Preparation Of Magnetic Hypercrosslinked Polymer And Its Adsorption Performance

In recent years,the design and synthesis of polymers with persistent microporous have gradually become one of hot spots in the field of microporous materials.Microporous organic polymers were widely used in gas storage and separation,heterogeneous catalysis,drug delivery and other fields due to their high specific surface area,easily controlled pore size and rich synthesis methods.Among them,hypercrosslinked polymers with low synthesis cost,high specific surface area and excellent chemical and thermal stability have attracted extensive attention of researchers.So far,in addition to the development of new methods for the synthesis of hypercrosslinked polymers,the research also focused on the development of magnetic hypercrosslinked polymers.The introduction of magnetic nanoparticle during the preparation of the hypercrosslinked polymer offered the composite more functionality.The synthesis of magnetic hypercrosslinked polymer provided a new idea for preparing magnetic polymers with low density and large specific surface area.Magnetic hypercrosslinked polymers have wide applications in many fields such as biotechnology,analytical chemistry and environmental engineering due to their convenient magnetic separation and high adsorption efficiency.In terms of published work,the most commonly used methods for the synthesis of magnetic hypercrosslinked polymers could be roughly divided into two categories:One kind of method was to modify the surface of Fe₃O₄ at first and then carry on the polymerization reaction.However,this method has the problems of uneven coating,easy phase separation of Fe₃O₄particles and polymer,and low synthesis efficiency.Moreover,the reaction conditions need to be strictly controlled in the synthesis process,and lengthy multi-step reactions would be involved.Another method was to impregnate the prepared hypercrosslinked polymer with an iron（II,III）salt solution,and then Fe₃O₄ particles would precipitate in the polymer matrix under the action of ammonia water,but the Fe₃O₄ particles formed by this method would block some of the pores in the magnetic polymer and reduce its surface area and pore volume.Although these two strategies have made some achievements in the preparation of magnetic hypercrosslinked polymers,these methods still had some shortcomings,such as unstable structure,low synthesis efficiency,low specific surface area,strict experimental conditions and tedious steps.Therefore,in view of three scientific difficulties:how to develop a simple method to prepare magnetic hypercrosslinked polymer with large specific surface area and excellent magnetic response performance;the uncertainty of the relationship between reaction conditions and pore structure of magnetic hypercrosslinked polymer and the lack of effective preparation method of uniform coating in core-shell coating mechanism,this paper explored the methods of synthesizing magnetic hypercrosslinked polymer with iron-containing precursor,the methods were simple and easy,and could avoid the require of rigorous experimental conditions.A series of magnetic hypercrosslinked polymers with good porosity,excellent magnetic properties and stable structure were successfully prepared,and their adsorption and separation properties for organic pollutants in water were discussed.The main research contents were as follows:（1）Hypercrosslinked polymers（HDs）with high specific surface area was prepared by a simple Friedel-Crafts reaction using DCX as a monomer.Subsequently,magnetic hypercrosslinked polymers（MHDs）could be obtained by placing the HDs in the thermal decomposition environment of Fe（acac）₃.The BET specific surface area of MHD-1 was 638 m²/g,and the saturation magnetization was 14.9 emu/g.The effects of various reaction conditions on the properties of HDs and MHDs were studied systematically,and the influence mechanisms of these factors on the pore properties of polymer were discussed.The results showed that DCE was a suitable solvent for the preparation of hypercrosslinked polymers,and HDs with excellent pore properties were prepared by adjusting the molar ratio of anhydrous Fe Cl₃ to monomer in the range of 0.5-2.In addition,the results showed that the MHDs prepared by thermal decomposition retained partial microporous structure of the original polymer and at the same time endowed the polymers with magnetic separation performance.Furthermore,aniline was used as model pollutant to study the adsorption properties of HDs and MHDs.The maximum adsorption capacities of HD-14 and MHD-1 for aniline were 769.23 mg/g and 513.85 mg/g at20°C.（2）A series of hydroxyl-based hypercrosslinked polymers（HBs）were synthesized by Friedel-Crafts reaction using BA as monomer,and then hydroxyl-based magnetic hypercrosslinked polymers（MHBs）could be obtained by placing the HBs in the thermal decomposition environment of Fe（acac）₃.The BET specific surface area of MHB-1 was 616 m²/g,and the saturation magnetization was 21.1 emu/g.The effects of reaction conditions on the pore properties of the prepared HBs and MHBs were investigated in detail.HBs with excellent pore properties could be prepared by adjusting the molar ratio of Fe Cl₃ and FDA to the monomer within a certain range.In addition,the specific surface areas of MHBs were negatively related to the saturation magnetization,which could be adjusted according to the practical application.Finally,the adsorption performance of MHB-1 on aniline was investigated.The maximum adsorption capacity of MHB-1 for aniline was 546.72 mg/g at 20°C.（3）The hypercrosslinked polymers（HFs）were prepared by external weaving method using ferrocene as monomer,and then the magnetic hypercrosslinked polymers（MHFs）were obtained by simple in-situ oxidation of the HFs.Compared with other methods,this method was simple and the structure of MHFs was stable.A series of MHFs with different specific surface areas,pore volumes and magnetic response were prepared by systematic study on oxidation time and addition amount of oxidant.The BET specific surface area of MHF was up to 729 m²/g,and the saturation magnetization was up to 12.4 emu/g.In the process of in-situ oxidation,some pores formed in the structure of the polymers,so the specific surface areas could increase slightly after oxidation.The saturation magnetization of MHFs increased first and then decreased with the increase of reaction time;when the addition amount of hydrogen peroxide was too much,the saturation magnetization of MHFs would also decrease.In addition,CAP and TC were used as model adsorbates to study the adsorption performance of MHFs to antibiotics.The maximum adsorption capacities of MHF-2 for CAP and TC were 114.94 and212.77 mg/g at 30°C.（4）Two kinds of magnetic hypercrosslinked polymers（MHFM,MHDF）were successfully synthesized by simple in-situ oxidation method,in which ferrocenyl alcohol and dimethylferrocenyl were used as monomers.The BET specific surface areas of MHFM and MHDF were 807 and 701 m²/g,and the saturation magnetization were 10.7 and 11.4 emu/g.The effect of the functional groups on the properties of obtained hypercrosslinked polymers and magnetic hypercrosslinked polymers were investigated.The results showed that the methyl and hydroxymethyl groups could promote the cross-linking reaction,but the increase of steric hindrance from ferrocene methanol to dimethylferrocene inhibited the further growth of the molecular chain.Therefore,under the same experimental conditions,the pore properties of HFMs were more excellent.In addition,CAP and TC were used as model adsorbates to study the adsorption performance of MHFM and MHDF to antibiotics.At 30°C,the maximum adsorption capacities of MHFM for CAP and TC were 133.76 and 230.68 mg/g,and the maximum adsorption capacities of MHDF for CAP and TC were 117.63 and 217.28 mg/g.（5）Ferrocene and DCX were selected as monomers,which provide the polymer with iron source for in-situ oxidation and functional groups with high cross-linking activity.The specific surface areas and pore volumes of the hypercrosslinked polymers（HFDs）and magnetic hypercrosslinked polymers（MHFDs）were controlled by adjusting the ratio of DCX to ferrocene.The BET specific surface areas of HFDs and MHFDs increased with the increase of ratio,BET specific surface areas of the prepared MHFDs were mainly controlled in the range of 782-1190 m²/g,and the saturation magnetization of MHFDs decreased with the increase of the ratio.Furthermore,MHFDs were used to remove the antibiotics from water.The results showed that the maximum adsorption capacities of MHFD-10 for CAP and TC were 176.21mg/g and 268.60 mg/g at 30°C.