Kinetics Study of the Solid-State Acid Hydrolysis of Chitosan: Evolution of the Crystallinity and Macromolecular Structure
- 19 April 2010
- journal article
- research article
- Published by American Chemical Society (ACS) in Biomacromolecules
- Vol. 11 (5), 1376-1386
- https://doi.org/10.1021/bm1001685
Abstract
The heterogeneous hydrolysis of fully deacetylated chitosan solid samples was carried out with concentrated HCl. The hydrolysis kinetics was studied at different temperatures and HCl concentrations. From 5 to 50 °C in the hydrolysis time range up to 50 h, a monomodal distribution of molecular weights was observed connected to the only degradation of amorphous domains. Between 70 and 90 °C and for the hydrolysis longest times, a multimodal distribution appeared with the additional hydrolysis of the crystalline phase. The crystallinity index increased from 57 to 73% with the elimination and partial recrystallization of amorphous regions. X-ray diffraction patterns revealed the presence of the anhydrous polymorph, absent in the starting materials only containing the hydrated polymorph. The apparent crystallite width (from the Scherrer equation) of both the anhydrous and hydrated allomorphs did not vary significantly with time despite the increase in the fraction of anhydrous allomorph. Therefore, the hydrolysis in the solid state was complex, revealing several regimes. The activation energy parameters were deduced, and the mechanisms were discussed.Keywords
This publication has 33 references indexed in Scilit:
- Direct chitosan nanoscaffold formation via chitin whiskersPolymer, 2007
- Crab Shell Chitin Whisker Reinforced Natural Rubber Nanocomposites. 1. Processing and Swelling BehaviorBiomacromolecules, 2003
- Morphological Investigation of Nanocomposites from Sorbitol Plasticized Starch and Tunicin WhiskersBiomacromolecules, 2002
- Nanocomposites of Chitin Whiskers from Riftia Tubes and Poly(caprolactone)Macromolecules, 2002
- Chitin Whisker Reinforced Thermoplastic NanocompositesMacromolecules, 2001
- Plasticized Starch/Tunicin Whiskers Nanocomposite Materials. 2. Mechanical BehaviorMacromolecules, 2001
- Polysaccharide Microcrystals Reinforced Amorphous Poly(β-hydroxyoctanoate) Nanocomposite MaterialsMacromolecules, 1999
- Water-solubility of partially N-acetylated chitosans as a function of pH: effect of chemical composition and depolymerisationCarbohydrate Polymers, 1994
- In vitro chiral nematic ordering of chitin crystallitesInternational Journal of Biological Macromolecules, 1993
- Biology of Fibrous CompositesPublished by Cambridge University Press (CUP) ,1993