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

•Degree of acetylation and crystallinity of chitosan can be evaluated by TD-NMR.•RK-ROSE signal decay is mainly associated with the methyl hydrogens of GlcNAc units of chitosan chain.•The rigid and mobile-part signals are modulated by the local chain packing. Chitosans with different average degrees...

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Bibliographic Details
Published in:Carbohydrate polymers 2021-03, Vol.256, p.117576-117576, Article 117576
Main Authors: Facchinatto, William Marcondes, dos Santos Garcia, Rodrigo Henrique, dos Santos, Danilo Martins, Fiamingo, Anderson, Menezes Flores, Douglas William, Campana-Filho, Sérgio Paulo, de Azevedo, Eduardo Ribeiro, Colnago, Luiz Alberto
Format: Article
Language:English
Subjects:
Acetylation
Acetylglucosamine - chemistry
Animals
Chitin - chemistry
Chitosan
Chitosan - chemistry
Crystallinity
Decapodiformes - chemistry
Degree of acetylation
Hydrogen - chemistry
Least-Squares Analysis
Magnetic Resonance Spectroscopy - methods
Molecular Weight
Multivariate Analysis
Relaxometry
TD-NMR
Temperature
Thermogravimetry
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Summary:•Degree of acetylation and crystallinity of chitosan can be evaluated by TD-NMR.•RK-ROSE signal decay is mainly associated with the methyl hydrogens of GlcNAc units of chitosan chain.•The rigid and mobile-part signals are modulated by the local chain packing. 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 - Radiofrequency 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.
ISSN:0144-8617
1879-1344
DOI:10.1016/j.carbpol.2020.117576