Study On Preparation Of Cyclodextrin-based Molecular Tubes And Performance Of Its Pervaporation Membranes

α-Cyclodextrin-based molecular tube (α-CD MT) is a hollow tubular polymer synthesized from threadedα-cyclodextrins. Recently, it has received extensive attention since its special molecular structure and the researches about it mainly focus on the modification of the preparation methods, it's inclusion complexation characteristic with numerous guest molecules, assembling mechanism and further the construction of novel self-assembly supramolecular architecture. However, the researches about the application ofα-CD MTs are not so comprehensive which still remain to be explored. Cyclodextrin and it's derivatives have been widely used as additives of pervaporation membranes to improve the separation selecivities for isomeric mixtures. Based on these findings, we synthesizedα-CD MTs and tried to use it as the additive of pervaporation membranes in order to explore it's application in separation of xylene isomers.We got the inclusion complexes (i.e., pseudopolyrotaxane) by self-assembling betweenα-CDs and PEG-BA. And then the pseudopolyrotaxane was capped with 2,4-dinitrofluorobenzene. After crosslinking ofα-CDs on the polyrotaxane and further the removal of the bulky stoppersα-CD MTs could be got. The product was dialyzed against water and then purified by the open gel permeation chromatography system which was set up in our lab. We used several testing technique and instruments such as XRD,TGA,1H NMR and 13C CP/MAS NMR to analyze the structures ofα-CD MTs and the intermediate products. It is concluded thatα-CD MTs have been prepared successfully.We chose chitosan and PAN ultra-filtration membrane as the membrane matrix material and supported layer, respectively. Two kinds of pervaporation membranes filled with cyclodextrins have been prepared,α-CDs/CS membrane andα-CD MTs/CS membrane. The membranes were characterized by FTIR, SEM and sorption measurement. Finally, the effects ofα-CDs,α-CD MTs content and feed composition on pervaporation performance of the membranes were investigated. It is concluded that introducing CDs into CS membrane could improve the pervaporation performance of the membrane greatly, especially forα-CD MTs. Both the separation performance and stability ofα-CD MTs/CS membrane were better than that ofα-CDs/CS membrane. For theα-CD MTs/CS membrane with 20wt.% content ofα-CD MTs, when the concentration of PX in feed mixture increased from 10wt.% to 30wt.%, the separation factorαp/o increased from 1.45 to 1.85 and the flux decreased from 70.9g/m2h to 43.8g/m2h. The results of pervaporation performance can be explained by solution-diffusion mechanism successfully.