(104a) Polymer-Surfactant Layer Structure Investigated with Soft Matter Imaging and Single Molecule Force Spectroscopy

A wide range of solution behavior for polymer-surfactant (PS) complexes can be achieved in response to changes in bulk surfactant and electrolyte concentration, which has driven their use in applications in personal care products, food formulations and pharmaceuticals. The association of the surfactant to the polymer provides a means to mediate a range of polymer properties including microstructure phase behavior and surface adsorption. PS complexes have along history of study from surface tension measurements and phase diagrams to more sophisticated scattering methods to probe solution and interfacial structure. Yet, there are still challenges in directly measuring the microscopic structure of adsorbed PS complex in a wide range of solution conditions as well as the molecular configurations of these complexes. In this work, a combination of colloidal probe force microscopy, force spectroscopy and a novel soft matter imaging method were used to determine the microstructure of oppositely charged PS complexes at a solid-liquid interface. Both colloidal probe measurements and a novel soft matter imaging approach were used to directly measure the PS complex layer thickness immobilized on surfaces with carefully controlled surface chemistry as a function of surfactant and electrolyte concentration. In addition, through both physical adsorption and covalent bonding of the PS complex to surfaces, force spectroscopy was used to probe the configuration of individual PS complexes. These data provide insight into the microscopic and molecular response of PS complexes to changes in surfactant and ionic strength when adsorbed on surfaces.