Self-Assembling Properties of Well-Defined Poly(ethylene oxide)-<i>b</i>-poly(ethyl acrylate) Diblock Copolymers

Abstract

Poly(ethylene oxide)-b-poly(ethyl acrylate) amphiphilic diblock copolymers were synthesized by atom transfer radical polymerization (ATRP). The controlled character of the polymerization was confirmed by kinetic studies, evolution of number-average molecular weight and polydispersity index with conversion. Various block copolymers with different PEA/PEO molar ratio were synthesized and their self-assembling properties in aqueous medium were studied by fluorescence measurements, static light scattering (SLS), and dynamic light scattering (DLS). The critical micelle concentrations (CMC) were determined by pyrene fluorescence analysis. The CMC was shown to decrease as the hydrophobic (PEA) block length increases. SLS and DLS allowed the determination of the aggregation numbers (Nagg) and hydrodynamic radii (Rh) of the core−shell micelles formed in water. Both Nagg and Rh exhibit a monotonic increase as a function of the PEA block length. TEM and cryo-TEM micrographs of the micelles showed spherical objects with a low polydispersity of sizes. The micelles formed in water are in a thermodynamic equilibrium and the aggregation number of the micelles was shown to vary with the temperature.