Preparation And Application Of Novel Impirnted Polymers Based On Carbon Nanotubes Surface

Carbon nanotubes （CNTs） have been the subject of intense interests due to theirexceptional thermal stability, remarkable mechanical and electronic properties. Theseproperties as well as extremely high surface-to-volume ratio of CNTs make themexcellent support candidates in preparing molecularly imprinted polymers （MIPs）. Inthis paper, a series of imprinted materials based on carbon nanotubes were prepared bya variety of new ways and applied in four parts of extraction of natural product,purification of protein, and enrichment adsorption of food additives. The results showedthe CNT-MIPs toward the template molecules were achieved the desired results on theseparation and enrichment process. The main contents are as follow:1. A new surface molecularly imprinted polymers was synthesized using poly（vinylalcohol）（PVA） modified multi-walled carbon nanotube （MWNTs） as the support matrix,ursolic acid （UA） as the template molecule, methacrylic acid （MAA） as the functionalmonomer, and ethylene glycol dimethacrylate （EGDMA） as the cross-linking agent.Different molar ratios of the functional monomer to the template to synthetized theMWNTs-MIPs was discussed, it was found that the optimum ratio was4:1. Themulti-walled carbon nanotube-molecular imprinted polymers （MWNTs-MIPs） werecharacterized by Fourier transform infrared spectroscopy （FT-IR） and scanning electronmicroscopy （SEM）. The results showed that a stable imprinted layer was grafted on theMWNTs with the average thickness of20²5nm. The adsorption properties weredemonstrated by static adsorption experiment And the result demonstrated that theMWNTs-MIPs had specific selectivity for UA, yielding an maximum adsorptioncapacity of53.1μmol/g. Imprinted solid-phase extraction condition was optimized，andthe optimal condition was washing with100%methanol and eluting with10%aceticacid methanol solution. Packed into the solid-phase extraction （SPE） column, theMWNTs-MIPs-SPE column could be applied to separate ursolic acid （UA） from similarstructure oleanolic acid （OA）, which indicated the MIPs has broad application in theactive ingredients in Chinese medicine.2. In this paper, a novel surface imprinting technique for the preparation ofmolecularly imprinted polymers/multi-walled carbon nanotubes （MIPs/MWNTs） waspresented for extraction of emodin from rhubarb. The MIPs/MWNTs were prepared byusing emodin as the template molecule, methacrylic acid （MAA） as the functionalmonomer, and ethylene glycol dimethacrylate （EGDMA） as the cross-linker. TheMIPs/MWNTs were characterized by scanning electron microscopy （SEM） and Fouriertransform-infrared spectroscopy （FT-IR）. The properties involving adsorption dynamics,static adsorption, and selective recognition capacity were evaluated. The MIPs/MWNTsexhibited good site accessibility in which it only took60min to achieve adsorption equilibrium and highly selective recognition for the template emodin. Furthermore, theperformance of the MIPs/MWNTs as solid phase extraction （SPE） material wasinvestigated in detail. The proposed MIPs/MWNTs-SPE procedure for emodinexhibited satisfactory recoveries ranging from89.2to93.8%for real samples. It wasused for the purification and enrichment of emodin from rhubarb successfully.3. A novel magnetic multi-walled carbon nanotubes@Fe₃O₄-molecularly imprintedpolymers （MWNTs@Fe₃O₄-MIPs） was successfully developed for protein recognition.The resultant MWNTs@Fe₃O₄-MIPs was characterized by scanning electronmicroscopy （SEM） and Fourier-transformed infrared spectroscopy （FT-IR）. Scanningelectron microscopy images showed that the Fe₃O₄nanospheres with diameter about50-60nm were coated with the MIPs layer with average thickness about15-20nm,which enabled the magnetic MIPs to have a sensitive and fast magnetic response. Themagnetic material can be easily dispersed and retrieved by the application of externalmagnetic field. Adsorption experiments showed that magnetic maximum amount ofBSA adsorbed on MWNTs@Fe₃O₄-MIPs were estimated to be52.8mg/g andequilibrium time take about60min. Meanwhile selective test employed several proteinswhich different in molecular weight and isoelectric point as reference, the result showedthat the magnetic MWNTs@Fe₃O₄-MIPs had an excellent recognition capacity to BSAcompared to the other non-template proteins. MWNTs@Fe₃O₄-MIPs was employed asHPLC stationary phase to separate template protein BSA from binary protein solution.It also applied as the selective adsorbent to extract BSA from bovine calf serum.4. A novel molecularly imprinted polymers （MIPs） based on phenyl group modifiedmulti-walled carbon nanotubes （MWNTs） was synthesized by using bis（2-ethylhexyl）phthalate （DEHP） as the template molecule, methacrylic acid （MAA） as the functionalmonomers and ethylene glycol dimethacrylate （EGDMA） as the cross-linkers. Themulti-walled carbon nanotubes-molecularly imprinted polymers （MWNTs-MIPs） werecharacterized by infrared spectroscopy （IR） and scanning electron microscopy （SEM）.The results showed that an imprinted layer with the average thickness of20-30nm wasgrafted on the MWNTs surface. The adsorption properties were investigated by highperformance liquid chromatography. Adsorption experiments showed that DEHPadsorbed on MWNTs-MIPs was estimated to be69.1μmol/g and the equilibriumadsorption reached about60min. Selective test showed that the MWNTs-MIPs had anexcellent recognition capacity toward DEHP compared to structural analogues. Packedinto the solid-phase extraction （SPE） column, the MWNTs-MIPs could separate andconcentrate DEHP from mango juice sample.