Preparation And Performance Research Of Dioctyl Phthalate Molecularly Imprinted Polymers Prepared By Pickering Emulsion Polymerization

MIPs are porous matrix having the same micro "cavity" in size, shape and functio n with the target molecule, which have many potential features, such as low cost, ease of synthesis, high stability and good reusability under the harsh physical and chemical conditions. The imprinting sites of surface molecular imprinting technology（SMIT） are at or near the surface of the imprinted material, improving the binding ability, increasing the specific surface area. In this paper, we chosen phthalic acid（2-ethylhexyl） phthalate（DEHP） as the template, also prepared three kinds of MIPs with a hydrophobic silane-modified montmorillonite（MMT） and Si O₂ nanoparticles as carrier. Finally temperature responsive monomer N-isopropyl acrylamide（NIPAM） was introduced, besides the optimal conditions, structure and adsorption properties of MIPs were studied. Details were as follows:（1） Preparation of DEHP-MIPs combined with MMT and surface molecular imprinting for selectively adsorption of PAEs in water environment, and the structure and properties of polymers were characterized, then the imprinting conditions were optimized to determine the best reaction conditions.Results were as follows: the molar ratio of DEHP, MAA and EGDMA was 1: 4:12, and acetonitrile was the best porogen. The adsorption properties of polymers, including kinetics, isotherms and selectivit y, were also investigated Results showed that the adsorption data of MIPs were more aligned with psedo-second-order dynamic model and Freundlich model, and NIPs were more in line with a psedo-first-order kinetic model and the Langmuir model.The fitting results indicated the differences of DEHP-MIPs and NIPs in adsorption mechanism to some extent. The possible reason was the presence of cavities for MIPs, so the main adsorption process included surface diffusion and internal diffusion, however NIPs mainly depended on surface diffusion. During the selective experiments, the relative selectivity coefficient K ’ was greater than 1, indicating that MIPs had the excellent selective adsorption of DEHP, which was due that the functional group formed with template and monomers had the specific direction during the preparation of polymers, which could identify and re-adsorb DEHP in a single.（2） According to the high stability and good environmental compatibility for Pickering emulsion, and Si O₂ nanoparticles acting as the most common droplet / particle stabilizer, so we prepared monodisperse porous molecular imprint ing polymeric microspheres（MIPMs） with Pickering emulsion. It not only solved the problem of polymer coalescing with montmorillonite as carrier in the previous chapter, but also MIPMs had larger surface area and better adsorption capacity, which could extract DEHP in environmental water samples at low concentrations by means of SPE-HPLC.During the adsorption performance test, adsorption data of MIPMs were more in line with psedo-second-order dynamic model and Freundlich model, however NIPMs were psedo-first-order kinetic and Langmuir model. Finally, bottled water was detected for DEHP at low concentrations with the help of SPE-HPLC, and results were significant.（3） To undertake the previous chapter of Si O₂ nanoparticles bound to a carrier by means of Pickering emulsion polymerization, this section we still chosen MAA as functional monomer to identify the target molecule（DEHP）, but added temperature-responsive monomer N-isopropyl acrylamide（NIPAM）. It simultaneously has a hydrophilic amide group and hydrophobic isopropyl, exhibiting the amphiphil ic properities, which shows the temperature phase-change behavior changing with the ambient temperature. DEHP-TNIPs and TNIPs gel particles were prepared, the specific advantages belong to good performance with the temperature response, selectivity and reusability, which can achieve the goal of a single enrichment and detection DEHP under low concentrations by changing the ambient temperature. In addition, the chapter characterized the swel ing and shrinkage of the colloidal particles during the change of ambient temperature with the optical microscope（OM）, which confirmed the performance of temperature responsive for colloidal particles. At the same time, adsorption properties of TMIPs / TNIPs were studied under three temperatures（298K, 308 K and 318K）. The adsorption results showed that adsorption data of TMIPs were in more consistent with psedo-second-order dynamic and Freundlich model at 298 K and 308 K, while TMIPs at 318 K and TNIPs were more in line with a psedo-first-order kinetic and Langmuir model. In the experiment of real samples testing, the prepared TMIPs colloidal particles could distinctly detect DEHP in water environment by means of SPE-HPLC.In summary, this paper we have discussed the preparation and optimization of experimental conditions of phthalate esters（PAEs）, and studied the adsorption mechanism of MIPs towards DEHP. Besides the temperature sensitive colloida l particles were prepared, which could reach the purposes of enrichment and detection DEHP simply by changing the ambient temperature. It provides a feasible directions for future research in separation and enrichment of hydrophobic organic pollutants.