Study On The Preparation And Performance Of Chiral Selective Membrane

The resolution from racemic mixture is the main way to get enantiomers to make pure chiral medicine. Solid membrane separation processes get much more attention as they have the characteristics of low energy consumption, high stability and continuous operation capablility.Chiral selective membrane (CSM) was prepared by casting an aqueous solution of poly(vinyl alcohol) PVA as basic material andβ-cyclodextrin (β-CD) as chiral selector. When PVA was acetalizated by formaldehyde solution in acid medium,β-CD would react with PVA. The preparation process of another type of membrane was that acetalizated PVA membrane was grafted withβ-CD by plasma technique. The surface of acetalizated PVA was modified byβ-CD. Dialysis experiments showed thatβ-CD had chiral selectivity to D- HPG over L- HPG in acid medium and L- HPG over D- HPG in base medium. The ratio of PVA:β-CD was controlled about 8:3 in casted membrane and the swelling ratio was about 30-50%. The graft time of plasma membrane was about 60min and the swelling ratio was under 70%.Experiments showedβ-CD not only had chiral selectivity to racemic mixture, but also could effectively facilitate the mass transport process. The dissertation expatiated on the dialysis resolution process by concentration grade as impetus. By analyse, it was not appropriate to simply classify the chiral selective membrane into diffusion-selective membrane and sorption-selective membrane. It was necessary to increase the third chiral selective membrane between the above two kinds of membrane, called diffusion and sorption-selective membrane.To improve the flux, chiral selective cation-exchange membrane (CSCM) and chiral selective anion-exchange membrane (CSAM) were prepared by blending PVA as basic material,β-CD as chiral selector, and polyacrylic acid (PAA) or cation-exchange resin as cation-exchange materials, andanion-exchange resin as anion-exchange materials. When the membrane was acetalizated by formaldehyde solution in acid medium,β-CD and PAA would react with PVA. The ratio of PVA:resin :β-CD was controlled about 8:3:3 and the swelling ratio was about 30-50%. Chiral selective capacities of these membranes were evaluated by electrodialysis resolution experiments and were similar to dialysis experiments, while the fluxes were greatly improved.The dissertation studied the inclusion phenomena ofβ-CD with HPG and the pH effect on resolution. 1HNMR proved that HPG inserted the cavum ofβ-CD andβ-CD had different chiral recognition ability on D-HPG and L-HPG.