Synthesis of High Molecular Weight Chitosan from Chitin by Mechanochemistry and Aging

Abstract

Chitosan can be obtained from the deacetylation of chitin. This process is however difficult and usually accompanied by depolymerization, affording low molecular weight chitosan. We report a novel path, relying on a combination of mechanochemitry and aging, to afford high molecular weight chitosan with minimal use of energy and solvent. This method is versatile and applicable to a number of chitin sources, including crude crustaceans and insect shells, yielding deacetylation up to 98% and remarkably high molecular weights. Chitin deacetylation was measured by magic angle spinning nuclear magnetic resonance and molecular weight by viscometry. This process affords chitosan in a safer fashion and with less materials and energy usage than the classic hydrothermal one.

Mechanochemical Phosphorylation of Polymers and Synthesis of Flame-Retardant Cellulose Nanocrystals

“…Very recently, it was demonstrated that mechanochemistry could be used to functionalize polymers with Schiff base moieties postproduction . Our group also reported a ball-milling method to effectively functionalize poly­(ethylene glycol) (PEG) with 5 different functional groups without affecting the main chain and a mechanochemical/aging one for the deacetylation of chitin to chitosan while maintaining high-molecular weight …”

“…16 Our group also reported a ball-milling method to effectively functionalize poly(ethylene glycol) (PEG) with 5 different functional groups without affecting the main chain 9 and a mechanochemical/aging one for the deacetylation of chitin to chitosan while maintaining high-molecular weight. 17 Phosphorylation is a key transformation to access biocompatible or flame-retardant materials, a class of chemicals able to slow the ignition and progression of fire. Regulations imposing the use of such molecules in construction, furniture, electronics, and textiles have had an overall positive effect on both the human and material costs associated with fires.…”

Eco-Friendly Production of Hyper-Cross-Linked Polymers Using Mechanosynthesis and Bioresources: A Critical Review

“…For example, chitosan can be produced by deacetylation of chitin, which is usually accompanied by a reduction in molecular weight due to some depolymerization. However, Di Nardo et al 43 reported that MS can produce chitosan with deacetylation levels ranging from 73% to 95%, while maintaining high molecular weights (see a summary of the MS protocol in Figure 4H). For this purpose, the amorphization of the initial polymer is a very important step, as crystallinity usually hinders the reactivity of polymers.…”

Mechanochemical amorphization of chitin: impact of apparatus material on performance and contamination

“…Amorphization is a common process whereby the crystallinity of a material is reduced by mechanical forces [17,24,50–51] or otherwise [52] by deforming particles and breaking lattice imperfections [50]. For biomass processing, amorphization has been used in several studies [24,53–54], either as a pretreatment [21] prior to deacetylation [18,55], enzymatic [22,56–57] or acidic depolymerization [23–24] and simultaneously during processing [42], yielding oligomers and monomers. Differentiating these regions of impact would be of great value for biomass processing.…”