Adjustable Fabrication and Evaluation of Regenerated Chitin Fibers with Partial Deacetylation

doi:10.21203/rs.3.rs-4641239/v1

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Adjustable Fabrication and Evaluation of Regenerated Chitin Fibers with Partial Deacetylation

https://doi.org/10.21203/rs.3.rs-4641239/v1

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Chitin, distinguished by its nitrogen-rich acetamido and amino groups, imparts a distinctive cationic nature, enabling chitin with indispensable features in various applications. However, the degree of deacetylation (DD)- a key molecular-level structural determinant- has not been adequately addressed in prior studies despite its critical role in influencing chitin's properties across multiple scales. Here, by controlling the degree of acetylation, we achieved extensive tunability of the properties of regenerated chitin fibers and systematically investigated the effects of deacetylation on their structure-property relationship, relying on an aqueous KOH/urea solution green dissolution system. It is found that deacetylation is associated with the decrease of solution viscosity and the increase of solution stability, thereby improving the spinnability and augmenting the mechanical and antimicrobial qualities of fibers. Optimal overall performance is achieved with chitin exhibiting a DD of 30–40%. This work provides a deeper understanding of the structure, properties, and applications of chitin, and endows more possibilities for the production of regenerated chitin.

alkali/urea

deacetylation

regenerated chitin fibers

In the shift towards a circular economy, society prioritizes enhancing living standards, environmental protection, and the use of renewable resources. Transitioning from the unsustainable petrochemical economy to a bioeconomy underscores the importance of renewable resources. (Beach et al. 2009; Yang et al. 2020; Bai et al. 2022). Chitin, as the most abundant nitrogen-containing natural biopolymer and the second most abundant renewable polysaccharide in nature, is extensively researched and applied in biomedicine, biopharmaceutical, agriculture, food engineering and packaging for its distinctive biodegradability, biofriendliness, and antibacterial properties(Yang et al. 2016, 2020; Shariatinia 2019; Islam et al. 2020; Yu et al. 2022; Pawariya et al. 2024). The extraction of chitin from the 6–8 million tons of seafood waste generated annually is crucial for environmental sustainability and represents a significant step towards leveraging renewable resources effectively(Yan and Chen 2015).

However, chitin's practical application is hindered by its insolubility and non-meltability due to its extensive hydrogen bonding, high crystallinity, and complex hierarchical structure. (Tardy et al. 2021; Li et al. 2022a; Luan et al. 2022; Cao et al. 2023). Huge efforts have been made to develop suitable solvents, such as ionic liquids, deep eutectic and salt/organic acid, salt/mineral acid, and inorganic salt aqueous, etc.(Pillai et al. 2009; Duan et al. 2018; Shamshina 2019; Yang et al. 2021; Özel and Elibol 2021; Sun et al. 2022). Especially, as an emerging green solvent without any toxic organic components, alkali/urea aqueous solutions have demonstrated that cellulose and chitin can be dissolved in suitable alkali/urea solutions (NaOH/urea and LiOH/urea, etc.) at low temperatures by Zhang and co-authors(Cai and Zhang 2005, 2015). Furthermore, Cai et al. found that chitin can be rapidly dissolved in a KOH/urea aqueous solution at the appropriate concentration within a few minutes without requiring freezing(Huang et al. 2020, 2021; Zhong et al. 2023). The discovery of this ingenious and energy-efficient dissolution system provides powerful support for the scalable production and utilization of chitin. What’s more, depending on the good solubility in alkali/urea aqueous solution, the regenerated chitin/chitosan exhibits better strength compared to other systems(Huang et al. 2017; Chen et al. 2021; Zhang et al. 2021). However, especially based on the KOH/urea solution, there are few reports on the continuous production of regenerated chitin, which is a potential production system deserving further refinement and exploration.

The primary requirement for incorporating natural resources into industrial processes is the selection of the correct molecular composition. Notably, chitin (poly (β-(1–4)-N-acetyl-D-glucosamine)) is generally applied in the form of chitosan (poly (β-(1–4)- D-glucosamine)) after deep deacetylation, whose degree of deacetylation (DD) is controlled to above 50% to acquire better solubility in acid solution and processability. The DD significantly influences chitin's solubility and processability, serving as a molecular cornerstone that affects its properties across different scales. Thus, the DD may be the key to understanding structure–property relations of regenerated chitin at multi scales. Despite some studies, even molecular simulation, have peeked at the intrinsic relationship between the DD and diverse properties of chitin/chitosan, but in fact, the effect of deacetylation on the structure and properties of regenerated chitin is rarely mentioned(Kasaai 2009; Yu and Lau 2017; Lim et al. 2021; Yu et al. 2023).

In order to achieve extensive tunability of the properties of regenerated chitin and establish a further understanding of the structure-properties of regenerated chitin fibers based on deacetylation, here, raw chitin is deacetylated to acquire a series of chitin with different DD until it is transformed into chitosan. What’s more, the corresponding chitin solution dissolved in KOH/urea aqueous solution and continuous chitin fibers regenerated by wet-spinning are evaluated. The properties of chitin solutions with different DD are explored, and the microstructure, mechanical properties, wet and thermal property, as well as antimicrobial properties of the regenerated chitin fibers are also extensively tuned and evaluated. Processability, structure, and properties can be significantly modulated through deacetylation. Notably, deacetylation reduces the solution viscosity from 50.2 to 16.0 mPa·s and substantially increased the gelation temperature from 19.1°C to 37.0°C, greatly enhancing processability and stability. Additionally, the strength and elongation of regenerated fibers are dynamically adjusted within broad ranges of 62.8-107.6 MPa and 5.9%-22.5%, respectively. Besides, regenerated chitin fibers with lower DD values possess better humidity and temperature stability. In conclusion, adjustable fabrication of regenerated chitin fibers can be realized by partial deacetylation. This work may promote the application of partially deacetylated chitin instead of solely relying on chitosan, as the main derivative and application form of chitin. Moreover, understanding the structural evolution and structure-property relationship between deacetylation and regenerated chitin based on KOH/urea aqueous solution can provide certain insights into the alkaline/urea dissolution system and the production of high-performance regenerated chitin.

Materials

All reagents were used without any further purification as received. HCl, KOH, NaClO₂, phytic acid, and sodium sulfate with analytical grade were purchased from Chron Chemicals Co.Ltd. (Chengdu, China). Raw chitin (chitin powders) was provided by Golden-Shell Biochemical Co. Ltd. (Zhejiang, China), and was processed to acquire purified chitin based on previous reports(Duan et al. 2013; Zhu et al. 2019). The purified chitin was treated for different times to deacetylation with 60% KOH aqueous solution at 80°C, and the deacetylated chitin was respectively named CH-x (x = 5, 14, 25, 34, 58; x represents the treatment time (min)), in which, CH-0, CH-58 were raw chitin without deacetylating and chitin deacetylated to chitosan. Unless otherwise specified, all deacetylated products are collectively referred to as chitin in this work) The DD of deacetylated chitin was calculated from solid CP/MAS ¹³C NMR spectra; in detail, the integral of carbonyl carbon was divided by the summation of all carbon’s integral on the D-glucopyranosyl ring. As follows:

$$\:DD=100\text{%}-{[I}_{{CH}_{3}}/(1/6\sum\:{I}_{main\:chain\:carbons}\left)\right]\times\:100$$

Preparation of the chitin spinning dope and wet-spinning of regenerated chitin fibers

The 20 wt% KOH/4 wt% urea aqueous solution was prepared according to previous reports(Zhu et al. 2019; Huang et al. 2020). Then, a desired amount of chitin was dispersed in a prepared KOH/urea aqueous solution and stirred at -32°C until a clear, viscous solution was obtained. Next, the above solution was degassed at 5°C by centrifugation. The chitin wet-spinning dope was loaded into a syringe and pumped through a needle with a diameter of 300 µm by a single-channel syringe pump (LSP 101-BH, LONGER, China). Subsequently, the extruded solution passed through the coagulation bath (a distance of 60 cm, composed of 15 wt% phytic acid / 5 wt% sodium sulfate aqueous solution) at a set speed and turned into a gel-like fiber, which was then directly collected through a winder(Zhu et al. 2019). The take-up rollers with fibers were then immersed in DI water to remove additional ions until a PH of 7, and air-dried to acquire dry fibers.

Characterizations

To evaluate the fluidity, gel temperature, and modulus of deacetylation chitin solution, the rotational rheometer with a diameter of 40 mm (Discovery HR-1, TA) was used at a set distance of 500 µm between two work plates. All solutions were centrifuged to remove air bubbles at 5°C before use. Firstly, frequency sweeps were executed to understand the viscosity of chitin solutions with different DD at a shear rate range from 0.1–100 Hz at 5°C. What’s more, the effect of different DD chitin solutions with ranged concentrations on modulus (storage modulus-G’ and loss modulus-G’’) was examined to assess the spinnability of the solutions. The temperature-gelation relationships of different samples were also analyzed at an oscillation frequency of 1Hz and a strain of 10% with a rate of 1°C/min in the range of 5–50°C. The internal structure of gel fibers and the surface morphology of dry fibers were observed by scanning electron microscope (SEM, NavoNanoSEM450, USA) scanning electron microscope (SEM, NavoNanoSEM450, USA) at an accelerating voltage of 5 kV. The gel fibers were immersed in liquid N₂ and then freeze-dried to observe its cross-section sputtering with gold. The diameter of fibers was also obtained from SEM images by Image J software. The samples were heated on alumina pans, held for 10 min at 100°C to remove excess moisture, and then heated from 100°C to 600°C at 10°C/min in N₂ atmosphere using TA instrument (TGA Q500, TA Instruments, USA) to characterize the thermal degradation behavior. The Solid CP/MAS ¹³C NMR spectra were obtained from a Bruker Advance III 500 MHz NMR spectrometer with a spinning speed of 5 kHz at ambient temperature (The contact and delay times were 20 ms and 1 s, respectively, and 2000 scans were performed.). The XRD analysis was carried out by a x-ray diffraction (Ultima IV, Rigaku, Japan) operating with Cu-Kα radiation source (λ = 0.154 nm) in reflection mode from 5 to 60°. Before test, all samples were crushed into powders. The crystallinity was calculated based on the total integrated area of the crystalline profile relative to all diffraction profile by muti-peak fitting. The oriented degree of fibers from 2D WAXD pattens was detected by 2D wide-angel X-ray scattering using a Bruker D8 Discover X-ray diffractometer equipped with Vantec 500 detector. The orientation parameter (f) is used to quantify the degree of orientation, and is calculated according to the following formula:

$$\:f=\frac{180-\text{F}\text{W}\text{H}\text{M}}{180}$$

The chemical structure of the samples was verified via FT-IR spectra from FT-IR spectrometer (iN 10MX, Thermo Fisher Scientific). The measurement wavelength ranges from 4000 − 400 cm^− 1 at a resolution of 2 cm^− 1and all 32 scans were collected. The mechanical tests of fibers were performed on a tensile tester (LLY-06ED, Laizhou Electronic Instrument Co., Ltd. China) at a strain rate of 20 mm/min. At least 15 independent samples were tested to obtain mechanical properties for each fiber prototype. The antibacterial activities of chitin fibers of different DD were evaluated against both the Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus). In brief, 0.1 g chitin fibers were crushed into powders and then dispensed into flask together with 1 ml inoculum. After incubation at 37°C for 1 hour, 100 ml of pH 7 phosphate buffer solution (PBS) of pH 7 was added into flask and mixed thoroughly. The bacteria suspension was diluted with the same buffer at a ratio of 1:10, and then 1 mL of the resulting dilution was applied onto nutrient agar for coating. The inoculated nutrient agar plates were incubated at 37°C for 24 h, followed by counting the viable colonies. The control group was set up without chitin and all procedures were the same as described above.

The wet-spinning of chitin fibers

Chitin fibers were produced by wet-spinning as illustrated in Fig. 1. Firstly, the raw chitin powders were purified to obtain pure chitin and then subjected to alkaline deacetylation for a certain time to acquire partially deacetylated chitin with different DD (Fig. 1a). The structural transformations of chitin during deacetylation were confirmed by X-ray diffraction (XRD) patterns, which showcased diffraction peaks corresponding to specific chitin crystal reflections (Fig. 1b). It can be found that the diffraction peaks at 2θ = 9.4°, 12.9°, 19.3°, 20.9°, 23.4°, 26.4°, corresponding to the reflection of chitin crystals (020), (021), (110), (120), (130) and (013), respectively. With deacetylation, the characteristic diffraction peaks of chitin crystals are gradually diminished. Only two distinct characteristic diffraction peaks at 9.4° and 20.9° appear in CH-58, which is attributed to 020 and 200/220 diffraction peaks originating from chitosan hydrated crystals, respectively(Ogawa et al. 2004; Chen et al. 2021; Zhang et al. 2021). The changes in XRD patterns indicate that the acetyl groups are successfully removed and aggregate structure changes on deacetylation. Further analysis through solid CP/MAS 13C NMR spectra quantified the DD in the partially deacetylated chitin (Fig. S1 and Table S1). Subsequently, the obtained chitin powder was dissolved in 20 wt% KOH/4 wt% urea aqueous solution under continuous stirring at -32℃. As shown in Fig. 1c, after low-temperature dissolution and centrifugal defoaming, homogeneous solutions were obtained. The coloration of these solutions, which shifted to a deeper yellow upon partial deacetylation. The chitin wet-spinning dope was extruded through a needle and passed through the coagulation bath to acquire gel fibers. After water-washing and drying, the final regenerated fibers with a shiny and uniform appearance were obtained (Fig. 1d, e, f).

3.2 The properties of deacetylated chitin spinning dopes

The properties of the spinning dope are critical for wet-spinning, with its viscosity and stability directly affecting the spinnability, and the solution storability. The alkali/chitin complex forms a hydrogen-bonded structure, encapsulated by urea hydrates, facilitating chitin's effective dissolution in alkali/urea aqueous solutions. (Huang et al. 2020). In such a complex dissolved system, hydrophobic interactions and a large number of entanglements between molecular chains are involved in addition to abundant hydrogen bonding. As shown in Fig. 2a, b, all chitin solutions show a clear shear-thinning behavior, which is advantageous for wet-spinning. At the same DD, the viscosity of the solutions gradually increases with the increase of the content of chitin. A similar tendency is also reflected in the dynamic modulus of the solutions (Fig. 2c), where the storage and loss modulus of the chitin solutions gradually improve with the increase of the concentration, which is attributed to the increase of internal interactions as well as the interchain entanglement brought about by more molecular chains. Interestingly, chitin solutions with higher DD result in lower viscosity and modulus for the same chitin content (Fig. 2c, d). When the concentration of CH-5 further increases to 11%, the storage modulus is higher than the loss modulus at low shear frequency, indicating that the solution has no fluidity and spinnability. With the process of deacetylation, the loss modulus become higher than the storage modulus, the fluidity gradually appears, and the spinnability increases. This may be due to the stronger hydrophobic interactions and molecular chain rigidity resulting from the hydrophobicity and greater steric hindrance of the acetyl group compared with amino group. Generally speaking, the higher the concentration of the solution has a higher solution strength, can withstand stronger drafting and spinning speed, which is more favorable for spinning. On the other hand, lower viscosity is more conducive to the ordered arrangement of molecular chain to construct orientation structure of fibers in the spinning process. Therefore, it is necessary for high-quality spinning to increase the concentration of spinning dope and make it have lower viscosity at high concentrations. What's more, in alkali/urea dissolution system, low temperature is favorable for the stability of the solution, and the increase of temperature will lead to the change of internal interactions, especially the increase of hydrophobic interactions, especially the increase of hydrophobic interaction, resulting in the gelation of the solution. It can be found in Fig. 2e, f that, the gelation temperature of the solutions occurs at higher temperatures with the decrease of the content of chitin and the increase of DD. In other words, the lower content and deacetylation of chitin can weaken the internal interaction of the solution to improve its stability and storability. In conclusion, deacetylation is necessary for the preparation of high-quality spinning dope with high chitin content and excellent storability.

Structural evolution of the regenerated fibers

SEM elucidates the structural evolution of regenerated chitin fibers across different degrees of deacetylation (DD), revealing a transition from interconnected nanofibers to larger pore structures during the regeneration process (Fig. 3a). This self-assembly into a microporous architecture is mediated by a balance of hydrogen bonding and hydrophobic interactions. Notably, the removal of acetyl groups diminishes hydrophobic interactions, allowing for a more extended assembly period for molecular chains in higher DD fibers, leading to the formation of thicker pore walls and enlarged pore structures. Transitioning from nano- to micron-scale pores, the internal structure becomes less dense with increasing DD, impacting the mechanical integrity of the fibers. The SEM images also show that dry fibers exhibit a longitudinally organized micro-structure, contributing to enhanced mechanical strength. With increasing DD, fiber surfaces become smoother, and the micro-structure more compact, indicative of a denser alignment of molecular chains. In Fig. 3c, 2D WAXD is employed to quantitatively assess the orientation of several regenerated fibers. Shearing during spinning induces a high degree of orientation, with the orientation parameter increasing from 0.66 to 0.76 alongside DD (Fig. S2). This increase is attributed to reduced viscosity and steric hindrance from deacetylation, promoting tighter chitin chain contractility and alignment during spinning. These structural and orientational modifications underscore the nuanced relationship between deacetylation, fiber microstructure, and mechanical performance, establishing a foundation for understanding the mechanical properties of regenerated chitin fibers.

Mechanical properties and internal structures of fibers

FT-IR and solid CP/MAS ¹³C NMR are used to reveal the differences in the internal molecular structure of regenerated chitin fibers with different DD. Firstly, there is no significant change in the DD of chitin during the process of dissolution and regeneration into fibers (Fig. S3). Figure 3a shows the FT-IR spectra, the characteristic absorption peaks at 3455 cm^− 1 are attributed to the stretching vibration of O-H, peaks at 3255 cm^− 1 and 3109 cm^− 1 originate from the stretching vibration of N-H (amide I band), peaks at 1654 cm^− 1 and 1642 cm^− 1 are attributed to the stretching vibration of C = O (amide II band), and the characteristic peak at 1561 cm^− 1 are caused by the bending vibration of N-H (amide II band). On deacetylation, peaks at 1654 cm^− 1 are gradually weakened and merge with peaks at 1642 cm^− 1, while the absorption peaks of methyl group at 2890 cm^− 1 significantly weaken, indicating the gradual reduction of acetylamino group with the production of amino. The peaks of O-H stretching vibration are slightly redshifted from 3455 cm^− 1 ( CH-5) to 3453 cm^− 1 (CH-58), demonstrating that the deacetylation creates new hydrogen bond (C6-OH⋯NH₂) between the chitin chain. It can be found in Fig. 4b that the peaks of C(C-O) at 173.6 ppm and C(CH₃) at 22.3 ppm gradually diminish with deacetylation, which corroborates with the FT-IR spectra, proving the reduction of acetyl groups. Moreover, the C2 resonances gradually weaken and shift upfield near C6 resonances, indicating that the conversion from acetylamino to amino group increases the electron cloud density of -NH₂ compared with -NH, resulting in the change of C2 resonances. XRD is used to further confirm the difference in the internal aggregation structure of regenerated chitin fibers with different DD. Consistent with the patterns observed in the raw chitin powder, the diffraction peaks of the regenerated fiber do not exhibit significant changes, indicating that the regenerated fiber still retains a crystal structure similar to that of the raw material (Fig. 4c). What’s more, CH-58, unlike the lightly deacetylated chitin fibers, has formed hydrated crystals of chitosan (200/220). The mechanical properties of the fibers are strongly related to the concentration of the spinning dopes and the DD, so, the mechanical properties of regenerated deacetylated chitin fibers spun at different concentrations are evaluated (Fig. 3e, f). The strength and elongation of regenerated fibers are dynamically adjusted within broad ranges of 70–120 MPa and 5%-30%, respectively. As previously discussed, a higher concentration is conducive to increasing the strength of the solution to obtain higher-strength fibers. However, if the concentration becomes excessively high, it may slightly reduce the elongation of the fibers. With an increase in DD, the strength of deacetylated chitin fibers increases primarily due to a tighter and higher orientation structure. When the deacetylated chitin falls within the range of chitin (DD <50%), the removal of rigid acetyl groups and the reduction in crystallinity enhance the mobility of molecular chains (Fig. 4d), thereby increasing the elongation. However, when the DD is further increased (CH-58), the regenerated fiber undergoes a transformation from chitin to chitosan fiber. This transformation significantly alters the crystal type and the degree of orientation, resulting in a slight decrease in elongation.

Thermal and wet performance of fibers

The environmental tolerance of natural polysaccharide fibers, crucial for their application, was assessed through water contact angle measurements and moisture regain properties. (Fig. 5a,b) The introduction of more amino groups through deacetylation significantly enhances hydrophilicity, as evidenced by decreased water contact angles in regenerated deacetylated chitin fibers. the moisture regain properties of the fiber is evaluated at relative humidity (RH) of 81%, which increased from 10.9% of CH-5 to 18.9% of CH-58. Furthermore, due to the plasticizing effect of water molecules, the mechanical strength of the fiber decreases obviously, and the elongation increases greatly. After washing in hot water at 50℃ for 1 h, although the elongation can reach up to 80%, the strength is dropped to within 20 MPa. In addition, in Fig. 5f, deacetylation will reduce the thermal stability of the fiber, so that the thermal degradation of the fiber occurs at a lower temperature, which is mainly caused by the amide group endowing the chitin chain with greater rigidity. It can be seen that although partial deacetylation enhances the mechanical properties of the regenerated fibers, it makes its stability worse.

Antibacterial behaviors

The antibacterial efficacy of chitin/chitosan fibers, especially in forms like surgical sutures, underscores the biomedical significance of this natural polymer(Anitha et al. 2014; Li et al. 2016, 2022b; Shahid-ul-Islam and Butola 2019). The antibacterial activities of chitin fibers with different DD against both the Gram-negative E. coli and Gram-positive S. aureus were tested to further understand the structure-bioactivity of chitin fibers regenerated from KOH/urea solution. As shown in Fig. 5a, all deacetylation samples showed efficient antimicrobial properties against both E. coli and S. aureus compared to the control group. What’s more, the number of colonies on the agar decreased significantly with increasing deacetylation of fibers, especially, the regenerated fibers of raw chitin without deacetylation showed limited antibacterial activity, which indicates the amino exposure originating in deacetylation promotes the antibacterial activity of regenerated chitin. Notably, the inhibition of E. coli is stronger than that of S. aureus in the case of more minor partial deacetylation. There may be an antibacterial mechanism of chitin/chitosan against E. coli and S. aureus: Chitin/chitosan will be adsorbed on the surface of the bacterial cells and interact with it, preventing the entry of nutrients and further disrupting these physiological activities. What’s more, Gram-negative bacteria possess abundant negative charges on the cell surface, which can strongly interact with the amino groups on chitin/chitosan, whereas the interaction of Gram-positive bacteria is comparatively weaker(Li et al. 2016, 2022b). Therefore, a stronger antibacterial effect against Gram-negative bacteria was observed with mild deacetylation, such as CH-5 and CH-14. However, when an ample amount of the antimicrobial factor-amino is exposed with further deacetylation, the disparity in antibacterial efficacy against Gram-negative and Gram-positive bacteria becomes less pronounced, leading to outstanding antibacterial properties against both E. coli and S. aureus.

This study achieved extensive tunability of the properties of regenerated chitin fibers with partial deacetylation and systematically explores the impact of deacetylation on the structure and properties of chitin fibers regenerated through wet-spinning in an alkali/urea system. Our comprehensive analysis reveals how the degree of deacetylation—a fundamental aspect of chitin's molecular structure—influences the spinning solution characteristics, fiber structural evolution, and the mechanical, wet, thermal, and antibacterial properties of the regenerated fibers. We demonstrate that partial deacetylation is crucial for enhancing the mechanical properties of chitin fibers. However, it is essential to balance these improvements against the energy consumption associated with the deacetylation process and the fibers' reduced thermal and wet tolerance. Our findings indicate that chitin fibers with a degree of deacetylation between 30–40% exhibit optimal comprehensive properties, striking a balance between performance and environmental tolerance. This research significantly advances our understanding of the relationship between chitin's degree of deacetylation and its resultant properties. It sets a new foundation for the judicious selection and efficient use of chitin, particularly towards the high-quality, large-scale production of regenerated chitin materials. Our work underscores the potential of using an environmentally friendly KOH/urea aqueous solution system for future applications, offering valuable insights for the development of sustainable materials in the biomedical field and beyond.

Acknowledgments

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author contributions

Sen Xue: Conceptualization; Visualization; Writing - Original Draft; Writing - Review & Editing; Methodology; Resources; Investigation; Formal analysis; Zihao Zhang: Methodology; Investigation; Guorui Zhang: Methodology; Data Curation; Kai Wu: Conceptualization; Writing - Review & Editing; Resources; Project administration Supervision; Hong Tan: Writing - Review & Editing; Resources; Formal analysis; Project administration Supervision; Qiang Fu: Conceptualization; Writing - Review & Editing; Resources; Formal analysis; Project administration Supervision.

Funding

Not applicable.

Data availability

No datasets were generated or analyzed during the current study.

Ethical approval

Not applicable.

Consent for publication

All the authors consent for the publication of this article.

Competing interests

The authors declare no competing interests.

Appendix A. Supplementary data

Supplementary data associated with this article can be found in the online version.

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Adjustable Fabrication and Evaluation of Regenerated Chitin Fibers with Partial Deacetylation

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Abstract

Figures

Introduction

Materials and methods

Materials

Preparation of the chitin spinning dope and wet-spinning of regenerated chitin fibers

Characterizations

Results and discussion

The wet-spinning of chitin fibers

3.2 The properties of deacetylated chitin spinning dopes

Structural evolution of the regenerated fibers

Mechanical properties and internal structures of fibers

Antibacterial behaviors

Conclusion

Declarations

References

Additional Declarations

Supplementary Files

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