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

A facile 'one-pot' synthesis for poly(gamma -methyl-L-glutamate) (PMLG) membranes is reported. Despite having an alpha -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(R) 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. (C) 2001 Elsevier Science B.V. All rights reserved.