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

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