Mechanical Amorphization of Chitosan with Different Molecular Weights.

Area of Science:

• Materials Science
• Polymer Chemistry
• Crystallography

Background:

• Chitosan's properties are highly dependent on its crystalline structure.
• Mechanical amorphization is a promising technique for modifying chitosan.
• Accurate determination of crystallinity index (CrI) is crucial for understanding chitosan's behavior.

Purpose of the Study:

• To investigate the mechanical amorphization of chitosan with varying molecular weights.
• To compare different techniques for determining the crystallinity index (CrI) of chitosan.
• To develop an improved method for CrI calculation using X-ray diffraction (XRD) and density functional theory (DFT).

Main Methods:

• Planetary ball milling for mechanical amorphization.
• X-ray diffraction (XRD) for structural analysis.
• Comparison of CrI determination methods: peak height, amorphous standard, peak deconvolution, and Rietveld analysis.
• Density functional theory (DFT) for structure optimization.

Main Results:

• Chitosan amorphization is independent of molecular weight, achieving maximum amorphization within 600 seconds.
• Specific energy consumption for amorphization is comparable to cellulose but higher than starch.
• The peak deconvolution method offers higher accuracy for CrI determination, though Rietveld analysis with DFT-optimized structures provides refined results.
• An eighth-order Fourier model for amorphous chitosan improves XRD data processing.

Conclusions:

• Mechanical amorphization is an effective method for producing amorphous chitosan.
• Accurate CrI determination is essential, with peak deconvolution and Rietveld methods showing promise.
• The proposed Fourier model for amorphous chitosan can serve as a universal standard for CrI calculations.