376338 Surface-Mediated Formation of Orientationally Ordered Nanocomposite Materials with Anisotropic Properties

Monday, November 17, 2014: 1:35 PM
208 (Hilton Atlanta)
Bradley F. Chmelka, Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA and Justin P. Jahnke, Chemical Engineering, UC Santa Barbara, Santa Barbara, CA

    Surface interactions are important to understanding and controlling the compositions, structures, and macroscopic properties of a wide range of self-assembled inorganic-organic materials with nanoscale order. For many applications, the possibility of introducing macroscopic orientational order into such materials is attractive, due to the anisotropic properties that are expected to result, including enhanced molecular or electronic transport across membranes or films. However, incorporating high degrees of macroscopic orientational order into nanocomposite materials is challenging, due to the difficulty of managing the complicated and coupled mass transport, self-assembly, and non-equilibrium reaction processes that occur during their syntheses.

    Nevertheless, by exploiting the molecular-level interactions and mass transport effects at surface(s) where nucleation of self-assembled nanocomposite materials occurs, high degrees of macroscopic orientational order can be achieved. Furthermore, by incorporating functional guest species into such orientationally ordered materials, anisotropic properties can result that enhance the performances of hybrid photovoltaic devices or ion-conducting membranes. The properties of such materials depend crucially on the interactions among the functional guest molecules, solvents, structure-directing surfactant species, and inorganic frameworks (e.g., silica or titania), along with the surfaces on which they form. Such interactions can be controllably modified by adjusting the compositions and conditions used during materials syntheses and processing. This includes especially the judicious selection of surfactant and surface species, along with the rates and direction of solvent removal. Insights on material properties from molecular to macroscopic length scales are provided by complementary techniques, such as NMR spectroscopy, X-ray diffraction, electron microscopy, and macroscopic property measurements. New results will be presented specifically for orientationally ordered nanocomposite materials containing light-responsive conjugated polymers or protein guest species, with novel properties for applications in photovoltaic or electrochemical devices.

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