Driven diffusion in nanoscaled materials

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The newly formed project aims at the investigation of diffusion in liquids and in thin liquid crystal layers at solid-liquid interfaces, in pores and in frustrated liquid crystal layers in the range between a few nm and a few μm. Experimentally two approaches are envisaged, namely single tracer diffusion (via optical techniques) and self-diffusion in nano-compartments (via field gradient NMR). The link between these two approaches is based on elaborated data evaluation and theoretical modeling. We will cover an extremely broad time range from 10 ns to several minutes. The central goal is the investigation of confinement effects due to spatial restrictions and specific interface interactions of physico-chemical nature. One of the major challenges is the comparison of data from single quantum object observations and bulk experiments, since they allow for a comparison of time and ensemble averaging and thus the investigation of ergodicity of nanoscaled systems. For this reason it is mandatory that all classes of envisaged materials should be accessible by both experimental approaches. Special emphasis will be on motion driven by external gradients such as gradients of the chemical potential and electric or magnetic fields. Gradients of the chemical potential will be used to study the freezing front in nanopores via NMR and, in comparison, via rotational dynamics of surface attached molecular rotors. As an additional restricted nanosystem we will study diffusion dynamics in frustrated liquid crystal films. The “frustration” of individual smectic liquid crystal layers will be controlled by the competition between applied external electric or magnetic fields and the physicochemical potentials at the solid-liquid interface. Theoretically challenging tasks are the tensor-like diffusion in such heterogeneous systems and the occurrence of phase transitions in nanoscaled environments.