Synthesis and self-association behavior of biodegradable amphiphilic poly[bis(ethyl glycinat-N-yl)phosphazene]-poly(ethylene oxide) block copolymers

Amphiphilic diblock copolymers with varying compositions of hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly[bis(ethyl glycinat-N-yl)phosphazene] (PNgly) were synthesized via the controlled cationic-induced polymerization of a phosphoranimine (Cl₃P=NSiMe₃) at ambient temperature using a PEO-phosphoranimine macroinitiator. The aqueous-phase transition behavior of PEO-PNgly-3 (M_n = 10 000) and micelle formation of both PEO-PNgly-3 and PEO-PNgly-4 (M_n = 8500) were investigated using fluorescence techniques and dynamic light scattering. The critical micelle concentrations (cmc's) of PEO-PNgly-3 and PEO-PNgly-4 were determined to be 3 and 12 mg/L with the mean diameters of micelles being 120 and 130 nm, respectively. The hydrolytic degradation of these diblock copolymers was also studied in solution. These studies coupled with the biodegradability of the poly[bis(ethyl glycinat-N-yl)-phosphazene] block to give benign products make PEO-PNgly copolymers well-suited for a wide variety of biomedical applications including novel biodegradable drug-delivery systems.