New insights into micellar structural evolution and interaction using voltammetric methods

Abstract

The development of electrochemical techniques as applied to self-assembled supramolecular systems (e. g. micelles) has advanced over the past decade. The main properties that have been elucidated by these techniques have been micellar selfdiffusion and size. Although there are reports that have paid attention to the qualitative influence of intermicellar interactions on the behaviour of the micellar system, quantitative assessments of interaction are very limited. In this thesis, the application of rotating disk voltammetry, primarily, has led to a quantitative rationalisation of intermicellar interactions in cationic and nonionic micellar systems over a range of surfactant and electrolyte concentrations. Two `normal' micellar systems are studied with aggregates formed from cationic (CTAC) and nonionic (Triton X-100) surfactants. Initial measurements and analysis yields micellar sizes that are consistent with published values, demonstrating the validity and the ease of application of electrochemical techniques. Measuring self-diffusion coefficients over a range of electrolytes provides a comprehensive assessment of micellar phase behaviour and yields further structural parameters which are conventionally determined using a variety of methods. The first reported study of electrochemistry in a reverse micelle `nanoemulsion' is presented. The growth in micellar size on the addition of a solubilised probe gives important inferences for the careful control of particle growth in a reverse micelle `nano-reactor'. In summary, the thesis, as the title states, gives new insights pertaining to micellar structural evolution and interaction. The thesis will examine the benefits of applying electrochemical techniques to study micellar systems and concentrate, predominately, on the wealth of information that can be obtained by the resultant analysis. The work forms an excellent basis for not only further quantitative analysis but also as a phenomenological template for employment in the study of a diversity of self-assembled supramolecular species.