Temperature-sensitive aliphatic polyesters: synthesis and characterization of γ-substituted caprolactone monomers and polymers

Synthesis and ring-opening polymerization of γ-substituted ε-caprolactone monomers containing octyloxy and 2-[2-(2-methoxyethoxy)ethoxy]ethoxy functional groups is reported. An amphiphilic block copolymer containing hydrophobic poly(γ-octyloxy-ε-caprolactone) and hydrophilic poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone} forms micelles in aqueous solution above the critical micellar concentration of 1.74 × 10−3 g L−1. Poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone} and its block copolymer with poly(γ-octyloxy-ε-caprolactone) are thermoresponsive polymers. The LCST measured for poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone} is 47.5 °C, while the LCST decreased to 37.5 °C for the amphiphilic block copolymer poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone}-b-poly(γ-octyloxy-ε-caprolactone).