Preparation And Properties Of Imprinted Microspheres By Photo-activated RAFT Suspension Polymerization At Room Temperature

In recent years,Molecular imprinting polymers(MIPs)has attracted more and more attention from researchers due to its advantages such as high separation efficiency,stable physical and chemical properties,simple preparation,as well as the application prospects for enrichment,separation and purification of Chinese herbal medicines.our group had used RAFT precipitation polymerization to prepare a molecularly imprinted polymer of aristolochic acid(AAI-MIPs),and the polymer was used to study the adsorption of AAI,finding that MIPs can effectively remove AAI from Guan Mu Tong.To further study the application of MIT in the field of Chinese herbal medicine,this study used Brucine as a template molecule to prepare a molecularly imprinted polymer by RAFT polymerization under visible light at room temperature,and its properties were explored.The specific research content is as follows:(1)Preparation of MIPs:Brucine as a template molecule,MAA as a functional monomer,ethylene glycol dimethacrylate(EGDMA)as a crosslinking agent,EDMAT as a chain transfer agent,TPO as an initiator,toluene as an organic phase,Using PVA as dispersants,Brucine-MIPs were successfully prepared by photoactivated room-temperature RAFT suspension polymerization,NIPs are the same as the preparation method of MIPs except that no template molecule is added.The effects of PVA content and oil-water ratio on MIPs microspheres were investigated.It was found that when the PVA content was 0.2%and the oil-water ratio was 49:600,the resulting MIPs microspheres were regular and uniform.(2)Characterization of MIPs through FT-IR,thermogravimetric analysis,nitrogen adsorption,and SEM.The FT-IR spectra showed that MIPs and NIPs had the same structure.In addition,it could be seen from the thermogravimetric analysis that the components of MIPs and NIPs were basically the same.From Nitrogen adsorption experiments,we could see that the specific surface area of MIPs was greater than NIPs(MIPs,NIPs were 202.1 m2/g and 161.9 m2/g,respectively),and the average pore size was slightly different(MIPs and NIPs were 29.7 nm and 37.1 nm,respectively).The SEM results presented that the MIPs had uniform and coarse particles,while the NIPs were reversed.(3)The adsorption properties of polymer microspheres analyzed by four isothermal adsorption models and adsorption kinetics models,such as Langmuir,Scatchard,Freundlich and Temkin.The adsorption of MIPs and NIPs was not consistent with Langmuir model.Meanwhile,the Scatchard model showed that there were two types of binding sites for MIPs,whereas NIPs had only one,and MIPs were smaller than the dissociation equilibrium constants of NIPs,indicating that MIPs had stronger affinity for strychnine than NIPs;In the Freundlich model,the 1/n of MIPs and NIPs were between 0-1,revealing that the polymer material could adsorb brucine.In the Temkin model,the R2 was around 0.9,and the linear fitting was better.Finally,MIPs and NIPs were more in line with the second-order kinetic model,showed by the adsorption kinetics experiments.(4)The effect of MIPs on the adsorption of Brucine in Strychnos nudicae.In order to investigate it,the strychnine extract was adsorbed by HPLC,and it was concluded that Brucine has a virtual template.The prepared MIPs have certain specific adsorption for strychnine,and also adsorb strychnine and their nitrogen oxides in the total base of Strychnos nucifera,and thus can purify the total base of strychnine..In summary,photo-activated ambient temperature RAFT suspension polymerization had successfully constructed the Brucine-MIPs with a certain degree of specific adsorption capacity,thus providing a new method for the construction of MIPs,and new ideas for the enrichment,purification as well as separation of Chinese herbal medicine.