Quaternization of chitosan and partial destruction of the quaternized derivatives making them suitable for electrospinning

Abstract

Quaternization of chitosan by the use of (2,3-epoxypropyl) trimethylammonium chloride (EPTMAC) was studied. In acidic or neutral media, N-quaternized derivatives of chitosan (N-HTCC) with a degree of quaternization (DQ) varying from 30 to 68% were synthesized while additional quaternization of N-HTCC in alkaline media through its hydroxyl groups enabled to increase DQ of chitosan up to 95%. Quaternization of chitosan present in chitosan-dodecyl sulfate complexes was less successful resulting in chitosan derivatives with DQ about 20% which were insoluble in water. In order to decrease dynamic viscosity (DV) of the solutions of the quaternized chitosans and make them suitable for production of nanofibers by electrospinning, partial degradation of the polymers by UV irradiation or enzymatic hydrolysis was studied. UV irradiation helped to decrease DV of the solutions of the quaternized chitosans with high DQ (>50%). Enzymatic hydrolysis of the quaternized chitosans by pectinase or cellulase in their solutions was very fast resulting in the products with thirtyfold lower DV within 2–3 hours. Enzymatic hydrolysis of the quaternized chitosans stopped at a certain stage producing oligomeric cationic chitosan derivatives instead of the quaternized glucosamine.