Schiff base functionalized chitosan anion exchange membranes with 1,4-dichlorobutane as the crosslinker

Abstract

A series of composite membranes (CS-PY-DLx) were synthesized by using schiff base functionalized chitosan (CS-PY) as the polymer matrix, 1,4-dichlorobutane (DL) as the crosslinker, the quaternization reagent is iodomethane. In this work, pyridine groups grafted on chitosan were converted into quaternary ammonium salt while forming cross-linked network structure. The FT-IR shows that the CS-PY-DLx membranes has been successfully prepared. The introduction of cross-linked structure enhances the alkali resistance, thermal stability and other properties of CS-PY-DLx membranes. When the cross-linked degree is 25%, the anion exchange membrane had the maximum tensile strength (24.45 MPa), and the anionic conductivity reaches 7.08 × 10−3 S cm−1 at 70 °C. The alkali resistance test was researched under the condition of 3 mol L−1 KOH solution for 120 h at 80 °C, which showed that the OH− conductivity of CS-PY-DL25 membranes retains approximately 79.7% of its initial conductivity, revealing the excellent alkali resistance. Methanol permeability was only 0.37–0.72% of the Nafion-117 membrane in 3M methanol at 60 °C, indicating an excellent resistance to alcohol.