Chiral Electrospun Nanofibrous Composite Membranes For Chiral Separation Applications

There are many chiral compounds in nature,which show different physiological activities due to their different spatial configurations.However,the limitation of categories and amounts of naturally chiral compounds,inspires a great deal of research works focusing on physiological and pharmacological areas and development of separation methodology to obtain a single enantiomer from natural resources.Traditional chiral separation methods are mainly classical crystallization,chemical separation,chromatographic separation and biological separation.However,membrane separation approach e.g.,molecular imprinted membrane,draws more and more retention and becomes hot topic recently in a separation process due to its advantages of high yield,low energy consumption and zero pollution.Especially,the fabrication and application of nanofibrous membrane by electrospinning technology opens new pathway for separation and purification industry.Electrospun nanofibrous membranes with high porosity,high surface-to-volume ratio,interconnected pore geometry,and facile functionalization offer great advantages over conventional separation media and have been used extensively,and particularly,for separation of chiral isomers from natural chiral pool.Chiral electrospun nanofibrous membranes with nanoscale fiber diameter were fabricated from synthetic polymers,D-menthol and L-menthol methacrylates,respectively,and employed as filters for chiral selective separation of natural products.The structure and morphology of chiral nanofibrous membranes were controlled by adjusting the molecular weight of the polymer,the solution concentration,and the composition of solvents,verified with SEM measurements.To enhance the mechanical properties of a chiral nanofibrous membrane,polyacrylonitrile was employed as the second nanofibrous component,where a chiral nanofibrous composite membrane was fabricated through a two-nozzle electrospinning approach.Different chiral products including chiral phenylethylamines,tyrosines and diisopripyl tartrates were employed to challenge the separation efficiency of D-and L-menthol methacrylate nanofibrous membranes,in term of the selective adsorption capability and permeation flux,where high selective factors were achieved,implying that the chiral nanofibrous membrane could be used potentially for the chiral separation of natural products.