Molecularly imprinted membrane with innovative structure and high performance for chiral separation of amino acids

Abstract

ABSTRACTAn advanced surface imprinting technique, i.e., the technique of synchronously graft/crosslinking polymerizing of monomer and imprinting of template on the surface of membrane, was designed and used, and a kind of graft-type molecularly imprinted membranes of the single enantiomer of amino acids was successfully prepared. The microfiltration membrane of chloromethylated polysulfone (CMPSF) was used as substrate membrane, and then the aminated polysulfone (AMPSF) membrane was obtained by amination modification. Whereupon, a surface-initiating system of –NH2/ was formed at the interface between AMPSF membrane and an aqueous solution, in which all of the functional monomer dimethylaminoethyl methacrylate (DMAEMA), the crosslinking agent N,N′-methylenebisacrylamide (MBA), initiator (NH4)2S2O8, and L-aspartic acid (L-Asp) as template were dissolved. In the aqueous solution, DMAEMA molecules automatically combined around L-Asp molecules by right of the mutual strong interactions, electrostatic interaction and hydrogen bonding. By initiating of the radicals produced on the surface of AMPSF membrane, the graft/crosslinking polymerization of DMAEMA and MBA took place, and at the same time, L-Asp molecules were embedded into the crosslinked networks. In this way, the grafting-type L-Asp-molecularly imprinted membrane (L-Asp-MIM) was formed. The experimental results show that L-Asp-MIM has high flux and strong mechanical strength like CMPSF microfiltration membrane, and more importantly, it possesses fine chiral recognition selectivity and excellent enantioseparation ability. The selectivity coefficient of L-Asp-MIM for L-Asp reaches 7.52 relative to D-Asp. In the permeation experiment of a raceme solution of Asp, the combination of “gate effect” and “barrier effect” makes the raceme solution of Asp to be well separated, and the optical purity (ee value) of the penetrating fluid gets up to 82%.