Synthesis,characterization And Application Of Molecularly Imprinted Polymers For Selective Separation Of Cyclodextrins With Different Forms

In this paper,the molecular imprinting technique was used to separate and purify cyclodextrins with different forms.At present,cyclodextrin(CD)and branched cyclodextrin(BCD)are mostly produced by enzymatic methods,and the products obtained by converting the substrate using enzyme are complicated,and it is expensive and time-consuming to separate and purify a specific cyclodextrin from the enzyme conversion product,which considerly increase the cost of production.Molecularly imprinted polymers have attracted considerable interest due to their predetermination,specific recognition and practicability as a new type and high-efficiency molecular recognition technology.Due to the low preparation cost,relatively simple process,good stability and reusable utilization,molecularly imprinted polymers have been utilized in a variety of fields,including separation and purification,food testing,solid phase extraction and so on.In this thesis,the molecularly imprinted polymers with different structures were synthesized,which were easy and effective methods for the separation and purification of CD or BCD.Main researches and conclusions were as follows:1.The photo-responsive molecularly imprinted polymers(PMIPs)were prepared using 4-methylacryloyloxy azobenzene(MAA)as the functional monomer,6-O-?-D-maltosyl-?-cyclodextrin(Mal-?-CD)as template molecule,2,2-Azobisisobutyronitrile(AIBN)as initiator,and ethylene glycol dimethacrylate(EGDMA)as crosslinking agent.Ultraviolet-visible spectroscopy(UV-vis),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR)and thermogravimetric analysis were used to characterize the photoisomerization characteristics,morphology,structure,and thermal properties of PMIPs.Meanwhile,the safety of Mal-?-CD separated by PMIPs was evaluated.The results revealed that MAA has good restorability and reversibility in the process of UV and visible light irradiation.PMIPs were spherical with a particle size of?1.5-2 ?m.Meanwhile,the binding capacities of PMIPs toward Mal-?-CD were investigated using selective recognition,equilibrium adsorption,kinetic adsorption,and Scatchard analysis.PMIPs had significantly higher selectivity and binding capacities toward Mal-?-CD.The association constant(Ka)and the maximum apparent binding site(Nmax)of the binding site were 1.72×104 M-1 and 7.93?mol/g,respectively.The purity of Mal-?-CD could reach 90.8%after separation and purification by PMIPs.The results of subacute and subchronic toxicity studies showed that Mal-?-CD elicited no toxicological effects.2.The photoirradiation surface molecularly imprinted polymers(PSMIPs)were synthesized using nano silica gel as a matrix and GOTMS as silane coupling agent.The morphology and structure of PSMIPs were characterized by FTIR,SEM and TEM.The monodisperse spherical PSMIPs had a rough surface with a mean size of?0.8 ?m.TEM images showed that PSMIPs had a silica core and an imprinted polymer shell with shell thickness of 35 nm.The selective adsorption of PSMIPs toward Mal-?-CD,?-CD and maltose was compared.PSMIPs exhibited higher distribution coefficient and selectivity coefficient,which indicated that PSMIPs had more significant selectivity for Mal-?-CD.The binding amount of PSMIPs toward Mal-?-CD could reach equilibrium within 2 h with adsorption capacity of 72.8%.Meanwhile,PSMIPs had two different binding sites,specific binding sites and non-specific binding sites.The photocontrolled uptake and release of PSMIPs toward Mal-?-CD were measured by HPLC and the absorption rate and release rate were 100.0%and 80.27%,respectively.3.The photoresponsive surface molecularly imprinted polymers(PSMIPs)with controllable nanoshell thicknesses were fabricated by varying the amount of template molecule,functional monomer,cross-linker and initiator.The obtained PSMIPs were spherical and monodisperse with nanoshell thicknesses between 10 and 60 nm.And the monodisperse PSMIPs possessed surface areas of 275.3-391.6 m2/g and average pore diameters of?3.1-3.5 nm.In addition,the influence of PSMIPs with different shell thickness on the binding and release of Mal-P-CD was systematically investigated.The results showed that the adsorption capacity,desorption capacity,selective capacity,and reusability of PSMIPs toward Mal-?-CD were strongly correlated to the shell thickness of PSMIPs.The Langmuir adsorption isotherm and the pseudo-second-order kinetic model were quite suitable to the isothermal adsorption and the adsorption kinetics of PSMIPs with different shell thicknesses,respectively.Maximum binding capacity and release capacity were obtained when 0.64 g of modified silica nanospheres,0.5 mmol of Mal-?-CD,4.0 mmol of EGDMA,and 0.16 g of AIBN were used,while the shell thickness was about 30 nm.4.The monodisperse photoresponsive hollow-shell structured molecularly imprinted polymers(PHSMIPs)were fabricated on sacrificial silica microspheres via surface imprinting technique.And the sacrificial silica core was subsequently removed using 20 vol.%HF aqueous solution.The morphology,structure and the binding properties of PHSMIPs and PSMIPs were compared.The results showed the average diameter of PHSMIPs were about 480 nm with an approximately 40 nm shell.PHSMIPs possessed BET surface areas of 273.4 m2/g,the pore volume of 0.333 cm3/g,and average pore diameters of 4.3 nm.PHSMIPs displayed higher binding capacity,better recognition ability,and faster mass transfer rate toward a-CD than PSMIPs.Furthermore,PHSMIPs was successfully used in the separation of CD in real reaction solution,indicating potential application for purification and selective extraction of CD and its derivative from complex environment.5.The dual-template hollow core-shell molecular imprinted polymers(DPHSMIPs)were synthesized by using ?-CD and ?-CD as template molecules in different molar ratios.The selective recognition,adsorption capacity and desorption capacity of DPHSMIPs toward a-CD and ?-CD investigated.Meanwhile,the reaction solution of y-CD prepared by enzymatic conversion was used to study the practical application of DPHSMIPs.The results showed that DPHSMIPs prepared by dual-template with different molar ratios poccessed hollow core-shell structure,and the silica has been completely removed from DPHSIMPs.There were no significant differences in the values of BET surface area,the average diameter of the BJH pores,and the pore volume of DPHSMIPs prepared by dual templates with different molar ratios.Meanwhile,DPHSMIPs with ?-CD and ?-CD as templates in different molar ratios had almost no adsorption capacity to ?-CD.When adding the same amount of DPHSMIPs,DPHSMIPs prepared by ?-CD:?-CD=3:7 could almost completely remove ?-CD and ?-CD from the solution.DPHSMIPs were successfully used in the removal of ?-CD and ?-CD from complex environment by one-step method.