rods. Aligning the dyedoped rods in a 9 T magnetic field resulted in a single-domain nematic phase with a marked dichroism. This was due to the restricted orientations of the dye molecules within the zeolitic channels of sepiolite. The order parameter of the dye in the aligned colloidal rods was up to 0.5, similar to typical values for dye in aligned molecular liquid crystals.

In 1952 Sir Charles Frank popularised the idea that the stability of super-cooled liquids arises from a tendency of the particles to cluster together into small structures that are geometrically incommensurate with crystallisation. In this thesis the local structural arrangement of particles within a number of systems is considered. A method called the topological cluster classification (TCC) is used to detect local structures of particles that are equivalent to the potential energy minimum clusters of 13 or fewer particles in isolation. The dynamics of different local structural arrangements within a bulk are considered by developing an algorithm to quantify the lifetimes that the structures persist within the system. The first system considered is a model colloid -polymer mixture, where the colloids self-assemble into small clusters. The structures of the clusters that form are mapped out as a function of attraction and repulsion strength of the colloidal interactions, and the density of the system. In the case of six-particle clusters, the entropic contribution to the free -energy must be accounted for in order to correctly predict the structures that prevail. As the strength of the colloidal attractions is increased, ergodicity is broken and the clusters become kinetically trapped. The structures formed under these conditions are determined by the aggregation sequence of the colloids from the random initial configuration. The effect of long-ranged electrostatic repulsions between clusters on the intra-cluster structure is considered. As the repulsion strength and density increase it is possible for the intra -cluster structure to be perturbed by the presence of neighbouring clusters, demonstrating that it may not always be appropriate to consider each cluster as if it were an isolated system. The structure at liquid -gas interfaces is considered with the TCC algorithm by measuring the fraction of particles participating within dusters as a function of distance from the interface. The participation ratios monotonically decrease in the interfacial region between the liquid and the gas. For interfaces with a high surface tension, the orientations of two types of elongated cluster are found to align near to the free surface and to oscillate with respect to the density fluctuations of the interfacial layers that propagate into the bulk liquid . The clustering of particles in two model super-cooled liquids is considered. The temperature behaviour of the participation fractions of particles in clusters and the dynamical persistence of clusters at low temperatures are measured. The domains of long-lived clusters in the super-cooled regime are characterised and an association with spatial heterogeneities in the dynamics is demonstrated. Correlation lengths for the static structure and the dynamic heterogeneities are found to grow on cooling, however the manners in which the lengths grow are different. An inverse power law reference potential for one of these systems shows clustering that is significantly different to the full system with attract ions, even though the viscous slowdown of the two models is the same. We propose avenues for further research to clarify the relationship between local structure and the glass transition.

Three approaches were used for the preparation of polymer colloids, including block copolymer micellization, miniemulsion and dispersion polymerisation. Polymers, ego PDMAEMA, PDMAEMA-b-PBMA, P(PDMA-PS)4, P(PS-PDMA)4, involved in the preparation were synthesized using reversible addition fragmentation chain transfer (RAFT) polymerisation. The details of each approach are given below. In the first approach, well-defined amphiphilic star block copolymers, P-(PS- PDMA)4 and P-(PDMA-PS)4 (P: porphyrin) were prepared from a free base porphyrin-cored chain transfer agent (CTA-FBP) and used for self-assembly studies. In methanol, a selective solvent for PDMA, spherical micelles were observed for both block copolymers, as characterized by TEM. UV-VIS studies suggested that star-like micelles were formed from P-(PS-PDMA)4, while P-(PDMA-PS)4 aggregated into flower-like micelles. In the second approach, miniemulsions, prepared using PDMAEMA-b-PBMA or PDMAEMA polymers were used as templates for the synthesis of polymer nanocapsules via the quaternization cross-linking of PDMAEMA (block), using 1, 2- bis(2-iodoethoxy)ethane (BIEE) as a bifunctional crosslinker. The miniemulsion prepared from block copolymers of PDMAEMA-b-PBMA were used as templates for the synthesis of Prussian Blue nanoshells, while cross-linked PDMAEMA homopolymer miniemulsions were used as capsules for hydrophobic dyes. In the last approach, PDMS-CTAs (poly(dimethylsiloxane)-based chain transfer agents) were prepared and used as stabilizers in the dispersion polymerisation of methyl methacrylate (MMA) in hexane. The effect of several factors, including the molecular weight of the PDMS and the concentration of the initiator, on the MMA polymerisation was investigated. The kinetics of the polymerisation in the presence of two CTAs were also investigated.

No description available.

No description available.