pH-dependent structural and mechanical properties in chitosan and its stabilization by oxidized chitin doping

Area of Science:

• Biopolymer Science
• Materials Science
• Sustainable Chemistry

Background:

• Chitin is a globally abundant biopolymer, with chitosan (CS) applications limited by its pH-dependent dissolution.
• Chitosan's positive charge at pH < 6.3 weakens interactions, causing dissolution and hindering its use.
• Developing pH-stable chitosan-based materials is crucial for expanding its applications.

Purpose of the Study:

• To investigate structural and mechanical differences in chitosan films at acidic and neutral pH.
• To explore composites of chitosan with C6-oxidized chitin (OC) for enhanced pH stability.
• To create novel chitin-derived materials with tunable, pH-responsive properties.

Main Methods:

• Comparative analysis of chitosan films in acidic and neutral states.
• Fabrication and characterization of chitosan-oxidized chitin composites.
• Assessment of structural reorganization, mechanical properties, and swelling behavior across pH variations.

Main Results:

• Neutralization stabilized chitosan films, enhancing mechanical strength (6-fold) and reducing water uptake.
• Incorporating 15 wt% oxidized chitin prevented chitosan dissolution at pH 3 and stabilized mechanical properties.
• Chitosan-oxidized chitin composites exhibited retained acidic swelling and improved mechanical stability.
• Adding chitosan to oxidized chitin improved processability and increased neutral pH swelling.

Conclusions:

• Ionic bridging with oxidized chitin stabilizes chitosan over an extended pH range without covalent cross-linking.
• Two novel chitin-derived materials with complementary pH-responsive properties and extended stability were developed.
• These materials offer expanded opportunities in biomedicine, agrochemistry, and sustainable packaging.