Preparation of anion exchange membranes by an efficient chloromethylation method and homogeneous quaternization/crosslinking strategy

A novel chloromethylation method and homogeneous quaternization/crosslinking strategy for a series of polymers are demonstrated in this paper. The chloromethylation is accomplished by using 1, 4-bis (chloromethoxy) butane (BCMB) as the chloromethylating reagent and concentrated sulfuric acid as the solvent and catalyst. BCMB is a kind of high-efficient, non-carcinogenic and inexpensive chloromethylating reagent, and concentrated sulfuric acid replaces toxic halogenated hydrocarbon. Study results indicated that BCMB had higher reactivity than chloromethyl octyl ether under similar reaction conditions. The chloromethylated poly (phthalazinon ether sulfone ketone) (PPESK) was then crosslinked and quarternized by using N, N, N′, N′-tetramethyl-1, 6-hexanediamine (TMHDA) as the homogeneous quaternizing and crosslinking agent during the solvent evaporation. The ion exchange capacity (IEC) of the crosslinked membranes (C-QAPPESK/OH) was very close to the theoretical value, higher than that of the membranes quaternized by trimethylamine (TMA) aqueous solutions (QAPPESK/OH). In addition to higher IEC, C-QAPPESK/OH membranes possessed greater hydroxide conductivity and chemical stability than that of QAPPESK/OH membranes. The results suggest that this efficient chloromethylation together with the homogeneous quaternizing and crosslinking method is a time-saving strategy with potential application in the preparation of anion exchange membranes.