Synthesis and characterization of polyion complex micelles between poly(ethylene glycol)-grafted poly(aspartic acid) and cetyltrimethyl ammonium bromide

Graft copolymers, poly(ethylene glycol)-grafted poly(aspartic acid) (PEG-g-PAsp), were synthesized by ring opening reaction of polysuccinimide with α-methoxy-ω-amino-poly(ethylene glycol) (PEG-NH2) and sodium hydroxide. Through changing the amount of PEG-NH2, varying grafting degrees of PEG-g-PAsp could be obtained. Polyion complex micelles (PIC) were prepared by mixing PEG-g-PAsp with CTAB in water. When the carboxyl groups were exactly neutralized by CTAB, the formed micellar solution had maximal turbidity and minimal polydispersity. The CAC of polymer–surfactant complex was much smaller than the CMC of the pure surfactant CTAB. ξ-Potential of the complex micelles was studied by varying the ratio of PEG-g-PAsp and CTAB. The polyion complex micelles were spherical particles with clear core/shell structures. The composition of the graft copolymers had great influence on the particle size of the micelles. The higher the PEG content in the graft copolymer, the smaller the size of PIC micelles.