Microscopy, diffraction and spectroscopy of surfactant monolayer films

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The goals of this research program in surfactant films are: (1) to investigate molecular-level structure-function relationships in monolayer films comprised of a new type of anionic gemini surfactant; (2) to investigate electronic energy transfer dynamics in multifluorophoric photopolymer films using single-molecule fluorescence spectroscopy; and (3) to develop cutting-edge spectroscopy tools for molecular-level characterization of monolayers at the air-water interface. The program will generate fundamental knowledge that will inform applied aspects of our group's research, including work on crop protection and edible oil encapsulation, as well as provide high-caliber training of HQP in areas of economic importance to Canada. Over the program's duration, we will investigate: (1) Fundamental structure-function relationships in monolayer films comprised of a newly-discovered class of anionic gemini surfactants. The key issue of interest is how the molecular structure of surfactants affects fundamental monolayer properties including lateral packing density, ion-binding capacity, mechanical stability and shear rheology. Studies will involve thermodynamic, microscopic and diffraction-based structural characterization of monolayers supported by chemical synthesis to prepare custom surfactants as required. (2) Molecular-level factors that regulate electronic energy transfer efficiency in coupled, luminescent molecules in thin films. The systems of interest are fluorescent polydiacetylene films prepared from polymerizable surfactants. We will measure energy transfer efficiency in these films and correlate alignment of individual fluorophores in the photopolymers with energy transfer dynamics. Measurements will use single-molecule fluorescence anisotropy imaging in combination with traditional fluorescence measurements supported by quantum chemical calculations. (3) New spectroscopic tools for measuring molecular-level structure of films at the air-water interface, including polarization modulated infrared reflection absorption spectroscopy and sum frequency generation vibrational spectroscopy. The former will make use of unique, high-intensity synchrotron radiation to enable unprecedented temporal resolution, and the latter will build on our expertise with pico- and femtosecond laser instrumentation. This program will advance fundamental research in materials science, inform applied surfactant research and provide world-class training of HQP in areas of national importance.