| The research described in this thesis focused on the development of principles for spatial and temporal control of surfactant-based systems in microfluidic channels using electrochemical methods. The methods involve the use of the redox-active surfactant, (11-ferrocenylundecyl) trimethyl- ammonium bromide (FTMA) and build from past studies which have established that FTMA exhibits a critical micelle concentration of 0.1 mM whereas oxidized FTMA remains dispersed in a monomeric state up to concentrations of at least 30 mM.;By using a thin-film electrochemical cell, we measured steady state currents of equal magnitude to be passed at each electrode after the application of the potentials of 0 V (vs Ag∣AgCl) and +0.3 V (vs Ag∣AgCl) to electrodes. Comparison of experimental measurements and model predictions reveals good overall agreement, consistent with the presence of one-dimensional gradients in concentration of monomeric FTMA and micelles of FTMA in the solution between the electrodes.;In microfluidic channels, we directly measured lateral gradients in concentration of oxidized FTMA and reduced FTMA to be generated across the microfluidic channels. The lateral concentration profiles of reduced and oxidized FTMA, and thus the patterning of micelles within the microfluidic channels, were manipulated via changes in the inlet FTMA concentration, potentials applied to the electrodes and flow rate. The concentration gradients in surfactants and micelles can be exploited to drive the formation of gradients in solute concentration because of the selective interactions of solutes with surfactant/micelle. These principles offer the basis of a continuous process for the purification or separation of solutes in microscale chemical process systems.;The final part of this thesis characterizes the nanostructure of complexes formed by oligonucleotides with a single-chain cationic surfactant in aqueous solution. For single-stranded oligonucleotides, the measurements are consistent with the presence of multilamellar vesicles. The nucleotide composition of the single-stranded oligonucleotides was also found to impact the interaction of oligomer with CTAB. For double-stranded oligonucleotides, the measurements indicate formation of a hexagonal nanostructure. These results provide insights into the intermolecular interactions that occur between cationic amphiphiles and oligonucleotides, and provide guidance for the design of oligonucleotide complexes with cationic amphiphiles. UN)... |
