Association Behavior of Amphiphilic ABA Triblock Copolymer Composed of Poly(2-methoxyethyl acrylate) (A) and Poly(ethylene oxide) (B) in Aqueous Solution

Poly(2-methoxyethyl acrylate) (PMEA) and poly(ethylene oxide) (PEO) have protein-antifouling properties and blood compatibility. ABA triblock copolymers (PMEA(l)-PEO(11340)-PMEA(m) (MEOM(n); n is average value of l and m)) were prepared using single-electron transfer-living radical polymerization (SET-LRP) using a bifunctional PEO macroinitiator. Two types of MEOM(n) composed of PMEA blocks with degrees of polymerization (DP = n) of 85 and 777 were prepared using the same PEO macroinitiator. MEOM(n) formed flower micelles with a hydrophobic PMEA (A) core and hydrophilic PEO (B) loop shells in diluted water with a similar appearance to petals. The hydrodynamic radii of MEOM(85) and MEOM(777) were 151 and 108 nm, respectively. The PMEA block with a large DP formed a tightly packed core. The aggregation number (N(agg)) of the PMEA block in a single flower micelle for MEOM(85) and MEOM(777) was 156 and 164, respectively, which were estimated using a light scattering technique. The critical micelle concentrations (CMCs) for MEOM(85) and MEOM(777) were 0.01 and 0.002 g/L, respectively, as determined by the light scattering intensity and fluorescence probe techniques. The size, N(agg), and CMC for MEOM(85) and MEOM(777) were almost the same independent of hydrophobic DP of the PMEA block.