Synthesis and self-association behavior of poly[bis(2-(2-methoxyethoxy) ethoxy)phosphazene]-b-poly(propylene glycol) triblock copolymers

Amphilic triblock copolymers with varying ratios of hydrophilic poly[bis (methoxyethoxyethoxy)phosphazene] (MEEP) and relatively hydrophobic poly(propylene glycol) (PPG) blocks were synthesized via the controlled cationic-induced living polymerization of a phosphoranimine (Cl ₃P=NSiMe ₃) at ambient temperature. A PPG block can function as either a classical hydrophobic block or a less hydrophobic component by varying the nature of a phosphazene block. The aqueous phase behavior of MEEP-PPG-MEEP block copolymers was investigated using fluorescence techniques, TEM, and dynamic light scattering (DLS). The critical micelle concentrations (cmcs) of MEEP-PPG-MEEP block copolymers were determined to be in the range of 3.7-16.8 mg/L. The mean diameters of MEEP-PPG-MEEP polymeric micelles, measured by DLS, were between 31 and 44 nm. The equilibrium constants of pyrene in these micelles ranged from 4.7 × 10 ⁴ to 9.6 × 10 ⁴.