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Evaluation of chitosan crystallinity: A high-resolution solid-state NMR spectroscopy approach
William Marcondes Facchinatto1, Danilo Martins Dos Santos2, Anderson Fiamingo3
1São Carlos Institute of Chemistry, University of São Paulo, Av. Trabalhador Sao-Carlense 400, CEP 13566-590, Caixa Postal 780, São Carlos, São Paulo, Brazil.
Carbohydrate Polymers
|October 14, 2020
Summary
High-resolution solid-state 13C NMR spectroscopy quantifies chitosan crystallinity. Crystallinity increases with degree of acetylation, offering a new prediction method without amorphous standards.
Area of Science:
- Materials Science
- Polymer Chemistry
- Analytical Chemistry
Background:
- Chitosan's properties are highly dependent on its crystallinity.
- Quantifying chitosan crystallinity is crucial for its applications.
- Existing methods for crystallinity assessment can be complex or require specific standards.
Purpose of the Study:
- To develop and validate a novel method for quantifying the crystallinity index of chitosan.
- To investigate the relationship between chitosan's degree of acetylation (DA¯) and its crystallinity.
- To explore the utility of solid-state 13C NMR spectroscopy for predicting chitosan crystallinity.
Main Methods:
- High-resolution solid-state 13C NMR spectroscopy, including Dipolar Chemical Shift Correlation (DIPSHIFT) and 1H-13C Heteronuclear Correlation (2D HETCOR).
- 13C Cross-Polarization Magic Angle Spinning (CPMAS) for analyzing short-range ordering.
- Singular Value Decomposition (SVD) multivariate analysis for data interpretation.
Main Results:
- The study successfully quantified the crystallinity index of chitosans with varying degrees of acetylation (5-60%) and molecular weights.
- 13C CPMAS analysis revealed that short-range ordering correlates with C4/C6 signals.
- Deconvolution of disordered and ordered phases demonstrated a clear increase in crystallinity with increasing degree of acetylation (DA¯).
Conclusions:
- Solid-state 13C NMR spectroscopy, particularly 13C CPMAS, is a reliable technique for predicting chitosan crystallinity.
- The developed method allows for the quantification of chitosan crystallinity without the need for amorphous standards.
- This approach enhances the understanding of structure-property relationships in chitosan based on its acetylation degree.
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