Separation of structural isomers using soluble beta-cyclodextrin polymer by ultrafiltration

To improve selectivity and flux in the separation of isomers using beta -cy clodextrin (PCD) by ultrafiltration. the use of soluble-beta CD polymer is being proposed. Polymerization of beta CD using epichlorohydrin (EPC) in a batch system was carried out by varying molar ratio of EPC to beta CD r and beta CD concentration to optimize conditions for preparation of soluble-be ta CD polymers. To observe the effect of r and temperature in the polymeriz ation on the binding constant, K-B and the separation factor. S, of p-nitro phenols (pNP) over o-nitrophenol (oNP) by ultrafiltration, soluble beta CD polymers produced at r = 3 (beta CDP-3) and 10 (beta CDP-10) at the beta CD concentration of 35%, w/v were chosen from the resulting ternary phase dia gram of the beta CD polymerization. In beta CD polymerization by a fed-batc h reactor, it is found that the higher the molar ratio of EPC to beta CD an d temperature, the higher the molecular weight of water-soluble beta CD pol ymer. Analysis by GPC suggests that beta CDP-3 with MW about 3000-4500 may consist of beta CD-ethers and beta CD dimers, while beta CDP-10 with MW abo ut 7800-9000 is likely to be dominated by polymers containing more than 3 u nits of beta CD moieties. The beta CD polymers were used as host molecules in inclusion of pNP over oNP. Compared to the parent beta CD, binding const ants and separation factors of oNP and pNP with beta CDP-3 by a PLBC ultraf iltration membrane (MWCO of 3000) decrease slightly. In contrast, the bindi ng constant of pNP with beta CDP-10 increases significantly, while that of oNP remains constant. This suggests the presence of secondary cavities betw een beta CD moieties in beta CDP-10. Polymerization at higher temperature d ecreases binding constants of beta CDP-10 slightly. (C) 2001 Elsevier Scien ce B.V. All rights reserved.