Hybrid polyion complex micelles from poly(vinylphosphonic acid)-based double hydrophilic block copolymers and divalent transition metal ions

Abstract

Double-hydrophilic block copolymers (DHBC) containing neutral polyacrylamide and ionizable poly(vinylphosphonic acid) blocks were directly synthesized by quantitative chain extension of a polyacrylamide macroxanthate with vinylphosphonic acid. Formation of hybrid polyion complex (HPIC) micelles was investigated at low pH with divalent transition metal ions with an emphasis on the comparison with polyacrylate-based DHBC. The tendency to form HPIC micelles as a function of the polyvinylphosphonate block length was as follows Ni2+, Co2+ < Mn2+ < Cu2+ > Zn2+; it did not follow the charge to size ratio of cations or the Irving–Williams series, but was similar to the order obtained with phosphonate-bearing nucleotides and nucleic acids. The inclination to form HPIC micelles with asymmetric DHBC at low pH was stronger with polyvinylphosphonate-based than with polyacrylate-based polymers in accordance with the higher basicity of the phosphonate group. Moreover, it increased with the polyion block length.