(6gf) Interfacial Interactions and the Design of Smart Materials

Interactions at interfaces (solid/solid, solid/liquid, liquid/vapor) mediate many processes, including colloidal/self-assembly, charge transfer, and separation. One type of system in which these interactions are important is stimuli-responsive materials. Stimuli-responsive materials are typically comprised of various components and phases of matter, therefore having many types of interfaces. Thus, the study of appropriate interfacial phenomena can greatly aid in the design of smart materials. First, the engineering of systems responsive to magnetic field and light is presented. These systems are complex multiphase dispersions fabricated by exploiting interactions between anisotropic particles in solution and at air-liquid interfaces. We examine the magnitude of material response to an applied field as a function of system composition and rheological properties. Next, the study of interactions at solution-particle interfaces is presented in context of its importance to carbon nanotube separations. The effect of a molecular dispersant on the nature of the effective particle facilitates nanotube separation by diameter, electronic type, and chirality in solution-based purification processes. In our studies, chirality and length sorted single-wall carbon nanotubes dispersed in ionic surfactant serve as model colloids for refining analytical ultracentrifugation as a tool to characterize colloidal systems, and for understanding nanotube-surfactant interactions. From these works, it is clear that studying interactions at particle-complex solution interfaces, particle-particle interfaces, as well as liquid-vapor interfaces at different environmental conditions and for non-spherical particles is not only fundamentally and industrially relevant but is also crucial for the intelligent design of smart materials.