Facile preparation of chitin gels with calcium bromide dihydrate/methanol media and their efficient conversion into porous chitins

Abstract

In this study, we found that a chitin gel was facilely obtained by stirring a mixture of chitin with a highly concentrated CaBr₂·2H₂O/methanol solution at room temperature. We also examined the conversion of the resulting gel into a porous chitin by a regeneration technique. When the mixtures of chitin (0.9–3.5% (w/v)) with 3.85 mol L⁻¹ CaBr₂·2H₂O/methanol solution were stirred at room temperature, chitin was gradually swollen, leading to a gelling form after 48 h. The mixtures of chitin (1.8% (w/v)) with CaBr₂·2H₂O/methanol solutions in different concentrations also turned into a gelling form by the same procedure. The dynamic viscoelastic measurement of the resulting chitin gels supported their gelling state. Then, porous chitins were efficiently prepared by removing methanol from the gels under reduced pressure, followed by washing with water and lyophilization. The α-chitin crystalline structure of the porous chitin was confirmed by powder X-ray diffraction measurement. The morphology of the porous chitins was evaluated by the SEM measurement. Consequently, it was found that the porosities were depending on contents of chitin in the gels. Furthermore, the mechanical properties of the porous chitins were investigated by compressive testing, which were affected by the pore sizes of the materials. On the other hand, the amounts of CaBr₂·2H₂O in the gels did not strongly affect the porosities and mechanical properties of the porous chitins.