Design,Synthesis And Application Of Nitrogen-Containing Heterocyclic Polymer Microspheres

Functional microspheres have attracted intensive interest because of superior physical and chemical properties,including small particle size,high specific surface area,and favorable dispersibility.In addition,the polymer particles show unique functionalities due to the presence of versatile functional groups on the particle surface,offering great potential for extensive applications in the fields of biomedicine,catalytic support,adsorption,and separation.In this paper,a series of functional polymer microspheres with different morphologies and structures of spherical,core-shell,and hollow structures were prepared based on nitrogen-containing heterocyclic monomers,including 4-vinylpyridine(4-VP),N-phenylmaleimide(N-PMI),and 1-vinylimidazole(1-VIm),and the hollow polymer microspheres were further modified and served as adsorbent for the removal of Congo red(CR).The detailed research work is as follows:1.Poly(N-PMI-co-4-VP)copolymer microspheres were prepared by self-stabilized precipitation polymerization using 4-VP and N-PMI as comonomers.The effects of the reaction medium,monomer concentration,and monomer ratio on the morphology,particle size,and size distribution of the as-prepared copolymer microspheres were investigated,and the chemical composition and thermal stability of the copolymer were characterized in detail.Poly(N-PMI-co-4-VP)copolymer microspheres with an average particle size of 1.84 ?m were prepared in the reaction medium of ethyl benzoate/n-heptane=6:4(v/v).The thermal decomposition temperature T10%of the microspheres is 300?,and the temperature of the maximum weight loss rate is up to 370?.2.Core-shell microspheres(PMS@PDVN)with high-density pyridine group in the shell layer were synthesized via template method,using poly(styrene-maleic anhydride)(PMS)particles as template cores,4-VP and N-PMI as shell monomer,and divinylbenzene(DVB)as crosslinker.The PMS template was further removed to obtain hollow polymer microspheres(PDVN-HPP).The effects of different reaction conditions on the size and morphology of the resultant core-shell and hollow microspheres were investigated and PDVN-HPP with a constant diameter of 1.4 ?m and controllable shell thickness(from 66 nm to 110 nm)were successfully obtained.3.Cationic functionalized hollow polymer microspheres(PDVN-HPP+)were prepared through the modification of PDVN-HPP with HCI.Anionic dye Congo red(CR)was selected as the model dye to study the adsorption behavior of the as-formed PDVN-HPP+.The effects of CR concentrations,contact time,and solution pH value on the adsorption performance of PDVN-HPP+were investigated in detail.The experimental result showed that PDVN-HPP+has a relatively high adsorption capacity(qe=159 mg/g)for CR at 25?.Moreover,the adsorption process can be well described by the pseudo-second-order and Langmuir model.When the solution pH is in the range of 3 to 8,the adsorption capacity remained at 135 mg/g,indicating that the adsorption process was not affected by pH.4.The ionic liquid monomer 1-hexyl-3-vinylimidazole bromide([C6VIm]Br)was prepared by quaternization of 1-vinylimidazole(1-VIm),which was used as a polymerizable stabilizer for dispersion polymerization of styrene.The formation mechanism of ionic liquid functionalized polystyrene(PS)microspheres was discussed,and the effects of different reaction conditions on the morphology and size of the resultant microspheres were investigated.[C6VIm]Br functionalized PS microspheres with particle size ranging from 1.4 ?m to 2.1 ?m were successfully prepared.