Fast-forward approach of time-domain NMR relaxometry for solid-state chemistry of chitosan


Chitosans with different average degrees of acetylation and weight molecular weight were analyzed by time-domain NMR relaxometry using the recently proposed pulse sequence named Rhim and Kessemeier - Radio- frequency Optimized Solid-Echo (RK-ROSE) to acquire 1H NMR signal of solid-state materials. The NMR signal decay was composed of faster (tenths of μs) and longer components, where the mobile-part fraction exhibited an effective relaxation transverse time assigned to methyl hydrogens from N-acetyl-D-glucosamine (GlcNAc) units. The higher intrinsic mobility of methyl groups was confirmed via DIPSHIFT experiments by probing the 1H-13C dipolar interaction. RK-ROSE data were modeled by using Partial Least Square (PLS) multivariate regression, which showed a high coefficient of determination (R2 > 0.93) between RK-ROSE signal profile and average degrees of acetylation and crystallinity index, thus indicating that time-domain NMR consists in a promising tool for structural and morphological characterization of chitosan.


Facchinatto, William Marcondes; dos Santos Garcia, Rodrigo Henrique; dos Santos, Danilo Martins; Fiamingo, Anderson; Flores, Douglas William Menezes; Campana-Filho, Sérgio Paulo; deAzevedo, Eduardo Ribeiro; Colnago, Luiz Alberto

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