Correlating Surface Chemistry to Surface Relaxivity via TD-NMR Studies of Polymer Particle Suspensions.

This study elucidates the impact of surface chemistry on solvent spin relaxation rates via time-domain nuclear magnetic resonance (TD-NMR). Suspensions of polymer particles of known surface chemistry were prepared in water and n -decane. Trends in solvent transverse relaxation rates demonstrated that surface polar functional groups induce stronger interactions with water with the opposite effect for n -decane. NMR surface relaxivities (ρ 2 ) calculated for the solid-fluid pairs ranged from 0.4 to 8.0 μm s -1 and 0.3 to 5.4 μm s -1 for water and n -decane, respectively. The values of ρ 2 for water displayed an inverse relationship to contact angle measurements on surfaces of similar composition, supporting the correlation of the TD-NMR output with polymer wettability. Surface composition, i.e., H/C ratios and heteroatom content, mainly contributed to the observed surface relaxivities compared to polymer % crystallinity and mean particle sizes via multiple linear regression. Ultimately, these findings emphasize the significance of surface chemistry in TD-NMR measurements and provide a quantitative foundation for future research involving TD-NMR investigations of wetted surface area and fluid-surface interactions. A comprehensive understanding of the factors influencing solvent relaxation in porous media can aid the optimization of industrial processes and the design of materials with enhanced performance.