High Resolution Magic Angle Spinning (HRMAS) Pulse Field Gradient (PFG) NMR Diffusometry Studies of Swollen Polymers

Abstract

In this chapter, the combination of high resolution magic angle spinning (HRMAS) NMR spectroscopy and pulse field gradient (PFG) NMR diffusometry techniques to study solvent transport in swollen polymers is presented. The MAS suppression of magnetic susceptibility differences that exist for liquids absorbed in heterogenous polymer materials is shown to provide significant improvements in the NMR spectral resolution, thereby allowing the use of PFG NMR diffusion experiments to probe multiple chemical environments simultaneously. Recent examples of using 1H HRMAS PFG NMR experiments to measure solvent diffusion in 3D-printed siloxane polymer composites are detailed, along with an example of characterizing diffusion in methanol fuel cell anion exchange polymer membranes. These results demonstrate the power of HRMAS PFG NMR diffusometry to obtain information for complex chemical mixtures absorbed in polymers.