Studies of Polyelectrolyte Multilayers with the SNS Liquids Reflectometer

Orateur : S. John ANKNER (Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA)

Layer-by-Layer (LbL) assembly performed via alternating adsorption of water-soluble polymers at surfaces enables fabrication of films on almost any substrate, with nano-scale control over film composition, structure, and properties. Neutron reflectivity offers a window into the internal structure of Layer-by-Layer grown films. The dependence of neutron refractive index on nuclear rather than electronic scattering allows one to substitute deuterons (2H) for protons (1H) to highlight features of interest within a film. Deuterated precursors are available for a wide range of polyelectrolytes and the polymers themselves for commonly used species, such as poly(styrene sulfonate) and poly(methacrylic acid). By imposing rigorous mass balance and employing simplified block models, one can reduce the number of model parameters and extract meaningful structural information from reflectivity data. We will describe how to construct and constrain multilayer models and present application of these methods to various LbL structural problems, such as environmental response, the dependence of film quality on deposition parameters, adsorption of protein layers, asymmetric and salt-mediated diffusion, and the formation, structure, and pH-response of hydrogels [1-6].

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