Amphiphilic Diblock Copolymers Based on Poly(2-ethyl-2-oxazoline) and Poly(1,3-trimethylene carbonate): Synthesis and Micellar Characteristics

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Amphiphilic diblock copolymers with various block compositions were synthesized on the basis of poly(2-ethyl-2-oxazoline) (PEtOz) as a hydrophilic block and poly(1,3-trimethylene carbonate) (PTMC) as a hydrophobic block. Their aqueous solutions were characterized using fluorescence techniques and dynamic light scattering. The block copolymers formed micelles with critical micelle concentrations (cmc's) in the range 2.8−25 mg/L in an aqueous phase. As the length of the hydrophobic PTMC block became longer, lower cmc values were generated. The mean diameters of the micelles were in the range 199−210 nm, with a narrow distribution. The partition equilibrium constants ( K v ) of pyrene in the micellar solutions of the block copolymers were 0.91 × 10 5 −1.61 × 10 5 . The K v value increased as the length of the hydrophobic block increased. The steady-state fluorescence anisotropy values ( r ) of 1,6-diphenyl-1,3,5-hexatriene (DPH) in PEtOz−PTMC solutions were 0.292−0.302. The anisotropy values were not significantly influenced by the length of the hydrophobic block. The micelles underwent hydrogen bonding at pH < 3.6 with poly(acrylic acid) resulting in polymer complex precipitates, which could be reversibly dispersed as micelles at pH > 3.9.