Poly(N-isopropylmethacrylamide-co-4-acrylamidobenzo-18-crown-6) microgels with expanded networks for excellent adsorption of lead(II) ions

Lead(II) (Pb2+) ions are toxic heavy metal ions that can accumulate in the human body through water and cause severe health problems, including neurotoxicity, nephrotoxicity, hematological toxicity and even genotoxicity effects. To remove Pb2+ selectively and effectively from aqueous solutions, we develop a novel type of Pb2+-recognizable microgels with excellent adsorption capacity to Pb2+, which are fabricated from 4-acrylamidobenzo-18-crown-6 (B18C6Am) and N-isopropylmethacrylamide (NIPMAM) monomers by precipitation copolymerization method. The prepared poly(N-isopropylmethacrylamide-co-4-acrylamidobenzo-18-crown-6) (PNMB) microgels exhibit expanded structures, because the electron-donating methyl groups at α-carbon could descend the polarity of C=O in the NIPMAM monomers and thus weaken the polymer segment···segment interactions. The expanded structures of PNMB microgels are beneficial for adsorption of Pb2+ due to the low steric hindrance in the polymeric networks. The Pb2+ adsorption isotherms of PNMB microgels are consistent with the Langmuir model for monolayer adsorption. The results indicate that the prepared Pb2+-recognizable PNMB microgels are highly promising for the selective removal of lead(II) ions from aqueous solutions.