Thermoresponsive and Biodegradable Amphiphilic Block Copolymers with Pendant Functional Groups.

BACKGROUND

To develop the biodegradability and thermoresponsive hydrogel, in this work we designed a pendant-functionalized, thermoresponsive, amphiphilic block copolymer.

METHODS

Methoxy poly(ethylene glycol) (MPEG)--[poly(ε-caprolactone)--poly(ε-caprolactone-3-one)--polylactic acid] (MCL) and (MPEG--[PCL--POD--PLA]) [MCL-(CO)] block copolymers were prepared by ring-opening polymerization of ε-caprolactone, OD and lactide monomers. The subsequent derivatization of MCL-(CO) provided MPEG--[PCL--poly(ε-caprolactone-3-COOH)--PLA] [MCL-(COOH)] with COOH pendant groups and MPEG--[PCL--poly(ε-caprolactone-3-NH)--PLA] [MCL-(NH)] with NH pendant groups.

RESULTS

The measured segment ratios of MCL-(CO), MCL-(COOH), and MCL-(NH) agreed well with the target ratios. The abundances of the COOH and NH groups in the MCL-(COOH) and MCL-(NH) copolymers were determined by H- and C-nuclear magnetic resonance spectroscopy, and agreed well with the target abundances. MCL-(CO), MCL-(COOH), and MCL-(NH) formed homogeneous, white, opaque emulsions at room temperature. Rheological analysis of the block copolymer suspensions indicated a solution-to-hydrogel phase transition as a function of temperature. The solution-to-hydrogel phase transitions and the biodegradation of MCL-(CO), MCL-(COOH), and MCL-(NH) were affected by varying the type (ketone, COOH, or NH) and abundance of the pendant groups.

CONCLUSION

MCL-(CO), MCL-(COOH), and MCL-(NH) with ketone, COOH, and NH pendant groups showed solution-to-hydrogel phase transitions and biodegradation behaviors that depended on both the type and number of pendant groups.