Synthesis And Properties Of MWNTs/ADMPC CSPs For HPLC

Among the recently widely developed various methods of preparing enantiomericpurities, high-performance liquid chromatography （HPLC） has been becoming one of the bestmethods to enantiomers seperation. The chiral recognition ability of amylose tris （3,5-dimethylphenylcarbamate）（ADMPC） which is commercialized as Chiralpak AD, issignificantly high and it has become the hottest studied CSP besides Chiralcel OD. Bycontrast, and despite its clear potential, ADMPC as CSP has been restricted, mainly becauseof its plaint molecular structure and the considerable difficulty of rendering itself soluble insome solutions.It was for the aforementioned reasons, amongst others, we decided to explore thepossibility of molecular control of encapsulation of helical amylose using MWNTs. With therigid MWNTs in the loose cavity of amylose, the wapping amylose （MWNTs/Amylose） hasdifferent configuration. The derivatives of MWNTs/Amylose used as CSPs for HPLC, whichare synthesized with isocyante, are acknowledged of their solube ability, chiral recognitionability and regulations.First of all, we have developed a simple, efficient process for the solubilization ofMWNTs with amylose in aqueous DMSO as well as in pure water. This process requires twoimportant conditions, presonication of MWNTs in water and subsequent treatment of the fineMWNTs dispersion with amylose in a specified DMSO-H₂O mixture, followed by apostsonication. The former step disaggregates the NT bundles, and the latter step maximizescooperative interactions between MWNTs and amylose, leading to the immediate andcomplete solubilization. The SEM displays images of twisted ribbons in the encapsulation ofMWNTs by amylose. Raman, IR and TG repeatedly prove the formation ofMWNTs/Amylose.We thus used MWNTs/Amylose and3,5-dimethylphenylisocyanate synthesisngMWNTs/Amylose phenylcarbamate derivatives （MWNTs/ADMPC prepared by coating） andevaluated their （QRM-1and QRM-2） recognition ability. MWNTs/ADMPC as CSP forchromatographic resolution of racemates does have an outstanding recognition ability, whichsome racemates separated by chiralpak AD are better separated by MWNTs/ADMPC, butshows a negative recognition ability to a few racemates. It turns out that the applicaton of MWNTs enhances the recognition ability ofMWNTs/ADMPC, which can effectively separate some of the racemates with benzene.Because the superior solvent-resistance of MWNTs, it can also reinforce the stability of CSPs,which makes its commercialization possible. Due to the insertion of MWNTs, the rigidity ofamylose derivatives on some degree can be enhanced, but it still possesses the excellentseparation ability to some racemates. All the work discloses more directions to the research ofnew polysaccharide derivativess more evidence for the chiral recognition mechanism onamylose derivatives from structural factor.