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Guest-Host Interactions in Self-Assembling Solutions and Solids

Brad Chmelka Department of Chemical Engineering, University of California, Santa Barbara

Guest molecule interactions and distributions within self-assembling host species exert important influences on the properties of diverse complex fluid solutions and heterogeneous solids. These include technologically important systems, such as micelle or vesicle hosts for drug delivery, proteins that interact with small-molecule agents, and functionalized inorganic-organic hybrid materials. In such mixtures, guest-host distributions are generally influenced by competing interactions among numerous and diverse hydrophobic, hydrophilic, and/or surfactant species present. These interactions affect guest-host binding, component mobilities, phase behaviors, and macroscopic mixture properties, though are highly system-dependent and challenging to elucidate and understand. Scattering, microscopy, calorimetry, and optical spectroscopy measurements are sensitive, though often limited in their resolution, especially in the absence of long-range order. By comparison, multidimensional and pulsed-field-gradient diffusion NMR methods provide high molecular-level resolution with respect to the locations, distributions, and dynamics of different component species. Recent results and new insights will be presented on guest-molecule interactions with self-assembling host species, e.g., photo-responsive porphyrins, conjugated polymers, or surfactants in heterogeneous micellar, vesicle, or protein solutions and block-copolymer-directed solids.