Solvent-less carboxymethylation-induced electrostatic crosslinking of chitosan

Area of Science:

• Materials Science
• Polymer Chemistry
• Green Chemistry

Background:

• Chitosan, a biopolymer, offers potential for chemical modification due to its reactive amine groups.
• Developing solvent-free and catalyst-free modification methods for chitosan is crucial for sustainable chemistry.
• Crosslinked chitosan derivatives can exhibit enhanced properties for various applications.

Purpose of the Study:

• To report a novel, solvent-free, and catalyst-free method for N-carboxymethylation and crosslinking of solid chitosan.
• To characterize the resulting crosslinked carboxymethyl chitosan.
• To evaluate the performance of the modified chitosan in adsorption and catalysis.

Main Methods:

• Heating solid chitosan with solid monochloroacetic acid without solvents or catalysts.
• Confirmation of N-carboxymethylation using NMR spectroscopy and control reactions (lysine).
• Assessment of crosslinking via insolubility in acidic solutions and FTIR spectroscopy; control reaction (ethyl chloroacetate).

Main Results:

• Successful N-carboxymethylation and crosslinking of solid chitosan achieved through a simple heating process.
• Characterization confirmed the formation of N-carboxymethyl chitosan with crosslinking attributed to electrostatic interactions.
• The resulting material effectively adsorbed methyl orange and fluorescein, and catalyzed organic reactions (aza-Michael, Hantzsch, perimidine synthesis).

Conclusions:

• A green and efficient method for modifying chitosan into crosslinked N-carboxymethyl chitosan has been developed.
• The synthesized material exhibits promising applications in pollutant adsorption and organic catalysis.
• This approach highlights the potential of solid-state reactions for functionalizing biopolymers.