Although chitin has limited solubility in common solvents, chitin and chitin derivatives have been electrospun into fibers for various applications. To produce electrospun fibers, chitin was first depolymerized using irradiation and then dissolved using 1,1,1,3,3,3-hexafluoro 2-propanol and fibers with average diameters of 110 nm were obtained [04Min]. After electrospinning, the chitin mats were deacetylated using 40 % aqueous NaOH solution at 60-100 °C to achieve about 85 % deacetylation and form chitosan fibers. SEM images and some of the properties of the chitin and chitosan fibers obtained after deacetylation of the spun chitin membranes are shown in Fig. 58.1. Minimal changes were observed in the diameters of the fibers before and after deacetylation.

Chitin has been chemically modified to facilitate dissolution and obtain electrospun fibers [09Du]. Chitin was acylated to obtain dibutyryl chitin that was soluble in electrospinnable solvents such as acetone, dimethyl formamide, dimethyl acetate, ethanol, and acetic acid. Modified chitin was electrospun into fibers in 100 % form and also as blends with cellulose acetate. Electrospun fibers were later treated with NaOH to convert the chitin into chitosan and cellulose acetate into cellulose. Fibers obtained had diameters from 200 to 550 nm depending on the ratio of chitin and cellulose acetate. It was suggested that the combined one-step

Diameter (nm)

Fig. 58.1 SEM images and physical properties of fibers obtained from chitin and chitosan hydrolysis of chitin and cellulose acetate would be beneficial to develop nanofiber membranes for various applications [09Du].

To improve dissolvability in HFIP, chitin (Mw 920,000; 8 % degree of deacetylation) was irradiated with gamma rays to reduce the Mw to 91,000. Electrospun chitin nanofibers had diameters of 163 nm and electrospun chitin microfibers had an average diameter of 8.8 pm. After being in PBS solution containing lysozyme for 15 days, the chitin nanofibers had about 20 % weight loss indicating that they were considerably stable.

58.1 Electrospun Chitosan Fibers