Applications of NMR in the study of gel systems

VELASCO, MANUEL I.

Simposio; virtual symposium on nano and microgels; 2020

polymat

In the last decades, the amount of application of Nuclear Magnetic Resonance (NMR) techniques to study complex systems has increased dramatically. This increment has been mainly due to the very well-known advantages of the technique, that is non-destructive, non-invasive, and the possibility to study the systems in a non-altered condition. The last benefit is particularly handy when exploring gel-like systems, where a solvent or liquid phase is a crucial constituent and has a determinant factor over the system properties. The most popular application of NMR is the spectroscopical study of samples, where molecular structural information is obtained. However, there are a plethora of ?non-spectroscopical? experiments that can be very useful to characterize gel systems. Time domain and Diffusion NMR experiments provide an insight into the physicochemical phenomena that are taking place. So, NMR is useful not only to obtain chemical structural information, but also to understand the different dynamical processes that undergo in the system. Also, most of these experiments can be performed at low magnetic fields, reducing the need for costly and high maintenance equipment. Because there is no superconducting magnet, benchtop equipment costs a fraction of traditional high field systems to purchase and requires no expensive ongoing cryogen refills. In addition, single-sided equipment provides spatially resolved information, making them very suitable for the study of non-continuous systems. The presentation aims to explore a few examples where time domain and diffusion NMR is used to determine valuable information from micro/nanogel systems, such as swelling, viscosity, hydrodynamic radius, solvent mobility, solvent dynamics, phase transition, phase sizes determination, among others.