Journal of Membrane and Separation Technology, 2012, 1, 1-8 1 E-ISSN: 1929-6037/12 © 2012 Lifescience Global Polysulfones with Phenylalanine Derivatives as Chiral Selectors – Membranes for Chiral Separation Jun Isezaki 1 , Masakazu Yoshikawa 1,* , Nanwen Li 2 , Gilles P. Robertson 3 and Michael D. Guiver 2,3 1 Department of Biomolecular Engineering, Kyoto Institute of Technology, Matsugasaki, Kyoto 606-8585, Japan 2 Department of Energy Engineering, Hanyang University, Seoul 133-791, Republic of Korea 3 Institute for Chemical Process and Environmental Technology, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada Abstract: Polysulfone with a derivative of phenylalanyl residue as a chiral selector (PSf-Ac-D-Phe or PSf-Ac-L-Phe) were prepared by polymer reaction of benzylamine-modified polysulfones with N--acetyl-D-phenylalanine or N--acetyl- L-phenylalanine. Both polysulfones having a chiral selector gave durable self-standing membranes. The specific rotations of those polymers revealed that the chiral selectors were successfully introduced into the polysulfone. PSf-Ac- D-Phe membrane incorporated L-Glu in preference to D-Glu and vice versa. The chiral separation ability was studied by applying a concentration gradient as a driving force for membrane transport. Permselectivities for those two types of membrane reflected their adsorption selectivities. PSf-Ac-D-Phe membrane selectively transported L-Glu and vice versa. Predicted permselectivities by adopting membrane resistance coincided with the observed ones. Keywords: Chiral separation, membrane, optical resolution, permselectivity, polysulfone. INTRODUCTION Membrane separation is perceived to economically and ecologically competitive to other conventional separation methods since membrane separations, excepting pervaporation, are operated without phase transition. In addition to this, membrane separation is continuously operated under mild conditions. So far, membrane separation has been applied in various fields, such as water purification by reverse osmosis (RO), production of ultrapure water by nanofiltration (NF), waste water treatment by microfiltration (MF) or ultrafiltration (UF), concentration and recovery of valuable substrates by MF or UF, concentration or removal of charged materials by electrodialysis (ED), gas separation for recovery of H 2 , for concentration of O 2 , and for removal of CO 2 , hemodialysis, hemofiltration, and so forth. However, chiral separation has not been practically carried out by membrane separation technique. The demand for chiral separation by membrane has been required in industries, involving pharmaceuticals, agrochemicals, food additives, perfumes, and so forth. In chiral separation, excepting optical activity, the target enantiomer and the antipode show same physical and chemical properties under achiral environment [1-3]. From this, the existence of *Address corresponding to this author at the Department of Biomolecular Engineering, Kyoto Institute of Technology, Matsugasaki, Kyoto 606-8585, Japan; Tel: +81-75-724-7816; Fax: +81-75-724-7800; E-mail: masahiro@kit.ac.jp NRCC Publication No. 53124. chiral environment or chiral recognition site is requisite in membrane or membrane separation system so that chiral separation can be achieved by using membrane [4-7]. The authors’ research group studied polymeric membranes having molecular recognition sites introduced by applying an alternative molecular imprinting [8-11] and those with chiral environment in a main chain [12, 13] or in a side chain [14] for chiral separation. As a side chain, alanyl derivatives were attached onto polysulfone via amide linkage. Among amino acids, there are 38 kinds of amino acid residue, which are expected to work as chiral environments or chiral selectors. In the present study, the authors focused their attentions on phenylalanine derivatives. Phenylalanine, containing benzyl moiety as a side chain of amino acid, was adopted as chiral selector in the present study. Phenylalanine has a larger and a more hydrophobic side chain, which might effectively exhibit chiral recognition ability, compared with alanine. To this end, N--acetyl-D-phenylalanine (Ac-D-Ala-OH) or N--acetyl-L-phenylalanine (Ac-L-Ala-OH) was adopted as a candidate for a chiral selector and each of those was introduced into polysulfone with benzylamine group (PSf-NH 2 ) by polymer reaction. Chiral separation ability, such as adsorption selectivity and permslectivity, for those membranes were studied adopting racemic mixture of Glu as model racemates. In addition to these, a facile way to evaluate chiral separation ability of those membranes will be proposed