X-ray diffractometer

• Subject Area: Condensed Matter Physics
• Term: Funded in 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 509059014

For the structural analysis of soft matter on molecular to mesoscopic length scales (Å to µm range), we are proposing to acquire a powerful and versatile X-ray diffractometer. Besides small angle X-ray scattering (SAXS) on bulk samples, the main task is to characterise thin films at liquid/gas and solid/gas interfaces by X-ray reflection (XRR) and grazing incidence SAXS (Grazing Incidence Small Angle and Wide X-ray Scattering, GISAXS/GIWAXS). The combination of a brilliant X-ray source (rotating anode) and a high-resolution, primary beam-resistant 2D detector enables the investigation of structures on length scales from a few Å to µm at interfaces and in bulk samples with a single laboratory instrument. In general, the aim is to elucidate and control the relationships between structure, properties and functions of colloidal systems in order to develop new functional materials. Examples of samples are thin stimuli-responsive polymer films of different molecular architecture (polymer brushes, polyelectrolyte multilayers, (micro-)gel layers) that swell in solvents or their vapours. These are usually adsorbed on solid substrates and eventually loaded with inorganic particles for coupling to external fields (light, magnetic field). Here we will investigate to what extent the structure influences the swelling behaviour, dynamics and mechanics of the films. Other types of thin films to be investigated are porous films whose structure is adjusted in a controlled way, e.g. by sol-gel chemistry. In other projects, the structure formation of surface-active additives (lipids, proteins, surfactants, particles, microgels) at the water-air interface is investigated. These can, for example, (de)stabilise foams and emulsions on demand or affect the osmotic pressure in biological membrane systems. The main users are the two research groups of the applicant and of Emanuel Schneck, whose labs are located in the same building where the X-ray diffractometer will be set up. In addition, there are a number of collaborations where the proposed instrument will be used. We currently have a SAXS system (more than 40 years old) and an X-ray reflectometer (15 years old) with which, for example, measurements of lateral order (grazing incidence) are not possible. The group of Wolfgang Donner at the TU Darmstadt has a number of different X-ray diffractometers for structural analysis, especially of crystals, i.e. with optimisation for the wide-angle range. The special requirements for the sample preparation and sample environment for investigation of soft matter with x-rays (ultrapure water treatment, Langmuir trough or humidity cell) exclude the use of the thin-film X-ray diffractometer of the group of Lambert Alff (TU Darmstadt).

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Röntgendiffraktometer
• Instrumentation Group: 4010 Einkristall-Diffraktometer
• Applicant Institution: Technische Universität Darmstadt
• Leader: Professorin Dr. Regine von Klitzing