Soft Matter studies seek to unravel the link between a material’s microstructure and dynamics, and its macroscopic properties. This chapter presents a broad set of examples from the morphology of synthetic polymer fibres to structural dynamics of biomolecules in bulk and at interfaces. These studies involve a diverse class of systems from supercooled liquids to highly self-assembled biological complexes. This diversity is one of the particular strengths of the activities at the Soft Condensed Matter Group beamlines, articulating significant overlap with other disciplines such as materials science, biology, and surface science.

The past year saw many important scientific and technical developments. It has been a very hectic year with preparation for the ESRF Upgrade Programme and joint review of all four beamlines in the Soft Condensed Matter Group (ID02, ID10A, ID10B, and ID13) in spring 2008. The outcome of this review was very positive, without exception. The review panels recognised the outstanding technical status and scientific accomplishments of these beamlines. The review panels also approved the upgrade proposals for the beamlines.

The highlights selected for this chapter represent only a sub-set of the many interesting scientific results and technical developments over the year. A large fraction of the articles illustrate the unique feature of scattering techniques in terms of the combined access to the relevant length and time scales not readily feasible by other techniques. Studies of dynamic processes especially at interfaces are receiving increased attention.

The first two articles deal with adsorption of biomolecules at curved and planar interfaces. In the first article, the adsorption of proteins onto tethered polyelectrolyte brushes was probed in real time by SAXS, which revealed the sub-diffusive motions of proteins in the grafted polyelectrolyte layer. The second article presents the structural details of the adsorbed monolayer of DNA on a solid substrate with a soft functionalised organic layer, elucidating their two-dimensional order by X-ray reflectivity. This is followed by a study of low frequency viscoelastic behaviour of a supercooled liquid near the glass transition probed by XPCS at grazing incidence which demonstrated striking similarities in the temperature dependence of viscosity and elasticity. The fourth article reports diffuse scattering and reflectivity investigations of the formation and self-organisation of gold nanoparticles at liquid-liquid and air-water interfaces illustrating an unexpected clustering of particles. 

Soft Condensed Matter Group beamlines are involved in a variety of technical developments. The first article in this category demonstrates that hard X-ray holographic diffraction imaging is an excellent technique for determining electron density profiles of nanostructures. With the availability of higher coherent flux, this technique offers the possibility of imaging fast dynamic processes. In conventional fibre diffraction experiments, the fibre axis is perpendicular to the X-ray beam. With special specimen preparation, the possibility of passing the microbeam along the fibre axis has been demonstrated, which then reveals fine details of skin-core morphology without requiring elaborate modelling. Manipulating micrometre-size objects in solution within a microbeam is a challenging task. In the subsequent article, the effectiveness of laser traps for manipulating large multilamellar liposomes in a microdiffraction experiment has been illustrated.

The final two articles present structural dynamics of proteins when they perform their biological functions. In the first article, the quaternary transition of human haemoglobin from ligand bound relaxed state to unbound tense state and back to the relaxed state was studied by nanosecond pump-probe techniques at beamline ID09B. In the last article, the molecular mechanism of muscle braking action under rapid stretch was revealed by X-ray interference combined with high-resolution muscle mechanics.

The joint review process of the beamlines also set the momentum for the Partnership for Soft Condensed Matter (PSCM) together with the ILL. The ESRF Science Advisory Committee supported the establishment of the PSCM on a step-by-step basis, initially as a support laboratory for ancillary equipments. As a first step, the support laboratories within the SCM group are becoming better streamlined. The scientific scope and content for the partnership is being refined. Further discussion with the User Community is foreseen in the near future.

T. Narayanan