Synthesis and Micellar Behavior of Novel Amphiphilic Poly[bis(trifluoroethoxy)phosphazene]-co-poly[(dimethylamino)ethyl methacrylate] Block Copolymers

Abstract

A number of amphiphilic diblock copolymers based on poly[bis(trifluoroethoxy)phosphazene] (TFE) as the hydrophobic block and poly[(dimethylamino)ethyl methacrylate] (PDMAEMA) as the hydrophilic block were developed. The TFE block was synthesized first by the controlled living cationic polymerization of a phosphoranimine, followed by replacement of all the chlorine atoms using sodium trifluoroethoxide. To allow for the growth of the PDMAEMA block, 3-azidopropyl-2-bromo-2-methylpropanoate, an atom transfer radical polymerization (ATRP) initiator, was grafted onto the end-cap of the TFE block via the “click” reaction followed by the ATRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA). Once synthesized, micelles were formed by a standard method, and their characteristics were examined using fluorescence techniques, dynamic light scattering, and transmission electron microscopy. The critical micelle concentrations of the diblock copolymers as determined by fluorescence techniques using pyrene as a hydrophobic probe were between 3.47 and 9.55 mg/L, with the partition equilibrium constant of pyrene in these micelles ranging from 0.12 × 105 to 1.52 × 105. The diameters measured by dynamic light scattering were 100–142 nm at 25 °C with a narrow distribution, which were also confirmed by transmission electron microscopy.