NMR spectrometer for studies of molecular transport

• Subject Area: Polymer Research
• Term: Funded in 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 525518783

A 300 MHz NMR spectrometer with additional equipment for studies of molecular transport (diffusion and electrophoretic NMR) is envisioned. For this purpose pulsed field gradient methods are used, which require a gradient pulse controller as well as a high power gradient amplifier and a dedicated probe head with appropriate gradient coils (one dimensional, z-gradient). The focus of the application is on transport and structural studies in self-organized soft matter on the one hand and in ion transport processes in battery electrolytes on the other hand. Self-organized materials include colloidal systems such as surfactant micelles, liposomes or emulsions in which the diffusion coefficients of the molecular components are determined using 1H PFG NMR. These provide information about the respective molecular localization, aggregate sizes and, if applicable, exchange processes. In particular, the focus is on the development of switchable materials, in which structural changes are induced by molecular switches under light irradiation and are to be monitored under in-situ NMR at the same time. Furthermore, self-organized polymer systems (block or graft copolymers, polymer gels) are optimized with regard to various fields of application. PFG-NMR Diffusion is used here to study molecular transport processes in constrained geometry, i.e. in mesophases and nanochannels. In the second focus of application, various Li+-conducting battery electrolytes such as ionic liquids, organic liquid electrolytes, locally highly concentrated liquid electrolytes or polymer gel electrolytes are examined and optimized with regard to their Li+ transport properties. This includes multinuclear diffusion measurements of 1H, 7Li and 19F to characterize all species in their diffusivity, complemented by electrochemical methods. In particular, electrophoretic NMR is used on these systems in order to determine drift velocities in the electric field. With the help of multinuclear characterization (1H, 7Li and 19F), not only ionic species, but also neutral components that coordinate to them can be characterized with regard to co-migration in the electric field. This allows a complete description of the transport process of all species, the elucidation of the relevance of coordination and cluster formation, up to the determination of correlation coefficients. Sufficiently high magnetic field gradients (> 15 T/m) are required for the above applications in order to also be able to quantify large aggregates and slow diffusion in polymer materials. Furthermore, a broadband diffusion probe head is required for the electrolyte systems, with which the cores 7Li, 1H and 19F can be measured automatically in sequence.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: NMR-Spektrometer für molekulare Transportmessungen
• Instrumentation Group: 1740 Hochauflösende NMR-Spektrometer
• Applicant Institution: Universität Münster
• Leader: Professorin Dr. Monika Schönhoff