Self-assembly behavior of amphiphilic polyelectrolyte with ultrahigh charge density

A series of novel amphiphilic polyelectrolytes with ultrahigh charge density were synthesized by copolymerization of monomers with double-quaternary ammonium groups. The self-assembly properties of the amphiphilic polyelectrolyte with ultrahigh charge density in aqueous solutions have been investigated by means of steady-state fluorescence, dynamic light scattering (DLS), transmission electric microscopy (TEM), and zeta potential measurements. The critical aggregation concentrations (cac) of the polyelectrolytes decreased as the molar content of hydrophobic segments and the length of hydrophobic carbon chains increased. The sizes of the aggregates in the polyelectrolyte solution increased as the concentration of the solution and the molar content of hydrophobic units increased. Compared with the counterparts of the single quaternized ammonium groups in hydrophilic units, the values of cac of the novel ultrahigh charge density polyelectrolytes were larger; however, the size and the zeta potential of aggregates in aqueous solutions were smaller than that of the former. These phenomena were ascribed to the strong hydrophilic capacity and electrostatic repulsions existed in the double quaternized groups of polyelectrolytes.