Topics for Bachelor's and Master's theses

Topics may change at short notice. In principle, all topics are suitable for Master's theses as well as Bachelor's theses, provided this is indicated. If you have any questions, please contact us by email or telephone:

 

Siegfried Stapf, Tel. 3671 - Carlos Mattea, Tel. 3787

  • 1st NMR study on the solid content in solutions with microplastics (Bachelor) How can the solids content of polymers be quantified quickly and easily using NMR pulse sequences? What is the optimal magnetic field strength?The current and planned EU directives on minimizing microplastics in the environment contain definitions of size and strength; however, the latter in particular is not practicable for aqueous solutions and multi-component systems. New and efficient methods are being sought to determine the proportion of solids, with NMR relaxation being an obvious choice: viscous and solid substances are characterized by shorter T2 times and specific magnetic field dependencies of the T1 times. Using model polymers (e.g. PVP), measurement methods and correlations are to be established; the project is being carried out in close cooperation with global research at BASF SE/Ludwigshafen. Focus: experiment, data analysis
  • 2. relaxation and diffusion of liquids in mesoporous silica (Bachelor) How do the molecular dynamics change within regular pores of a few nm diameter? Does diffusion depend on molecular size or polarity?The NMR relaxation of adsorbed liquids in mesoporous glass (i.e. pore sizes below 50 nm) strongly depends on the polarity of the molecules and the nature of the interaction with the surface. Previous studies have dealt with materials in the disordered pore structure of glasses. This work deals with artificially prepared cylindrical silica structures (SBA-15) with hexagonal cross-section of 4 to 12 nm diameter and aims at the measurement of T1 and T2 relaxation times of polar and non-polar adsorbates and the determination of their diffusion coefficients with a desktop NMR spectrometer. If necessary, they will be supplemented by 2H experiments in a field of 7 T. Focus: preparation, experiment
  • 3. ageing of engine and lubricating oil (Bachelor/Master) How can the ageing and decomposition of engine oil be characterized using ESR and NMR?When engine oil is used in automobiles and other vehicles as well as lubricating oil in industrial plants, thermal stress and other external influences such as combustion, contamination, light, etc. lead to degradation processes that require the oil to be replaced after a certain period of time. The service life of the oil is estimated empirically, but depends on the exact working conditions; a detailed analysis of viscosity, chemical composition, mechanical properties, transparency, etc. has proven to be time-consuming and not universally applicable. As the degradation of the oil is usually accompanied by the formation of stable radicals, ESR spectroscopy is a simple and fast (less than 1 min) method for quality control. The stability of various precursor oils (without additives) and commercial products (with antioxidants and other additives) will be examined by subjecting them to different cycles of heating, UV treatment and oxidation; the correlation between the radical concentration and these parameters will be checked. If necessary, NMR relaxation measurements are also carried out, as the presence of radicals can also manifest itself in the relaxation times.The project is being carried out in cooperation with the Universidad Nacional de Cordoba, Argentina.Focus: sample treatment, experiment, documentation
  • 4. NMR multipulse method for polymers and ordered systems (Bachelor/Master) How can the mean displacement squared of molecules be determined using novel echo methods? What are the possible applications for biological samples and porous media?A robust multiecho method was developed for the dynamics in polymer melts, which determines the mean displacement square for anomalous diffusion (subdiffusive processes) in a time range that is not accessible with other methods. The method is now to be applied to new polymers, biomacromolecules and liquids in porous media. The device allows temperature control up to around 470 K.Focus: Experiment, data analysis, theory
  • 5. deuterated polymer mixtures in confinement (Bachelor/Master) How does confinement in narrow pores influence the dynamics of polymer melts?In the department we are working on a long-term project to analyze polymer melts using differently isotope-diluted mixtures of polyethylene oxide (both 1Hand 2H resonance). One aspect of the DFG project investigates the question of what differences arise in the dynamics of inclusion in rigid porous media (e.g. Vycor glass, 4 nm, as an established standard). The literature has so far only succeeded in measuring undeuterated PEO.Main topics: Sample preparation, experiment
  • 6. concepts for the detection of flowing water on Mars (Bachelor/Master)How must a sensor be designed to measure water on Mars under realistic conditions (T, pH, Fe, salt)?Several bachelor theses have already dealt with the behavior of water at high salt concentrations, high iron oxide content, and low temperatures on Mars simulation soils. Diffusion has been successfully measured, here NMR is the only option to determine not only the amount but also the mobility of water in situ. For the preparation of publications, the time-dependent analysis of diffusion at low water contents and the investigation of soil types according to recent findings on the south polar cap of Mars, i.e. the presence of water-binding clay, are still missing.Main focus: Preparation, experiment
  • 7. rheology of polymer melts in a magnetic field (Master) Can mechanical stress have a measurable influence on molecular dynamics?Use of an existing apparatus to systematically analyze the change in the NMR relaxation properties of sheared polymer melts and possibly other complex fluids with spectral resolution. Measurements either in the high field or in the variable field (field-cycling relaxometer). Main focus: Sample preparation, measurement; documentation and optimization of measurement parameters; data analysis and literature
  • 8. construction of a unit with field modulation traces (master) How should field modulation coils be dimensioned to perform the integrated solid effect?Dynamic Nuclear Polarization (DNP) is one of the methods currently used for signal enhancement in NMR; it is based on microwave irradiation. For many substances with broad absorption lines, however, excitation by microwaves is far too weak; here the magnetic field must be modulated at high frequency in order to cover the entire width of the (electron) spectrum. For this purpose, additional coils must be constructed that are close to the sample in order to minimize the necessary current strengths and heating effects. The design is based on commercial solutions for field gradient coils.Main focus: Design, construction - knowledge of electronics
  • 9. protein dynamics using radicals and DNP (Master)How can subgroups of proteins in aqueous solution be selectively amplified and measured in the low field and variable field?In a completed work, the distribution of the relaxation times of native and denatured dissolved proteins was investigated. The diffusion coefficient was used to demonstrate the change in protein form due to denaturation. The influence of added radicals is understood in principle. Building on this, a second study will use known proteins to determine where the radical attacks, how it influences relaxation and how selective signal amplification can be achieved using DNP. What is the minimum protein concentration that can still be measured with this method?Main topics: Sample preparation, experiment, literature