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. 2025 Mar 29;17(7):927.
doi: 10.3390/polym17070927.

How Molar Mass, Acid Type, and Coagulation Bath Composition Influence Coagulation Kinetics, Mechanical Properties, and Swelling Behavior of Chitosan Filaments: A Full Factorial Approach

Henrique Nunes da Silva  1 , Milena Costa da Silva Barbosa  1 , Matheus Ferreira de Souza  1 , Athirson Mikael de Sousa Lima  1 , Rafaella Resende de Almeida Duarte  1 , Rômulo Feitosa Navarro  2 , Suédina Maria de Lima Silva  1 , Marcus Vinícius Lia Fook  1
Affiliations

How Molar Mass, Acid Type, and Coagulation Bath Composition Influence Coagulation Kinetics, Mechanical Properties, and Swelling Behavior of Chitosan Filaments: A Full Factorial Approach

Henrique Nunes da Silva et al. Polymers (Basel). .

Abstract

In this study, a full multilevel factorial design (21 × 31 × 21) × 2 was conducted to investigate the effects of molar mass of chitosan (CS), the type of acid used for dissolution, and the composition of the coagulation bath on the coagulation, mechanical properties, and swelling of the filaments. The results showed the statistical significance of the factors in the characteristics of these filaments. The coagulation followed Fick's second law of diffusion, with an increase in the chitosan molar mass reducing the coagulation rate, as did the use of acetic acid instead of lactic acid. CS with higher molar mass produced filaments with larger diameters, but without a proportional increase in tensile strength. Swelling was influenced by the acid and composition of the coagulation bath. The interaction of CS with acid and the CS molar mass factor were the terms of greatest statistical significance. Crystallinity was higher for samples dissolved in aqueous solutions of acetic acid and coagulated with ethanol, while lactic acid induced greater structural disorder. Samples coagulated with ethanol presented more homogeneous surfaces, while methanol resulted in rougher filaments. These findings emphasize the critical role of processing conditions in tailoring the properties of CS filaments, providing valuable insights for their optimization for biomedical applications.

Keywords: chitosan; coagulation process; full factorial design; mechanical properties; swelling behavior; wet spinning.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Coagulation system used to evaluate coagulation kinetics.
Figure 2
Figure 2
Adherence to Fick’s law of coagulated thickness evolution compared to the square root of time for the evaluated systems. Samples were prepared with chitosan of variable molar mass (3, 2, and 1) and (a) acetic acid and ethanol, (b) acetic acid and methanol, (c) lactic acid and ethanol, and (d) lactic acid and methanol.
Figure 2
Figure 2
Adherence to Fick’s law of coagulated thickness evolution compared to the square root of time for the evaluated systems. Samples were prepared with chitosan of variable molar mass (3, 2, and 1) and (a) acetic acid and ethanol, (b) acetic acid and methanol, (c) lactic acid and ethanol, and (d) lactic acid and methanol.
Figure 3
Figure 3
Possible interactions between the acetate and lactate anions with protonated chitosan.
Figure 4
Figure 4
Average swelling degree exhibited by the evaluated systems.
Figure 5
Figure 5
Pareto chart of the standardized effects for (a) coagulation rate; (b) tensile strength; (c) Young’s modulus; and (d) swelling degree. Chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 5
Figure 5
Pareto chart of the standardized effects for (a) coagulation rate; (b) tensile strength; (c) Young’s modulus; and (d) swelling degree. Chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 6
Figure 6
Contour (1) and surface (2) plots of the coagulation rate with variances of chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 6
Figure 6
Contour (1) and surface (2) plots of the coagulation rate with variances of chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 7
Figure 7
Contour (1) and surface (2) plots of the tensile strength with variances of chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 7
Figure 7
Contour (1) and surface (2) plots of the tensile strength with variances of chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 8
Figure 8
Contour (1) and surface (2) plots of the Young’s modulus with variances of chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 8
Figure 8
Contour (1) and surface (2) plots of the Young’s modulus with variances of chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 9
Figure 9
Contour (1) and surface (2) plots of the swelling degree with variances of chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 9
Figure 9
Contour (1) and surface (2) plots of the swelling degree with variances of chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 10
Figure 10
Main effects plot for (a) coagulation rate; (b) tensile strength; (c) Young’s modulus; and (d) swelling degree. Chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 11
Figure 11
Interaction effects of factors on the (a) coagulation rate; (b) tensile strength; (c) Young’s modulus; and (d) swelling degree. Chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 12
Figure 12
Optimization plot for coagulation rate, tensile strength, Young’s modulus, and swelling degree. Chitosan molar mass (A), acid (B), and coagulation bath (C).
Figure 13
Figure 13
X-ray diffraction patterns of chitosan powder samples and filaments obtained with high molar mass chitosan.
Figure 14
Figure 14
FT-IR spectra of chitosan powder samples and filaments obtained with high molar mass chitosan.
Figure 15
Figure 15
Scanning electron microscopy (SEM) images of filament samples obtained with high molar mass chitosan: (a) 3LAE (1: 100, 2: 250, and 3: 500×); (b) 3AAE (1: 100, 2: 250, and 3: 500×); (c) 3LAM (1: 100, 2: 250, and 3: 500×); (d) 3AAM (1: 100, 2: 250, and 3: 500×).
See this image and copyright information in PMC

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