Spinning of hydroalcoholic chitosan solutions

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Chitosan fibers are versatile biomaterials with applications in drug delivery and tissue engineering.
• Controlling the crystalline structure (allomorphs) of chitosan fibers is crucial for tailoring their properties.
• Traditional methods for achieving specific allomorphs often lead to molecular weight degradation.

Purpose of the Study:

• To investigate the spinning of hydroalcoholic chitosan solutions.
• To optimize dope composition for continuous alcogel fiber formation.
• To control the allomorphic composition (anhydrous vs. hydrated) of chitosan fibers during processing.

Main Methods:

• Extrusion of hydroalcoholic chitosan solutions followed by heating to induce water evaporation and form alcogel fibers.
• Neutralization of alcogel fibers in aqueous alkali baths and subsequent washing to remove residual alcohol and salts.
• Controlled drying of the neutralized fibers.
• Analysis of fiber allomorph content based on alcohol content during neutralization and solvent hydrophobicity.

Main Results:

• Continuous alcogel fibers were successfully produced via controlled water evaporation.
• Semicrystalline chitosan fibers with varying proportions of anhydrous and hydrated allomorphs were obtained.
• Neutralization under hydrophobic conditions (high alcohol content) favored the formation of anhydrous crystals.
• This method achieved mainly anhydrous crystals without significant chitosan molecular weight decrease, unlike annealing.

Conclusions:

• The hydrophobicity of the solvent during the neutralization step is a key factor in controlling chitosan allomorph content.
• This optimized spinning and neutralization process allows for the production of chitosan fibers with tailored crystalline structures.
• The method offers a way to obtain anhydrous chitosan crystals without compromising molecular integrity.