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Soft matter crystallography - Christopher Garvey

Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation

Small angle scattering is an excellent choice for studying the low-resolution structure of objects in the size range of microns to nanometers. Scattering studies are often applied in the dilute regime with the scattering curves typically being featureless and diffuse and of limited information content. These constraints have driven in particular, the development of pin-hole small angle neutron scattering instrumentation. By contrast real space methods, such as electron microscopy, with improving sample preparation and some technical advances in instrumentation and data analysis, provide a conceptually easier visualization of objects which is beginning to rival, in terms of the minimum length-scales and information content, the view point of small angle scattering. However for real space imaging methods, the impracticalities of large sampling statistical deviations from defined structure (disorder) or non-destructively visualizing internal structure inside cells or soft matter in the presence of some external field or stimulus, are major drawbacks to this experimental approach. Furthermore, for highly condensed systems where there is ordering of the internal structure, diffraction provides a possibility for providing novel structural perspectives on soft matter non-destructively. These perspectives are the nature of the crystallographic unit cell, orientation/texture and deviations from this unit cell (i.e. disorder). This talk will examine : the power of scattering techniques in tackling problems of industrial, technological and biological relevance ; and limitations in current instrumentation with a view to possible instrumental developments for the future. The particular examples that will be examined are the : membrane biophysics of cryo- and anhydro- biology ; controlled kinetics of photodegradation of agricultural polyethylene films ; gaining an understanding of the growth of photonic crystals in the wings of some butterflies ; and understanding disorder in the important biopolymer cellulose.


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