Mechanical Amorphization of Chitosan with Different Molecular Weights

Abstract

Mechanical amorphization of three chitosan samples with high, medium, and low molecular weight was studied. It is shown that there are no significant differences between the course of amorphization process in a planetary ball mill of chitosan with different molecular weights, and the maximum degree of amorphization was achieved in 600 s of high intensity mechanical action. Specific energy consumption was 28 kJ/g, being comparable to power consumption for amorphization of cellulose determined previously (29 kJ/g) and 5–7-fold higher than that for amorphization of starch (4–6 kJ/g). Different techniques for determining the crystallinity index (CrI) of chitosan (analysis of the X-ray diffraction (XRD) data, the peak height method, the amorphous standard method, peak deconvolution, and full-profile Rietveld analysis) were compared. The peak height method is characterized by a broader working range but provides deviated CrI values. The peak deconvolution method (with the amorphous Voigt function) makes it possible to calculate the crystallinity index of chitosan with greater accuracy, but the analysis becomes more difficult with samples subjected to mechanical processing. In order to refine the structure and calculation of CrI by the Rietveld method, an attempt to optimize the structure file by the density functional theory (DFT) method was performed. The averaged profile of amorphous chitosan approximated by an eighth-order Fourier model improved the correctness of the description of the amorphous contribution for XRD data processing. The proposed equation may be used as a universal standard model of amorphous chitosan to determine the crystallinity index both for the amorphous standard method and for peak deconvolution of XRD patterns for arbitrary chitosan samples.

Biopolymeric hydrogel electrolytes obtained by using natural polysaccharide–poly(itaconic acid-co-2-hydroxyethyl methacrylate) in deep eutectic solvents for rechargeable Zn–air batteries

“…This and the intensity method have been widely used to determine the crystallinity index of materials such as chitosan and cellulose. [41][42][43][44] This index is important in these types of materials since it correlates with the properties exhibited. In particular, the conductive properties improve as the amorphous phase increases.…”

Hyaluronic Acid-Coated Chitosan Nanoparticles as an Active Targeted Carrier of Alpha Mangostin for Breast Cancer Cells

“…The XRD patterns are displayed in Figure 3 . The AM showed sharp multiple peaks at 2θ of 5.4°, 11.6°, and 13.3°, which indicated a crystalline pattern [ 65 , 66 ], and the CS showed peaks at 10.4°, 19.7°, and 29.3° that exhibited semi-crystalline patterns [ 67 , 68 , 69 ]. The XRD spectrum of HA showed no specific diffraction pattern, indicating the amorphous nature of HA [ 64 ].…”

Physicochemical Characterization and Antimicrobial Analysis of Vegetal Chitosan Extracted from Distinct Forest Fungi Species

“…The sparse distribution of the β-chitin chains contributes to the augmented crystallinity of the chitosan. Nevertheless, the XRD pattern of the A. auricula-judae sample exhibits conspicuous peaks at around 37° and 51°, signifying the existence of other elements within the chitosan that have contributed to the overall compound’s crystallinity [ 16 , 17 ].…”

“…The crystallinity index of each sample was then calculated with the formula below. The maximum amplitude of the peak at 20° is denoted as I 110 , whereas the amplitude at 10° is denoted as I am [ 16 , 17 ]. CI 110 = (I 110 − I am ) × 100/I 110 …”