Positively Charged Polystyrene Blended Quaternized Chitosan for Anion Exchange Membranes

Abstract

A novel anion exchange composite membrane was prepared based on glutaraldehyde crosslinked quaternized chitosan (QCS) and positively charged polystyrene (PS). The PS was synthesized by emulsion polymerizing styrene monomers in an ethanol aqueous solution (1:2, v:v) containing a surfactant of cetyltrimethyl ammonium bromide (CTAB) and an initiator of potassium persulfate (KPS). The obtained PS microemulsion with an average diameter of 709 nm exhibited a zeta potential of +88.4 mV due to the enwrapped CTAB cations. The positive charges carried by the PS facilitated the composite membrane to have a high ion exchange capacity without increasing the methanol permeation. The conductivities of the membranes at a level of 10−2 S cm−1 were achieved at 80°C. The methanol permeability of the membranes was in a range of 2.7 × 10−6 - 3.3 × 10−7 cm2 s−1. The obtained anion exchange membranes were stable up to 200°C in air atmosphere according to the data of thermal gravimetric analysis. The tensile stress at break of the membranes was in a range of 16.9–24.9 MPa under ambient atmosphere, and 12.2–13.4 MPa of which were retained after immersing the membranes in a 10 mol L−1 KOH solution at room temperature for 96 h.