The Flux Regulation Properties of Poly(amino acid) Membranes

Abstract

The characterization of poly(amino acid) membranes, of which the transport properties are changeable by the variation of the physical state of the membranes, was studied.
α-Helix to random coil transition of crosslinked poly(glutamic acid) (PGA) membrane was confirmed by IR and the membrane length variation studies. The filtration coefficient, Lp, and the permeability coefficient of sucrose, ω₅, of PGA gradually increased with increasing solution pH below pH 5.0, but steeply increased above pFI 5. O. On the other hand, the ionic salt permeability of KCI, ω₁, decreased when pH was increased to 5.0 and markedly increased on further increasing of pH. The values of ω₅ and L_p in turn were reduced to the frictions, f_wm(water-membrane), f_2m (co-ion-membrane) and f_2w (co-ion-water); there was a direct correlation between the behavior of these frictions and the physical state of the membrane. The cross-membrane ionic conductance measurements were made by using poly-. (L-cysteine) (PLCys) inter-polymer membranes. As a result, it was confirmed that the equivalent ionic conductance of KCI, A_KCl, was strongly dependent on the oxidation reaction in bathing solution. The dperease of A_KCl was due to the effect of crosslinking reaction between side chain -SH groups. These results showed that the transport properties of these poly(amino acid) membranes may be regulated by pH induced phase transition and reaction controlled polymer conformational change in membrane phase.