选用价格较低且易得的微晶纤维素作为实验原料,用酯交换法与乙酰乙酸叔丁酯反应,通过控制反应时间制备不同取代度的乙酰乙酸纤维素(CAA),并利用溶剂挥发法制得CAA膜.通过1 H NMR、FTIR、SEM和TGA等测试CAA膜的化学结构、形貌和热稳定性.使用渗析器测试CAA膜对D,L-色氨酸的渗透拆分性质,利用二元高压梯度高效液相色谱测试渗透液中D-色氨酸和L-色氨酸的浓度.针对手性传输性质,研究了不同取代度的CAA膜对D,L-色氨酸的拆分机理.研究发现,低取代度的CAA膜有更好的手性拆分性能,而高取代度的CAA膜由于接触水溶液后自由体积增大,色氨酸容易通过渗透过膜,分离性能降低.经过对CAA膜对D-色氨酸和L-色氨酸的渗透、分配和扩散系数的分析可知,高取代度的CAA膜的手性拆分性能主要是由扩散控制.其中低取代度(DS=0.57)的CAA膜的对映体过量百分比在6 h内保持100％,超过6 h略微下降,之后趋于稳定.本研究通过简单的调控CAA的取代度制备了具有一定拆分性能的手性分离膜,为手性分离膜的设计提供了思路.
Study of chiral transport properties of cellulose acetoacetate membranes
In this study,the less expensive and readily available microcrystalline cellulose was chosen as the experimental raw material,and the reaction of tert-butyl acetoacetate with ester exchange method was used to prepare cellulose acetoacetate(CAA)with different degrees of substitution by controlling the reaction time,and the solvent evaporation method was used to obtain the CAA membrane.The chemical structure,morphology and thermal stability of CAA membranes were tested by 1H NMR,FTIR,SEM and TGA.The permeation splitting property of CAA membranes for D,L-tryptophan was tested using a dialyser,and the concentration of D-tryptophan and L-tryptophan in the permeate was tested using binary high-pressure gradient high-performance liquid chromatography(HPLC).The mechanism of D,L-tryptophan splitting by CAA membranes with different degree of substitution was investigated with respect to the chiral transport property.It was found that CAA membranes with low substitution degree had better chiral splitting performance,while CAA membranes with high substitution degree had lower separation performance due to the increase of free volume after contacting with aqueous solution,and the tryptophan could easily pass through the permeation periplasm.After analysing the permeation,partitioning and diffusion coefficients of D-tryptophan and L-tryptophan,it was concluded that the chiral splitting performance of CAA membranes with high substitution degree was mainly controlled by diffusion.The enantiomeric excess percentage of CAA membranes with low substitution degree(DS=0.57)remained 100％for 6 h,decreased slightly beyond 6 h,and then stabilised.In this study,chiral separation membranes with certain splitting performance were prepared by simply modulating the substitution degree of CAA,which provides ideas for the design of chiral separation membranes.
chiral separationcellulose acetoacetate membraneester exchange reactionchiral transport propertiesD,L-tryptophan
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维普
