Helical poly(N-propargylamide)s with functional catechol groups: Synthesis and adsorption of metal ions in aqueous solution

A novel type of helical N-propargylamide (PA) copolymer was synthesized by catalytic polymerization of monomer 1 (M1), which provided pendent functional catechol groups, and monomer 2 (M2), which endowed the expected copolymer backbones with helical structures. With [(nbd)Rh+B−(C6H5)4 (nbd = 2,5-norbornadiene)] as catalyst, PA copolymers could be obtained with moderate molecular weights (3800-14,000) in high yields (⩾96%). The functional catechol groups enhanced the hydrophilicity of the hydrophobic mono-substituted polyacetylenes and aided the helical PA copolymers in showing a considerable adsorbance toward metal ions [Fe(III), Cr(III), Ni(II), Zn(II), Cu(II) and Cu(I)] in aqueous solution. The prepared copolymer in which M1/M2 was 0.1/0.9 [mol/mol, poly(10.1-co-20.9)] showed the highest adsorption capacity among the examined helical copolymers. In particular, for Fe(III), the maximum adsorption capacity was 186 mg g−1.