Study On Smart Molecularly Imprinted Functional Materials Based On Konjac Glucomannan

Molecularly imprinted polymers(MIPs)are functional polymers with selective molecular recognition sites.Smart molecularly imprinted polymers are a novel type of MIPs that can respond to external environmental stimuli such as magnetic fields,light,pH,temperature,etc.Due to their unique properties and wide application prospects,smart MIPs have become a research hotspot at home and abroad.At present,most of these materials are prepared by chemical synthesis reagents,then their biocompatibility and biodegradability are not good.The application of renewable natural polysaccharides as the main raw material and the introduction of natural polymers into the construction of smart MIPs are in line with the "green" concept of sustainable development in today's society.Compared with fully synthetic materials,the obtained materials possess advantages in biocompatibility,degradability,and cost.There are relatively few reports on the application of konjac glucomannan(KGM),a natural polysaccharide,as a raw material for the construction of smart MIPs.Therefore,in this work,4 novel types of smart MIPs were fabricate using KGM as the matrix,which could not only enrich the types of smart MIPs but also broaden the research scope of KGM.This paper includes four sections as following.(1)Magnetic MIPs for urea were prepared using KGM as the substrate,methacrylic acid as the graft comonomer,ethylene glycol dimethacrylate as the crosslinker,and urea as the template molecule,respectively.The resultant MIPs were characterized by Fourier transform infrared spectroscope(FTIR),transmission electron microscope(TEM),X-ray diffraction(XRD),thermogravimetric analyzer(TGA),and vibrating sample magnetometer(VSM).The MIPs bore a core-shell with high paramagnetism and could be easily separated from the mixture by an external magnetic field.Moreover,the adsorption and the recognition performance of the resultant MIPs were also evaluated.The results showed that MIPs could specifically recognize urea,and the recognition capacity and adsorption performance almost remained unchanged after three cycles of adsorption and elution.The adsorption isotherms of MIPs for urea followed Langmuir equation with the maximum adsorption of 16.8 mg/g.The product is expected to be used as a new material for blood purification.(2)By combining the controllable core/shell strategy with graft the copolymerization of polysaccharide,controllable core/shell magnetic MIPs based on KGM were prepared and evaluated.By varying the dose of the polymeric precursors,the shell thickness of the core/shell structure could be regulated over a wide range.The magnetic nanoparticles encapsulated by polymers still had high magnetic performance and could be easily separated by an external magnetic field.The results of adsorption experiments showed that the MIPs could specifically recognize and adsorb trichlorfon with excellent selectivity,repeatability,and stability.The adsorption isotherm of MIPs could be fitted by the Langmuir equation.Besides,magnetic MIPs have been successfully applied to the detection of trichlorfon in real samples.The environmentally friendly MIPs would be particularly suitable for the enrichment and separation of pesticide residues in food samples.(3)A type of thermosensitive MIPs was prepared by the introduction of N-isopropylpropionamide,a thermosensitive monomer,into the KGM main chain by graft copolymerization.The obtained MIPs possessed switchable thermal regulation on the recognition and the delivery of 5-fluorouracil(5-Fu),an anticancer drug.The results of adsorption experiments showed that the MIPs had excellent adsorption capacity at a temperature below the lower critical solution temperature,and the MIPs could specifically recognize and adsorb 5-Fu with good selectivity,repeatability,and stability.Drug release experiments showed that under the same conditions,the cumulative release of 5-Fu at 25? was higher than that at 38?.The release curves of 5-Fu were fitted by zero-order,first-order,and Higuchi kinetic equations,respectively,indicating that the release of 5-Fu complied with the Fick's law.Compared with non-molecularly imprinted polymers,the MIPs could release 5-Fu continuously for a certain period with a good controlled release effect,implying that they possess great prospects as drug delivery materials.(4)Zipper-like heat-sensitive MIPs were prepared using KGM as the matrix,acrylamide(AM)as the functional monomer,2-acrylamido-2-methyl-1-propanesulfonic acid(AMPS)as the comonomer monomer,N,N?-methylenebis(acrylamide)as the crosslinking agent,ammonium ceric nitrate as the initiator and metformin as the template molecule.The resultant MIPs were characterized by FTIR,X-ray photoelectron spectroscopy(XPS),XRD,TGA,scanning electron micrographs and desorbing cyclic voltammetry.The results showed that the interaction between poly(AM)and poly(AMPS)enabled the imprinted polymers to possess the on/off switchability,which they were sensitive to temperature.By changing the external temperature,the adsorption/desorption of target molecules could be controlled by changing the external temperature.The results of adsorption experiments showed that the MIPs could specifically recognize and adsorb metformin with excellent selectivity,repeatability,and stability.The adsorption isotherms of MIPs could be fitted by Langmuir equation.The product is expected to serve as a novel adsorption and separation material.