Membranes based on poly(γ-methyl-l-glutamate): synthesis, characterization and use in chiral separations

A facile ‘one-pot’ synthesis for poly(γ-methyl-l-glutamate) (PMLG) membranes is reported. Despite having an α-helical secondary structure, as demonstrated via IR, these membranes did not show enantioselective behavior in pressure driven permeation of Trp. Therefore, the transesterification of PMLG with Igepal and Brij® 30 is introduced in a next step and the resulting polymers are characterized by means of IR and NMR. Supported membranes made from these materials show permselectivity towards d-Trp under a pressure gradient, but the enantiomeric excess of the permeate phase declines as a function of time. In order to realize a constant enantioselectivity, electrodialysis is demonstrated to be a suitable membrane process. Moreover, the obtained permeation rates of Ac-Trp are among the best ever reported for solid enantioselective membranes and approximate those realized with liquid membranes.