Investigation Of Positional Isomers Transport Performance In Polyelectrolyte Nanopores

A nanopore is a very small hole whose size is between1and100nm. Withincorporating functional groups on the pore wall, the pore can selectively transportspecific species. Layer-by-layer assembly (LBL) technique is a simple, quick,functional and low-cost method to construct varieties of nanostructures. In this thesis,LBL technique was employed to modify nanoporous track-etched polycarbonatemembranes with polyelectrolyte to anchor recognition site for separating positionalisomers and the transport experiment was performed in a U-tube setup and HPLC wasemployed for detection. The research work of this dissertation is summarized asfollows:Poly(sodium4-styrenesulfonate)(PSS) was vacuum filtered through track-etchedpolycarbonate nanopore membranes. A U-tube setup was used to perform thepermeation experiment, in which the feed and reservoir compartments were separatedby the functionalized nanoporous membrane. The positional isomers were put in thefeed compartment and the transported amount was detected by HPLC after samplingat the reservoir compartment. The HPLC conditions, such as detection wavelength,column temperature and the mobile phase composition, were optimized to separate thepositional isomers. The effect of pore size, the initial concentration of, solution pH,hight difference of the solution and functional group on the pore wall was alsoinvestigated. The results showed that, when the concentration of the feed solution was0.9mmol/L in pH=7.0phosphatic buffer, and the diameter of the nanopore membranewas10nm, these functionalized membranes exhibited high separation efficiency formeta-and ortho-benzenediol. These nanochannel membranes also possess selectivitytoward para-and ortho-isomers of nitrophenol and aminophenol. The uniqueselective transport in the nanopores could be attributed to the different hydrogenbonding ability between the inner surface of the PSS modified nanopore and theposition isomers, which caused different transport speed of the position isomers.Herein, meta-and para-isomers can not be separated effectively, and this may besolved by changing the polyelectrolyte for another one. The nanopore membraneshold great promise for selective separation of positional isomers in the future.